File reorganization for checker system.

1 files changed, 4759 insertions, 0 deletions

diff --git a/src/check_expr.c b/src/check_expr.c
new file mode 100644
index 000000000..2c772d149
--- /dev/null
+++ b/src/check_expr.c
@@ -0,0 +1,4759 @@
+void     check_expr                (Checker *c, Operand *operand, AstNode *expression);
+void     check_multi_expr          (Checker *c, Operand *operand, AstNode *expression);
+void     check_expr_or_type        (Checker *c, Operand *operand, AstNode *expression);
+ExprKind check_expr_base           (Checker *c, Operand *operand, AstNode *expression, Type *type_hint);
+Type *   check_type_extra          (Checker *c, AstNode *expression, Type *named_type);
+Type *   check_type                (Checker *c, AstNode *expression);
+void     check_type_decl           (Checker *c, Entity *e, AstNode *type_expr, Type *def);
+Entity * check_selector            (Checker *c, Operand *operand, AstNode *node);
+void     check_not_tuple           (Checker *c, Operand *operand);
+bool     check_value_is_expressible(Checker *c, ExactValue in_value, Type *type, ExactValue *out_value);
+void     convert_to_typed          (Checker *c, Operand *operand, Type *target_type, i32 level);
+gbString expr_to_string            (AstNode *expression);
+void     check_entity_decl         (Checker *c, Entity *e, DeclInfo *decl, Type *named_type);
+void     check_const_decl          (Checker *c, Entity *e, AstNode *type_expr, AstNode *init_expr, Type *named_type);
+void     check_proc_body           (Checker *c, Token token, DeclInfo *decl, Type *type, AstNode *body);
+void     update_expr_type          (Checker *c, AstNode *e, Type *type, bool final);
+bool     check_is_terminating      (AstNode *node);
+bool     check_has_break           (AstNode *stmt, bool implicit);
+void     check_stmt                (Checker *c, AstNode *node, u32 flags);
+void     check_stmt_list           (Checker *c, AstNodeArray stmts, u32 flags);
+void     check_init_constant       (Checker *c, Entity *e, Operand *operand);
+
+
+gb_inline Type *check_type(Checker *c, AstNode *expression) {
+	return check_type_extra(c, expression, NULL);
+}
+
+
+
+
+typedef struct DelayedEntity {
+	AstNode *   ident;
+	Entity *    entity;
+	DeclInfo *  decl;
+} DelayedEntity;
+
+typedef struct DelayedOtherFields {
+	Entity **other_fields;
+	isize other_field_count;
+	isize other_field_index;
+
+	MapEntity *entity_map;
+} DelayedOtherFields;
+
+typedef Array(DelayedEntity) DelayedEntities;
+
+void check_local_collect_entities(Checker *c, AstNodeArray nodes, DelayedEntities *delayed_entities, DelayedOtherFields *dof);
+
+void check_local_collect_entities_from_when_stmt(Checker *c, AstNodeWhenStmt *ws, DelayedEntities *delayed_entities, DelayedOtherFields *dof) {
+	Operand operand = {Addressing_Invalid};
+	check_expr(c, &operand, ws->cond);
+	if (operand.mode != Addressing_Invalid && !is_type_boolean(operand.type)) {
+		error_node(ws->cond, "Non-boolean condition in `when` statement");
+	}
+	if (operand.mode != Addressing_Constant) {
+		error_node(ws->cond, "Non-constant condition in `when` statement");
+	}
+	if (ws->body == NULL || ws->body->kind != AstNode_BlockStmt) {
+		error_node(ws->cond, "Invalid body for `when` statement");
+	} else {
+		if (operand.value.kind == ExactValue_Bool &&
+		    operand.value.value_bool) {
+			check_local_collect_entities(c, ws->body->BlockStmt.stmts, delayed_entities, dof);
+		} else if (ws->else_stmt) {
+			switch (ws->else_stmt->kind) {
+			case AstNode_BlockStmt:
+				check_local_collect_entities(c, ws->else_stmt->BlockStmt.stmts, delayed_entities, dof);
+				break;
+			case AstNode_WhenStmt:
+				check_local_collect_entities_from_when_stmt(c, &ws->else_stmt->WhenStmt, delayed_entities, dof);
+				break;
+			default:
+				error_node(ws->else_stmt, "Invalid `else` statement in `when` statement");
+				break;
+			}
+		}
+	}
+}
+
+// NOTE(bill): The `dof` is for use within records
+void check_local_collect_entities(Checker *c, AstNodeArray nodes, DelayedEntities *delayed_entities, DelayedOtherFields *dof) {
+	for_array(i, nodes) {
+		AstNode *node = nodes.e[i];
+		switch (node->kind) {
+		case_ast_node(ws, WhenStmt, node);
+			// Will be handled later
+		case_end;
+
+		case_ast_node(vd, ValueDecl, node);
+			if (vd->is_var) {
+				// NOTE(bill): Handled later
+			} else {
+				for_array(i, vd->names) {
+					AstNode *name = vd->names.e[i];
+					if (name->kind != AstNode_Ident) {
+						error_node(name, "A declaration's name must be an identifier, got %.*s", LIT(ast_node_strings[name->kind]));
+						continue;
+					}
+
+					AstNode *init = NULL;
+					if (i < vd->values.count) {
+						init = vd->values.e[i];
+					}
+
+					DeclInfo *d = make_declaration_info(c->allocator, c->context.scope);
+					Entity *e = NULL;
+
+					AstNode *up_init = unparen_expr(init);
+					if (init != NULL && is_ast_node_type(up_init)) {
+						e = make_entity_type_name(c->allocator, d->scope, name->Ident, NULL);
+						d->type_expr = init;
+						d->init_expr = init;
+					} else if (init != NULL && up_init->kind == AstNode_ProcLit) {
+						e = make_entity_procedure(c->allocator, d->scope, name->Ident, NULL, up_init->ProcLit.tags);
+						d->proc_lit = init;
+					} else {
+						e = make_entity_constant(c->allocator, d->scope, name->Ident, NULL, (ExactValue){0});
+						d->type_expr = vd->type;
+						d->init_expr = init;
+					}
+					GB_ASSERT(e != NULL);
+					e->identifier = name;
+
+					add_entity_and_decl_info(c, name, e, d);
+
+					DelayedEntity delay = {name, e, d};
+					array_add(delayed_entities, delay);
+				}
+
+				check_arity_match(c, vd);
+			}
+		case_end;
+#if 0
+		case_ast_node(pd, ProcDecl, node);
+			if (!ast_node_expect(pd->name, AstNode_Ident)) {
+				break;
+			}
+
+			Entity *e = make_entity_procedure(c->allocator, c->context.scope, pd->name->Ident, NULL);
+			e->identifier = pd->name;
+
+			DeclInfo *d = make_declaration_info(c->allocator, e->scope);
+			d->proc_lit = node;
+
+			add_entity_and_decl_info(c, pd->name, e, d);
+			check_entity_decl(c, e, d, NULL, NULL);
+		case_end;
+#endif
+		}
+	}
+
+	// NOTE(bill): `when` stmts need to be handled after the other as the condition may refer to something
+	// declared after this stmt in source
+	for_array(i, nodes) {
+		AstNode *node = nodes.e[i];
+		switch (node->kind) {
+		case_ast_node(ws, WhenStmt, node);
+			check_local_collect_entities_from_when_stmt(c, ws, delayed_entities, dof);
+		case_end;
+		}
+	}
+}
+
+void check_scope_decls(Checker *c, AstNodeArray nodes, isize reserve_size, DelayedOtherFields *dof) {
+	DelayedEntities delayed_entities;
+	array_init_reserve(&delayed_entities, heap_allocator(), reserve_size);
+	check_local_collect_entities(c, nodes, &delayed_entities, dof);
+
+	for_array(i, delayed_entities) {
+		DelayedEntity delayed = delayed_entities.e[i];
+		if (delayed.entity->kind == Entity_TypeName) {
+			check_entity_decl(c, delayed.entity, delayed.decl, NULL);
+		}
+	}
+	for_array(i, delayed_entities) {
+		DelayedEntity delayed = delayed_entities.e[i];
+		if (delayed.entity->kind == Entity_Constant) {
+			add_entity_and_decl_info(c, delayed.ident, delayed.entity, delayed.decl);
+			check_entity_decl(c, delayed.entity, delayed.decl, NULL);
+		}
+	}
+
+	array_free(&delayed_entities);
+}
+
+
+bool check_is_assignable_to_using_subtype(Type *dst, Type *src) {
+	bool src_is_ptr;
+	Type *prev_src = src;
+	src = type_deref(src);
+	src_is_ptr = src != prev_src;
+	src = base_type(src);
+
+	if (is_type_struct(src)) {
+		for (isize i = 0; i < src->Record.field_count; i++) {
+			Entity *f = src->Record.fields[i];
+			if (f->kind == Entity_Variable && (f->flags & EntityFlag_Anonymous)) {
+				if (are_types_identical(dst, f->type)) {
+					return true;
+				}
+				if (src_is_ptr && is_type_pointer(dst)) {
+					if (are_types_identical(type_deref(dst), f->type)) {
+						return true;
+					}
+				}
+				bool ok = check_is_assignable_to_using_subtype(dst, f->type);
+				if (ok) {
+					return true;
+				}
+			}
+		}
+	}
+	return false;
+}
+
+
+bool check_is_assignable_to(Checker *c, Operand *operand, Type *type) {
+	if (operand->mode == Addressing_Invalid ||
+	    type == t_invalid) {
+		return true;
+	}
+
+	if (operand->mode == Addressing_Builtin) {
+		return false;
+	}
+
+	Type *s = operand->type;
+
+	if (are_types_identical(s, type)) {
+		return true;
+	}
+
+	Type *src = base_type(s);
+	Type *dst = base_type(type);
+
+	if (is_type_untyped(src)) {
+		switch (dst->kind) {
+		case Type_Basic:
+			if (operand->mode == Addressing_Constant) {
+				return check_value_is_expressible(c, operand->value, dst, NULL);
+			}
+			if (src->kind == Type_Basic && src->Basic.kind == Basic_UntypedBool) {
+				return is_type_boolean(dst);
+			}
+			break;
+		}
+		if (type_has_nil(dst)) {
+			return operand->mode == Addressing_Value && operand->type == t_untyped_nil;
+		}
+	}
+
+	if (are_types_identical(dst, src) && (!is_type_named(dst) || !is_type_named(src))) {
+		return true;
+	}
+
+	if (is_type_maybe(dst)) {
+		Type *elem = base_type(dst)->Maybe.elem;
+		return are_types_identical(elem, s);
+	}
+
+	if (is_type_untyped_nil(src)) {
+		return type_has_nil(dst);
+	}
+
+	// ^T <- rawptr
+	// TODO(bill): Should C-style (not C++) pointer cast be allowed?
+	// if (is_type_pointer(dst) && is_type_rawptr(src)) {
+	    // return true;
+	// }
+
+	// rawptr <- ^T
+	if (is_type_rawptr(dst) && is_type_pointer(src)) {
+		// TODO(bill): Handle this properly
+		if (dst != type) {
+			return false;
+		}
+	    return true;
+	}
+
+
+
+	if (dst->kind == Type_Array && src->kind == Type_Array) {
+		if (are_types_identical(dst->Array.elem, src->Array.elem)) {
+			return dst->Array.count == src->Array.count;
+		}
+	}
+
+	if (dst->kind == Type_Slice && src->kind == Type_Slice) {
+		if (are_types_identical(dst->Slice.elem, src->Slice.elem)) {
+			return true;
+		}
+	}
+
+	if (is_type_union(dst)) {
+		for (isize i = 0; i < dst->Record.field_count; i++) {
+			Entity *f = dst->Record.fields[i];
+			if (are_types_identical(f->type, s)) {
+				return true;
+			}
+		}
+	}
+
+
+	if (is_type_any(dst)) {
+		// NOTE(bill): Anything can cast to `Any`
+		add_type_info_type(c, s);
+		return true;
+	}
+
+	return false;
+}
+
+
+// NOTE(bill): `content_name` is for debugging and error messages
+void check_assignment(Checker *c, Operand *operand, Type *type, String context_name) {
+	check_not_tuple(c, operand);
+	if (operand->mode == Addressing_Invalid) {
+		return;
+	}
+
+	if (is_type_untyped(operand->type)) {
+		Type *target_type = type;
+
+		if (type == NULL || is_type_any(type) || is_type_untyped_nil(type)) {
+			if (type == NULL && base_type(operand->type) == t_untyped_nil) {
+				error_node(operand->expr, "Use of untyped nil in %.*s", LIT(context_name));
+				operand->mode = Addressing_Invalid;
+				return;
+			}
+
+			add_type_info_type(c, type);
+			target_type = default_type(operand->type);
+		}
+		convert_to_typed(c, operand, target_type, 0);
+		if (operand->mode == Addressing_Invalid) {
+			return;
+		}
+	}
+
+	if (type != NULL) {
+		if (!check_is_assignable_to(c, operand, type)) {
+			gbString type_str    = type_to_string(type);
+			gbString op_type_str = type_to_string(operand->type);
+			gbString expr_str    = expr_to_string(operand->expr);
+
+			if (operand->mode == Addressing_Builtin) {
+				// TODO(bill): is this a good enough error message?
+				error_node(operand->expr,
+				           "Cannot assign builtin procedure `%s` in %.*s",
+				           expr_str,
+				           LIT(context_name));
+			} else {
+				// TODO(bill): is this a good enough error message?
+				error_node(operand->expr,
+				           "Cannot assign value `%s` of type `%s` to `%s` in %.*s",
+				           expr_str,
+				           op_type_str,
+				           type_str,
+				           LIT(context_name));
+			}
+			operand->mode = Addressing_Invalid;
+
+			gb_string_free(expr_str);
+			gb_string_free(op_type_str);
+			gb_string_free(type_str);
+			return;
+		}
+	}
+}
+
+
+void populate_using_entity_map(Checker *c, AstNode *node, Type *t, MapEntity *entity_map) {
+	t = base_type(type_deref(t));
+	gbString str = expr_to_string(node);
+
+	if (t->kind == Type_Record) {
+		for (isize i = 0; i < t->Record.field_count; i++) {
+			Entity *f = t->Record.fields[i];
+			GB_ASSERT(f->kind == Entity_Variable);
+			String name = f->token.string;
+			HashKey key = hash_string(name);
+			Entity **found = map_entity_get(entity_map, key);
+			if (found != NULL) {
+				Entity *e = *found;
+				// TODO(bill): Better type error
+				error(e->token, "`%.*s` is already declared in `%s`", LIT(name), str);
+			} else {
+				map_entity_set(entity_map, key, f);
+				add_entity(c, c->context.scope, NULL, f);
+				if (f->flags & EntityFlag_Anonymous) {
+					populate_using_entity_map(c, node, f->type, entity_map);
+				}
+			}
+		}
+	}
+
+	gb_string_free(str);
+}
+
+
+void check_fields(Checker *c, AstNode *node, AstNodeArray decls,
+                  Entity **fields, isize field_count,
+                  String context) {
+	gbTempArenaMemory tmp = gb_temp_arena_memory_begin(&c->tmp_arena);
+
+	MapEntity entity_map = {0};
+	map_entity_init_with_reserve(&entity_map, c->tmp_allocator, 2*field_count);
+
+	isize other_field_index = 0;
+	Entity *using_index_expr = NULL;
+
+	if (node->kind == AstNode_UnionType) {
+		isize field_index = 0;
+		fields[field_index++] = make_entity_type_name(c->allocator, c->context.scope, empty_token, NULL);
+		for_array(decl_index, decls) {
+			AstNode *decl = decls.e[decl_index];
+			if (decl->kind != AstNode_Field) {
+				continue;
+			}
+
+			ast_node(f, Field, decl);
+			Type *base_type = check_type_extra(c, f->type, NULL);
+
+			for_array(name_index, f->names) {
+				AstNode *name = f->names.e[name_index];
+				if (!ast_node_expect(name, AstNode_Ident)) {
+					continue;
+				}
+
+				Token name_token = name->Ident;
+
+				Type *type = make_type_named(c->allocator, name_token.string, base_type, NULL);
+				Entity *e = make_entity_type_name(c->allocator, c->context.scope, name_token, type);
+				type->Named.type_name = e;
+				add_entity(c, c->context.scope, name, e);
+
+				if (str_eq(name_token.string, str_lit("_"))) {
+					error(name_token, "`_` cannot be used a union subtype");
+					continue;
+				}
+
+				HashKey key = hash_string(name_token.string);
+				if (map_entity_get(&entity_map, key) != NULL) {
+					// TODO(bill): Scope checking already checks the declaration
+					error(name_token, "`%.*s` is already declared in this union", LIT(name_token.string));
+				} else {
+					map_entity_set(&entity_map, key, e);
+					fields[field_index++] = e;
+				}
+				add_entity_use(c, name, e);
+			}
+		}
+	} else {
+		isize field_index = 0;
+		for_array(decl_index, decls) {
+			AstNode *decl = decls.e[decl_index];
+			if (decl->kind != AstNode_Field) {
+				continue;
+			}
+			ast_node(f, Field, decl);
+
+			Type *type = check_type_extra(c, f->type, NULL);
+
+			if (f->is_using) {
+				if (f->names.count > 1) {
+					error_node(f->names.e[0], "Cannot apply `using` to more than one of the same type");
+				}
+			}
+
+			for_array(name_index, f->names) {
+				AstNode *name = f->names.e[name_index];
+				if (!ast_node_expect(name, AstNode_Ident)) {
+					continue;
+				}
+
+				Token name_token = name->Ident;
+
+				Entity *e = make_entity_field(c->allocator, c->context.scope, name_token, type, f->is_using, cast(i32)field_index);
+				e->identifier = name;
+				if (str_eq(name_token.string, str_lit("_"))) {
+					fields[field_index++] = e;
+				} else {
+					HashKey key = hash_string(name_token.string);
+					if (map_entity_get(&entity_map, key) != NULL) {
+						// TODO(bill): Scope checking already checks the declaration
+						error(name_token, "`%.*s` is already declared in this type", LIT(name_token.string));
+					} else {
+						map_entity_set(&entity_map, key, e);
+						fields[field_index++] = e;
+						add_entity(c, c->context.scope, name, e);
+					}
+					add_entity_use(c, name, e);
+				}
+			}
+
+
+			if (f->is_using) {
+				Type *t = base_type(type_deref(type));
+				if (!is_type_struct(t) && !is_type_raw_union(t) &&
+				    f->names.count >= 1 &&
+				    f->names.e[0]->kind == AstNode_Ident) {
+					Token name_token = f->names.e[0]->Ident;
+					if (is_type_indexable(t)) {
+						bool ok = true;
+						for_array(emi, entity_map.entries) {
+							Entity *e = entity_map.entries.e[emi].value;
+							if (e->kind == Entity_Variable && e->flags & EntityFlag_Anonymous) {
+								if (is_type_indexable(e->type)) {
+									if (e->identifier != f->names.e[0]) {
+										ok = false;
+										using_index_expr = e;
+										break;
+									}
+								}
+							}
+						}
+						if (ok) {
+							using_index_expr = fields[field_index-1];
+						} else {
+							fields[field_index-1]->flags &= ~EntityFlag_Anonymous;
+							error(name_token, "Previous `using` for an index expression `%.*s`", LIT(name_token.string));
+						}
+					} else {
+						error(name_token, "`using` on a field `%.*s` must be a `struct` or `raw_union`", LIT(name_token.string));
+						continue;
+					}
+				}
+
+				populate_using_entity_map(c, node, type, &entity_map);
+			}
+		}
+	}
+
+	gb_temp_arena_memory_end(tmp);
+}
+
+
+// TODO(bill): Cleanup struct field reordering
+// TODO(bill): Inline sorting procedure?
