cgen: avoid double generic str suffix for options

Author: medvednikov

vlib/v/gen/c/auto_str_methods.v

@@ -1218,7 +1218,7 @@ fn (mut g Gen) gen_str_for_struct(info ast.Struct, lang ast.Language, styp strin
 			}
 			if !g.pref.new_generic_solver {
 				if str_method := sym.find_method_with_generic_parent('str') {
-					if str_method.generic_names.len > 0 {
+					if str_method.generic_names.len > 0 && !ftyp_noshared.has_flag(.option) {
 						match sym.info {
 							ast.Struct, ast.SumType, ast.Interface, ast.Alias {
 								field_fn_name = g.generic_fn_name(g.str_method_concrete_types(ftyp_noshared, sym),

vlib/v/tests/generics/generic_sumtype_str_test.v

@@ -6,6 +6,10 @@ struct MaybeContainer[T] {
 	value Maybe[T]
 }
 
+struct MaybeOptionalContainer[T] {
+	value ?Maybe[T]
+}
+
 pub fn (m Maybe[T]) str[T]() string {
 	return if m is T {
 		x := m as T
@@ -87,3 +91,10 @@ fn test_auto_str_struct_field_with_generic_sumtype_str() {
 	}
 	assert '${c}'.contains('value: Some(456)')
 }
+
+fn test_auto_str_optional_field_with_generic_sumtype_str() {
+	c := MaybeOptionalContainer[int]{
+		value: some(789)
+	}
+	assert '${c}'.contains('Some(789)')
+}