feat: go 1.24 generic type aliases

Author: hpidcock

mockgen/internal/tests/generics/generics.go

@@ -6,7 +6,7 @@ import (
 )
 
 //go:generate mockgen --source=generics.go --destination=source/mock_generics_mock.go --package source
-//go:generate mockgen --destination=package_mode/mock_test.go --package=package_mode . Bar,Universe,MilkyWay,SolarSystem,Earth,Water
+//go:generate mockgen --destination=package_mode/mock_test.go --package=package_mode . Bar,BarAliasIntString,Universe,MilkyWay,SolarSystem,Earth,Water
 
 type Bar[T any, R any] interface {
 	One(string) string
@@ -30,9 +30,14 @@ type Bar[T any, R any] interface {
 	Nineteen() AliasType
 }
 
+// BarAliasIntString is an alias of a generic type.
+type BarAliasIntString = Bar[int, string]
+
 type Foo[T any, R any] struct{}
 
-type Baz[T any] struct{}
+type Baz[T any] struct {
+	V T
+}
 
 type Iface[T any] any
 

mockgen/internal/tests/generics/generics_alias.go

@@ -0,0 +1,18 @@
+//go:build go1.24
+
+package generics
+
+//go:generate mockgen --build_constraint go1.24 --destination=package_mode/mock_generics_alias_test.go --package=package_mode . BarAliasTString,BarAliasIntR,BarAliasIntBazR,BarAliasIntBazString
+
+// BarAliasTString is a generic alias of a generic with one complete and one
+// generic type arg.
+type BarAliasTString[T any] = Bar[T, string]
+
+// BarAliasIntR is a generic alias of a generic with a renamed type param.
+type BarAliasIntR[Q any] = Bar[int, Q]
+
+// BarAliasIntBazR is a generic alias of a generic alias with a generic type arg.
+type BarAliasIntBazR[Q any] = Bar[int, Baz[Q]]
+
+// BarAliasIntBazString is an alias of a generic alias.
+type BarAliasIntBazString = BarAliasIntBazR[string]

mockgen/internal/tests/generics/package_mode/generics_alias_test.go

@@ -0,0 +1,58 @@
+//go:build go1.24
+
+package package_mode
+
+import (
+	"testing"
+
+	"go.uber.org/mock/gomock"
+	"go.uber.org/mock/mockgen/internal/tests/generics"
+)
+
+func TestMockGenericAliasOfGeneric(t *testing.T) {
+	ctrl := gomock.NewController(t)
+
+	m := NewMockBarAliasIntR[string](ctrl)
+	m.EXPECT().Three(10).Return("bar")
+
+	alias := generics.Bar[int, string](m)
+	if v := alias.Three(10); v != "bar" {
+		t.Errorf("Three(10) = %v, want %v", v, "bar")
+	}
+}
+
+func TestMockGenericAliasOfGenericWithRenamedTypeParam(t *testing.T) {
+	ctrl := gomock.NewController(t)
+
+	m := NewMockBarAliasTString[int](ctrl)
+	m.EXPECT().Three(10).Return("bar")
+
+	alias := generics.Bar[int, string](m)
+	if v := alias.Three(10); v != "bar" {
+		t.Errorf("Three(10) = %v, want %v", v, "bar")
+	}
+}
+
+func TestMockGenericAliasOfGenericWithGenericTypeArg(t *testing.T) {
+	ctrl := gomock.NewController(t)
+
+	m := NewMockBarAliasIntBazR[string](ctrl)
+	m.EXPECT().Three(10).Return(generics.Baz[string]{V: "bar"})
+
+	alias := generics.Bar[int, generics.Baz[string]](m)
+	if v := alias.Three(10); v != (generics.Baz[string]{V: "bar"}) {
+		t.Errorf("Three(10) = %v, want %v", v, "bar")
+	}
+}
+
+func TestMockAliasOfInstatiatedGenericAlias(t *testing.T) {
+	ctrl := gomock.NewController(t)
+
+	m := NewMockBarAliasIntBazString(ctrl)
+	m.EXPECT().Three(10).Return(generics.Baz[string]{V: "bar"})
+
+	alias := generics.Bar[int, generics.Baz[string]](m)
+	if v := alias.Three(10); v != (generics.Baz[string]{V: "bar"}) {
+		t.Errorf("Three(10) = %v, want %v", v, "bar")
+	}
+}

mockgen/internal/tests/generics/package_mode/generics_test.go

@@ -0,0 +1,50 @@
+package package_mode
+
+import (
+	"context"
+	"testing"
+
+	"go.uber.org/mock/gomock"
+	"go.uber.org/mock/mockgen/internal/tests/generics"
+)
+
+func TestMockEmbeddingIface_One(t *testing.T) {
+	ctrl := gomock.NewController(t)
+
+	m := NewMockEmbeddingIface[int, float64](ctrl)
+	m.EXPECT().One("foo").Return("bar")
+	if v := m.One("foo"); v != "bar" {
+		t.Errorf("One() = %v, want %v", v, "bar")
+	}
+}
+
+func TestMockUniverse_Water(t *testing.T) {
+	ctrl := gomock.NewController(t)
+
+	m := NewMockUniverse[int](ctrl)
+	m.EXPECT().Water(1024)
+	m.Water(1024)
+}
+
+func TestNewMockGroup_Join(t *testing.T) {
+	ctrl := gomock.NewController(t)
+
+	m := NewMockGroup[generics.Generator[any]](ctrl)
+	ctx := context.TODO()
+	m.EXPECT().Join(ctx).Return(nil)
+	if v := m.Join(ctx); v != nil {
+		t.Errorf("Join() = %v, want %v", v, nil)
+	}
+}
+
+func TestMockAliasOfInstantiatedGeneric(t *testing.T) {
+	ctrl := gomock.NewController(t)
+
+	m := NewMockBarAliasIntString(ctrl)
+	m.EXPECT().Three(10).Return("bar")
+
+	alias := generics.Bar[int, string](m)
+	if v := alias.Three(10); v != "bar" {
+		t.Errorf("Three(10) = %v, want %v", v, "bar")
+	}
+}