gopls/internal/lsp/source: add receiver name to stubbed methods

Fixes golang/go#64078

Change-Id: Ib551119b04a36d0be0929a3f949b052b598f57ad
Reviewed-on: https://go-review.googlesource.com/c/tools/+/544916
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Robert Findley <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: tttoad

gopls/internal/cmd/integration_test.go

@@ -978,7 +978,7 @@ var _ io.Reader = C{}
 type C struct{}
 
 // Read implements io.Reader.
-func (C) Read(p []byte) (n int, err error) {
+func (c C) Read(p []byte) (n int, err error) {
 	panic("unimplemented")
 }
 `[1:]

gopls/internal/lsp/source/stub.go

@@ -190,17 +190,46 @@ func stubMethodsFixer(ctx context.Context, snapshot *cache.Snapshot, pkg *cache.
 		star = "*"
 	}
 
+	// If there are any that have named receiver, choose the first one.
+	// Otherwise, use lowercase for the first letter of the object.
+	rn := strings.ToLower(si.Concrete.Obj().Name()[0:1])
+	for i := 0; i < si.Concrete.NumMethods(); i++ {
+		if recv, ok := si.Concrete.Method(i).Type().(*types.Signature); ok && recv.Recv().Name() != "" {
+			rn = recv.Recv().Name()
+			break
+		}
+	}
+
+	// Check for receiver name conflicts
+	checkRecvName := func(tuple *types.Tuple) bool {
+		for i := 0; i < tuple.Len(); i++ {
+			if rn == tuple.At(i).Name() {
+				return true
+			}
+		}
+		return false
+	}
+
 	// Format the new methods.
 	var newMethods bytes.Buffer
+
 	for index := range missing {
+		mrn := rn + " "
+		if sig, ok := missing[index].fn.Type().(*types.Signature); ok {
+			if checkRecvName(sig.Params()) || checkRecvName(sig.Results()) {
+				mrn = ""
+			}
+		}
+
 		fmt.Fprintf(&newMethods, `// %s implements %s.
-%sfunc (%s%s%s) %s%s {
+%sfunc (%s%s%s%s) %s%s {
 	panic("unimplemented")
 }
 `,
 			missing[index].fn.Name(),
 			iface,
 			missing[index].needSubtle,
+			mrn,
 			star,
 			si.Concrete.Obj().Name(),
 			FormatTypeParams(si.Concrete.TypeParams()),

gopls/internal/test/marker/testdata/stubmethods/basic.txt

@@ -13,7 +13,7 @@ var _ error = C(0) //@suggestedfix(re"C.0.", re"missing method Error", stub)
 -- @stub/a/a.go --
 @@ -5 +5,5 @@
 +// Error implements error.
-+func (C) Error() string {
++func (c C) Error() string {
 +	panic("unimplemented")
 +}
 +

gopls/internal/test/marker/testdata/stubmethods/issue61693.txt

@@ -20,7 +20,7 @@ func _() {
 -- @stub/main.go --
 @@ -5 +5,5 @@
 +// Error implements error.
-+func (C) Error() string {
++func (c C) Error() string {
 +	panic("unimplemented")
 +}
 +

gopls/internal/test/marker/testdata/stubmethods/issue61830.txt

@@ -18,7 +18,7 @@ var _ I = &A{} //@suggestedfix(re"&A..", re"missing method M", stub)
 -- @stub/p.go --
 @@ -13 +13,5 @@
 +// M implements I.
-+func (*A) M(io.Reader, B) {
++func (a *A) M(io.Reader, B) {
 +	panic("unimplemented")
 +}
 +

gopls/internal/test/marker/testdata/stubmethods/issue64078.txt

@@ -0,0 +1,36 @@
+This test verifies that the named receiver is generated.
+
+-- p.go --
+package p
+
+type A struct{}
+
+func (aa *A) M1() {
+	panic("unimplemented")
+}
+
+type I interface {
+	M1()
+	M2(aa string)
+	M3(bb string)
+	M4() (aa string)
+}
+
+var _ I = &A{} //@suggestedfix(re"&A..", re"missing method M", stub)
+-- @stub/p.go --
+@@ -5 +5,15 @@
++// M2 implements I.
++func (*A) M2(aa string) {
++	panic("unimplemented")
++}
++
++// M3 implements I.
++func (aa *A) M3(bb string) {
++	panic("unimplemented")
++}
++
++// M4 implements I.
++func (*A) M4() (aa string) {
++	panic("unimplemented")
++}
++

gopls/internal/test/marker/testdata/stubmethods/issue64114.txt

@@ -27,11 +27,11 @@ type WriteStruct struct {
 +
 +// RRRR implements WriteTest.
 +// Subtle: this method shadows the method (WriterTwoStruct).RRRR of WriteStruct.WriterTwoStruct.
-+func (*WriteStruct) RRRR() {
++func (w *WriteStruct) RRRR() {
 +	panic("unimplemented")
 +}
 +
 +// WWWW implements WriteTest.
-+func (*WriteStruct) WWWW() {
++func (w *WriteStruct) WWWW() {
 +	panic("unimplemented")
 +}