+gb_global BaseTypeSizes __checker_sizes = {0};
+gb_global gbAllocator   __checker_allocator = {0};
+
+GB_COMPARE_PROC(cmp_struct_entity_size) {
+	// Rule:
+	// Biggest to smallest alignment
+	// if same alignment: biggest to smallest size
+	// if same size: order by source order
+	Entity *x = *(Entity **)a;
+	Entity *y = *(Entity **)b;
+	GB_ASSERT(x != NULL);
+	GB_ASSERT(y != NULL);
+	GB_ASSERT(x->kind == Entity_Variable);
+	GB_ASSERT(y->kind == Entity_Variable);
+	i64 xa = type_align_of(__checker_sizes, __checker_allocator, x->type);
+	i64 ya = type_align_of(__checker_sizes, __checker_allocator, y->type);
+	i64 xs = type_size_of(__checker_sizes, __checker_allocator, x->type);
+	i64 ys = type_size_of(__checker_sizes, __checker_allocator, y->type);
+
+	if (xa == ya) {
+		if (xs == ys) {
+			i32 diff = x->Variable.field_index - y->Variable.field_index;
+			return diff < 0 ? -1 : diff > 0;
+		}
+		return xs > ys ? -1 : xs < ys;
+	}
+	return xa > ya ? -1 : xa < ya;
+}
+
+void check_struct_type(Checker *c, Type *struct_type, AstNode *node) {
+	GB_ASSERT(is_type_struct(struct_type));
+	ast_node(st, StructType, node);
+
+	isize field_count = 0;
+	for_array(field_index, st->fields) {
+		AstNode *field = st->fields.e[field_index];
+		switch (field->kind) {
+		case_ast_node(f, Field, field);
+			field_count += f->names.count;
+		case_end;
+		}
+	}
+
+	Entity **fields = gb_alloc_array(c->allocator, Entity *, field_count);
+
+	check_fields(c, node, st->fields, fields, field_count, str_lit("struct"));
+
+	struct_type->Record.struct_is_packed    = st->is_packed;
+	struct_type->Record.struct_is_ordered   = st->is_ordered;
+	struct_type->Record.fields              = fields;
+	struct_type->Record.fields_in_src_order = fields;
+	struct_type->Record.field_count         = field_count;
+
+	if (!st->is_packed && !st->is_ordered) {
+		// NOTE(bill): Reorder fields for reduced size/performance
+
+		Entity **reordered_fields = gb_alloc_array(c->allocator, Entity *, field_count);
+		for (isize i = 0; i < field_count; i++) {
+			reordered_fields[i] = struct_type->Record.fields_in_src_order[i];
+		}
+
+		// NOTE(bill): Hacky thing
+		// TODO(bill): Probably make an inline sorting procedure rather than use global variables
+		__checker_sizes = c->sizes;
+		__checker_allocator = c->allocator;
+		// NOTE(bill): compound literal order must match source not layout
+		gb_sort_array(reordered_fields, field_count, cmp_struct_entity_size);
+
+		for (isize i = 0; i < field_count; i++) {
+			reordered_fields[i]->Variable.field_index = i;
+		}
+
+		struct_type->Record.fields = reordered_fields;
+	}
+
+	type_set_offsets(c->sizes, c->allocator, struct_type);
+}
+
+void check_union_type(Checker *c, Type *union_type, AstNode *node) {
+	GB_ASSERT(is_type_union(union_type));
+	ast_node(ut, UnionType, node);
+
+	isize field_count = 1;
+	for_array(field_index, ut->fields) {
+		AstNode *field = ut->fields.e[field_index];
+		switch (field->kind) {
+		case_ast_node(f, Field, field);
+			field_count += f->names.count;
+		case_end;
+		}
+	}
+
+	Entity **fields = gb_alloc_array(c->allocator, Entity *, field_count);
+
+	check_fields(c, node, ut->fields, fields, field_count, str_lit("union"));
+
+	union_type->Record.fields            = fields;
+	union_type->Record.field_count       = field_count;
+}
+
+void check_raw_union_type(Checker *c, Type *union_type, AstNode *node) {
+	GB_ASSERT(node->kind == AstNode_RawUnionType);
+	GB_ASSERT(is_type_raw_union(union_type));
+	ast_node(ut, RawUnionType, node);
+
+	isize field_count = 0;
+	for_array(field_index, ut->fields) {
+		AstNode *field = ut->fields.e[field_index];
+		switch (field->kind) {
+		case_ast_node(f, Field, field);
+			field_count += f->names.count;
+		case_end;
+		}
+	}
+
+	Entity **fields = gb_alloc_array(c->allocator, Entity *, field_count);
+
+	check_fields(c, node, ut->fields, fields, field_count, str_lit("raw_union"));
+
+	union_type->Record.fields = fields;
+	union_type->Record.field_count = field_count;
+}
+
+// GB_COMPARE_PROC(cmp_enum_order) {
+// 	// Rule:
+// 	// Biggest to smallest alignment
+// 	// if same alignment: biggest to smallest size
+// 	// if same size: order by source order
+// 	Entity *x = *(Entity **)a;
+// 	Entity *y = *(Entity **)b;
+// 	GB_ASSERT(x != NULL);
+// 	GB_ASSERT(y != NULL);
+// 	GB_ASSERT(x->kind == Entity_Constant);
+// 	GB_ASSERT(y->kind == Entity_Constant);
+// 	GB_ASSERT(x->Constant.value.kind == ExactValue_Integer);
+// 	GB_ASSERT(y->Constant.value.kind == ExactValue_Integer);
+// 	i64 i = x->Constant.value.value_integer;
+// 	i64 j = y->Constant.value.value_integer;
+
+// 	return i < j ? -1 : i > j;
+// }
+
+void check_enum_type(Checker *c, Type *enum_type, Type *named_type, AstNode *node) {
+	ast_node(et, EnumType, node);
+	GB_ASSERT(is_type_enum(enum_type));
+
+	gbTempArenaMemory tmp = gb_temp_arena_memory_begin(&c->tmp_arena);
+
+	Type *base_type = t_int;
+	if (et->base_type != NULL) {
+		base_type = check_type(c, et->base_type);
+	}
+
+	if (base_type == NULL || !(is_type_integer(base_type) || is_type_float(base_type))) {
+		error_node(node, "Base type for enumeration must be numeric");
+		return;
+	}
+
+	// NOTE(bill): Must be up here for the `check_init_constant` system
+	enum_type->Record.enum_base_type = base_type;
+
+	MapEntity entity_map = {0}; // Key: String
+	map_entity_init_with_reserve(&entity_map, c->tmp_allocator, 2*(et->fields.count));
+
+	Entity **fields = gb_alloc_array(c->allocator, Entity *, et->fields.count);
+	isize field_index = 0;
+
+	Type *constant_type = enum_type;
+	if (named_type != NULL) {
+		constant_type = named_type;
+	}
+
+	AstNode *prev_expr = NULL;
+
+	i64 iota = 0;
+
+	for_array(i, et->fields) {
+		AstNode *field = et->fields.e[i];
+		AstNode *ident = NULL;
+		if (field->kind == AstNode_FieldValue) {
+			ast_node(fv, FieldValue, field);
+			if (fv->field == NULL || fv->field->kind != AstNode_Ident) {
+				error_node(field, "An enum field's name must be an identifier");
+				continue;
+			}
+			ident = fv->field;
+			prev_expr = fv->value;
+		} else if (field->kind == AstNode_Ident) {
+			ident = field;
+		} else {
+			error_node(field, "An enum field's name must be an identifier");
+			continue;
+		}
+		String name = ident->Ident.string;
+
+		if (str_ne(name, str_lit("_"))) {
+			ExactValue v = make_exact_value_integer(iota);
+			Entity *e = make_entity_constant(c->allocator, c->context.scope, ident->Ident, constant_type, v);
+			e->identifier = ident;
+			e->flags |= EntityFlag_Visited;
+
+
+			AstNode *init = prev_expr;
+			if (init == NULL) {
+				error_node(field, "Missing initial expression for enumeration, e.g. iota");
+				continue;
+			}
+
+			ExactValue context_iota = c->context.iota;
+			c->context.iota = e->Constant.value;
+			e->Constant.value = (ExactValue){0};
+
+			Operand operand = {0};
+			check_expr(c, &operand, init);
+
+			check_init_constant(c, e, &operand);
+			c->context.iota = context_iota;
+
+			if (operand.mode == Addressing_Constant) {
+				HashKey key = hash_string(name);
+				if (map_entity_get(&entity_map, key) != NULL) {
+					error_node(ident, "`%.*s` is already declared in this enumeration", LIT(name));
+				} else {
+					map_entity_set(&entity_map, key, e);
+					add_entity(c, c->context.scope, NULL, e);
+					fields[field_index++] = e;
+					add_entity_use(c, field, e);
+				}
+			}
+		}
+		iota++;
+	}
+
+	GB_ASSERT(field_index <= et->fields.count);
+
+	enum_type->Record.fields = fields;
+	enum_type->Record.field_count = field_index;
+
+	gb_temp_arena_memory_end(tmp);
+}
+
+
+Type *check_get_params(Checker *c, Scope *scope, AstNodeArray params, bool *is_variadic_) {
+	if (params.count == 0) {
+		return NULL;
+	}
+
+	isize variable_count = 0;
+	for_array(i, params) {
+		AstNode *field = params.e[i];
+		if (ast_node_expect(field, AstNode_Field)) {
+			ast_node(f, Field, field);
+			variable_count += f->names.count;
+		}
+	}
+
+	bool is_variadic = false;
+	Entity **variables = gb_alloc_array(c->allocator, Entity *, variable_count);
+	isize variable_index = 0;
+	for_array(i, params) {
+		if (params.e[i]->kind != AstNode_Field) {
+			continue;
+		}
+		ast_node(p, Field, params.e[i]);
+		AstNode *type_expr = p->type;
+		if (type_expr) {
+			if (type_expr->kind == AstNode_Ellipsis) {
+				type_expr = type_expr->Ellipsis.expr;
+				if (i+1 == params.count) {
+					is_variadic = true;
+				} else {
+					error_node(params.e[i], "Invalid AST: Invalid variadic parameter");
+				}
+			}
+
+			Type *type = check_type(c, type_expr);
+			for_array(j, p->names) {
+				AstNode *name = p->names.e[j];
+				if (ast_node_expect(name, AstNode_Ident)) {
+					Entity *param = make_entity_param(c->allocator, scope, name->Ident, type, p->is_using);
+					add_entity(c, scope, name, param);
+					variables[variable_index++] = param;
+				}
+			}
+		}
+	}
+
+	variable_count = variable_index;
+
+	if (is_variadic) {
+		GB_ASSERT(params.count > 0);
+		// NOTE(bill): Change last variadic parameter to be a slice
+		// Custom Calling convention for variadic parameters
+		Entity *end = variables[variable_count-1];
+		end->type = make_type_slice(c->allocator, end->type);
+	}
+
+	Type *tuple = make_type_tuple(c->allocator);
+	tuple->Tuple.variables = variables;
+	tuple->Tuple.variable_count = variable_count;
+
+	if (is_variadic_) *is_variadic_ = is_variadic;
+
+	return tuple;
+}
+
+Type *check_get_results(Checker *c, Scope *scope, AstNodeArray results) {
+	if (results.count == 0) {
+		return NULL;
+	}
+	Type *tuple = make_type_tuple(c->allocator);
+
+	Entity **variables = gb_alloc_array(c->allocator, Entity *, results.count);
+	isize variable_index = 0;
+	for_array(i, results) {
+		AstNode *item = results.e[i];
+		Type *type = check_type(c, item);
+		Token token = ast_node_token(item);
+		token.string = str_lit(""); // NOTE(bill): results are not named
+		// TODO(bill): Should I have named results?
+		Entity *param = make_entity_param(c->allocator, scope, token, type, false);
+		// NOTE(bill): No need to record
+		variables[variable_index++] = param;
+	}
+	tuple->Tuple.variables = variables;
+	tuple->Tuple.variable_count = results.count;
+
+	return tuple;
+}
+
+
+void check_procedure_type(Checker *c, Type *type, AstNode *proc_type_node) {
+	ast_node(pt, ProcType, proc_type_node);
+
+	bool variadic = false;
+	Type *params  = check_get_params(c, c->context.scope, pt->params, &variadic);
+	Type *results = check_get_results(c, c->context.scope, pt->results);
+
+	isize param_count = 0;
+	isize result_count = 0;
+	if (params)  param_count  = params ->Tuple.variable_count;
+	if (results) result_count = results->Tuple.variable_count;
+
+	type->Proc.scope              = c->context.scope;
+	type->Proc.params             = params;
+	type->Proc.param_count        = param_count;
+	type->Proc.results            = results;
+	type->Proc.result_count       = result_count;
+	type->Proc.variadic           = variadic;
+	type->Proc.calling_convention = pt->calling_convention;
+}
+
+
+void check_identifier(Checker *c, Operand *o, AstNode *n, Type *named_type) {
+	GB_ASSERT(n->kind == AstNode_Ident);
+	o->mode = Addressing_Invalid;
+	o->expr = n;
+	Entity *e = scope_lookup_entity(c->context.scope, n->Ident.string);
+	if (e == NULL) {
+		if (str_eq(n->Ident.string, str_lit("_"))) {
+			error(n->Ident, "`_` cannot be used as a value type");
+		} else {
+			error(n->Ident, "Undeclared name: %.*s", LIT(n->Ident.string));
+		}
+		o->type = t_invalid;
+		o->mode = Addressing_Invalid;
+		if (named_type != NULL) {
+			set_base_type(named_type, t_invalid);
+		}
+		return;
+	}
+	add_entity_use(c, n, e);
+
+	check_entity_decl(c, e, NULL, named_type);
+
+	if (e->type == NULL) {
+		compiler_error("Compiler error: How did this happen? type: %s; identifier: %.*s\n", type_to_string(e->type), LIT(n->Ident.string));
+		return;
+	}
+
+
+	Type *type = e->type;
+
+	switch (e->kind) {
+	case Entity_Constant:
+		if (type == t_invalid) {
+			o->type = t_invalid;
+			return;
+		}
+		if (e == e_iota) {
+			if (c->context.iota.kind == ExactValue_Invalid) {
+				error(e->token, "Use of `iota` outside a enumeration is not allowed");
+				return;
+			}
+			o->value = c->context.iota;
+		} else {
+			o->value = e->Constant.value;
+		}
+		if (o->value.kind == ExactValue_Invalid) {
+			return;
+		}
+		o->mode = Addressing_Constant;
+		break;
+
+	case Entity_Variable:
+		e->flags |= EntityFlag_Used;
+		if (type == t_invalid) {
+			o->type = t_invalid;
+			return;
+		}
+	#if 0
+		if (e->Variable.param) {
+			o->mode = Addressing_Value;
+		} else {
+			o->mode = Addressing_Variable;
+		}
+	#else
+		o->mode = Addressing_Variable;
+		if (e->Variable.is_immutable) {
+			o->mode = Addressing_Value;
+		}
+	#endif
+		break;
+
+	case Entity_TypeName: {
+		o->mode = Addressing_Type;
+#if 1
+	// TODO(bill): Fix cyclical dependancy checker
+#endif
+	} break;
+
+	case Entity_Procedure:
+		o->mode = Addressing_Value;
+		break;
+
+	case Entity_Builtin:
+		o->builtin_id = e->Builtin.id;
+		o->mode = Addressing_Builtin;
+		break;
+
+	case Entity_ImportName:
+		error_node(n, "Use of import `%.*s` not in selector", LIT(e->ImportName.name));
+		return;
+
+	case Entity_Nil:
+		o->mode = Addressing_Value;
+		break;
+
+	case Entity_ImplicitValue:
+		o->mode = Addressing_Value;
+		break;
+
+	default:
+		compiler_error("Compiler error: Unknown EntityKind");
+		break;
+	}
+
+	o->type = type;
+}
+
+i64 check_array_count(Checker *c, AstNode *e) {
+	if (e == NULL) {
+		return 0;
+	}
+	Operand o = {0};
+	check_expr(c, &o, e);
+	if (o.mode != Addressing_Constant) {
+		if (o.mode != Addressing_Invalid) {
+			error_node(e, "Array count must be a constant");
+		}
+		return 0;
+	}
+	Type *type = base_type(base_enum_type(o.type));
+	if (is_type_untyped(type) || is_type_integer(type)) {
+		if (o.value.kind == ExactValue_Integer) {
+			i64 count = o.value.value_integer;
+			if (count >= 0) {
+				return count;
+			}
+			error_node(e, "Invalid array count");
+			return 0;
+		}
+	}
+
+	error_node(e, "Array count must be an integer");
+	return 0;
+}
+
+Type *check_type_extra(Checker *c, AstNode *e, Type *named_type) {
+	ExactValue null_value = {ExactValue_Invalid};
+	Type *type = NULL;
+	gbString err_str = NULL;
+
+	if (e == NULL) {
+		type = t_invalid;
+		goto end;
+	}
+
+	switch (e->kind) {
+	case_ast_node(i, Ident, e);
+		Operand o = {0};
+		check_identifier(c, &o, e, named_type);
+
+		switch (o.mode) {
+		case Addressing_Invalid:
+			break;
+		case Addressing_Type: {
+			type = o.type;
+			goto end;
+		} break;
+		case Addressing_NoValue:
+			err_str = expr_to_string(e);
+			error_node(e, "`%s` used as a type", err_str);
+			break;
+		default:
+			err_str = expr_to_string(e);
+			error_node(e, "`%s` used as a type when not a type", err_str);
+			break;
+		}
+	case_end;
+
+	case_ast_node(se, SelectorExpr, e);
+		Operand o = {0};
+		check_selector(c, &o, e);
+
+		switch (o.mode) {
+		case Addressing_Invalid:
+			break;
+		case Addressing_Type:
+			GB_ASSERT(o.type != NULL);
+			type = o.type;
+			goto end;
+		case Addressing_NoValue:
+			err_str = expr_to_string(e);
+			error_node(e, "`%s` used as a type", err_str);
+			break;
+		default:
+			err_str = expr_to_string(e);
+			error_node(e, "`%s` is not a type", err_str);
+			break;
+		}
+	case_end;
+
+	case_ast_node(pe, ParenExpr, e);
+		type = check_type_extra(c, pe->expr, named_type);
+		goto end;
+	case_end;
+
+	case_ast_node(ue, UnaryExpr, e);
+		if (ue->op.kind == Token_Pointer) {
+			type = make_type_pointer(c->allocator, check_type(c, ue->expr));
+			goto end;
+		} else if (ue->op.kind == Token_Maybe) {
+			type = make_type_maybe(c->allocator, check_type(c, ue->expr));
+			goto end;
+		}
+	case_end;
+
+	case_ast_node(ht, HelperType, e);
+		type = check_type(c, ht->type);
+		goto end;
+	case_end;
+
+	case_ast_node(pt, PointerType, e);
+		Type *elem = check_type(c, pt->type);
+		type = make_type_pointer(c->allocator, elem);
+		goto end;
+	case_end;
+
+	case_ast_node(mt, MaybeType, e);
+		Type *elem = check_type(c, mt->type);
+		type = make_type_maybe(c->allocator, elem);
+		goto end;
+	case_end;
+
+	case_ast_node(at, ArrayType, e);
+		if (at->count != NULL) {
+			Type *elem = check_type_extra(c, at->elem, NULL);
+			type = make_type_array(c->allocator, elem, check_array_count(c, at->count));
+		} else {
+			Type *elem = check_type(c, at->elem);
+			type = make_type_slice(c->allocator, elem);
+		}
+		goto end;
+	case_end;
+
+
+	case_ast_node(vt, VectorType, e);
+		Type *elem = check_type(c, vt->elem);
+		Type *be = base_type(elem);
+		i64 count = check_array_count(c, vt->count);
+		if (!is_type_boolean(be) && !is_type_numeric(be)) {
+			err_str = type_to_string(elem);
