Fix #2160 (deep subtyping through `using` of `_`)

1 files changed, 38 insertions, 0 deletions

diff --git a/src/types.cpp b/src/types.cpp
index fec324bf4..b9f2b375f 100644
--- a/src/types.cpp
+++ b/src/types.cpp
@@ -2526,6 +2526,44 @@ String lookup_subtype_polymorphic_field(Type *dst, Type *src) {
 	return str_lit("");
 }
 
+bool lookup_subtype_polymorphic_selection(Type *dst, Type *src, Selection *sel) {
+	Type *prev_src = src;
+	// Type *prev_dst = dst;
+	src = base_type(type_deref(src));
+	// dst = base_type(type_deref(dst));
+	bool src_is_ptr = src != prev_src;
+	// bool dst_is_ptr = dst != prev_dst;
+
+	GB_ASSERT(is_type_struct(src) || is_type_union(src));
+	for_array(i, src->Struct.fields) {
+		Entity *f = src->Struct.fields[i];
+		if (f->kind == Entity_Variable && f->flags & EntityFlags_IsSubtype) {
+			if (are_types_identical(dst, f->type)) {
+				array_add(&sel->index, cast(i32)i);
+				sel->entity = f;
+				return true;
+			}
+			if (src_is_ptr && is_type_pointer(dst)) {
+				if (are_types_identical(type_deref(dst), f->type)) {
+					array_add(&sel->index, cast(i32)i);
+					sel->indirect = true;
+					sel->entity = f;
+					return true;
+				}
+			}
+			if ((f->flags & EntityFlag_Using) != 0 && is_type_struct(f->type)) {
+				String name = lookup_subtype_polymorphic_field(dst, f->type);
+				if (name.len > 0) {
+					array_add(&sel->index, cast(i32)i);
+					return lookup_subtype_polymorphic_selection(dst, f->type, sel);
+				}
+			}
+		}
+	}
+	return false;
+}
+
+
 
 
 Type *strip_type_aliasing(Type *x) {