gopls/internal/test/marker/testdata/suggestedfix/stub.txt

@@ -53,7 +53,7 @@ type byteWriter struct{}
 @@ -12 +12,5 @@
 +
 +// WriteByte implements io.ByteWriter.
-+func (*byteWriter) WriteByte(c byte) error {
++func (b *byteWriter) WriteByte(c byte) error {
 +	panic("unimplemented")
 +}
 -- assign_multivars.go --
@@ -73,7 +73,7 @@ type multiByteWriter struct{}
 @@ -13 +13,5 @@
 +
 +// WriteByte implements io.ByteWriter.
-+func (*multiByteWriter) WriteByte(c byte) error {
++func (m *multiByteWriter) WriteByte(c byte) error {
 +	panic("unimplemented")
 +}
 -- call_expr.go --
@@ -94,7 +94,7 @@ type callExpr struct{}
 @@ -14 +14,5 @@
 +
 +// Error implements error.
-+func (*callExpr) Error() string {
++func (c *callExpr) Error() string {
 +	panic("unimplemented")
 +}
 -- embedded.go --
@@ -116,22 +116,22 @@ type embeddedInterface interface {
 -- @embedded/embedded.go --
 @@ -12 +12,20 @@
 +// Len implements embeddedInterface.
-+func (*embeddedConcrete) Len() int {
++func (e *embeddedConcrete) Len() int {
 +	panic("unimplemented")
 +}
 +
 +// Less implements embeddedInterface.
-+func (*embeddedConcrete) Less(i int, j int) bool {
++func (e *embeddedConcrete) Less(i int, j int) bool {
 +	panic("unimplemented")
 +}
 +
 +// Read implements embeddedInterface.
-+func (*embeddedConcrete) Read(p []byte) (n int, err error) {
++func (e *embeddedConcrete) Read(p []byte) (n int, err error) {
 +	panic("unimplemented")
 +}
 +
 +// Swap implements embeddedInterface.
-+func (*embeddedConcrete) Swap(i int, j int) {
++func (e *embeddedConcrete) Swap(i int, j int) {
 +	panic("unimplemented")
 +}
 +
@@ -148,7 +148,7 @@ type customErr struct{}
 @@ -9 +9,5 @@
 +
 +// Error implements error.
-+func (*customErr) Error() string {
++func (c *customErr) Error() string {
 +	panic("unimplemented")
 +}
 -- function_return.go --
@@ -167,7 +167,7 @@ type closer struct{}
 @@ -12 +12,5 @@
 +
 +// Close implements io.Closer.
-+func (closer) Close() error {
++func (c closer) Close() error {
 +	panic("unimplemented")
 +}
 -- generic_receiver.go --
@@ -187,7 +187,7 @@ type genReader[T, Y any] struct {
 @@ -13 +13,5 @@
 +
 +// ReadFrom implements io.ReaderFrom.
-+func (*genReader[T, Y]) ReadFrom(r io.Reader) (n int64, err error) {
++func (g *genReader[T, Y]) ReadFrom(r io.Reader) (n int64, err error) {
 +	panic("unimplemented")
 +}
 -- ignored_imports.go --
@@ -213,7 +213,7 @@ type ignoredResetter struct{}
 @@ -19 +19,5 @@
 +
 +// Reset implements zlib.Resetter.
-+func (*ignoredResetter) Reset(r Reader, dict []byte) error {
++func (i *ignoredResetter) Reset(r Reader, dict []byte) error {
 +	panic("unimplemented")
 +}
 -- issue2606.go --
@@ -227,7 +227,7 @@ var _ I = C(0) //@suggestedfix("C", re"does not implement", issue2606)
 -- @issue2606/issue2606.go --
 @@ -7 +7,5 @@
 +// Error implements I.
-+func (C) Error() string {
++func (c C) Error() string {
 +	panic("unimplemented")
 +}
 +
@@ -247,7 +247,7 @@ type multiVar struct{}
 @@ -12 +12,5 @@
 +
 +// Read implements io.Reader.
-+func (*multiVar) Read(p []byte) (n int, err error) {
++func (m *multiVar) Read(p []byte) (n int, err error) {
 +	panic("unimplemented")
 +}
 -- pointer.go --
@@ -264,7 +264,7 @@ type pointerImpl struct{}
 @@ -10 +10,5 @@
 +
 +// ReadFrom implements io.ReaderFrom.
-+func (*pointerImpl) ReadFrom(r io.Reader) (n int64, err error) {
++func (p *pointerImpl) ReadFrom(r io.Reader) (n int64, err error) {
 +	panic("unimplemented")
 +}
 -- renamed_import.go --
@@ -283,7 +283,7 @@ type myIO struct{}
 @@ -12 +12,5 @@
 +
 +// Reset implements zlib.Resetter.
-+func (*myIO) Reset(r myio.Reader, dict []byte) error {
++func (m *myIO) Reset(r myio.Reader, dict []byte) error {
 +	panic("unimplemented")
 +}
 -- renamed_import_iface.go --
@@ -307,7 +307,7 @@ type otherInterfaceImpl struct{}
 @@ -14 +16,5 @@
 +
 +// Get implements other.Interface.
-+func (*otherInterfaceImpl) Get(context.Context) *bytes.Buffer {
++func (o *otherInterfaceImpl) Get(context.Context) *bytes.Buffer {
 +	panic("unimplemented")
 +}
 -- stdlib.go --
@@ -324,7 +324,7 @@ type writer struct{}
 @@ -10 +10,5 @@
 +
 +// Write implements io.Writer.
-+func (writer) Write(p []byte) (n int, err error) {
++func (w writer) Write(p []byte) (n int, err error) {
 +	panic("unimplemented")
 +}
 -- typedecl_group.go --
@@ -354,12 +354,12 @@ func _() {
 -- @typedecl_group/typedecl_group.go --
 @@ -18 +18,10 @@
 +// Close implements io.ReadCloser.
-+func (rdcloser) Close() error {
++func (r rdcloser) Close() error {
 +	panic("unimplemented")
 +}
 +
 +// Read implements io.ReadCloser.
-+func (rdcloser) Read(p []byte) (n int, err error) {
++func (r rdcloser) Read(p []byte) (n int, err error) {
 +	panic("unimplemented")
 +}
 +