+			error_node(vt->elem, "Vector element type must be numerical or a boolean, got `%s`", err_str);
+		}
+		type = make_type_vector(c->allocator, elem, count);
+		goto end;
+	case_end;
+
+	case_ast_node(st, StructType, e);
+		type = make_type_struct(c->allocator);
+		set_base_type(named_type, type);
+		check_open_scope(c, e);
+		check_struct_type(c, type, e);
+		check_close_scope(c);
+		type->Record.node = e;
+		goto end;
+	case_end;
+
+	case_ast_node(ut, UnionType, e);
+		type = make_type_union(c->allocator);
+		set_base_type(named_type, type);
+		check_open_scope(c, e);
+		check_union_type(c, type, e);
+		check_close_scope(c);
+		type->Record.node = e;
+		goto end;
+	case_end;
+
+	case_ast_node(rut, RawUnionType, e);
+		type = make_type_raw_union(c->allocator);
+		set_base_type(named_type, type);
+		check_open_scope(c, e);
+		check_raw_union_type(c, type, e);
+		check_close_scope(c);
+		type->Record.node = e;
+		goto end;
+	case_end;
+
+	case_ast_node(et, EnumType, e);
+		type = make_type_enum(c->allocator);
+		set_base_type(named_type, type);
+		check_open_scope(c, e);
+		check_enum_type(c, type, named_type, e);
+		check_close_scope(c);
+		type->Record.node = e;
+		goto end;
+	case_end;
+
+	case_ast_node(pt, ProcType, e);
+		type = alloc_type(c->allocator, Type_Proc);
+		set_base_type(named_type, type);
+		check_open_scope(c, e);
+		check_procedure_type(c, type, e);
+		check_close_scope(c);
+		goto end;
+	case_end;
+
+
+	case_ast_node(ce, CallExpr, e);
+		Operand o = {0};
+		check_expr_or_type(c, &o, e);
+		if (o.mode == Addressing_Type) {
+			type = o.type;
+			goto end;
+		}
+	case_end;
+	}
+	err_str = expr_to_string(e);
+	error_node(e, "`%s` is not a type", err_str);
+
+	type = t_invalid;
+end:
+	gb_string_free(err_str);
+
+	if (type == NULL) {
+		type = t_invalid;
+	}
+
+	if (is_type_named(type)) {
+		if (type->Named.base == NULL) {
+			gbString name = type_to_string(type);
+			error_node(e, "Invalid type definition of %s", name);
+			gb_string_free(name);
+			type->Named.base = t_invalid;
+		}
+	}
+
+	if (is_type_typed(type)) {
+		add_type_and_value(&c->info, e, Addressing_Type, type, null_value);
+	} else {
+		gbString name = type_to_string(type);
+		error_node(e, "Invalid type definition of %s", name);
+		gb_string_free(name);
+		type = t_invalid;
+	}
+	set_base_type(named_type, type);
+
+
+
+	return type;
+}
+
+
+bool check_unary_op(Checker *c, Operand *o, Token op) {
+	// TODO(bill): Handle errors correctly
+	Type *type = base_type(base_enum_type(base_vector_type(o->type)));
+	gbString str = NULL;
+	switch (op.kind) {
+	case Token_Add:
+	case Token_Sub:
+		if (!is_type_numeric(type)) {
+			str = expr_to_string(o->expr);
+			error(op, "Operator `%.*s` is not allowed with `%s`", LIT(op.string), str);
+			gb_string_free(str);
+		}
+		break;
+
+	case Token_Xor:
+		if (!is_type_integer(type)) {
+			error(op, "Operator `%.*s` is only allowed with integers", LIT(op.string));
+		}
+		break;
+
+	case Token_Not:
+		if (!is_type_boolean(type)) {
+			str = expr_to_string(o->expr);
+			error(op, "Operator `%.*s` is only allowed on boolean expression", LIT(op.string));
+			gb_string_free(str);
+		}
+		break;
+
+	default:
+		error(op, "Unknown operator `%.*s`", LIT(op.string));
+		return false;
+	}
+
+	return true;
+}
+
+bool check_binary_op(Checker *c, Operand *o, Token op) {
+	// TODO(bill): Handle errors correctly
+	Type *type = base_type(base_enum_type(base_vector_type(o->type)));
+	switch (op.kind) {
+	case Token_Sub:
+	case Token_SubEq:
+		if (!is_type_numeric(type) && !is_type_pointer(type)) {
+			error(op, "Operator `%.*s` is only allowed with numeric or pointer expressions", LIT(op.string));
+			return false;
+		}
+		if (is_type_pointer(type)) {
+			o->type = t_int;
+		}
+		if (base_type(type) == t_rawptr) {
+			gbString str = type_to_string(type);
+			error_node(o->expr, "Invalid pointer type for pointer arithmetic: `%s`", str);
+			gb_string_free(str);
+			return false;
+		}
+		break;
+
+	case Token_Add:
+	case Token_Mul:
+	case Token_Quo:
+	case Token_AddEq:
+	case Token_MulEq:
+	case Token_QuoEq:
+		if (!is_type_numeric(type)) {
+			error(op, "Operator `%.*s` is only allowed with numeric expressions", LIT(op.string));
+			return false;
+		}
+		break;
+
+	case Token_And:
+	case Token_Or:
+	case Token_AndEq:
+	case Token_OrEq:
+		if (!is_type_integer(type) && !is_type_boolean(type)) {
+			error(op, "Operator `%.*s` is only allowed with integers or booleans", LIT(op.string));
+			return false;
+		}
+		break;
+
+	case Token_Mod:
+	case Token_Xor:
+	case Token_AndNot:
+	case Token_ModEq:
+	case Token_XorEq:
+	case Token_AndNotEq:
+		if (!is_type_integer(type)) {
+			error(op, "Operator `%.*s` is only allowed with integers", LIT(op.string));
+			return false;
+		}
+		break;
+
+	case Token_CmpAnd:
+	case Token_CmpOr:
+	case Token_CmpAndEq:
+	case Token_CmpOrEq:
+		if (!is_type_boolean(type)) {
+			error(op, "Operator `%.*s` is only allowed with boolean expressions", LIT(op.string));
+			return false;
+		}
+		break;
+
+	default:
+		error(op, "Unknown operator `%.*s`", LIT(op.string));
+		return false;
+	}
+
+	return true;
+
+}
+bool check_value_is_expressible(Checker *c, ExactValue in_value, Type *type, ExactValue *out_value) {
+	if (in_value.kind == ExactValue_Invalid) {
+		// NOTE(bill): There's already been an error
+		return true;
+	}
+
+	type = base_type(base_enum_type(type));
+
+	if (is_type_boolean(type)) {
+		return in_value.kind == ExactValue_Bool;
+	} else if (is_type_string(type)) {
+		return in_value.kind == ExactValue_String;
+	} else if (is_type_integer(type)) {
+		ExactValue v = exact_value_to_integer(in_value);
+		if (v.kind != ExactValue_Integer) {
+			return false;
+		}
+		if (out_value) *out_value = v;
+		i64 i = v.value_integer;
+		u64 u = *cast(u64 *)&i;
+		i64 s = 8*type_size_of(c->sizes, c->allocator, type);
+		u64 umax = ~0ull;
+		if (s < 64) {
+			umax = (1ull << s) - 1ull;
+		} else {
+			// TODO(bill): I NEED A PROPER BIG NUMBER LIBRARY THAT CAN SUPPORT 128 bit integers and floats
+			s = 64;
+		}
+		i64 imax = (1ll << (s-1ll));
+
+
+		switch (type->Basic.kind) {
+		case Basic_i8:
+		case Basic_i16:
+		case Basic_i32:
+		case Basic_i64:
+		// case Basic_i128:
+		case Basic_int:
+			return gb_is_between(i, -imax, imax-1);
+
+		case Basic_u8:
+		case Basic_u16:
+		case Basic_u32:
+		case Basic_u64:
+		// case Basic_u128:
+		case Basic_uint:
+			return !(u < 0 || u > umax);
+
+		case Basic_UntypedInteger:
+			return true;
+
+		default: GB_PANIC("Compiler error: Unknown integer type!"); break;
+		}
+	} else if (is_type_float(type)) {
+		ExactValue v = exact_value_to_float(in_value);
+		if (v.kind != ExactValue_Float) {
+			return false;
+		}
+
+		switch (type->Basic.kind) {
+		// case Basic_f16:
+		case Basic_f32:
+		case Basic_f64:
+		// case Basic_f128:
+			if (out_value) *out_value = v;
+			return true;
+
+		case Basic_UntypedFloat:
+			return true;
+		}
+	} else if (is_type_pointer(type)) {
+		if (in_value.kind == ExactValue_Pointer) {
+			return true;
+		}
+		if (in_value.kind == ExactValue_Integer) {
+			return true;
+		}
+		if (out_value) *out_value = in_value;
+	}
+
+
+	return false;
+}
+
+void check_is_expressible(Checker *c, Operand *o, Type *type) {
+	GB_ASSERT(is_type_constant_type(type));
+	GB_ASSERT(o->mode == Addressing_Constant);
+	if (!check_value_is_expressible(c, o->value, type, &o->value)) {
+		gbString a = expr_to_string(o->expr);
+		gbString b = type_to_string(type);
+		if (is_type_numeric(o->type) && is_type_numeric(type)) {
+			if (!is_type_integer(o->type) && is_type_integer(type)) {
+				error_node(o->expr, "`%s` truncated to `%s`", a, b);
+			} else {
+				error_node(o->expr, "`%s = %lld` overflows `%s`", a, o->value.value_integer, b);
+			}
+		} else {
+			error_node(o->expr, "Cannot convert `%s` to `%s`", a, b);
+		}
+
+		gb_string_free(b);
+		gb_string_free(a);
+		o->mode = Addressing_Invalid;
+	}
+}
+
+bool check_is_expr_vector_index(Checker *c, AstNode *expr) {
+	// HACK(bill): Handle this correctly. Maybe with a custom AddressingMode
+	expr = unparen_expr(expr);
+	if (expr->kind == AstNode_IndexExpr) {
+		ast_node(ie, IndexExpr, expr);
+		Type *t = type_deref(type_of_expr(&c->info, ie->expr));
+		if (t != NULL) {
+			return is_type_vector(t);
+		}
+	}
+	return false;
+}
+
+bool check_is_vector_elem(Checker *c, AstNode *expr) {
+	// HACK(bill): Handle this correctly. Maybe with a custom AddressingMode
+	expr = unparen_expr(expr);
+	if (expr->kind == AstNode_SelectorExpr) {
+		ast_node(se, SelectorExpr, expr);
+		Type *t = type_deref(type_of_expr(&c->info, se->expr));
+		if (t != NULL && is_type_vector(t)) {
+			return true;
+		}
+	}
+	return false;
+}
+
+void check_unary_expr(Checker *c, Operand *o, Token op, AstNode *node) {
+	switch (op.kind) {
+	case Token_Pointer: { // Pointer address
+		if (o->mode == Addressing_Type) {
+			o->type = make_type_pointer(c->allocator, o->type);
+			return;
+		}
+
+		if (o->mode != Addressing_Variable ||
+		    check_is_expr_vector_index(c, o->expr) ||
+		    check_is_vector_elem(c, o->expr)) {
+			if (ast_node_expect(node, AstNode_UnaryExpr)) {
+				ast_node(ue, UnaryExpr, node);
+				gbString str = expr_to_string(ue->expr);
+				error(op, "Cannot take the pointer address of `%s`", str);
+				gb_string_free(str);
+			}
+			o->mode = Addressing_Invalid;
+			return;
+		}
+		o->mode = Addressing_Value;
+		o->type = make_type_pointer(c->allocator, o->type);
+		return;
+	}
+
+	case Token_Maybe: { // Make maybe
+		Type *t = default_type(o->type);
+
+		if (o->mode == Addressing_Type) {
+			o->type = make_type_pointer(c->allocator, t);
+			return;
+		}
+
+		bool is_value =
+			o->mode == Addressing_Variable ||
+			o->mode == Addressing_Value ||
+			o->mode == Addressing_Constant;
+
+		if (!is_value || is_type_untyped(t)) {
+			if (ast_node_expect(node, AstNode_UnaryExpr)) {
+				ast_node(ue, UnaryExpr, node);
+				gbString str = expr_to_string(ue->expr);
+				error(op, "Cannot convert `%s` to a maybe", str);
+				gb_string_free(str);
+			}
+			o->mode = Addressing_Invalid;
+			return;
+		}
+		o->mode = Addressing_Value;
+		o->type = make_type_maybe(c->allocator, t);
+		return;
+	}
+	}
+
+	if (!check_unary_op(c, o, op)) {
+		o->mode = Addressing_Invalid;
+		return;
+	}
+
+	if (o->mode == Addressing_Constant) {
+		Type *type = base_type(o->type);
+		if (!is_type_constant_type(o->type)) {
+			gbString xt = type_to_string(o->type);
+			gbString err_str = expr_to_string(node);
+			error(op, "Invalid type, `%s`, for constant unary expression `%s`", xt, err_str);
+			gb_string_free(err_str);
+			gb_string_free(xt);
+			o->mode = Addressing_Invalid;
+			return;
+		}
+
+
+		i32 precision = 0;
+		if (is_type_unsigned(type)) {
+			precision = cast(i32)(8 * type_size_of(c->sizes, c->allocator, type));
+		}
+		o->value = exact_unary_operator_value(op.kind, o->value, precision);
+
+		if (is_type_typed(type)) {
+			if (node != NULL) {
+				o->expr = node;
+			}
+			check_is_expressible(c, o, type);
+		}
+		return;
+	}
+
+	o->mode = Addressing_Value;
+}
+
+void check_comparison(Checker *c, Operand *x, Operand *y, Token op) {
+	gbTempArenaMemory tmp = gb_temp_arena_memory_begin(&c->tmp_arena);
+
+	gbString err_str = NULL;
+
+	if (check_is_assignable_to(c, x, y->type) ||
+	    check_is_assignable_to(c, y, x->type)) {
+		Type *err_type = x->type;
+		bool defined = false;
+		switch (op.kind) {
+		case Token_CmpEq:
+		case Token_NotEq:
+			defined = is_type_comparable(x->type);
+			break;
+		case Token_Lt:
+		case Token_Gt:
+		case Token_LtEq:
+		case Token_GtEq: {
+			defined = is_type_ordered(x->type);
+		} break;
+		}
+
+		// CLEANUP(bill) NOTE(bill): there is an auto assignment to `any` which needs to be checked
+		if (is_type_any(x->type) && !is_type_any(y->type)) {
+			err_type = x->type;
+			defined = false;
+		} else if (is_type_any(y->type) && !is_type_any(x->type)) {
+			err_type = y->type;
+			defined = false;
+		}
+
+		if (!defined) {
+			gbString type_string = type_to_string(err_type);
+			err_str = gb_string_make(c->tmp_allocator,
+			                         gb_bprintf("operator `%.*s` not defined for type `%s`", LIT(op.string), type_string));
+			gb_string_free(type_string);
+		}
+	} else {
+		gbString xt = type_to_string(x->type);
+		gbString yt = type_to_string(y->type);
+		err_str = gb_string_make(c->tmp_allocator,
+		                         gb_bprintf("mismatched types `%s` and `%s`", xt, yt));
+		gb_string_free(yt);
+		gb_string_free(xt);
+	}
+
+	if (err_str != NULL) {
+		error_node(x->expr, "Cannot compare expression, %s", err_str);
+		x->type = t_untyped_bool;
+	} else {
+		if (x->mode == Addressing_Constant &&
+		    y->mode == Addressing_Constant) {
+			x->value = make_exact_value_bool(compare_exact_values(op.kind, x->value, y->value));
+		} else {
+			x->mode = Addressing_Value;
+
+			update_expr_type(c, x->expr, default_type(x->type), true);
+			update_expr_type(c, y->expr, default_type(y->type), true);
+		}
+
+		if (is_type_vector(base_type(y->type))) {
+			x->type = make_type_vector(c->allocator, t_bool, base_type(y->type)->Vector.count);
+		} else {
+			x->type = t_untyped_bool;
+		}
+	}
+
+	if (err_str != NULL) {
+		gb_string_free(err_str);
+	};
+
+	gb_temp_arena_memory_end(tmp);
+}
+
+void check_shift(Checker *c, Operand *x, Operand *y, AstNode *node) {
+	GB_ASSERT(node->kind == AstNode_BinaryExpr);
+	ast_node(be, BinaryExpr, node);
+
+	ExactValue x_val = {0};
+	if (x->mode == Addressing_Constant) {
+		x_val = exact_value_to_integer(x->value);
+	}
+
+	bool x_is_untyped = is_type_untyped(x->type);
+	if (!(is_type_integer(base_enum_type(x->type)) || (x_is_untyped && x_val.kind == ExactValue_Integer))) {
+		gbString err_str = expr_to_string(x->expr);
+		error_node(node, "Shifted operand `%s` must be an integer", err_str);
+		gb_string_free(err_str);
+		x->mode = Addressing_Invalid;
+		return;
+	}
+
+	if (is_type_unsigned(base_enum_type(y->type))) {
+
+	} else if (is_type_untyped(y->type)) {
+		convert_to_typed(c, y, t_untyped_integer, 0);
+		if (y->mode == Addressing_Invalid) {
+			x->mode = Addressing_Invalid;
+			return;
+		}
+	} else {
+		gbString err_str = expr_to_string(y->expr);
+		error_node(node, "Shift amount `%s` must be an unsigned integer", err_str);
+		gb_string_free(err_str);
+		x->mode = Addressing_Invalid;
+		return;
+	}
+
+
+	if (x->mode == Addressing_Constant) {
+		if (y->mode == Addressing_Constant) {
+			ExactValue y_val = exact_value_to_integer(y->value);
+			if (y_val.kind != ExactValue_Integer) {
+				gbString err_str = expr_to_string(y->expr);
+				error_node(node, "Shift amount `%s` must be an unsigned integer", err_str);
+				gb_string_free(err_str);
+				x->mode = Addressing_Invalid;
+				return;
+			}
+
+			u64 amount = cast(u64)y_val.value_integer;
+			if (amount > 1074) {
+				gbString err_str = expr_to_string(y->expr);
+				error_node(node, "Shift amount too large: `%s`", err_str);
+				gb_string_free(err_str);
+				x->mode = Addressing_Invalid;
+				return;
+			}
+
+			if (!is_type_integer(base_enum_type(x->type))) {
+				// NOTE(bill): It could be an untyped float but still representable
+				// as an integer
+				x->type = t_untyped_integer;
+			}
+
+			x->value = exact_value_shift(be->op.kind, x_val, make_exact_value_integer(amount));
+
+			if (is_type_typed(x->type)) {
+				check_is_expressible(c, x, base_type(base_enum_type(x->type)));
+			}
+			return;
+		}
+
+		if (x_is_untyped) {
+			ExprInfo *info = map_expr_info_get(&c->info.untyped, hash_pointer(x->expr));
+			if (info != NULL) {
+				info->is_lhs = true;
+			}
+			x->mode = Addressing_Value;
+			return;
+		}
+	}
+
+	if (y->mode == Addressing_Constant && y->value.value_integer < 0) {
+		gbString err_str = expr_to_string(y->expr);
+		error_node(node, "Shift amount cannot be negative: `%s`", err_str);
+		gb_string_free(err_str);
+	}
+
+	x->mode = Addressing_Value;
+}
+
+bool check_is_castable_to(Checker *c, Operand *operand, Type *y) {
+	if (check_is_assignable_to(c, operand, y)) {
+		return true;
+	}
+
+	Type *x = operand->type;
+	Type *xb = base_type(base_enum_type(x));
+	Type *yb = base_type(base_enum_type(y));
+	if (are_types_identical(xb, yb)) {
+		return true;
+	}
+
+
+	// Cast between booleans and integers
+	if (is_type_boolean(xb) || is_type_integer(xb)) {
+		if (is_type_boolean(yb) || is_type_integer(yb)) {
+			return true;
+		}
+	}
+
+	// Cast between numbers
+	if (is_type_integer(xb) || is_type_float(xb)) {
+		if (is_type_integer(yb) || is_type_float(yb)) {
+			return true;
+		}
+	}
+
+	// Cast between pointers
+	if (is_type_pointer(xb) && is_type_pointer(yb)) {
+		return true;
+	}
+
+	// (u)int <-> pointer
