ast, parser, checker: fix generic struct field with default struct value (#13158)

vlib/v/ast/ast.v

@@ -405,6 +405,7 @@ pub:
 pub mut:
 	unresolved           bool
 	pre_comments         []Comment
+	typ_str              string
 	typ                  Type
 	update_expr          Expr
 	update_expr_type     Type

vlib/v/checker/struct.v

@@ -325,8 +325,17 @@ pub fn (mut c Checker) struct_init(mut node ast.StructInit) ast.Type {
 				}
 			}
 			// Check uninitialized refs/sum types
-			for field in info.fields {
+			for i, field in info.fields {
-				if field.has_default_expr || field.name in inited_fields {
+				if field.name in inited_fields {
+					continue
+				}
+				if field.has_default_expr {
+					if field.default_expr is ast.StructInit && field.default_expr_typ == 0 {
+						idx := c.table.find_type_idx(field.default_expr.typ_str)
+						if idx != 0 {
+							info.fields[i].default_expr_typ = ast.new_type(idx)
+						}
+					}
 					continue
 				}
 				if field.typ.is_ptr() && !field.typ.has_flag(.shared_f) && !node.has_update_expr

vlib/v/parser/fn.v

@@ -126,7 +126,7 @@ pub fn (mut p Parser) call_args() []ast.CallArg {
 		mut expr := ast.empty_expr()
 		if p.tok.kind == .name && p.peek_tok.kind == .colon {
 			// `foo(key:val, key2:val2)`
-			expr = p.struct_init(true) // short_syntax:true
+			expr = p.struct_init(p.mod + '.' + p.tok.lit, true) // short_syntax:true
 		} else {
 			expr = p.expr(0)
 		}

vlib/v/parser/parser.v

@@ -2288,11 +2288,11 @@ pub fn (mut p Parser) name_expr() ast.Expr {
 			p.check(.rcbr)
 			return map_init
 		}
-		return p.struct_init(false) // short_syntax: false
+		return p.struct_init(p.mod + '.' + p.tok.lit, false) // short_syntax: false
 	} else if p.peek_tok.kind == .lcbr && p.inside_if && lit0_is_capital && !known_var
 		&& language == .v {
 		// if a == Foo{} {...}
-		return p.struct_init(false)
+		return p.struct_init(p.mod + '.' + p.tok.lit, false)
 	} else if p.peek_tok.kind == .dot && (lit0_is_capital && !known_var && language == .v) {
 		// T.name
 		if p.is_generic_name() {

vlib/v/parser/struct.v

@@ -335,7 +335,7 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 	}
 }
 
-fn (mut p Parser) struct_init(short_syntax bool) ast.StructInit {
+fn (mut p Parser) struct_init(typ_str string, short_syntax bool) ast.StructInit {
 	first_pos := (if short_syntax && p.prev_tok.kind == .lcbr { p.prev_tok } else { p.tok }).position()
 	typ := if short_syntax { ast.void_type } else { p.parse_type() }
 	p.expr_mod = ''
@@ -416,6 +416,7 @@ fn (mut p Parser) struct_init(short_syntax bool) ast.StructInit {
 	p.is_amp = saved_is_amp
 	return ast.StructInit{
 		unresolved: typ.has_flag(.generic)
+		typ_str: typ_str
 		typ: typ
 		fields: fields
 		update_expr: update_expr

vlib/v/tests/generics_struct_field_with_default_struct_value_test.v

@@ -0,0 +1,22 @@
+module main
+
+struct None {}
+
+type OptError = None | string
+
+struct Opt<T> {
+	value T
+	error OptError = None{}
+}
+
+struct MessageModify {
+	text Opt<string>
+}
+
+fn test_generic_struct_field_with_default_struct_value() {
+	edit_query := MessageModify{Opt<string>{
+		value: 'Hello there!'
+	}}
+	println(edit_query)
+	assert edit_query.text.value == 'Hello there!'
+}