`distinct` keyword for type declarations

6 files changed, 81 insertions, 39 deletions

diff --git a/src/check_decl.cpp b/src/check_decl.cpp
index f85e88c0f..0c4ff6735 100644
--- a/src/check_decl.cpp
+++ b/src/check_decl.cpp
@@ -170,22 +170,57 @@ void check_init_constant(Checker *c, Entity *e, Operand *operand) {
 	e->Constant.value = operand->value;
 }
 
-AstNode *remove_type_alias(AstNode *node) {
+
+bool is_type_distinct(AstNode *node) {
+	for (;;) {
+		if (node == nullptr) {
+			return false;
+		}
+		if (node->kind == AstNode_ParenExpr) {
+			node = node->ParenExpr.expr;
+		} else if (node->kind == AstNode_HelperType) {
+			node = node->HelperType.type;
+		} else {
+			break;
+		}
+	}
+
+	switch (node->kind) {
+	case AstNode_DistinctType:
+		return true;
+
+	case AstNode_StructType:
+	case AstNode_UnionType:
+	case AstNode_EnumType:
+	case AstNode_BitFieldType:
+	case AstNode_ProcType:
+		return true;
+
+	case AstNode_PointerType:
+	case AstNode_ArrayType:
+	case AstNode_DynamicArrayType:
+	case AstNode_MapType:
+		return true;
+	}
+	return false;
+}
+
+AstNode *remove_type_alias_clutter(AstNode *node) {
 	for (;;) {
 		if (node == nullptr) {
 			return nullptr;
 		}
 		if (node->kind == AstNode_ParenExpr) {
 			node = node->ParenExpr.expr;
-		} else if (node->kind == AstNode_AliasType) {
-			node = node->AliasType.type;
+		} else if (node->kind == AstNode_DistinctType) {
+			node = node->DistinctType.type;
 		} else {
 			return node;
 		}
 	}
 }
 
-void check_type_decl(Checker *c, Entity *e, AstNode *type_expr, Type *def, bool is_alias) {
+void check_type_decl(Checker *c, Entity *e, AstNode *type_expr, Type *def) {
 	GB_ASSERT(e->type == nullptr);
 
 	DeclInfo *decl = decl_info_of_entity(&c->info, e);
@@ -193,7 +228,8 @@ void check_type_decl(Checker *c, Entity *e, AstNode *type_expr, Type *def, bool
 		error(decl->attributes[0], "Attributes are not allowed on type declarations");
 	}
 
-	AstNode *te = remove_type_alias(type_expr);
+	bool is_distinct = is_type_distinct(type_expr);
+	AstNode *te = remove_type_alias_clutter(type_expr);
 	e->type = t_invalid;
 	String name = e->token.string;
 	Type *named = make_type_named(c->allocator, name, nullptr, e);
@@ -205,16 +241,20 @@ void check_type_decl(Checker *c, Entity *e, AstNode *type_expr, Type *def, bool
 
 	Type *bt = check_type(c, te, named);
 	named->Named.base = base_type(bt);
-	if (is_alias) {
-		if (is_type_named(bt)) {
-			e->type = bt;
-			e->TypeName.is_type_alias = true;
-		} else {
-			gbString str = type_to_string(bt);
-			error(type_expr, "Type alias declaration with a non-named type '%s'", str);
-			gb_string_free(str);
-		}
-	}
+	if (!is_distinct) {
+		e->type = bt;
+		e->TypeName.is_type_alias = true;
+	}
+	// if (is_alias) {
+	// 	if (is_type_named(bt)) {
+	// 		e->type = bt;
+	// 		e->TypeName.is_type_alias = true;
+	// 	} else {
+	// 		gbString str = type_to_string(bt);
+	// 		error(type_expr, "Type alias declaration with a non-named type '%s'", str);
+	// 		gb_string_free(str);
+	// 	}
+	// }
 }
 
 void check_const_decl(Checker *c, Entity *e, AstNode *type_expr, AstNode *init, Type *named_type) {
@@ -261,7 +301,7 @@ void check_const_decl(Checker *c, Entity *e, AstNode *type_expr, AstNode *init,
 				error(e->token, "A type declaration cannot have an type parameter");
 			}
 			d->type_expr = d->init_expr;
-			check_type_decl(c, e, d->type_expr, named_type, false);
+			check_type_decl(c, e, d->type_expr, named_type);
 			return;
 		}
 