+	if (is_type_int_or_uint(xb) && is_type_rawptr(yb)) {
+		return true;
+	}
+	if (is_type_rawptr(xb) && is_type_int_or_uint(yb)) {
+		return true;
+	}
+
+	// []byte/[]u8 <-> string
+	if (is_type_u8_slice(xb) && is_type_string(yb)) {
+		return true;
+	}
+	if (is_type_string(xb) && is_type_u8_slice(yb)) {
+		if (is_type_typed(xb)) {
+			return true;
+		}
+	}
+
+	// proc <-> proc
+	if (is_type_proc(xb) && is_type_proc(yb)) {
+		return true;
+	}
+
+	// proc -> rawptr
+	if (is_type_proc(xb) && is_type_rawptr(yb)) {
+		return true;
+	}
+	// rawptr -> proc
+	if (is_type_rawptr(xb) && is_type_proc(yb)) {
+		return true;
+	}
+
+	return false;
+}
+
+String check_down_cast_name(Type *dst_, Type *src_) {
+	String result = {0};
+	Type *dst = type_deref(dst_);
+	Type *src = type_deref(src_);
+	Type *dst_s = base_type(dst);
+	GB_ASSERT(is_type_struct(dst_s) || is_type_raw_union(dst_s));
+	for (isize i = 0; i < dst_s->Record.field_count; i++) {
+		Entity *f = dst_s->Record.fields[i];
+		GB_ASSERT(f->kind == Entity_Variable && f->flags & EntityFlag_Field);
+		if (f->flags & EntityFlag_Anonymous) {
+			if (are_types_identical(f->type, src_)) {
+				return f->token.string;
+			}
+			if (are_types_identical(type_deref(f->type), src_)) {
+				return f->token.string;
+			}
+
+			if (!is_type_pointer(f->type)) {
+				result = check_down_cast_name(f->type, src_);
+				if (result.len > 0) {
+					return result;
+				}
+			}
+		}
+	}
+
+	return result;
+}
+
+Operand check_ptr_addition(Checker *c, TokenKind op, Operand *ptr, Operand *offset, AstNode *node) {
+	GB_ASSERT(node->kind == AstNode_BinaryExpr);
+	ast_node(be, BinaryExpr, node);
+	GB_ASSERT(is_type_pointer(ptr->type));
+	GB_ASSERT(is_type_integer(offset->type));
+	GB_ASSERT(op == Token_Add || op == Token_Sub);
+
+	Operand operand = {0};
+	operand.mode = Addressing_Value;
+	operand.type = ptr->type;
+	operand.expr = node;
+
+	if (base_type(ptr->type) == t_rawptr) {
+		gbString str = type_to_string(ptr->type);
+		error_node(node, "Invalid pointer type for pointer arithmetic: `%s`", str);
+		gb_string_free(str);
+		operand.mode = Addressing_Invalid;
+		return operand;
+	}
+
+
+	if (ptr->mode == Addressing_Constant && offset->mode == Addressing_Constant) {
+		i64 elem_size = type_size_of(c->sizes, c->allocator, ptr->type);
+		i64 ptr_val = ptr->value.value_pointer;
+		i64 offset_val = exact_value_to_integer(offset->value).value_integer;
+		i64 new_ptr_val = ptr_val;
+		if (op == Token_Add) {
+			new_ptr_val += elem_size*offset_val;
+		} else {
+			new_ptr_val -= elem_size*offset_val;
+		}
+		operand.mode = Addressing_Constant;
+		operand.value = make_exact_value_pointer(new_ptr_val);
+	}
+
+	return operand;
+}
+
+void check_binary_expr(Checker *c, Operand *x, AstNode *node) {
+	GB_ASSERT(node->kind == AstNode_BinaryExpr);
+	Operand y_ = {0}, *y = &y_;
+
+	ast_node(be, BinaryExpr, node);
+
+	if (be->op.kind == Token_as) {
+		check_expr(c, x, be->left);
+		Type *type = check_type(c, be->right);
+		if (x->mode == Addressing_Invalid) {
+			return;
+		}
+
+		bool is_const_expr = x->mode == Addressing_Constant;
+		bool can_convert = false;
+
+		Type *bt = base_type(type);
+		if (is_const_expr && is_type_constant_type(bt)) {
+			if (bt->kind == Type_Basic) {
+				if (check_value_is_expressible(c, x->value, bt, &x->value)) {
+					can_convert = true;
+				}
+			}
+		} else if (check_is_castable_to(c, x, type)) {
+			if (x->mode != Addressing_Constant) {
+				x->mode = Addressing_Value;
+			}
+			can_convert = true;
+		}
+
+		if (!can_convert) {
+			gbString expr_str = expr_to_string(x->expr);
+			gbString to_type  = type_to_string(type);
+			gbString from_type = type_to_string(x->type);
+			error_node(x->expr, "Cannot cast `%s` as `%s` from `%s`", expr_str, to_type, from_type);
+			gb_string_free(from_type);
+			gb_string_free(to_type);
+			gb_string_free(expr_str);
+
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		if (is_type_untyped(x->type)) {
+			Type *final_type = type;
+			if (is_const_expr && !is_type_constant_type(type)) {
+				final_type = default_type(x->type);
+			}
+			update_expr_type(c, x->expr, final_type, true);
+		}
+
+		x->type = type;
+		return;
+	} else if (be->op.kind == Token_transmute) {
+		check_expr(c, x, be->left);
+		Type *type = check_type(c, be->right);
+		if (x->mode == Addressing_Invalid) {
+			return;
+		}
+
+		if (x->mode == Addressing_Constant) {
+			gbString expr_str = expr_to_string(x->expr);
+			error_node(x->expr, "Cannot transmute constant expression: `%s`", expr_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		if (is_type_untyped(x->type)) {
+			gbString expr_str = expr_to_string(x->expr);
+			error_node(x->expr, "Cannot transmute untyped expression: `%s`", expr_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		i64 srcz = type_size_of(c->sizes, c->allocator, x->type);
+		i64 dstz = type_size_of(c->sizes, c->allocator, type);
+		if (srcz != dstz) {
+			gbString expr_str = expr_to_string(x->expr);
+			gbString type_str = type_to_string(type);
+			error_node(x->expr, "Cannot transmute `%s` to `%s`, %lld vs %lld bytes", expr_str, type_str, srcz, dstz);
+			gb_string_free(type_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		x->type = type;
+
+		return;
+	} else if (be->op.kind == Token_down_cast) {
+		check_expr(c, x, be->left);
+		Type *type = check_type(c, be->right);
+		if (x->mode == Addressing_Invalid) {
+			return;
+		}
+
+		if (x->mode == Addressing_Constant) {
+			gbString expr_str = expr_to_string(node);
+			error_node(node, "Cannot `down_cast` a constant expression: `%s`", expr_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		if (is_type_untyped(x->type)) {
+			gbString expr_str = expr_to_string(node);
+			error_node(node, "Cannot `down_cast` an untyped expression: `%s`", expr_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		if (!(is_type_pointer(x->type) && is_type_pointer(type))) {
+			gbString expr_str = expr_to_string(node);
+			error_node(node, "Can only `down_cast` pointers: `%s`", expr_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		Type *src = type_deref(x->type);
+		Type *dst = type_deref(type);
+		Type *bsrc = base_type(src);
+		Type *bdst = base_type(dst);
+
+		if (!(is_type_struct(bsrc) || is_type_raw_union(bsrc))) {
+			gbString expr_str = expr_to_string(node);
+			error_node(node, "Can only `down_cast` pointer from structs or unions: `%s`", expr_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		if (!(is_type_struct(bdst) || is_type_raw_union(bdst))) {
+			gbString expr_str = expr_to_string(node);
+			error_node(node, "Can only `down_cast` pointer to structs or unions: `%s`", expr_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		String param_name = check_down_cast_name(dst, src);
+		if (param_name.len == 0) {
+			gbString expr_str = expr_to_string(node);
+			error_node(node, "Illegal `down_cast`: `%s`", expr_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		x->mode = Addressing_Value;
+		x->type = type;
+		return;
+	} else if (be->op.kind == Token_union_cast) {
+		check_expr(c, x, be->left);
+		Type *type = check_type(c, be->right);
+		if (x->mode == Addressing_Invalid) {
+			return;
+		}
+
+		if (x->mode == Addressing_Constant) {
+			gbString expr_str = expr_to_string(node);
+			error_node(node, "Cannot `union_cast` a constant expression: `%s`", expr_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		if (is_type_untyped(x->type)) {
+			gbString expr_str = expr_to_string(node);
+			error_node(node, "Cannot `union_cast` an untyped expression: `%s`", expr_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		bool src_is_ptr = is_type_pointer(x->type);
+		bool dst_is_ptr = is_type_pointer(type);
+		Type *src = type_deref(x->type);
+		Type *dst = type_deref(type);
+		Type *bsrc = base_type(src);
+		Type *bdst = base_type(dst);
+
+		if (src_is_ptr != dst_is_ptr) {
+			gbString src_type_str = type_to_string(x->type);
+			gbString dst_type_str = type_to_string(type);
+			error_node(node, "Invalid `union_cast` types: `%s` and `%s`", src_type_str, dst_type_str);
+			gb_string_free(dst_type_str);
+			gb_string_free(src_type_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		if (!is_type_union(src)) {
+			error_node(node, "`union_cast` can only operate on unions");
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		bool ok = false;
+		for (isize i = 1; i < bsrc->Record.field_count; i++) {
+			Entity *f = bsrc->Record.fields[i];
+			if (are_types_identical(f->type, dst)) {
+				ok = true;
+				break;
+			}
+		}
+
+		if (!ok) {
+			gbString expr_str = expr_to_string(node);
+			gbString dst_type_str = type_to_string(type);
+			error_node(node, "Cannot `union_cast` `%s` to `%s`", expr_str, dst_type_str);
+			gb_string_free(dst_type_str);
+			gb_string_free(expr_str);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		Entity **variables = gb_alloc_array(c->allocator, Entity *, 2);
+		variables[0] = make_entity_param(c->allocator, NULL, empty_token, type, false);
+		variables[1] = make_entity_param(c->allocator, NULL, empty_token, t_bool, false);
+
+		Type *tuple = make_type_tuple(c->allocator);
+		tuple->Tuple.variables = variables;
+		tuple->Tuple.variable_count = 2;
+
+		x->type = tuple;
+		x->mode = Addressing_Value;
+		return;
+	}
+
+	check_expr(c, x, be->left);
+	check_expr(c, y, be->right);
+	if (x->mode == Addressing_Invalid) {
+		return;
+	}
+	if (y->mode == Addressing_Invalid) {
+		x->mode = Addressing_Invalid;
+		x->expr = y->expr;
+		return;
+	}
+
+	Token op = be->op;
+
+	if (token_is_shift(op)) {
+		check_shift(c, x, y, node);
+		return;
+	}
+
+	if (op.kind == Token_Add || op.kind == Token_Sub) {
+		if (is_type_pointer(x->type) && is_type_integer(base_enum_type(y->type))) {
+			*x = check_ptr_addition(c, op.kind, x, y, node);
+			return;
+		} else if (is_type_integer(base_enum_type(x->type)) && is_type_pointer(y->type)) {
+			if (op.kind == Token_Sub) {
+				gbString lhs = expr_to_string(x->expr);
+				gbString rhs = expr_to_string(y->expr);
+				error_node(node, "Invalid pointer arithmetic, did you mean `%s %.*s %s`?", rhs, LIT(op.string), lhs);
+				gb_string_free(rhs);
+				gb_string_free(lhs);
+				x->mode = Addressing_Invalid;
+				return;
+			}
+			*x = check_ptr_addition(c, op.kind, y, x, node);
+			return;
+		}
+	}
+
+
+	convert_to_typed(c, x, y->type, 0);
+	if (x->mode == Addressing_Invalid) {
+		return;
+	}
+	convert_to_typed(c, y, x->type, 0);
+	if (y->mode == Addressing_Invalid) {
+		x->mode = Addressing_Invalid;
+		return;
+	}
+
+	if (token_is_comparison(op)) {
+		check_comparison(c, x, y, op);
+		return;
+	}
+
+	if (!are_types_identical(x->type, y->type)) {
+		if (x->type != t_invalid &&
+		    y->type != t_invalid) {
+			gbString xt = type_to_string(x->type);
+			gbString yt = type_to_string(y->type);
+			gbString expr_str = expr_to_string(x->expr);
+			error(op, "Mismatched types in binary expression `%s` : `%s` vs `%s`", expr_str, xt, yt);
+			gb_string_free(expr_str);
+			gb_string_free(yt);
+			gb_string_free(xt);
+		}
+		x->mode = Addressing_Invalid;
+		return;
+	}
+
+	if (!check_binary_op(c, x, op)) {
+		x->mode = Addressing_Invalid;
+		return;
+	}
+
+	switch (op.kind) {
+	case Token_Quo:
+	case Token_Mod:
+	case Token_QuoEq:
+	case Token_ModEq:
+		if ((x->mode == Addressing_Constant || is_type_integer(x->type)) &&
+		    y->mode == Addressing_Constant) {
+			bool fail = false;
+			switch (y->value.kind) {
+			case ExactValue_Integer:
+				if (y->value.value_integer == 0) {
+					fail = true;
+				}
+				break;
+			case ExactValue_Float:
+				if (y->value.value_float == 0.0) {
+					fail = true;
+				}
+				break;
+			}
+
+			if (fail) {
+				error_node(y->expr, "Division by zero not allowed");
+				x->mode = Addressing_Invalid;
+				return;
+			}
+		}
+	}
+
+	if (x->mode == Addressing_Constant &&
+	    y->mode == Addressing_Constant) {
+		ExactValue a = x->value;
+		ExactValue b = y->value;
+
+		Type *type = base_type(x->type);
+		if (is_type_pointer(type)) {
+			GB_ASSERT(op.kind == Token_Sub);
+			i64 bytes = a.value_pointer - b.value_pointer;
+			i64 diff = bytes/type_size_of(c->sizes, c->allocator, type);
+			x->value = make_exact_value_pointer(diff);
+			return;
+		}
+
+		if (!is_type_constant_type(type)) {
+			gbString xt = type_to_string(x->type);
+			gbString err_str = expr_to_string(node);
+			error(op, "Invalid type, `%s`, for constant binary expression `%s`", xt, err_str);
+			gb_string_free(err_str);
+			gb_string_free(xt);
+			x->mode = Addressing_Invalid;
+			return;
+		}
+
+		if (op.kind == Token_Quo && is_type_integer(type)) {
+			op.kind = Token_QuoEq; // NOTE(bill): Hack to get division of integers
+		}
+		x->value = exact_binary_operator_value(op.kind, a, b);
+		if (is_type_typed(type)) {
+			if (node != NULL) {
+				x->expr = node;
+			}
+			check_is_expressible(c, x, type);
+		}
+		return;
+	}
+
+	x->mode = Addressing_Value;
+}
+
+
+void update_expr_type(Checker *c, AstNode *e, Type *type, bool final) {
+	HashKey key = hash_pointer(e);
+	ExprInfo *found = map_expr_info_get(&c->info.untyped, key);
+	if (found == NULL) {
+		return;
+	}
+
+	switch (e->kind) {
+	case_ast_node(ue, UnaryExpr, e);
+		if (found->value.kind != ExactValue_Invalid) {
+			break;
+		}
+		update_expr_type(c, ue->expr, type, final);
+	case_end;
+
+	case_ast_node(be, BinaryExpr, e);
+		if (found->value.kind != ExactValue_Invalid) {
+			break;
+		}
+		if (!token_is_comparison(be->op)) {
+			if (token_is_shift(be->op)) {
+				update_expr_type(c, be->left,  type, final);
+			} else {
+				update_expr_type(c, be->left,  type, final);
+				update_expr_type(c, be->right, type, final);
+			}
+		}
+	case_end;
+	}
+
+	if (!final && is_type_untyped(type)) {
+		found->type = base_type(type);
+		map_expr_info_set(&c->info.untyped, key, *found);
+	} else {
+		ExprInfo old = *found;
+		map_expr_info_remove(&c->info.untyped, key);
+
+		if (old.is_lhs && !is_type_integer(type)) {
+			gbString expr_str = expr_to_string(e);
+			gbString type_str = type_to_string(type);
+			error_node(e, "Shifted operand %s must be an integer, got %s", expr_str, type_str);
+			gb_string_free(type_str);
+			gb_string_free(expr_str);
+			return;
+		}
+
+		add_type_and_value(&c->info, e, found->mode, type, found->value);
+	}
+}
+
+void update_expr_value(Checker *c, AstNode *e, ExactValue value) {
+	ExprInfo *found = map_expr_info_get(&c->info.untyped, hash_pointer(e));
+	if (found) {
+		found->value = value;
+	}
+}
+
+void convert_untyped_error(Checker *c, Operand *operand, Type *target_type) {
+	gbString expr_str = expr_to_string(operand->expr);
+	gbString type_str = type_to_string(target_type);
+	char *extra_text = "";
+
+	if (operand->mode == Addressing_Constant) {
+		if (operand->value.value_integer == 0) {
+			if (str_ne(make_string_c(expr_str), str_lit("nil"))) { // HACK NOTE(bill): Just in case
+				// NOTE(bill): Doesn't matter what the type is as it's still zero in the union
+				extra_text = " - Did you want `nil`?";
+			}
+		}
+	}
+	error_node(operand->expr, "Cannot convert `%s` to `%s`%s", expr_str, type_str, extra_text);
+
+	gb_string_free(type_str);
+	gb_string_free(expr_str);
+	operand->mode = Addressing_Invalid;
+}
+
+// NOTE(bill): Set initial level to 0
+void convert_to_typed(Checker *c, Operand *operand, Type *target_type, i32 level) {
+	GB_ASSERT_NOT_NULL(target_type);
+	if (operand->mode == Addressing_Invalid ||
+	    is_type_typed(operand->type) ||
+	    target_type == t_invalid) {
+		return;
+	}
+
+	if (is_type_untyped(target_type)) {
+		GB_ASSERT(operand->type->kind == Type_Basic);
+		GB_ASSERT(target_type->kind == Type_Basic);
+		BasicKind x_kind = operand->type->Basic.kind;
+		BasicKind y_kind = target_type->Basic.kind;
+		if (is_type_numeric(operand->type) && is_type_numeric(target_type)) {
+			if (x_kind < y_kind) {
+				operand->type = target_type;
+				update_expr_type(c, operand->expr, target_type, false);
+			}
+		} else if (x_kind != y_kind) {
+			convert_untyped_error(c, operand, target_type);
+		}
+		return;
+	}
+
+	Type *t = base_type(base_enum_type(target_type));
+	switch (t->kind) {
+	case Type_Basic:
+		if (operand->mode == Addressing_Constant) {
+			check_is_expressible(c, operand, t);
+			if (operand->mode == Addressing_Invalid) {
+				return;
+			}
+			update_expr_value(c, operand->expr, operand->value);
+		} else {
+			switch (operand->type->Basic.kind) {
+			case Basic_UntypedBool:
+				if (!is_type_boolean(target_type)) {
+					convert_untyped_error(c, operand, target_type);
+					return;
+				}
+				break;
+			case Basic_UntypedInteger:
+			case Basic_UntypedFloat:
+			case Basic_UntypedRune:
+				if (!is_type_numeric(target_type)) {
+					convert_untyped_error(c, operand, target_type);
