gopls/internal/lsp/source: fix renaming of type parameters

Type parameters were incorrectly being treated as exported for the
purpose of renaming checks, and imported type parameters do not have the
correct scope information for rename checks to work.

Fixes golang/go#61635

Change-Id: I4261c5e7b3622affbeb81a96ea4f510a5b9e4fe3
Reviewed-on: https://go-review.googlesource.com/c/tools/+/513916
gopls-CI: kokoro <[email protected]>
Reviewed-by: Hyang-Ah Hana Kim <[email protected]>
Run-TryBot: Robert Findley <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

gopls/internal/lsp/source/rename.go

@@ -350,8 +350,13 @@ func renameOrdinary(ctx context.Context, snapshot Snapshot, f FileHandle, pp pro
 		// So we take a scenic route.
 		switch obj.(type) { // avoid "obj :=" since cases reassign the var
 		case *types.TypeName:
-			if named, ok := obj.Type().(*types.Named); ok {
-				obj = named.Obj()
+			switch t := obj.Type().(type) {
+			case *types.Named:
+				obj = t.Obj()
+			case *typeparams.TypeParam:
+				// As with capitalized function parameters below, type parameters are
+				// local.
+				goto skipObjectPath
 			}
 		case *types.Func:
 			obj = funcOrigin(obj.(*types.Func))

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

@@ -0,0 +1,117 @@
+This test exercises various renaming features on generic code.
+
+Fixed bugs:
+
+- golang/go#61614: renaming a method of a type in a package that uses type
+  parameter composite lits used to panic, because previous iterations of the
+  satisfy analysis did not account for this language feature.
+
+- golang/go#61635: renaming type parameters did not work when they were
+  capitalized and the package was imported by another package.
+
+-- flags --
+-min_go=go1.18
+
+-- go.mod --
+module example.com
+go 1.20
+
+-- a.go --
+package a
+
+type I int
+
+func (I) m() {} //@rename("m", M, mToM)
+
+func _[P ~[]int]() {
+	_ = P{}
+}
+
+-- @mToM/a.go --
+package a
+
+type I int
+
+func (I) M() {} //@rename("m", M, mToM)
+
+func _[P ~[]int]() {
+	_ = P{}
+}
+
+-- g.go --
+package a
+
+type S[P any] struct { //@rename("P", Q, PToQ)
+	P P
+	F func(P) P
+}
+
+func F[R any](r R) {
+	var _ R //@rename("R", S, RToS)
+}
+
+-- @PToQ/g.go --
+package a
+
+type S[Q any] struct { //@rename("P", Q, PToQ)
+	P Q
+	F func(Q) Q
+}
+
+func F[R any](r R) {
+	var _ R //@rename("R", S, RToS)
+}
+
+-- @RToS/g.go --
+package a
+
+type S[P any] struct { //@rename("P", Q, PToQ)
+	P P
+	F func(P) P
+}
+
+func F[S any](r S) {
+	var _ S //@rename("R", S, RToS)
+}
+
+-- issue61635/p.go --
+package issue61635
+
+type builder[S ~[]F, F ~string] struct { //@rename("S", T, SToT)
+	name string
+	elements S
+	elemData map[F][]ElemData[F]
+	// other fields...
+}
+
+type ElemData[F ~string] struct {
+  Name F
+  // other fields...
+}
+
+type BuilderImpl[S ~[]F, F ~string] struct{ builder[S, F] }
+
+-- importer/i.go --
+package importer
+
+import "example.com/issue61635" // importing is necessary to repro golang/go#61635
+
+var _ issue61635.ElemData[string]
+
+-- @SToT/issue61635/p.go --
+package issue61635
+
+type builder[T ~[]F, F ~string] struct { //@rename("S", T, SToT)
+	name string
+	elements T
+	elemData map[F][]ElemData[F]
+	// other fields...
+}
+
+type ElemData[F ~string] struct {
+  Name F
+  // other fields...
+}
+
+type BuilderImpl[S ~[]F, F ~string] struct{ builder[S, F] }
+