@@ -866,8 +906,7 @@ void check_entity_decl(Checker *c, Entity *e, DeclInfo *d, Type *named_type) {
 		check_const_decl(c, e, d->type_expr, d->init_expr, named_type);
 		break;
 	case Entity_TypeName: {
-		bool is_alias = unparen_expr(d->type_expr)->kind == AstNode_AliasType;
-		check_type_decl(c, e, d->type_expr, named_type, is_alias);
+		check_type_decl(c, e, d->type_expr, named_type);
 		break;
 	}
 	case Entity_Procedure:
diff --git a/src/check_expr.cpp b/src/check_expr.cpp
index 0f874f5cd..e066a2c01 100644
--- a/src/check_expr.cpp
+++ b/src/check_expr.cpp
@@ -57,7 +57,7 @@ ExprKind check_expr_base                (Checker *c, Operand *operand, AstNode *
 void     check_expr_with_type_hint      (Checker *c, Operand *o, AstNode *e, Type *t);
 Type *   check_type                     (Checker *c, AstNode *expression, Type *named_type = nullptr);
 Type *   make_optional_ok_type          (gbAllocator a, Type *value);
-void     check_type_decl                (Checker *c, Entity *e, AstNode *type_expr, Type *def, bool alias);
+void     check_type_decl                (Checker *c, Entity *e, AstNode *type_expr, Type *def);
 Entity * check_selector                 (Checker *c, Operand *operand, AstNode *node, Type *type_hint);
 Entity * check_ident                    (Checker *c, Operand *o, AstNode *n, Type *named_type, Type *type_hint, bool allow_import_name);
 Entity * find_polymorphic_struct_entity (Checker *c, Type *original_type, isize param_count, Array<Operand> ordered_operands);
@@ -6255,12 +6255,11 @@ gbString write_expr_to_string(gbString str, AstNode *node) {
 		str = write_expr_to_string(str, ht->type);
 	case_end;
 
-	case_ast_node(ht, AliasType, node);
-		str = gb_string_appendc(str, "#type_alias ");
+	case_ast_node(ht, DistinctType, node);
+		str = gb_string_appendc(str, "distinct ");
 		str = write_expr_to_string(str, ht->type);
 	case_end;
 
-
 	case_ast_node(pt, PolyType, node);
 		str = gb_string_append_rune(str, '$');
 		str = write_expr_to_string(str, pt->type);
diff --git a/src/check_type.cpp b/src/check_type.cpp
index 167b55c75..3252c8bf6 100644
--- a/src/check_type.cpp
+++ b/src/check_type.cpp
@@ -1963,10 +1963,10 @@ bool check_type_internal(Checker *c, AstNode *e, Type **type, Type *named_type)
 		return check_type_internal(c, ht->type, type, named_type);
 	case_end;
 
-	case_ast_node(at, AliasType, e);
-		error(e, "Invalid use of '#type_alias'");
+	case_ast_node(dt, DistinctType, e);
+		error(e, "Invalid use of a distinct type");
 		// NOTE(bill): Treat it as a HelperType to remove errors
-		return check_type_internal(c, at->type, type, named_type);
+		return check_type_internal(c, dt->type, type, named_type);
 	case_end;
 
 	case_ast_node(pt, PolyType, e);
diff --git a/src/parser.cpp b/src/parser.cpp
index de028eb45..e37dffe25 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -80,7 +80,7 @@ Token ast_node_token(AstNode *node) {
 
 	case AstNode_TypeType:         return node->TypeType.token;
 	case AstNode_HelperType:       return node->HelperType.token;
-	case AstNode_AliasType:        return node->AliasType.token;
+	case AstNode_DistinctType:     return node->DistinctType.token;
 	case AstNode_PolyType:         return node->PolyType.token;
 	case AstNode_ProcType:         return node->ProcType.token;
 	case AstNode_PointerType:      return node->PointerType.token;
@@ -321,8 +321,8 @@ AstNode *clone_ast_node(gbAllocator a, AstNode *node) {
 	case AstNode_HelperType:
 		n->HelperType.type = clone_ast_node(a, n->HelperType.type);
 		break;
-	case AstNode_AliasType:
-		n->AliasType.type = clone_ast_node(a, n->AliasType.type);
+	case AstNode_DistinctType:
+		n->DistinctType.type = clone_ast_node(a, n->DistinctType.type);
 		break;
 	case AstNode_ProcType:
 		n->ProcType.params  = clone_ast_node(a, n->ProcType.params);
@@ -837,14 +837,13 @@ AstNode *ast_helper_type(AstFile *f, Token token, AstNode *type) {
 	return result;
 }
 