+					return;
+				}
+				break;
+
+			case Basic_UntypedNil:
+				if (!type_has_nil(target_type)) {
+					convert_untyped_error(c, operand, target_type);
+					return;
+				}
+				break;
+			}
+		}
+		break;
+
+	case Type_Maybe:
+		if (is_type_untyped_nil(operand->type)) {
+			// Okay
+		} else if (level == 0) {
+			convert_to_typed(c, operand, t->Maybe.elem, level+1);
+			return;
+		}
+
+	default:
+		if (!is_type_untyped_nil(operand->type) || !type_has_nil(target_type)) {
+			convert_untyped_error(c, operand, target_type);
+			return;
+		}
+		break;
+	}
+
+
+
+	operand->type = target_type;
+}
+
+bool check_index_value(Checker *c, AstNode *index_value, i64 max_count, i64 *value) {
+	Operand operand = {Addressing_Invalid};
+	check_expr(c, &operand, index_value);
+	if (operand.mode == Addressing_Invalid) {
+		if (value) *value = 0;
+		return false;
+	}
+
+	convert_to_typed(c, &operand, t_int, 0);
+	if (operand.mode == Addressing_Invalid) {
+		if (value) *value = 0;
+		return false;
+	}
+
+	if (!is_type_integer(base_enum_type(operand.type))) {
+		gbString expr_str = expr_to_string(operand.expr);
+		error_node(operand.expr, "Index `%s` must be an integer", expr_str);
+		gb_string_free(expr_str);
+		if (value) *value = 0;
+		return false;
+	}
+
+	if (operand.mode == Addressing_Constant &&
+	    (c->context.stmt_state_flags & StmtStateFlag_bounds_check) != 0) {
+		i64 i = exact_value_to_integer(operand.value).value_integer;
+		if (i < 0) {
+			gbString expr_str = expr_to_string(operand.expr);
+			error_node(operand.expr, "Index `%s` cannot be a negative value", expr_str);
+			gb_string_free(expr_str);
+			if (value) *value = 0;
+			return false;
+		}
+
+		if (max_count >= 0) { // NOTE(bill): Do array bound checking
+			if (value) *value = i;
+			if (i >= max_count) {
+				gbString expr_str = expr_to_string(operand.expr);
+				error_node(operand.expr, "Index `%s` is out of bounds range 0..<%lld", expr_str, max_count);
+				gb_string_free(expr_str);
+				return false;
+			}
+
+			return true;
+		}
+	}
+
+	// NOTE(bill): It's alright :D
+	if (value) *value = -1;
+	return true;
+}
+
+Entity *check_selector(Checker *c, Operand *operand, AstNode *node) {
+	ast_node(se, SelectorExpr, node);
+
+	bool check_op_expr = true;
+	Entity *expr_entity = NULL;
+	Entity *entity = NULL;
+	Selection sel = {0}; // NOTE(bill): Not used if it's an import name
+
+	AstNode *op_expr  = se->expr;
+	AstNode *selector = unparen_expr(se->selector);
+	if (selector == NULL) {
+		goto error;
+	}
+
+	if (ast_node_expect(selector, AstNode_Ident)) {
+
+	}
+
+	if (op_expr->kind == AstNode_Ident) {
+		String name = op_expr->Ident.string;
+		Entity *e = scope_lookup_entity(c->context.scope, name);
+		add_entity_use(c, op_expr, e);
+		expr_entity = e;
+		if (e != NULL && e->kind == Entity_ImportName &&
+		    selector->kind == AstNode_Ident) {
+			String sel_name = selector->Ident.string;
+			check_op_expr = false;
+			entity = scope_lookup_entity(e->ImportName.scope, sel_name);
+			if (entity == NULL) {
+				error_node(op_expr, "`%.*s` is not declared by `%.*s`", LIT(sel_name), LIT(name));
+				goto error;
+			}
+			if (entity->type == NULL) { // Not setup yet
+				check_entity_decl(c, entity, NULL, NULL);
+			}
+			GB_ASSERT(entity->type != NULL);
+
+			b32 is_not_exported = true;
+			Entity **found = map_entity_get(&e->ImportName.scope->implicit, hash_string(sel_name));
+			if (found == NULL) {
+				is_not_exported = false;
+			} else {
+				Entity *f = *found;
+				if (f->kind == Entity_ImportName) {
+					is_not_exported = true;
+				}
+			}
+
+			if (is_not_exported) {
+				gbString sel_str = expr_to_string(selector);
+				error_node(op_expr, "`%s` is not exported by `%.*s`", sel_str, LIT(name));
+				gb_string_free(sel_str);
+				// NOTE(bill): Not really an error so don't goto error
+			}
+
+			add_entity_use(c, selector, entity);
+		}
+	}
+	if (check_op_expr) {
+		check_expr_base(c, operand, op_expr, NULL);
+		if (operand->mode == Addressing_Invalid) {
+			goto error;
+		}
+	}
+
+
+	if (entity == NULL && selector->kind == AstNode_Ident) {
+		sel = lookup_field(c->allocator, operand->type, selector->Ident.string, operand->mode == Addressing_Type);
+		entity = sel.entity;
+	}
+	if (entity == NULL) {
+		gbString op_str   = expr_to_string(op_expr);
+		gbString type_str = type_to_string(operand->type);
+		gbString sel_str  = expr_to_string(selector);
+		error_node(op_expr, "`%s` (`%s`) has no field `%s`", op_str, type_str, sel_str);
+		gb_string_free(sel_str);
+		gb_string_free(type_str);
+		gb_string_free(op_str);
+		goto error;
+	}
+
+	if (expr_entity != NULL && expr_entity->kind == Entity_Constant && entity->kind != Entity_Constant) {
+		gbString op_str   = expr_to_string(op_expr);
+		gbString type_str = type_to_string(operand->type);
+		gbString sel_str  = expr_to_string(selector);
+		error_node(op_expr, "Cannot access non-constant field `%s` from `%s`", sel_str, op_str);
+		gb_string_free(sel_str);
+		gb_string_free(type_str);
+		gb_string_free(op_str);
+		goto error;
+	}
+
+
+	add_entity_use(c, selector, entity);
+
+	switch (entity->kind) {
+	case Entity_Constant:
+		operand->mode = Addressing_Constant;
+		operand->value = entity->Constant.value;
+		break;
+	case Entity_Variable:
+		// TODO(bill): This is the rule I need?
+		if (sel.indirect || operand->mode != Addressing_Value) {
+			operand->mode = Addressing_Variable;
+		}
+		break;
+	case Entity_TypeName:
+		operand->mode = Addressing_Type;
+		break;
+	case Entity_Procedure:
+		operand->mode = Addressing_Value;
+		break;
+	case Entity_Builtin:
+		operand->mode = Addressing_Builtin;
+		operand->builtin_id = entity->Builtin.id;
+		break;
+
+	// NOTE(bill): These cases should never be hit but are here for sanity reasons
+	case Entity_Nil:
+		operand->mode = Addressing_Value;
+		break;
+	case Entity_ImplicitValue:
+		operand->mode = Addressing_Value;
+		break;
+	}
+
+	operand->type = entity->type;
+	operand->expr = node;
+
+	return entity;
+
+error:
+	operand->mode = Addressing_Invalid;
+	operand->expr = node;
+	return NULL;
+}
+
+bool check_builtin_procedure(Checker *c, Operand *operand, AstNode *call, i32 id) {
+	GB_ASSERT(call->kind == AstNode_CallExpr);
+	ast_node(ce, CallExpr, call);
+	BuiltinProc *bp = &builtin_procs[id];
+	{
+		char *err = NULL;
+		if (ce->args.count < bp->arg_count) {
+			err = "Too few";
+		} else if (ce->args.count > bp->arg_count && !bp->variadic) {
+			err = "Too many";
+		}
+
+		if (err) {
+			ast_node(proc, Ident, ce->proc);
+			error(ce->close, "`%s` arguments for `%.*s`, expected %td, got %td",
+			      err, LIT(proc->string),
+			      bp->arg_count, ce->args.count);
+			return false;
+		}
+	}
+
+	switch (id) {
+	case BuiltinProc_new:
+	case BuiltinProc_new_slice:
+	case BuiltinProc_size_of:
+	case BuiltinProc_align_of:
+	case BuiltinProc_offset_of:
+	case BuiltinProc_type_info:
+		// NOTE(bill): The first arg may be a Type, this will be checked case by case
+		break;
+	default:
+		check_multi_expr(c, operand, ce->args.e[0]);
+	}
+
+	switch (id) {
+	default:
+		GB_PANIC("Implement builtin procedure: %.*s", LIT(builtin_procs[id].name));
+		break;
+
+	case BuiltinProc_new: {
+		// new :: proc(Type) -> ^Type
+		Operand op = {0};
+		check_expr_or_type(c, &op, ce->args.e[0]);
+		Type *type = op.type;
+		if ((op.mode != Addressing_Type && type == NULL) || type == t_invalid) {
+			error_node(ce->args.e[0], "Expected a type for `new`");
+			return false;
+		}
+		operand->mode = Addressing_Value;
+		operand->type = make_type_pointer(c->allocator, type);
+	} break;
+	case BuiltinProc_new_slice: {
+		// new_slice :: proc(Type, len: int) -> []Type
+		Operand op = {0};
+		check_expr_or_type(c, &op, ce->args.e[0]);
+		Type *type = op.type;
+		if ((op.mode != Addressing_Type && type == NULL) || type == t_invalid) {
+			error_node(ce->args.e[0], "Expected a type for `new_slice`");
+			return false;
+		}
+
+		check_expr(c, &op, ce->args.e[1]);
+		if (op.mode == Addressing_Invalid) {
+			return false;
+		}
+		if (!is_type_integer(base_enum_type(op.type))) {
+			gbString type_str = type_to_string(op.type);
+			error_node(call, "Length for `new_slice` must be an integer, got `%s`", type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		operand->mode = Addressing_Value;
+		operand->type = make_type_slice(c->allocator, type);
+	} break;
+
+	case BuiltinProc_size_of: {
+		// size_of :: proc(Type) -> untyped int
+		Type *type = check_type(c, ce->args.e[0]);
+		if (type == NULL || type == t_invalid) {
+			error_node(ce->args.e[0], "Expected a type for `size_of`");
+			return false;
+		}
+
+		operand->mode = Addressing_Constant;
+		operand->value = make_exact_value_integer(type_size_of(c->sizes, c->allocator, type));
+		operand->type = t_untyped_integer;
+
+	} break;
+
+	case BuiltinProc_size_of_val:
+		// size_of_val :: proc(val: Type) -> untyped int
+		check_assignment(c, operand, NULL, str_lit("argument of `size_of_val`"));
+		if (operand->mode == Addressing_Invalid) {
+			return false;
+		}
+
+		operand->mode = Addressing_Constant;
+		operand->value = make_exact_value_integer(type_size_of(c->sizes, c->allocator, operand->type));
+		operand->type = t_untyped_integer;
+		break;
+
+	case BuiltinProc_align_of: {
+		// align_of :: proc(Type) -> untyped int
+		Type *type = check_type(c, ce->args.e[0]);
+		if (type == NULL || type == t_invalid) {
+			error_node(ce->args.e[0], "Expected a type for `align_of`");
+			return false;
+		}
+		operand->mode = Addressing_Constant;
+		operand->value = make_exact_value_integer(type_align_of(c->sizes, c->allocator, type));
+		operand->type = t_untyped_integer;
+	} break;
+
+	case BuiltinProc_align_of_val:
+		// align_of_val :: proc(val: Type) -> untyped int
+		check_assignment(c, operand, NULL, str_lit("argument of `align_of_val`"));
+		if (operand->mode == Addressing_Invalid) {
+			return false;
+		}
+
+		operand->mode = Addressing_Constant;
+		operand->value = make_exact_value_integer(type_align_of(c->sizes, c->allocator, operand->type));
+		operand->type = t_untyped_integer;
+		break;
+
+	case BuiltinProc_offset_of: {
+		// offset_of :: proc(Type, field) -> untyped int
+		Operand op = {0};
+		Type *bt = check_type(c, ce->args.e[0]);
+		Type *type = base_type(bt);
+		if (type == NULL || type == t_invalid) {
+			error_node(ce->args.e[0], "Expected a type for `offset_of`");
+			return false;
+		}
+
+		AstNode *field_arg = unparen_expr(ce->args.e[1]);
+		if (field_arg == NULL ||
+		    field_arg->kind != AstNode_Ident) {
+			error_node(field_arg, "Expected an identifier for field argument");
+			return false;
+		}
+		if (is_type_array(type) || is_type_vector(type)) {
+			error_node(field_arg, "Invalid type for `offset_of`");
+			return false;
+		}
+
+
+		ast_node(arg, Ident, field_arg);
+		Selection sel = lookup_field(c->allocator, type, arg->string, operand->mode == Addressing_Type);
+		if (sel.entity == NULL) {
+			gbString type_str = type_to_string(bt);
+			error_node(ce->args.e[0],
+			      "`%s` has no field named `%.*s`", type_str, LIT(arg->string));
+			gb_string_free(type_str);
+			return false;
+		}
+		if (sel.indirect) {
+			gbString type_str = type_to_string(bt);
+			error_node(ce->args.e[0],
+			      "Field `%.*s` is embedded via a pointer in `%s`", LIT(arg->string), type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		operand->mode = Addressing_Constant;
+		operand->value = make_exact_value_integer(type_offset_of_from_selection(c->sizes, c->allocator, type, sel));
+		operand->type  = t_untyped_integer;
+	} break;
+
+	case BuiltinProc_offset_of_val: {
+		// offset_of_val :: proc(val: expression) -> untyped int
+		AstNode *arg = unparen_expr(ce->args.e[0]);
+		if (arg->kind != AstNode_SelectorExpr) {
+			gbString str = expr_to_string(arg);
+			error_node(arg, "`%s` is not a selector expression", str);
+			return false;
+		}
+		ast_node(s, SelectorExpr, arg);
+
+		check_expr(c, operand, s->expr);
+		if (operand->mode == Addressing_Invalid) {
+			return false;
+		}
+
+		Type *type = operand->type;
+		if (base_type(type)->kind == Type_Pointer) {
+			Type *p = base_type(type);
+			if (is_type_struct(p)) {
+				type = p->Pointer.elem;
+			}
+		}
+		if (is_type_array(type) || is_type_vector(type)) {
+			error_node(arg, "Invalid type for `offset_of_val`");
+			return false;
+		}
+
+		ast_node(i, Ident, s->selector);
+		Selection sel = lookup_field(c->allocator, type, i->string, operand->mode == Addressing_Type);
+		if (sel.entity == NULL) {
+			gbString type_str = type_to_string(type);
+			error_node(arg,
+			      "`%s` has no field named `%.*s`", type_str, LIT(i->string));
+			return false;
+		}
+		if (sel.indirect) {
+			gbString type_str = type_to_string(type);
+			error_node(ce->args.e[0],
+			      "Field `%.*s` is embedded via a pointer in `%s`", LIT(i->string), type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		operand->mode = Addressing_Constant;
+		// IMPORTANT TODO(bill): Fix for anonymous fields
+		operand->value = make_exact_value_integer(type_offset_of_from_selection(c->sizes, c->allocator, type, sel));
+		operand->type  = t_untyped_integer;
+	} break;
+
+	case BuiltinProc_type_of_val:
+		// type_of_val :: proc(val: Type) -> type(Type)
+		check_assignment(c, operand, NULL, str_lit("argument of `type_of_val`"));
+		if (operand->mode == Addressing_Invalid || operand->mode == Addressing_Builtin) {
+			return false;
+		}
+		operand->mode = Addressing_Type;
+		break;
+
+
+	case BuiltinProc_type_info: {
+		// type_info :: proc(Type) -> ^Type_Info
+		if (c->context.scope->is_global) {
+			compiler_error("`type_info` Cannot be declared within a #shared_global_scope due to how the internals of the compiler works");
+		}
+
+		// NOTE(bill): The type information may not be setup yet
+		init_preload(c);
+		AstNode *expr = ce->args.e[0];
+		Type *type = check_type(c, expr);
+		if (type == NULL || type == t_invalid) {
+			error_node(expr, "Invalid argument to `type_info`");
+			return false;
+		}
+
+		add_type_info_type(c, type);
+
+		operand->mode = Addressing_Value;
+		operand->type = t_type_info_ptr;
+	} break;
+
+	case BuiltinProc_type_info_of_val: {
+		// type_info_of_val :: proc(val: Type) -> ^Type_Info
+		if (c->context.scope->is_global) {
+			compiler_error("`type_info` Cannot be declared within a #shared_global_scope due to how the internals of the compiler works");
+		}
+
+		// NOTE(bill): The type information may not be setup yet
+		init_preload(c);
+		AstNode *expr = ce->args.e[0];
+		check_assignment(c, operand, NULL, str_lit("argument of `type_info_of_val`"));
+		if (operand->mode == Addressing_Invalid || operand->mode == Addressing_Builtin)
+			return false;
+		add_type_info_type(c, operand->type);
+
+		operand->mode = Addressing_Value;
+		operand->type = t_type_info_ptr;
+	} break;
+
+
+
+	case BuiltinProc_compile_assert:
+		// compile_assert :: proc(cond: bool)
+
+		if (!is_type_boolean(operand->type) && operand->mode != Addressing_Constant) {
+			gbString str = expr_to_string(ce->args.e[0]);
+			error_node(call, "`%s` is not a constant boolean", str);
+			gb_string_free(str);
+			return false;
+		}
+		if (!operand->value.value_bool) {
+			gbString str = expr_to_string(ce->args.e[0]);
+			error_node(call, "Compile time assertion: `%s`", str);
+			gb_string_free(str);
+		}
+		break;
+
+	case BuiltinProc_assert:
+		// assert :: proc(cond: bool)
+
+		if (!is_type_boolean(operand->type)) {
+			gbString str = expr_to_string(ce->args.e[0]);
+			error_node(call, "`%s` is not a boolean", str);
+			gb_string_free(str);
+			return false;
+		}
+
+		operand->mode = Addressing_NoValue;
+		break;
+
+	case BuiltinProc_panic:
+		// panic :: proc(msg: string)
+
+		if (!is_type_string(operand->type)) {
+			gbString str = expr_to_string(ce->args.e[0]);
+			error_node(call, "`%s` is not a string", str);
+			gb_string_free(str);
+			return false;
+		}
+
+		operand->mode = Addressing_NoValue;
+		break;
+
+	case BuiltinProc_copy: {
+		// copy :: proc(x, y: []Type) -> int
+		Type *dest_type = NULL, *src_type = NULL;
+
+		Type *d = base_type(operand->type);
+		if (d->kind == Type_Slice) {
+			dest_type = d->Slice.elem;
+		}
+		Operand op = {0};
+		check_expr(c, &op, ce->args.e[1]);
+		if (op.mode == Addressing_Invalid) {
+			return false;
+		}
+		Type *s = base_type(op.type);
+		if (s->kind == Type_Slice) {
+			src_type = s->Slice.elem;
+		}
+
+		if (dest_type == NULL || src_type == NULL) {
+			error_node(call, "`copy` only expects slices as arguments");
+			return false;
+		}
+
+		if (!are_types_identical(dest_type, src_type)) {
+			gbString d_arg = expr_to_string(ce->args.e[0]);
+			gbString s_arg = expr_to_string(ce->args.e[1]);
