ast: fix fn_type_signature for anon functions with alias arguments (#13024)

vlib/v/ast/table.v

@@ -200,8 +200,13 @@ pub fn (t &Table) fn_type_signature(f &Fn) string {
 		// TODO: for now ignore mut/pts in sig for now
 		typ := arg.typ.set_nr_muls(0)
 		arg_type_sym := t.sym(typ)
-		sig += arg_type_sym.str().to_lower().replace_each(['.', '__', '&', '', '[', 'arr_', 'chan ',
-			'chan_', 'map[', 'map_of_', ']', '_to_', '<', '_T_', ',', '_', ' ', '', '>', ''])
+		if arg_type_sym.kind == .alias {
+			sig += arg_type_sym.cname
+		} else {
+			sig += arg_type_sym.str().to_lower().replace_each(['.', '__', '&', '', '[', 'arr_',
+				'chan ', 'chan_', 'map[', 'map_of_', ']', '_to_', '<', '_T_', ',', '_', ' ', '',
+				'>', ''])
+		}
 		if i < f.params.len - 1 {
 			sig += '_'
 		}
@@ -209,7 +214,11 @@ pub fn (t &Table) fn_type_signature(f &Fn) string {
 	if f.return_type != 0 && f.return_type != void_type {
 		sym := t.sym(f.return_type)
 		opt := if f.return_type.has_flag(.optional) { 'option_' } else { '' }
-		sig += '__$opt$sym.kind'
+		if sym.kind == .alias {
+			sig += '__$opt$sym.cname'
+		} else {
+			sig += '__$opt$sym.kind'
+		}
 	}
 	return sig
 }

vlib/v/tests/anon_fn_with_alias_args_test.v

@@ -0,0 +1,36 @@
+type MyString = string
+type MyInt = int
+
+struct S1 {
+	x fn (a int) MyString
+}
+
+struct S2 {
+	y fn (a int) MyInt
+}
+
+fn get_string(a int) MyString {
+	return '$a'
+}
+
+fn get_int(a int) MyInt {
+	return a
+}
+
+fn test_anon_fn_with_alias_args() {
+	s1 := S1{
+		x: get_string
+	}
+	println(s1.x)
+	ret1 := s1.x(22)
+	println(ret1)
+	assert ret1 == '22'
+
+	s2 := S2{
+		y: get_int
+	}
+	println(s2.y)
+	ret2 := s2.y(22)
+	println(ret2)
+	assert ret2 == 22
+}