Generating mocks (reflect mode) fails if interface contains methods with generic types

[yz89122]

Actual behavior A clear and concise description of what the bug is.

Same issue from github.com/golang/mock golang/mock#677.

Interface:

package mypkg

type S struct{}

type GS[T any] struct {
	T T
}

type I interface {
	M() GS[*S]
}

Mock package:

package mypkgmock

//go:generate go run go.uber.org/mock/mockgen -destination=mock.go -package=$GOPACKAGE github.com/yz89122/gomock-test/mypkg I

Command:

go generate ./...

2024/04/24 06:33:24 Failed to format generated source code: mock.go:42:39: missing ',' in type argument list (and 1 more errors)
// Code generated by MockGen. DO NOT EDIT.
// Source: github.com/yz89122/gomock-test/mypkg (interfaces: I)
//
// Generated by this command:
//
//      mockgen -destination=mock.go -package=mypkgmock github.com/yz89122/gomock-test/mypkg I
//

// Package mypkgmock is a generated GoMock package.
package mypkgmock

import (
        mypkg "github.com/yz89122/gomock-test/mypkg"
        gomock "go.uber.org/mock/gomock"
        reflect "reflect"
)

// MockI is a mock of I interface.
type MockI struct {
        ctrl     *gomock.Controller
        recorder *MockIMockRecorder
}

// MockIMockRecorder is the mock recorder for MockI.
type MockIMockRecorder struct {
        mock *MockI
}

// NewMockI creates a new mock instance.
func NewMockI(ctrl *gomock.Controller) *MockI {
        mock := &MockI{ctrl: ctrl}
        mock.recorder = &MockIMockRecorder{mock}
        return mock
}

// EXPECT returns an object that allows the caller to indicate expected use.
func (m *MockI) EXPECT() *MockIMockRecorder {
        return m.recorder
}

// M mocks base method.
func (m *MockI) M() mypkg.GS[*github.com/yz89122/gomock-test/mypkg.S] {
        m.ctrl.T.Helper()
        ret := m.ctrl.Call(m, "M")
        ret0, _ := ret[0].(mypkg.GS[*github.com/yz89122/gomock-test/mypkg.S])
        return ret0
}

// M indicates an expected call of M.
func (mr *MockIMockRecorder) M() *gomock.Call {
        mr.mock.ctrl.T.Helper()
        return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "M", reflect.TypeOf((*MockI)(nil).M))
}
exit status 1

Expected behavior A clear and concise description of what you expected to
happen.

No error.

To Reproduce Steps to reproduce the behavior

1. Run go generate ./... for above code.

Additional Information

• gomock mode (reflect or source): reflect
• gomock version or git ref: v0.4.0
• golang version: 1.22.2

Triage Notes for the Maintainers

[cebilon123]

Okay, I find it annoying and it blocks me.
Can I take care of this one? 😄

[tchung1118]

@cebilon123 You can submit a PR if you have a fix. We welcome any contribution.

[arxeiss]

Any progress? If I understand correctly, there is some issue with reflect package itself.
But there should be new API in Go 1.22 based on this comment #197 (comment)

Can that help fix this issue too?