+			gbString d_str = type_to_string(dest_type);
+			gbString s_str = type_to_string(src_type);
+			error_node(call,
+			      "Arguments to `copy`, %s, %s, have different elem types: %s vs %s",
+			      d_arg, s_arg, d_str, s_str);
+			gb_string_free(s_str);
+			gb_string_free(d_str);
+			gb_string_free(s_arg);
+			gb_string_free(d_arg);
+			return false;
+		}
+
+		operand->type = t_int; // Returns number of elems copied
+		operand->mode = Addressing_Value;
+	} break;
+
+	#if 0
+	case BuiltinProc_append: {
+		// append :: proc(x : ^[]Type, y : Type) -> bool
+		Type *x_type = NULL, *y_type = NULL;
+		x_type = base_type(operand->type);
+
+		Operand op = {0};
+		check_expr(c, &op, ce->args.e[1]);
+		if (op.mode == Addressing_Invalid) {
+			return false;
+		}
+		y_type = base_type(op.type);
+
+		if (!(is_type_pointer(x_type) && is_type_slice(x_type->Pointer.elem))) {
+			error_node(call, "First argument to `append` must be a pointer to a slice");
+			return false;
+		}
+
+		Type *elem_type = x_type->Pointer.elem->Slice.elem;
+		if (!check_is_assignable_to(c, &op, elem_type)) {
+			gbString d_arg = expr_to_string(ce->args.e[0]);
+			gbString s_arg = expr_to_string(ce->args.e[1]);
+			gbString d_str = type_to_string(elem_type);
+			gbString s_str = type_to_string(y_type);
+			error_node(call,
+			      "Arguments to `append`, %s, %s, have different element types: %s vs %s",
+			      d_arg, s_arg, d_str, s_str);
+			gb_string_free(s_str);
+			gb_string_free(d_str);
+			gb_string_free(s_arg);
+			gb_string_free(d_arg);
+			return false;
+		}
+
+		operand->type = t_bool; // Returns if it was successful
+		operand->mode = Addressing_Value;
+	} break;
+	#endif
+
+	case BuiltinProc_swizzle: {
+		// swizzle :: proc(v: {N}T, T...) -> {M}T
+		Type *vector_type = base_type(operand->type);
+		if (!is_type_vector(vector_type)) {
+			gbString type_str = type_to_string(operand->type);
+			error_node(call,
+			      "You can only `swizzle` a vector, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		isize max_count = vector_type->Vector.count;
+		isize arg_count = 0;
+		for_array(i, ce->args) {
+			if (i == 0) {
+				continue;
+			}
+			AstNode *arg = ce->args.e[i];
+			Operand op = {0};
+			check_expr(c, &op, arg);
+			if (op.mode == Addressing_Invalid) {
+				return false;
+			}
+			Type *arg_type = base_type(op.type);
+			if (!is_type_integer(arg_type) || op.mode != Addressing_Constant) {
+				error_node(op.expr, "Indices to `swizzle` must be constant integers");
+				return false;
+			}
+
+			if (op.value.value_integer < 0) {
+				error_node(op.expr, "Negative `swizzle` index");
+				return false;
+			}
+
+			if (max_count <= op.value.value_integer) {
+				error_node(op.expr, "`swizzle` index exceeds vector length");
+				return false;
+			}
+
+			arg_count++;
+		}
+
+		if (arg_count > max_count) {
+			error_node(call, "Too many `swizzle` indices, %td > %td", arg_count, max_count);
+			return false;
+		}
+
+		Type *elem_type = vector_type->Vector.elem;
+		operand->type = make_type_vector(c->allocator, elem_type, arg_count);
+		operand->mode = Addressing_Value;
+	} break;
+
+#if 0
+	case BuiltinProc_ptr_offset: {
+		// ptr_offset :: proc(ptr: ^T, offset: int) -> ^T
+		// ^T cannot be rawptr
+		Type *ptr_type = base_type(operand->type);
+		if (!is_type_pointer(ptr_type)) {
+			gbString type_str = type_to_string(operand->type);
+			defer (gb_string_free(type_str));
+			error_node(call,
+			      "Expected a pointer to `ptr_offset`, got `%s`",
+			      type_str);
+			return false;
+		}
+
+		if (ptr_type == t_rawptr) {
+			error_node(call,
+			      "`rawptr` cannot have pointer arithmetic");
+			return false;
+		}
+
+		AstNode *offset = ce->args.e[1];
+		Operand op = {0};
+		check_expr(c, &op, offset);
+		if (op.mode == Addressing_Invalid)
+			return false;
+		Type *offset_type = base_type(op.type);
+		if (!is_type_integer(offset_type)) {
+			error_node(op.expr, "Pointer offsets for `ptr_offset` must be an integer");
+			return false;
+		}
+
+		if (operand->mode == Addressing_Constant &&
+		    op.mode == Addressing_Constant) {
+			i64 ptr = operand->value.value_pointer;
+			i64 elem_size = type_size_of(c->sizes, c->allocator, ptr_type->Pointer.elem);
+			ptr += elem_size * op.value.value_integer;
+			operand->value.value_pointer = ptr;
+		} else {
+			operand->mode = Addressing_Value;
+		}
+
+	} break;
+
+	case BuiltinProc_ptr_sub: {
+		// ptr_sub :: proc(a, b: ^T) -> int
+		// ^T cannot be rawptr
+		Type *ptr_type = base_type(operand->type);
+		if (!is_type_pointer(ptr_type)) {
+			gbString type_str = type_to_string(operand->type);
+			defer (gb_string_free(type_str));
+			error_node(call,
+			      "Expected a pointer to `ptr_add`, got `%s`",
+			      type_str);
+			return false;
+		}
+
+		if (ptr_type == t_rawptr) {
+			error_node(call,
+			      "`rawptr` cannot have pointer arithmetic");
+			return false;
+		}
+		AstNode *offset = ce->args[1];
+		Operand op = {0};
+		check_expr(c, &op, offset);
+		if (op.mode == Addressing_Invalid)
+			return false;
+		if (!is_type_pointer(op.type)) {
+			gbString type_str = type_to_string(operand->type);
+			defer (gb_string_free(type_str));
+			error_node(call,
+			      "Expected a pointer to `ptr_add`, got `%s`",
+			      type_str);
+			return false;
+		}
+
+		if (base_type(op.type) == t_rawptr) {
+			error_node(call,
+			      "`rawptr` cannot have pointer arithmetic");
+			return false;
+		}
+
+		if (!are_types_identical(operand->type, op.type)) {
+			gbString a = type_to_string(operand->type);
+			gbString b = type_to_string(op.type);
+			defer (gb_string_free(a));
+			defer (gb_string_free(b));
+			error_node(op.expr,
+			      "`ptr_sub` requires to pointer of the same type. Got `%s` and `%s`.", a, b);
+			return false;
+		}
+
+		operand->type = t_int;
+
+		if (operand->mode == Addressing_Constant &&
+		    op.mode == Addressing_Constant) {
+			u8 *ptr_a = cast(u8 *)operand->value.value_pointer;
+			u8 *ptr_b = cast(u8 *)op.value.value_pointer;
+			isize elem_size = type_size_of(c->sizes, c->allocator, ptr_type->Pointer.elem);
+			operand->value = make_exact_value_integer((ptr_a - ptr_b) / elem_size);
+		} else {
+			operand->mode = Addressing_Value;
+		}
+	} break;
+#endif
+
+	case BuiltinProc_slice_ptr: {
+		// slice_ptr :: proc(a: ^T, len: int) -> []T
+		// ^T cannot be rawptr
+		Type *ptr_type = base_type(operand->type);
+		if (!is_type_pointer(ptr_type)) {
+			gbString type_str = type_to_string(operand->type);
+			error_node(call,
+			      "Expected a pointer to `slice_ptr`, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		if (ptr_type == t_rawptr) {
+			error_node(call,
+			      "`rawptr` cannot have pointer arithmetic");
+			return false;
+		}
+
+		AstNode *len = ce->args.e[1];
+
+		Operand op = {0};
+		check_expr(c, &op, len);
+		if (op.mode == Addressing_Invalid)
+			return false;
+		if (!is_type_integer(op.type)) {
+			gbString type_str = type_to_string(operand->type);
+			error_node(call,
+			      "Length for `slice_ptr` must be an integer, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		operand->type = make_type_slice(c->allocator, ptr_type->Pointer.elem);
+		operand->mode = Addressing_Value;
+	} break;
+
+	case BuiltinProc_min: {
+		// min :: proc(a, b: comparable) -> comparable
+		Type *type = base_type(operand->type);
+		if (!is_type_comparable(type) || !(is_type_numeric(type) || is_type_string(type))) {
+			gbString type_str = type_to_string(operand->type);
+			error_node(call,
+			      "Expected a comparable numeric type to `min`, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		AstNode *other_arg = ce->args.e[1];
+		Operand a = *operand;
+		Operand b = {0};
+		check_expr(c, &b, other_arg);
+		if (b.mode == Addressing_Invalid) {
+			return false;
+		}
+		if (!is_type_comparable(b.type) || !(is_type_numeric(b.type) || is_type_string(b.type))) {
+			gbString type_str = type_to_string(b.type);
+			error_node(call,
+			      "Expected a comparable numeric type to `min`, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		if (a.mode == Addressing_Constant &&
+		    b.mode == Addressing_Constant) {
+			ExactValue x = a.value;
+			ExactValue y = b.value;
+
+			operand->mode = Addressing_Constant;
+			if (compare_exact_values(Token_Lt, x, y)) {
+				operand->value = x;
+				operand->type = a.type;
+			} else {
+				operand->value = y;
+				operand->type = b.type;
+			}
+		} else {
+			operand->mode = Addressing_Value;
+			operand->type = type;
+
+			convert_to_typed(c, &a, b.type, 0);
+			if (a.mode == Addressing_Invalid) {
+				return false;
+			}
+			convert_to_typed(c, &b, a.type, 0);
+			if (b.mode == Addressing_Invalid) {
+				return false;
+			}
+
+			if (!are_types_identical(operand->type, b.type)) {
+				gbString type_a = type_to_string(a.type);
+				gbString type_b = type_to_string(b.type);
+				error_node(call,
+				      "Mismatched types to `min`, `%s` vs `%s`",
+				      type_a, type_b);
+				gb_string_free(type_b);
+				gb_string_free(type_a);
+				return false;
+			}
+		}
+
+	} break;
+
+	case BuiltinProc_max: {
+		// min :: proc(a, b: comparable) -> comparable
+		Type *type = base_type(operand->type);
+		if (!is_type_comparable(type) || !(is_type_numeric(type) || is_type_string(type))) {
+			gbString type_str = type_to_string(operand->type);
+			error_node(call,
+			      "Expected a comparable numeric or string type to `max`, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		AstNode *other_arg = ce->args.e[1];
+		Operand a = *operand;
+		Operand b = {0};
+		check_expr(c, &b, other_arg);
+		if (b.mode == Addressing_Invalid) {
+			return false;
+		}
+		if (!is_type_comparable(b.type) || !(is_type_numeric(b.type) || is_type_string(b.type))) {
+			gbString type_str = type_to_string(b.type);
+			error_node(call,
+			      "Expected a comparable numeric or string type to `max`, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		if (a.mode == Addressing_Constant &&
+		    b.mode == Addressing_Constant) {
+			ExactValue x = a.value;
+			ExactValue y = b.value;
+
+			operand->mode = Addressing_Constant;
+			if (compare_exact_values(Token_Gt, x, y)) {
+				operand->value = x;
+				operand->type = a.type;
+			} else {
+				operand->value = y;
+				operand->type = b.type;
+			}
+		} else {
+			operand->mode = Addressing_Value;
+			operand->type = type;
+
+			convert_to_typed(c, &a, b.type, 0);
+			if (a.mode == Addressing_Invalid) {
+				return false;
+			}
+			convert_to_typed(c, &b, a.type, 0);
+			if (b.mode == Addressing_Invalid) {
+				return false;
+			}
+
+			if (!are_types_identical(operand->type, b.type)) {
+				gbString type_a = type_to_string(a.type);
+				gbString type_b = type_to_string(b.type);
+				error_node(call,
+				      "Mismatched types to `max`, `%s` vs `%s`",
+				      type_a, type_b);
+				gb_string_free(type_b);
+				gb_string_free(type_a);
+				return false;
+			}
+		}
+
+	} break;
+
+	case BuiltinProc_abs: {
+		// abs :: proc(n: numeric) -> numeric
+		Type *type = base_type(operand->type);
+		if (!is_type_numeric(type)) {
+			gbString type_str = type_to_string(operand->type);
+			error_node(call,
+			      "Expected a numeric type to `abs`, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		if (operand->mode == Addressing_Constant) {
+			switch (operand->value.kind) {
+			case ExactValue_Integer:
+				operand->value.value_integer = gb_abs(operand->value.value_integer);
+				break;
+			case ExactValue_Float:
+				operand->value.value_float = gb_abs(operand->value.value_float);
+				break;
+			default:
+				GB_PANIC("Invalid numeric constant");
+				break;
+			}
+		} else {
+			operand->mode = Addressing_Value;
+		}
+
+		operand->type = type;
+	} break;
+
+	case BuiltinProc_clamp: {
+		// clamp :: proc(a, min, max: comparable) -> comparable
+		Type *type = base_type(operand->type);
+		if (!is_type_comparable(type) || !(is_type_numeric(type) || is_type_string(type))) {
+			gbString type_str = type_to_string(operand->type);
+			error_node(call,
+			      "Expected a comparable numeric or string type to `clamp`, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		AstNode *min_arg = ce->args.e[1];
+		AstNode *max_arg = ce->args.e[2];
+		Operand x = *operand;
+		Operand y = {0};
+		Operand z = {0};
+
+		check_expr(c, &y, min_arg);
+		if (y.mode == Addressing_Invalid) {
+			return false;
+		}
+		if (!is_type_comparable(y.type) || !(is_type_numeric(y.type) || is_type_string(y.type))) {
+			gbString type_str = type_to_string(y.type);
+			error_node(call,
+			      "Expected a comparable numeric or string type to `clamp`, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		check_expr(c, &z, max_arg);
+		if (z.mode == Addressing_Invalid) {
+			return false;
+		}
+		if (!is_type_comparable(z.type) || !(is_type_numeric(z.type) || is_type_string(z.type))) {
+			gbString type_str = type_to_string(z.type);
+			error_node(call,
+			      "Expected a comparable numeric or string type to `clamp`, got `%s`",
+			      type_str);
+			gb_string_free(type_str);
+			return false;
+		}
+
+		if (x.mode == Addressing_Constant &&
+		    y.mode == Addressing_Constant &&
+		    z.mode == Addressing_Constant) {
+			ExactValue a = x.value;
+			ExactValue b = y.value;
+			ExactValue c = z.value;
+
+			operand->mode = Addressing_Constant;
+			if (compare_exact_values(Token_Lt, a, b)) {
+				operand->value = b;
+				operand->type = y.type;
+			} else if (compare_exact_values(Token_Gt, a, c)) {
+				operand->value = c;
+				operand->type = z.type;
+			} else {
+				operand->value = a;
+				operand->type = x.type;
+			}
+		} else {
+			operand->mode = Addressing_Value;
+			operand->type = type;
+
+			convert_to_typed(c, &x, y.type, 0);
+			if (x.mode == Addressing_Invalid) { return false; }
+			convert_to_typed(c, &y, x.type, 0);
+			if (y.mode == Addressing_Invalid) { return false; }
+			convert_to_typed(c, &x, z.type, 0);
+			if (x.mode == Addressing_Invalid) { return false; }
+			convert_to_typed(c, &z, x.type, 0);
+			if (z.mode == Addressing_Invalid) { return false; }
+			convert_to_typed(c, &y, z.type, 0);
+			if (y.mode == Addressing_Invalid) { return false; }
+			convert_to_typed(c, &z, y.type, 0);
+			if (z.mode == Addressing_Invalid) { return false; }
+
+			if (!are_types_identical(x.type, y.type) || !are_types_identical(x.type, z.type)) {
+				gbString type_x = type_to_string(x.type);
+				gbString type_y = type_to_string(y.type);
+				gbString type_z = type_to_string(z.type);
+				error_node(call,
+				      "Mismatched types to `clamp`, `%s`, `%s`, `%s`",
+				      type_x, type_y, type_z);
+				gb_string_free(type_z);
+				gb_string_free(type_y);
+				gb_string_free(type_x);
+				return false;
+			}
+		}
+	} break;
+	}
+
+	return true;
+}
+
+
+void check_call_arguments(Checker *c, Operand *operand, Type *proc_type, AstNode *call) {
+	GB_ASSERT(call->kind == AstNode_CallExpr);
+	GB_ASSERT(proc_type->kind == Type_Proc);
+	ast_node(ce, CallExpr, call);
+
+	isize param_count = 0;
+	bool variadic = proc_type->Proc.variadic;
+	bool vari_expand = (ce->ellipsis.pos.line != 0);
+
+	if (proc_type->Proc.params != NULL) {
+		param_count = proc_type->Proc.params->Tuple.variable_count;
+		if (variadic) {
+			param_count--;
+		}
+	}
+
+	if (vari_expand && !variadic) {
+		error(ce->ellipsis,
+		      "Cannot use `..` in call to a non-variadic procedure: `%.*s`",
+		      LIT(ce->proc->Ident.string));
+		return;
+	}
+
+	if (ce->args.count == 0 && param_count == 0) {
+		return;
+	}
+
+	gbTempArenaMemory tmp = gb_temp_arena_memory_begin(&c->tmp_arena);
+
+	Array(Operand) operands;
+	array_init_reserve(&operands, c->tmp_allocator, 2*param_count);
+
+	for_array(i, ce->args) {
+		Operand o = {0};
+		check_multi_expr(c, &o, ce->args.e[i]);
+		if (o.type->kind != Type_Tuple) {
+			array_add(&operands, o);
+		} else {
+			TypeTuple *tuple = &o.type->Tuple;
+			if (variadic && i >= param_count) {
+				error_node(ce->args.e[i], "`..` in a variadic procedure cannot be applied to a %td-valued expression", tuple->variable_count);
+				operand->mode = Addressing_Invalid;
+				goto end;
+			}
+			for (isize j = 0; j < tuple->variable_count; j++) {
+				o.type = tuple->variables[j]->type;
+				array_add(&operands, o);
+			}
+		}
+	}
+
+	i32 error_code = 0;
+	if (operands.count < param_count) {
+		error_code = -1;
+	} else if (!variadic && operands.count > param_count) {
+		error_code = +1;
+	}
+	if (error_code != 0) {
+		char *err_fmt = "Too many arguments for `%s`, expected %td arguments";
+		if (error_code < 0) {
+			err_fmt = "Too few arguments for `%s`, expected %td arguments";
+		}
+
+		gbString proc_str = expr_to_string(ce->proc);
