default struct fields

compiler/parser/parser.odin

@@ -2532,6 +2532,7 @@ parse_record_body :: proc(
 	allow_anonymous_struct_payload := false,
 	allow_keyword_names := false,
 	tuple_result: ^bool = nil,
+	defaults: ^[dynamic]ast.Expr_Id = nil,
 ) -> bool {
 	if _, ok := allow(parser, .Left_Brace); !ok {
 		source.add(parser.diagnostics, current(parser).span, expected_open)
@@ -2557,6 +2558,9 @@ parse_record_body :: proc(
 			mode = 2
 			field_type := parse_type(parser)
 			append(fields, types.Field{name=0, type=field_type})
+			if defaults != nil {
+				append(defaults, ast.INVALID_EXPR)
+			}
 		} else {
 			if mode == 2 {
 				source.add(parser.diagnostics, current(parser).span, "struct fields cannot mix named and unnamed forms")
@@ -2575,6 +2579,14 @@ parse_record_body :: proc(
 			}
 			field_type := parse_record_field_type(parser, allow_anonymous_struct_payload)
 			append(fields, types.Field{name=u32(field_name.symbol), type=field_type})
+			if defaults != nil {
+				value := ast.INVALID_EXPR
+				if _, ok := allow(parser, .Equal); ok {
+					skip_newlines(parser)
+					value = parse_expression(parser)
+				}
+				append(defaults, value)
+			}
 		}
 		if _, ok := allow(parser, .Comma); ok {
 			skip_newlines(parser)
@@ -2678,6 +2690,9 @@ parse_struct :: proc(parser: ^Parser, name: token.Token, c_layout, file_hidden:
 	fields: [dynamic]types.Field
 	fields.allocator = parser.module.allocator
 	defer delete(fields)
+	defaults: [dynamic]ast.Expr_Id
+	defaults.allocator = parser.module.allocator
+	defer delete(defaults)
 	allow_anonymous_struct_payload := is_union && (inferred_tag || types.is_valid(declared_tag))
 	tuple := false
 	_ = parse_record_body(
@@ -2687,7 +2702,13 @@ parse_struct :: proc(parser: ^Parser, name: token.Token, c_layout, file_hidden:
 		allow_anonymous_struct_payload,
 		allow_anonymous_struct_payload,
 		&tuple,
+		&defaults,
 	)
+	for value in defaults {
+		if value != ast.INVALID_EXPR && (c_layout || is_union || tuple) {
+			source.add(parser.diagnostics, parser.module.exprs[value].span, "field defaults are only supported by named native structs")
+		}
+	}
 	if tuple && (c_layout || is_union) {
 		source.add(parser.diagnostics, start.span, "unnamed fields are only supported by native structs")
 		tuple = false
@@ -2697,6 +2718,19 @@ parse_struct :: proc(parser: ^Parser, name: token.Token, c_layout, file_hidden:
 	}
 	if !types.define_record(&parser.module.type_store, id, fields[:], c_layout, false, is_union, tag=tag, declared_tag=declared_tag, tuple=tuple) {
 		source.addf(parser.diagnostics, name.span, "duplicate type declaration '%s'", token_text(parser, name))
+	} else if !c_layout && !is_union && !tuple {
+		for value, index in defaults {
+			if value == ast.INVALID_EXPR {
+				continue
+			}
+			append(&parser.module.struct_field_defaults, ast.Struct_Field_Default{
+				record=id,
+				field=symbol.Id(fields[index].name),
+				expr=value,
+				pkg=parser.pkg,
+				file=parser.file,
+			})
+		}
 	}
 	_ = finish_statement(parser)
 }