cgen: fix alias enum used in comptime $for (fix #25211) (#25212)

vlib/v/gen/c/comptime.v

@@ -781,7 +781,12 @@ fn (mut g Gen) comptime_for(node ast.ComptimeFor) {
 					if g.pref.translated && node.typ.is_number() {
 						g.writeln('_const_main__${val};')
 					} else {
-						g.writeln('${g.styp(node.typ)}__${val};')
+						node_sym := g.table.sym(node.typ)
+						if node_sym.info is ast.Alias {
+							g.writeln('${g.styp(node_sym.info.parent_type)}__${val};')
+						} else {
+							g.writeln('${g.styp(node.typ)}__${val};')
+						}
 					}
 					enum_attrs := sym.info.attrs[val]
 					if enum_attrs.len == 0 {

vlib/v/tests/comptime/comptime_enum_values_test.v

@@ -5,6 +5,8 @@ enum CharacterGroup {
 	special
 }
 
+type AnotherCharGroup = CharacterGroup
+
 fn (self CharacterGroup) value() string {
 	return match self {
 		.chars { 'first' }
@@ -33,3 +35,21 @@ fn test_main() {
 	assert values == [CharacterGroup.chars, CharacterGroup.alphanumerics, CharacterGroup.numeric,
 		CharacterGroup.special]
 }
+
+fn test_alias_enum() {
+	mut values := []EnumData{}
+	$for entry in AnotherCharGroup.values {
+		values << entry
+	}
+	assert values[0].value == int(CharacterGroup.chars)
+	assert values[0].name == CharacterGroup.chars.str()
+
+	assert values[1].value == int(CharacterGroup.alphanumerics)
+	assert values[1].name == CharacterGroup.alphanumerics.str()
+
+	assert values[2].value == int(CharacterGroup.numeric)
+	assert values[2].name == CharacterGroup.numeric.str()
+
+	assert values[3].value == int(CharacterGroup.special)
+	assert values[3].name == CharacterGroup.special.str()
+}