+		error_node(call, err_fmt, proc_str, param_count);
+		gb_string_free(proc_str);
+		operand->mode = Addressing_Invalid;
+		goto end;
+	}
+
+	GB_ASSERT(proc_type->Proc.params != NULL);
+	Entity **sig_params = proc_type->Proc.params->Tuple.variables;
+	isize operand_index = 0;
+	for (; operand_index < param_count; operand_index++) {
+		Type *arg_type = sig_params[operand_index]->type;
+		Operand o = operands.e[operand_index];
+		if (variadic) {
+			o = operands.e[operand_index];
+		}
+		check_assignment(c, &o, arg_type, str_lit("argument"));
+	}
+
+	if (variadic) {
+		bool variadic_expand = false;
+		Type *slice = sig_params[param_count]->type;
+		GB_ASSERT(is_type_slice(slice));
+		Type *elem = base_type(slice)->Slice.elem;
+		Type *t = elem;
+		for (; operand_index < operands.count; operand_index++) {
+			Operand o = operands.e[operand_index];
+			if (vari_expand) {
+				variadic_expand = true;
+				t = slice;
+				if (operand_index != param_count) {
+					error_node(o.expr, "`..` in a variadic procedure can only have one variadic argument at the end");
+					break;
+				}
+			}
+			check_assignment(c, &o, t, str_lit("argument"));
+		}
+	}
+end:
+	gb_temp_arena_memory_end(tmp);
+}
+
+
+Entity *find_using_index_expr(Type *t) {
+	t = base_type(t);
+	if (t->kind != Type_Record) {
+		return NULL;
+	}
+
+	for (isize i = 0; i < t->Record.field_count; i++) {
+		Entity *f = t->Record.fields[i];
+		if (f->kind == Entity_Variable &&
+		    f->flags & (EntityFlag_Anonymous|EntityFlag_Field)) {
+			if (is_type_indexable(f->type)) {
+				return f;
+			}
+			Entity *res = find_using_index_expr(f->type);
+			if (res != NULL) {
+				return res;
+			}
+		}
+	}
+	return NULL;
+}
+
+ExprKind check_call_expr(Checker *c, Operand *operand, AstNode *call) {
+	GB_ASSERT(call->kind == AstNode_CallExpr);
+	ast_node(ce, CallExpr, call);
+	check_expr_or_type(c, operand, ce->proc);
+
+	if (operand->mode == Addressing_Invalid) {
+		for_array(i, ce->args) {
+			check_expr_base(c, operand, ce->args.e[i], NULL);
+		}
+		operand->mode = Addressing_Invalid;
+		operand->expr = call;
+		return Expr_Stmt;
+	}
+
+
+	if (operand->mode == Addressing_Builtin) {
+		i32 id = operand->builtin_id;
+		if (!check_builtin_procedure(c, operand, call, id)) {
+			operand->mode = Addressing_Invalid;
+		}
+		operand->expr = call;
+		return builtin_procs[id].kind;
+	}
+
+	Type *proc_type = base_type(operand->type);
+	if (proc_type == NULL || proc_type->kind != Type_Proc ||
+	    !(operand->mode == Addressing_Value || operand->mode == Addressing_Variable)) {
+		AstNode *e = operand->expr;
+		gbString str = expr_to_string(e);
+		error_node(e, "Cannot call a non-procedure: `%s`", str);
+		gb_string_free(str);
+
+		operand->mode = Addressing_Invalid;
+		operand->expr = call;
+
+		return Expr_Stmt;
+	}
+
+	check_call_arguments(c, operand, proc_type, call);
+
+	switch (proc_type->Proc.result_count) {
+	case 0:
+		operand->mode = Addressing_NoValue;
+		break;
+	case 1:
+		operand->mode = Addressing_Value;
+		operand->type = proc_type->Proc.results->Tuple.variables[0]->type;
+		break;
+	default:
+		operand->mode = Addressing_Value;
+		operand->type = proc_type->Proc.results;
+		break;
+	}
+
+	operand->expr = call;
+	return Expr_Stmt;
+}
+
+void check_expr_with_type_hint(Checker *c, Operand *o, AstNode *e, Type *t) {
+	check_expr_base(c, o, e, t);
+	check_not_tuple(c, o);
+	char *err_str = NULL;
+	switch (o->mode) {
+	case Addressing_NoValue:
+		err_str = "used as a value";
+		break;
+	case Addressing_Type:
+		err_str = "is not an expression";
+		break;
+	case Addressing_Builtin:
+		err_str = "must be called";
+		break;
+	}
+	if (err_str != NULL) {
+		gbString str = expr_to_string(e);
+		error_node(e, "`%s` %s", str, err_str);
+		gb_string_free(str);
+		o->mode = Addressing_Invalid;
+	}
+}
+
+bool check_set_index_data(Operand *o, Type *t, i64 *max_count) {
+	t = base_type(type_deref(t));
+
+	switch (t->kind) {
+	case Type_Basic:
+		if (is_type_string(t)) {
+			if (o->mode == Addressing_Constant) {
+				*max_count = o->value.value_string.len;
+			}
+			if (o->mode != Addressing_Variable) {
+				o->mode = Addressing_Value;
+			}
+			o->type = t_u8;
+			return true;
+		}
+		break;
+
+	case Type_Array:
+		*max_count = t->Array.count;
+		if (o->mode != Addressing_Variable) {
+			o->mode = Addressing_Value;
+		}
+		o->type = t->Array.elem;
+		return true;
+
+	case Type_Vector:
+		*max_count = t->Vector.count;
+		if (o->mode != Addressing_Variable) {
+			o->mode = Addressing_Value;
+		}
+		o->type = t->Vector.elem;
+		return true;
+
+
+	case Type_Slice:
+		o->type = t->Slice.elem;
+		o->mode = Addressing_Variable;
+		return true;
+	}
+
+	return false;
+}
+
+
+bool check_is_giving(AstNode *node, AstNode **give_expr) {
+	switch (node->kind) {
+	case_ast_node(es, ExprStmt, node);
+		if (es->expr->kind == AstNode_GiveExpr) {
+			if (give_expr) *give_expr = es->expr;
+			return true;
+		}
+	case_end;
+
+	case_ast_node(ge, GiveExpr, node);
+		if (give_expr) *give_expr = node;
+		return true;
+	case_end;
+
+	case_ast_node(be, BlockExpr, node);
+		// Iterate backwards
+		for (isize n = be->stmts.count-1; n >= 0; n--) {
+			AstNode *stmt = be->stmts.e[n];
+			if (stmt->kind == AstNode_EmptyStmt) {
+				continue;
+			}
+			if (stmt->kind == AstNode_ExprStmt && stmt->ExprStmt.expr->kind == AstNode_GiveExpr) {
+				if (give_expr) *give_expr = stmt->ExprStmt.expr;
+				return true;
+			}
+		}
+	case_end;
+	}
+
+	if (give_expr) *give_expr = NULL;
+	return false;
+}
+
+ExprKind check__expr_base(Checker *c, Operand *o, AstNode *node, Type *type_hint) {
+	ExprKind kind = Expr_Stmt;
+
+	o->mode = Addressing_Invalid;
+	o->type = t_invalid;
+
+	switch (node->kind) {
+	default:
+		goto error;
+		break;
+
+	case_ast_node(be, BadExpr, node)
+		goto error;
+	case_end;
+
+	case_ast_node(i, IntervalExpr, node);
+		error_node(node, "Invalid use of an interval expression");
+		goto error;
+	case_end;
+
+	case_ast_node(i, Ident, node);
+		check_identifier(c, o, node, type_hint);
+	case_end;
+
+	case_ast_node(bl, BasicLit, node);
+		Type *t = t_invalid;
+		switch (bl->kind) {
+		case Token_Integer: t = t_untyped_integer; break;
+		case Token_Float:   t = t_untyped_float;   break;
+		case Token_String:  t = t_untyped_string;  break;
+		case Token_Rune:    t = t_untyped_rune;    break;
+		default:            GB_PANIC("Unknown literal"); break;
+		}
+		o->mode  = Addressing_Constant;
+		o->type  = t;
+		o->value = make_exact_value_from_basic_literal(*bl);
+	case_end;
+
+	case_ast_node(pl, ProcLit, node);
+		Type *type = check_type(c, pl->type);
+		if (type == NULL || !is_type_proc(type)) {
+			gbString str = expr_to_string(node);
+			error_node(node, "Invalid procedure literal `%s`", str);
+			gb_string_free(str);
+			check_close_scope(c);
+			goto error;
+		}
+		if (pl->tags != 0) {
+			error_node(node, "A procedure literal cannot have tags");
+			pl->tags = 0; // TODO(bill): Should I zero this?!
+		}
+
+		check_open_scope(c, pl->type);
+		check_procedure_later(c, c->curr_ast_file, empty_token, c->context.decl, type, pl->body, pl->tags);
+		// check_proc_body(c, empty_token, c->context.decl, type, pl->body);
+		check_close_scope(c);
+
+		o->mode = Addressing_Value;
+		o->type = type;
+	case_end;
+
+	case_ast_node(ge, GiveExpr, node);
+		if (c->proc_stack.count == 0) {
+			error_node(node, "A give expression is only allowed within a procedure");
+			goto error;
+		}
+
+		if (ge->results.count == 0) {
+			error_node(node, "`give` has no results");
+			goto error;
+		}
+
+		gbTempArenaMemory tmp = gb_temp_arena_memory_begin(&c->tmp_arena);
+
+		Array(Operand) operands;
+		array_init_reserve(&operands, c->tmp_allocator, 2*ge->results.count);
+
+		for_array(i, ge->results) {
+			AstNode *rhs = ge->results.e[i];
+			Operand o = {0};
+			check_multi_expr(c, &o, rhs);
+			if (!is_operand_value(o)) {
+				error_node(rhs, "Expected a value for a `give`");
+				continue;
+			}
+			if (o.type->kind != Type_Tuple) {
+				array_add(&operands, o);
+			} else {
+				TypeTuple *tuple = &o.type->Tuple;
+				for (isize j = 0; j < tuple->variable_count; j++) {
+					o.type = tuple->variables[j]->type;
+					array_add(&operands, o);
+				}
+			}
+		}
+
+		if (operands.count == 0) {
+			error_node(node, "`give` has no value");
+			gb_temp_arena_memory_end(tmp);
+			goto error;
+		} else if (operands.count == 1) {
+			Operand operand = operands.e[0];
+			if (type_hint != NULL) {
+				convert_to_typed(c, &operand, type_hint, 0);
+			}
+			o->type = default_type(operand.type);
+			o->mode = Addressing_Value;
+		} else {
+			Type *tuple = make_type_tuple(c->allocator);
+
+			Entity **variables = gb_alloc_array(c->allocator, Entity *, operands.count);
+			isize variable_index = 0;
+			for_array(i, operands) {
+				Operand operand = operands.e[i];
+				// Type *type = default_type(operand.type);
+				Type *type = operand.type;
+				switch (operand.mode) {
+				case Addressing_Constant:
+					variables[variable_index++] = make_entity_constant(c->allocator, NULL, empty_token, type, operand.value);
+					break;
+				default:
+					variables[variable_index++] = make_entity_param(c->allocator, NULL, empty_token, type, false);
+					break;
+				}
+			}
+			tuple->Tuple.variables = variables;
+			tuple->Tuple.variable_count = operands.count;
+
+			o->type = tuple;
+			o->mode = Addressing_Value;
+		}
+		gb_temp_arena_memory_end(tmp);
+	case_end;
+
+	case_ast_node(be, BlockExpr, node);
+		if (c->proc_stack.count == 0) {
+			error_node(node, "A block expression is only allowed within a procedure");
+			goto error;
+		}
+
+		for (isize i = be->stmts.count-1; i >= 0; i--) {
+			if (be->stmts.e[i]->kind != AstNode_EmptyStmt) {
+				break;
+			}
+			be->stmts.count--;
+		}
+
+		if (be->stmts.count == 0) {
+			error_node(node, "Empty block expression");
+			goto error;
+		}
+
+		check_open_scope(c, node);
+		check_stmt_list(c, be->stmts, Stmt_GiveAllowed);
+		check_close_scope(c);
+
+		AstNode *give_node = NULL;
+		if (!check_is_giving(node, &give_node) || give_node == NULL) {
+			error_node(node, "Missing give statement at end of block expression");
+			goto error;
+		}
+
+		GB_ASSERT(give_node != NULL && give_node->kind == AstNode_GiveExpr);
+		be->give_node = give_node;
+
+		Type *type = type_of_expr(&c->info, give_node);
+		if (type == NULL) {
+			goto error;
+		} else if (type == t_invalid) {
+			o->type = t_invalid;
+			o->mode = Addressing_Invalid;
+		} else {
+			o->type = type;
+			o->mode = Addressing_Value;
+		}
+	case_end;
+
+	case_ast_node(ie, IfExpr, node);
+		if (c->proc_stack.count == 0) {
+			error_node(node, "An if expression is only allowed within a procedure");
+			goto error;
+		}
+
+		check_open_scope(c, node);
+
+		if (ie->init != NULL) {
+			check_stmt(c, ie->init, 0);
+		}
+
+		Operand operand = {Addressing_Invalid};
+		check_expr(c, &operand, ie->cond);
+		if (operand.mode != Addressing_Invalid && !is_type_boolean(operand.type)) {
+			error_node(ie->cond, "Non-boolean condition in if expression");
+		}
+
+
+		Operand x = {Addressing_Invalid};
+		Operand y = {Addressing_Invalid};
+		Type *if_type = NULL;
+		Type *else_type = NULL;
+		check_expr(c, &x, ie->body);
+		if_type = x.type;
+
+		if (ie->else_expr != NULL) {
+			switch (ie->else_expr->kind) {
+			case AstNode_IfExpr:
+			case AstNode_BlockExpr:
+				check_expr(c, &y, ie->else_expr);
+				else_type = y.type;
+				break;
+			default:
+				error_node(ie->else_expr, "Invalid else expression in if expression");
+				break;
+			}
+		} else {
+			error_node(ie->else_expr, "An if expression must have an else expression");
+			check_close_scope(c);
+			goto error;
+		}
+
+		check_close_scope(c);
+
+		if (if_type == NULL || if_type == t_invalid ||
+		    else_type == NULL || else_type == t_invalid) {
+			goto error;
+		}
+
+		convert_to_typed(c, &x, y.type, 0);
+		if (x.mode == Addressing_Invalid) {
+			goto error;
+		}
+		convert_to_typed(c, &y, x.type, 0);
+		if (y.mode == Addressing_Invalid) {
+			x.mode = Addressing_Invalid;
+			goto error;
+		}
+
+
+		if (!are_types_identical(if_type, else_type)) {
+			gbString its = type_to_string(if_type);
+			gbString ets = type_to_string(else_type);
+			error_node(node, "Mismatched types in if expression, %s vs %s", its, ets);
+			gb_string_free(ets);
+			gb_string_free(its);
+			goto error;
+		}
+
+		o->type = if_type;
+		o->mode = Addressing_Value;
+	case_end;
+
+	case_ast_node(cl, CompoundLit, node);
+		Type *type = type_hint;
+		bool ellipsis_array = false;
+		bool is_constant = true;
+		if (cl->type != NULL) {
+			type = NULL;
+
+			// [..]Type
+			if (cl->type->kind == AstNode_ArrayType && cl->type->ArrayType.count != NULL) {
+				if (cl->type->ArrayType.count->kind == AstNode_Ellipsis) {
+					type = make_type_array(c->allocator, check_type(c, cl->type->ArrayType.elem), -1);
+					ellipsis_array = true;
+				}
+			}
+
+			if (type == NULL) {
+				type = check_type(c, cl->type);
+			}
+		}
+
+		if (type == NULL) {
+			error_node(node, "Missing type in compound literal");
+			goto error;
+		}
+
+		Type *t = base_type(type);
+		switch (t->kind) {
+		case Type_Record: {
+			if (!is_type_struct(t)) {
+				if (cl->elems.count != 0) {
+					error_node(node, "Illegal compound literal");
+				}
+				break;
+			}
+			if (cl->elems.count == 0) {
+				break; // NOTE(bill): No need to init
+			}
+			{ // Checker values
+				isize field_count = t->Record.field_count;
+				if (cl->elems.e[0]->kind == AstNode_FieldValue) {
+					bool *fields_visited = gb_alloc_array(c->allocator, bool, field_count);
+
+					for_array(i, cl->elems) {
+						AstNode *elem = cl->elems.e[i];
+						if (elem->kind != AstNode_FieldValue) {
+							error_node(elem, "Mixture of `field = value` and value elements in a structure literal is not allowed");
+							continue;
+						}
+						ast_node(fv, FieldValue, elem);
+						if (fv->field->kind != AstNode_Ident) {
+							gbString expr_str = expr_to_string(fv->field);
+							error_node(elem, "Invalid field name `%s` in structure literal", expr_str);
+							gb_string_free(expr_str);
+							continue;
+						}
+						String name = fv->field->Ident.string;
+
+						Selection sel = lookup_field(c->allocator, type, name, o->mode == Addressing_Type);
+						if (sel.entity == NULL) {
+							error_node(elem, "Unknown field `%.*s` in structure literal", LIT(name));
+							continue;
+						}
+
+						if (sel.index.count > 1) {
+							error_node(elem, "Cannot assign to an anonymous field `%.*s` in a structure literal (at the moment)", LIT(name));
+							continue;
+						}
+
+						Entity *field = t->Record.fields[sel.index.e[0]];
+						add_entity_use(c, fv->field, field);
+
+						if (fields_visited[sel.index.e[0]]) {
+							error_node(elem, "Duplicate field `%.*s` in structure literal", LIT(name));
+							continue;
+						}
+
+						fields_visited[sel.index.e[0]] = true;
+						check_expr(c, o, fv->value);
+
+						if (base_type(field->type) == t_any) {
+							is_constant = false;
+						}
+						if (is_constant) {
+							is_constant = o->mode == Addressing_Constant;
+						}
+
+
+						check_assignment(c, o, field->type, str_lit("structure literal"));
+					}
+				} else {
+					for_array(index, cl->elems) {
+						AstNode *elem = cl->elems.e[index];
+						if (elem->kind == AstNode_FieldValue) {
+							error_node(elem, "Mixture of `field = value` and value elements in a structure literal is not allowed");
+							continue;
+						}
+						Entity *field = t->Record.fields_in_src_order[index];
+
+						check_expr(c, o, elem);
+						if (index >= field_count) {
+							error_node(o->expr, "Too many values in structure literal, expected %td", field_count);
+							break;
+						}
+
+						if (base_type(field->type) == t_any) {
+							is_constant = false;
+						}
+						if (is_constant) {
+							is_constant = o->mode == Addressing_Constant;
+						}
+
+						check_assignment(c, o, field->type, str_lit("structure literal"));
+					}
+					if (cl->elems.count < field_count) {
+						error(cl->close, "Too few values in structure literal, expected %td, got %td", field_count, cl->elems.count);
+					}
+				}
+			}
+
+		} break;
+
+		case Type_Slice:
+		case Type_Array:
+		case Type_Vector:
+		{
+			Type *elem_type = NULL;
+			String context_name = {0};
+			if (t->kind == Type_Slice) {
+				elem_type = t->Slice.elem;
+				context_name = str_lit("slice literal");
+			} else if (t->kind == Type_Vector) {
+				elem_type = t->Vector.elem;
+				context_name = str_lit("vector literal");
+			} else {
+				elem_type = t->Array.elem;
+				context_name = str_lit("array literal");
+			}
+
+
+			i64 max = 0;
+			isize index = 0;
+			isize elem_count = cl->elems.count;
