gopls/internal/lsp/source: fix incorrect 'origin' logic for named types

Type names of named types are always canonical. The existing logic to
canonicalize them was ineffective, and had the side effect of breaking
aliases.

Also add more tests of generic name renaming.

Fixes golang/go#61625

Change-Id: I318a758176aea6712da16dde29394ffb08bdf715
Reviewed-on: https://go-review.googlesource.com/c/tools/+/513917
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>

gopls/internal/lsp/source/rename.go

@@ -343,17 +343,15 @@ func renameOrdinary(ctx context.Context, snapshot Snapshot, f FileHandle, pp pro
 	// Find objectpath, if object is exported ("" otherwise).
 	var declObjPath objectpath.Path
 	if obj.Exported() {
-		// objectpath.For requires the origin of a generic
-		// function or type, not an instantiation (a bug?).
-		// Unfortunately we can't call {Func,TypeName}.Origin
-		// as these are not available in go/types@go1.18.
-		// So we take a scenic route.
+		// objectpath.For requires the origin of a generic function or type, not an
+		// instantiation (a bug?). Unfortunately we can't call Func.Origin as this
+		// is not available in go/types@go1.18. So we take a scenic route.
+		//
+		// Note that unlike Funcs, TypeNames are always canonical (they are "left"
+		// of the type parameters, unlike methods).
 		switch obj.(type) { // avoid "obj :=" since cases reassign the var
 		case *types.TypeName:
-			switch t := obj.Type().(type) {
-			case *types.Named:
-				obj = t.Obj()
-			case *typeparams.TypeParam:
+			if _, ok := obj.Type().(*typeparams.TypeParam); ok {
 				// As with capitalized function parameters below, type parameters are
 				// local.
 				goto skipObjectPath

gopls/internal/regtest/marker/testdata/rename/basic.txt

@@ -3,12 +3,28 @@ This test performs basic coverage of 'rename' within a single package.
 -- basic.go --
 package p
 
-func f(x int) { println(x) } //@rename("x", y, param_x)
+func f(x int) { println(x) } //@rename("x", y, xToy)
 
--- @param_x/basic.go --
+-- @xToy/basic.go --
 package p
 
-func f(y int) { println(y) } //@rename("x", y, param_x)
+func f(y int) { println(y) } //@rename("x", y, xToy)
+
+-- alias.go --
+package p
+
+// from golang/go#61625
+type LongNameHere struct{}
+type A = LongNameHere //@rename("A", B, AToB)
+func Foo() A
+
+-- @AToB/alias.go --
+package p
+
+// from golang/go#61625
+type LongNameHere struct{}
+type B = LongNameHere //@rename("A", B, AToB)
+func Foo() B
 
 -- errors.go --
 package p

gopls/internal/regtest/marker/testdata/rename/generics.txt

@@ -115,3 +115,126 @@ type ElemData[F ~string] struct {
 
 type BuilderImpl[S ~[]F, F ~string] struct{ builder[S, F] }
 
+-- instances/type.go --
+package instances
+
+type R[P any] struct { //@rename("R", u, Rtou)
+	Next *R[P] //@rename("R", s, RTos)
+}
+
+func (rv R[P]) Do(R[P]) R[P] { //@rename("Do", Do1, DoToDo1)
+	var x R[P]
+	return rv.Do(x) //@rename("Do", Do2, DoToDo2)
+}
+
+func _() {
+	var x R[int] //@rename("R", r, RTor)
+	x = x.Do(x)
+}
+
+-- @RTos/instances/type.go --
+package instances
+
+type s[P any] struct { //@rename("R", u, Rtou)
+	Next *s[P] //@rename("R", s, RTos)
+}
+
+func (rv s[P]) Do(s[P]) s[P] { //@rename("Do", Do1, DoToDo1)
+	var x s[P]
+	return rv.Do(x) //@rename("Do", Do2, DoToDo2)
+}
+
+func _() {
+	var x s[int] //@rename("R", r, RTor)
+	x = x.Do(x)
+}
+
+-- @Rtou/instances/type.go --
+package instances
+
+type u[P any] struct { //@rename("R", u, Rtou)
+	Next *u[P] //@rename("R", s, RTos)
+}
+
+func (rv u[P]) Do(u[P]) u[P] { //@rename("Do", Do1, DoToDo1)
+	var x u[P]
+	return rv.Do(x) //@rename("Do", Do2, DoToDo2)
+}
+
+func _() {
+	var x u[int] //@rename("R", r, RTor)
+	x = x.Do(x)
+}
+
+-- @DoToDo1/instances/type.go --
+package instances
+
+type R[P any] struct { //@rename("R", u, Rtou)
+	Next *R[P] //@rename("R", s, RTos)
+}
+
+func (rv R[P]) Do1(R[P]) R[P] { //@rename("Do", Do1, DoToDo1)
+	var x R[P]
+	return rv.Do1(x) //@rename("Do", Do2, DoToDo2)
+}
+
+func _() {
+	var x R[int] //@rename("R", r, RTor)
+	x = x.Do1(x)
+}
+
+-- @DoToDo2/instances/type.go --
+package instances
+
+type R[P any] struct { //@rename("R", u, Rtou)
+	Next *R[P] //@rename("R", s, RTos)
+}
+
+func (rv R[P]) Do2(R[P]) R[P] { //@rename("Do", Do1, DoToDo1)
+	var x R[P]
+	return rv.Do2(x) //@rename("Do", Do2, DoToDo2)
+}
+
+func _() {
+	var x R[int] //@rename("R", r, RTor)
+	x = x.Do2(x)
+}
+
+-- instances/func.go --
+package instances
+
+func Foo[P any](p P) { //@rename("Foo", Bar, FooToBar)
+	Foo(p) //@rename("Foo", Baz, FooToBaz)
+}
+
+-- @FooToBar/instances/func.go --
+package instances
+
+func Bar[P any](p P) { //@rename("Foo", Bar, FooToBar)
+	Bar(p) //@rename("Foo", Baz, FooToBaz)
+}
+
+-- @FooToBaz/instances/func.go --
+package instances
+
+func Baz[P any](p P) { //@rename("Foo", Bar, FooToBar)
+	Baz(p) //@rename("Foo", Baz, FooToBaz)
+}
+
+-- @RTor/instances/type.go --
+package instances
+
+type r[P any] struct { //@rename("R", u, Rtou)
+	Next *r[P] //@rename("R", s, RTos)
+}
+
+func (rv r[P]) Do(r[P]) r[P] { //@rename("Do", Do1, DoToDo1)
+	var x r[P]
+	return rv.Do(x) //@rename("Do", Do2, DoToDo2)
+}
+
+func _() {
+	var x r[int] //@rename("R", r, RTor)
+	x = x.Do(x)
+}
+