-AstNode *ast_alias_type(AstFile *f, Token token, AstNode *type) {
-	AstNode *result = make_ast_node(f, AstNode_AliasType);
-	result->AliasType.token = token;
-	result->AliasType.type  = type;
+AstNode *ast_distinct_type(AstFile *f, Token token, AstNode *type) {
+	AstNode *result = make_ast_node(f, AstNode_DistinctType);
+	result->DistinctType.token = token;
+	result->DistinctType.type  = type;
 	return result;
 }
 
-
 AstNode *ast_poly_type(AstFile *f, Token token, AstNode *type, AstNode *specialization) {
 	AstNode *result = make_ast_node(f, AstNode_PolyType);
 	result->PolyType.token = token;
@@ -1277,8 +1276,8 @@ bool is_semicolon_optional_for_node(AstFile *f, AstNode *s) {
 
 	case AstNode_HelperType:
 		return is_semicolon_optional_for_node(f, s->HelperType.type);
-	case AstNode_AliasType:
-		return is_semicolon_optional_for_node(f, s->AliasType.type);
+	case AstNode_DistinctType:
+		return is_semicolon_optional_for_node(f, s->DistinctType.type);
 
 	case AstNode_PointerType:
 		return is_semicolon_optional_for_node(f, s->PointerType.type);
@@ -1614,15 +1613,19 @@ AstNode *parse_operand(AstFile *f, bool lhs) {
 		return ast_paren_expr(f, operand, open, close);
 	}
 
+	case Token_distinct: {
+		Token token = expect_token(f, Token_distinct);
+		AstNode *type = parse_type(f);
+		return ast_distinct_type(f, token, type);
+	}
+
 	case Token_Hash: {
 		Token token = expect_token(f, Token_Hash);
 		if (allow_token(f, Token_type)) {
 			return ast_helper_type(f, token, parse_type(f));
 		}
 		Token name = expect_token(f, Token_Ident);
-		if (name.string == "type_alias") {
-			return ast_alias_type(f, token, parse_type(f));
-		} else if (name.string == "run") {
+		if (name.string == "run") {
 			AstNode *expr = parse_expr(f, false);
 			operand = ast_run_expr(f, token, name, expr);
 			if (unparen_expr(expr)->kind != AstNode_CallExpr) {
diff --git a/src/parser.hpp b/src/parser.hpp
index 67c063de5..8d15f3128 100644
--- a/src/parser.hpp
+++ b/src/parser.hpp
@@ -408,7 +408,7 @@ AST_NODE_KIND(_TypeBegin, "", struct {}) \
 		Token token; \
 		AstNode *type; \
 	}) \
-	AST_NODE_KIND(AliasType, "alias type", struct { \
+	AST_NODE_KIND(DistinctType, "distinct type", struct { \
 		Token token; \
 		AstNode *type; \
 	}) \
diff --git a/src/tokenizer.cpp b/src/tokenizer.cpp
index ad4bb511a..d19024026 100644
--- a/src/tokenizer.cpp
+++ b/src/tokenizer.cpp
@@ -110,6 +110,7 @@ TOKEN_KIND(Token__KeywordBegin, "_KeywordBegin"), \
 	TOKEN_KIND(Token_dynamic,                "dynamic"),                \
 	TOKEN_KIND(Token_cast,                   "cast"),                   \
 	TOKEN_KIND(Token_transmute,              "transmute"),              \
+	TOKEN_KIND(Token_distinct,               "distinct"),               \
 	TOKEN_KIND(Token_using,                  "using"),                  \
 	TOKEN_KIND(Token_inline,                 "inline"),                 \
 	TOKEN_KIND(Token_no_inline,              "no_inline"),              \