+
+			if (base_type(elem_type) == t_any) {
+				is_constant = false;
+			}
+
+			for (; index < elem_count; index++) {
+				AstNode *e = cl->elems.e[index];
+				if (e->kind == AstNode_FieldValue) {
+					error_node(e,
+					      "`field = value` is only allowed in struct literals");
+					continue;
+				}
+
+				if (t->kind == Type_Array &&
+				    t->Array.count >= 0 &&
+				    index >= t->Array.count) {
+					error_node(e, "Index %lld is out of bounds (>= %lld) for array literal", index, t->Array.count);
+				}
+				if (t->kind == Type_Vector &&
+				    t->Vector.count >= 0 &&
+				    index >= t->Vector.count) {
+					error_node(e, "Index %lld is out of bounds (>= %lld) for vector literal", index, t->Vector.count);
+				}
+
+				Operand operand = {0};
+				check_expr_with_type_hint(c, &operand, e, elem_type);
+				check_assignment(c, &operand, elem_type, context_name);
+
+				if (is_constant) {
+					is_constant = operand.mode == Addressing_Constant;
+				}
+			}
+			if (max < index) {
+				max = index;
+			}
+
+			if (t->kind == Type_Vector) {
+				if (t->Vector.count > 1 && gb_is_between(index, 2, t->Vector.count-1)) {
+					error_node(cl->elems.e[0], "Expected either 1 (broadcast) or %td elements in vector literal, got %td", t->Vector.count, index);
+				}
+			}
+
+			if (t->kind == Type_Array && ellipsis_array) {
+				t->Array.count = max;
+			}
+		} break;
+
+		default: {
+			gbString str = type_to_string(type);
+			error_node(node, "Invalid compound literal type `%s`", str);
+			gb_string_free(str);
+			goto error;
+		} break;
+		}
+
+		if (is_constant) {
+			o->mode = Addressing_Constant;
+			o->value = make_exact_value_compound(node);
+		} else {
+			o->mode = Addressing_Value;
+		}
+		o->type = type;
+	case_end;
+
+	case_ast_node(pe, ParenExpr, node);
+		kind = check_expr_base(c, o, pe->expr, type_hint);
+		o->expr = node;
+	case_end;
+
+
+	case_ast_node(te, TagExpr, node);
+		// TODO(bill): Tag expressions
+		error_node(node, "Tag expressions are not supported yet");
+		kind = check_expr_base(c, o, te->expr, type_hint);
+		o->expr = node;
+	case_end;
+
+	case_ast_node(re, RunExpr, node);
+		// TODO(bill): Tag expressions
+		kind = check_expr_base(c, o, re->expr, type_hint);
+		o->expr = node;
+	case_end;
+
+
+	case_ast_node(ue, UnaryExpr, node);
+		check_expr(c, o, ue->expr);
+		if (o->mode == Addressing_Invalid) {
+			goto error;
+		}
+		check_unary_expr(c, o, ue->op, node);
+		if (o->mode == Addressing_Invalid) {
+			goto error;
+		}
+	case_end;
+
+
+	case_ast_node(be, BinaryExpr, node);
+		check_binary_expr(c, o, node);
+		if (o->mode == Addressing_Invalid) {
+			goto error;
+		}
+	case_end;
+
+
+
+	case_ast_node(se, SelectorExpr, node);
+		check_selector(c, o, node);
+	case_end;
+
+
+	case_ast_node(ie, IndexExpr, node);
+		check_expr(c, o, ie->expr);
+		if (o->mode == Addressing_Invalid) {
+			goto error;
+		}
+
+		Type *t = base_type(type_deref(o->type));
+		bool is_const = o->mode == Addressing_Constant;
+
+		i64 max_count = -1;
+		bool valid = check_set_index_data(o, t, &max_count);
+
+		if (is_const) {
+			valid = false;
+		}
+
+		if (!valid && (is_type_struct(t) || is_type_raw_union(t))) {
+			Entity *found = find_using_index_expr(t);
+			if (found != NULL) {
+				valid = check_set_index_data(o, found->type, &max_count);
+			}
+		}
+
+		if (!valid) {
+			gbString str = expr_to_string(o->expr);
+			if (is_const) {
+				error_node(o->expr, "Cannot index a constant `%s`", str);
+			} else {
+				error_node(o->expr, "Cannot index `%s`", str);
+			}
+			gb_string_free(str);
+			goto error;
+		}
+
+		if (ie->index == NULL) {
+			gbString str = expr_to_string(o->expr);
+			error_node(o->expr, "Missing index for `%s`", str);
+			gb_string_free(str);
+			goto error;
+		}
+
+		i64 index = 0;
+		bool ok = check_index_value(c, ie->index, max_count, &index);
+
+	case_end;
+
+
+
+	case_ast_node(se, SliceExpr, node);
+		check_expr(c, o, se->expr);
+		if (o->mode == Addressing_Invalid) {
+			goto error;
+		}
+
+		bool valid = false;
+		i64 max_count = -1;
+		Type *t = base_type(type_deref(o->type));
+		switch (t->kind) {
+		case Type_Basic:
+			if (is_type_string(t)) {
+				valid = true;
+				if (o->mode == Addressing_Constant) {
+					max_count = o->value.value_string.len;
+				}
+				o->type = t_string;
+			}
+			break;
+
+		case Type_Array:
+			valid = true;
+			max_count = t->Array.count;
+			if (o->mode != Addressing_Variable) {
+				gbString str = expr_to_string(node);
+				error_node(node, "Cannot slice array `%s`, value is not addressable", str);
+				gb_string_free(str);
+				goto error;
+			}
+			o->type = make_type_slice(c->allocator, t->Array.elem);
+			break;
+
+		case Type_Slice:
+			valid = true;
+			break;
+		}
+
+		if (!valid) {
+			gbString str = expr_to_string(o->expr);
+			error_node(o->expr, "Cannot slice `%s`", str);
+			gb_string_free(str);
+			goto error;
+		}
+
+		o->mode = Addressing_Value;
+
+		i64 indices[2] = {0};
+		AstNode *nodes[2] = {se->low, se->high};
+		for (isize i = 0; i < gb_count_of(nodes); i++) {
+			i64 index = max_count;
+			if (nodes[i] != NULL) {
+				i64 capacity = -1;
+				if (max_count >= 0)
+					capacity = max_count;
+				i64 j = 0;
+				if (check_index_value(c, nodes[i], capacity, &j)) {
+					index = j;
+				}
+			} else if (i == 0) {
+				index = 0;
+			}
+			indices[i] = index;
+		}
+
+		for (isize i = 0; i < gb_count_of(indices); i++) {
+			i64 a = indices[i];
+			for (isize j = i+1; j < gb_count_of(indices); j++) {
+				i64 b = indices[j];
+				if (a > b && b >= 0) {
+					error(se->close, "Invalid slice indices: [%td > %td]", a, b);
+				}
+			}
+		}
+
+	case_end;
+
+
+	case_ast_node(ce, CallExpr, node);
+		return check_call_expr(c, o, node);
+	case_end;
+
+	case_ast_node(de, DerefExpr, node);
+		check_expr_or_type(c, o, de->expr);
+		if (o->mode == Addressing_Invalid) {
+			goto error;
+		} else {
+			Type *t = base_type(o->type);
+			if (t->kind == Type_Pointer) {
+				o->mode = Addressing_Variable;
+				o->type = t->Pointer.elem;
+ 			} else {
+ 				gbString str = expr_to_string(o->expr);
+ 				error_node(o->expr, "Cannot dereference `%s`", str);
+ 				gb_string_free(str);
+ 				goto error;
+ 			}
+		}
+	case_end;
+
+	case_ast_node(de, DemaybeExpr, node);
+		check_expr_or_type(c, o, de->expr);
+		if (o->mode == Addressing_Invalid) {
+			goto error;
+		} else {
+			Type *t = base_type(o->type);
+			if (t->kind == Type_Maybe) {
+				Entity **variables = gb_alloc_array(c->allocator, Entity *, 2);
+				Type *elem = t->Maybe.elem;
+				Token tok = make_token_ident(str_lit(""));
+				variables[0] = make_entity_param(c->allocator, NULL, tok, elem, false);
+				variables[1] = make_entity_param(c->allocator, NULL, tok, t_bool, false);
+
+				Type *tuple = make_type_tuple(c->allocator);
+				tuple->Tuple.variables = variables;
+				tuple->Tuple.variable_count = 2;
+
+				o->type = tuple;
+				o->mode = Addressing_Variable;
+ 			} else {
+ 				gbString str = expr_to_string(o->expr);
+ 				error_node(o->expr, "Cannot demaybe `%s`", str);
+ 				gb_string_free(str);
+ 				goto error;
+ 			}
+		}
+	case_end;
+
+	case AstNode_ProcType:
+	case AstNode_PointerType:
+	case AstNode_MaybeType:
+	case AstNode_ArrayType:
+	case AstNode_VectorType:
+	case AstNode_StructType:
+	case AstNode_UnionType:
+	case AstNode_RawUnionType:
+	case AstNode_EnumType:
+		o->mode = Addressing_Type;
+		o->type = check_type(c, node);
+		break;
+	}
+
+	kind = Expr_Expr;
+	o->expr = node;
+	return kind;
+
+error:
+	o->mode = Addressing_Invalid;
+	o->expr = node;
+	return kind;
+}
+
+ExprKind check_expr_base(Checker *c, Operand *o, AstNode *node, Type *type_hint) {
+	ExprKind kind = check__expr_base(c, o, node, type_hint);
+	Type *type = NULL;
+	ExactValue value = {ExactValue_Invalid};
+	switch (o->mode) {
+	case Addressing_Invalid:
+		type = t_invalid;
+		break;
+	case Addressing_NoValue:
+		type = NULL;
+		break;
+	case Addressing_Constant:
+		type = o->type;
+		value = o->value;
+		break;
+	default:
+		type = o->type;
+		break;
+	}
+
+	if (type != NULL && is_type_untyped(type)) {
+		add_untyped(&c->info, node, false, o->mode, type, value);
+	} else {
+		add_type_and_value(&c->info, node, o->mode, type, value);
+	}
+	return kind;
+}
+
+
+void check_multi_expr(Checker *c, Operand *o, AstNode *e) {
+	gbString err_str = NULL;
+	check_expr_base(c, o, e, NULL);
+	switch (o->mode) {
+	default:
+		return; // NOTE(bill): Valid
+
+	case Addressing_NoValue:
+		err_str = expr_to_string(e);
+		error_node(e, "`%s` used as value", err_str);
+		break;
+	case Addressing_Type:
+		err_str = expr_to_string(e);
+		error_node(e, "`%s` is not an expression", err_str);
+		break;
+	}
+	gb_string_free(err_str);
+	o->mode = Addressing_Invalid;
+}
+
+void check_not_tuple(Checker *c, Operand *o) {
+	if (o->mode == Addressing_Value) {
+		// NOTE(bill): Tuples are not first class thus never named
+		if (o->type->kind == Type_Tuple) {
+			isize count = o->type->Tuple.variable_count;
+			GB_ASSERT(count != 1);
+			error_node(o->expr,
+			      "%td-valued tuple found where single value expected", count);
+			o->mode = Addressing_Invalid;
+		}
+	}
+}
+
+void check_expr(Checker *c, Operand *o, AstNode *e) {
+	check_multi_expr(c, o, e);
+	check_not_tuple(c, o);
+}
+
+
+void check_expr_or_type(Checker *c, Operand *o, AstNode *e) {
+	check_expr_base(c, o, e, NULL);
+	check_not_tuple(c, o);
+	if (o->mode == Addressing_NoValue) {
+		gbString str = expr_to_string(o->expr);
+		error_node(o->expr, "`%s` used as value or type", str);
+		gb_string_free(str);
+		o->mode = Addressing_Invalid;
+	}
+}
+
+
+gbString write_expr_to_string(gbString str, AstNode *node);
+
+gbString write_params_to_string(gbString str, AstNodeArray params, char *sep) {
+	for_array(i, params) {
+		ast_node(p, Field, params.e[i]);
+		if (i > 0) {
+			str = gb_string_appendc(str, sep);
+		}
+
+		str = write_expr_to_string(str, params.e[i]);
+	}
+	return str;
+}
+
+gbString string_append_token(gbString str, Token token) {
+	if (token.string.len > 0) {
+		return gb_string_append_length(str, token.string.text, token.string.len);
+	}
+	return str;
+}
+
+
+gbString write_expr_to_string(gbString str, AstNode *node) {
+	if (node == NULL)
+		return str;
+
+	if (is_ast_node_stmt(node)) {
+		GB_ASSERT("stmt passed to write_expr_to_string");
+	}
+
+	switch (node->kind) {
+	default:
+		str = gb_string_appendc(str, "(BadExpr)");
+		break;
+
+	case_ast_node(i, Ident, node);
+		str = string_append_token(str, *i);
+	case_end;
+
+	case_ast_node(bl, BasicLit, node);
+		str = string_append_token(str, *bl);
+	case_end;
+
+	case_ast_node(pl, ProcLit, node);
+		str = write_expr_to_string(str, pl->type);
+	case_end;
+
+	case_ast_node(cl, CompoundLit, node);
+		str = write_expr_to_string(str, cl->type);
+		str = gb_string_appendc(str, "{");
+		for_array(i, cl->elems) {
+			if (i > 0) {
+				str = gb_string_appendc(str, ", ");
+			}
+			str = write_expr_to_string(str, cl->elems.e[i]);
+		}
+		str = gb_string_appendc(str, "}");
+	case_end;
+
+	case_ast_node(be, BlockExpr, node);
+		str = gb_string_appendc(str, "block expression");
+	case_end;
+	case_ast_node(ie, IfExpr, node);
+		str = gb_string_appendc(str, "if expression");
+	case_end;
+
+	case_ast_node(te, TagExpr, node);
+		str = gb_string_appendc(str, "#");
+		str = string_append_token(str, te->name);
+		str = write_expr_to_string(str, te->expr);
+	case_end;
+
+	case_ast_node(ue, UnaryExpr, node);
+		str = string_append_token(str, ue->op);
+		str = write_expr_to_string(str, ue->expr);
+	case_end;
+
+	case_ast_node(de, DerefExpr, node);
+		str = write_expr_to_string(str, de->expr);
+		str = gb_string_appendc(str, "^");
+	case_end;
+
+	case_ast_node(de, DemaybeExpr, node);
+		str = write_expr_to_string(str, de->expr);
+		str = gb_string_appendc(str, "?");
+	case_end;
+
+	case_ast_node(be, BinaryExpr, node);
+		str = write_expr_to_string(str, be->left);
+		str = gb_string_appendc(str, " ");
+		str = string_append_token(str, be->op);
+		str = gb_string_appendc(str, " ");
+		str = write_expr_to_string(str, be->right);
+	case_end;
+
+	case_ast_node(pe, ParenExpr, node);
+		str = gb_string_appendc(str, "(");
+		str = write_expr_to_string(str, pe->expr);
+		str = gb_string_appendc(str, ")");
+	case_end;
+
+	case_ast_node(se, SelectorExpr, node);
+		str = write_expr_to_string(str, se->expr);
+		str = gb_string_appendc(str, ".");
+		str = write_expr_to_string(str, se->selector);
+	case_end;
+
+	case_ast_node(ie, IndexExpr, node);
+		str = write_expr_to_string(str, ie->expr);
+		str = gb_string_appendc(str, "[");
+		str = write_expr_to_string(str, ie->index);
+		str = gb_string_appendc(str, "]");
+	case_end;
+
+	case_ast_node(se, SliceExpr, node);
+		str = write_expr_to_string(str, se->expr);
+		str = gb_string_appendc(str, "[");
+		str = write_expr_to_string(str, se->low);
+		str = gb_string_appendc(str, ":");
+		str = write_expr_to_string(str, se->high);
+		str = gb_string_appendc(str, "]");
+	case_end;
+
+	case_ast_node(e, Ellipsis, node);
+		str = gb_string_appendc(str, "..");
+	case_end;
+
+	case_ast_node(fv, FieldValue, node);
+		str = write_expr_to_string(str, fv->field);
+		str = gb_string_appendc(str, " = ");
+		str = write_expr_to_string(str, fv->value);
+	case_end;
+
+	case_ast_node(pt, PointerType, node);
+		str = gb_string_appendc(str, "^");
+		str = write_expr_to_string(str, pt->type);
+	case_end;
+
+	case_ast_node(mt, MaybeType, node);
+		str = gb_string_appendc(str, "?");
+		str = write_expr_to_string(str, mt->type);
+	case_end;
+
+	case_ast_node(at, ArrayType, node);
+		str = gb_string_appendc(str, "[");
+		str = write_expr_to_string(str, at->count);
+		str = gb_string_appendc(str, "]");
+		str = write_expr_to_string(str, at->elem);
+	case_end;
+
+	case_ast_node(vt, VectorType, node);
+		str = gb_string_appendc(str, "[vector ");
+		str = write_expr_to_string(str, vt->count);
+		str = gb_string_appendc(str, "]");
+		str = write_expr_to_string(str, vt->elem);
+	case_end;
+
+	case_ast_node(p, Field, node);
+		if (p->is_using) {
+			str = gb_string_appendc(str, "using ");
+		}
+		for_array(i, p->names) {
+			AstNode *name = p->names.e[i];
+			if (i > 0) {
+				str = gb_string_appendc(str, ", ");
+			}
+			str = write_expr_to_string(str, name);
+		}
+
+		str = gb_string_appendc(str, ": ");
+		str = write_expr_to_string(str, p->type);
+	case_end;
+
+	case_ast_node(ce, CallExpr, node);
+		str = write_expr_to_string(str, ce->proc);
+		str = gb_string_appendc(str, "(");
+
+		for_array(i, ce->args) {
+			AstNode *arg = ce->args.e[i];
+			if (i > 0) {
+				str = gb_string_appendc(str, ", ");
+			}
+			str = write_expr_to_string(str, arg);
+		}
+		str = gb_string_appendc(str, ")");
+	case_end;
+
+	case_ast_node(pt, ProcType, node);
+		str = gb_string_appendc(str, "proc(");
+		str = write_params_to_string(str, pt->params, ", ");
+		str = gb_string_appendc(str, ")");
+	case_end;
+
+	case_ast_node(st, StructType, node);
+		str = gb_string_appendc(str, "struct ");
+		if (st->is_packed)  str = gb_string_appendc(str, "#packed ");
+		if (st->is_ordered) str = gb_string_appendc(str, "#ordered ");
+		for_array(i, st->fields) {
+			if (i > 0) {
+				str = gb_string_appendc(str, "; ");
+			}
+			str = write_expr_to_string(str, st->fields.e[i]);
+		}
+		// str = write_params_to_string(str, st->decl_list, ", ");
+		str = gb_string_appendc(str, "}");
+	case_end;
+
+	case_ast_node(st, RawUnionType, node);
+		str = gb_string_appendc(str, "raw_union {");
+		for_array(i, st->fields) {
+			if (i > 0) {
+				str = gb_string_appendc(str, "; ");
+			}
+			str = write_expr_to_string(str, st->fields.e[i]);
+		}
+		// str = write_params_to_string(str, st->decl_list, ", ");
+		str = gb_string_appendc(str, "}");
+	case_end;
+
+	case_ast_node(st, UnionType, node);
+		str = gb_string_appendc(str, "union {");
+		for_array(i, st->fields) {
+			if (i > 0) {
+				str = gb_string_appendc(str, "; ");
+			}
+			str = write_expr_to_string(str, st->fields.e[i]);
+		}
+		// str = write_params_to_string(str, st->decl_list, ", ");
+		str = gb_string_appendc(str, "}");
+	case_end;
+
+	case_ast_node(et, EnumType, node);
+		str = gb_string_appendc(str, "enum ");
+		if (et->base_type != NULL) {
+			str = write_expr_to_string(str, et->base_type);
+			str = gb_string_appendc(str, " ");
+		}
+		str = gb_string_appendc(str, "{");
+		str = gb_string_appendc(str, "}");
+	case_end;
+
+	case_ast_node(ht, HelperType, node);
+		str = gb_string_appendc(str, "type ");
+		str = write_expr_to_string(str, ht->type);
+	case_end;
+	}
+
+	return str;
+}
+
+gbString expr_to_string(AstNode *expression) {
+	return write_expr_to_string(gb_string_make(heap_allocator(), ""), expression);
+}