gopls/rename: Fix spurious package name conflicts.

Fixes golang/go#67069

Change-Id: I537308c8941a5f2f2c6e10791e75b529574d170b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/586336
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Alan Donovan <adonovan@google.com>

gopls/internal/golang/rename_check.go

@@ -167,18 +167,20 @@ func (r *renamer) checkInPackageBlock(from types.Object) {
 		}
 	}
 
-	// Check for conflicts between package block and all file blocks.
-	for _, f := range r.pkg.Syntax() {
-		fileScope := r.pkg.TypesInfo().Scopes[f]
-		b, prev := fileScope.LookupParent(r.to, token.NoPos)
-		if b == fileScope {
-			r.errorf(from.Pos(), "renaming this %s %q to %q would conflict", objectKind(from), from.Name(), r.to)
-			var prevPos token.Pos
-			if prev != nil {
-				prevPos = prev.Pos()
+	// In the declaring package, check for conflicts between the
+	// package block and all file blocks.
+	if from.Pkg() == r.pkg.Types() {
+		for _, f := range r.pkg.Syntax() {
+			fileScope := r.pkg.TypesInfo().Scopes[f]
+			if fileScope == nil {
+				continue // type error? (golang/go#40835)
+			}
+			b, prev := fileScope.LookupParent(r.to, token.NoPos)
+			if b == fileScope {
+				r.errorf(from.Pos(), "renaming this %s %q to %q would conflict", objectKind(from), from.Name(), r.to)
+				r.errorf(prev.Pos(), "\twith this %s", objectKind(prev))
+				return // since checkInPackageBlock would report redundant errors
 			}
-			r.errorf(prevPos, "\twith this %s", objectKind(prev))
-			return // since checkInPackageBlock would report redundant errors
 		}
 	}
 
@@ -436,7 +438,6 @@ func (r *renamer) checkLabel(label *types.Label) {
 // checkStructField checks that the field renaming will not cause
 // conflicts at its declaration, or ambiguity or changes to any selection.
 func (r *renamer) checkStructField(from *types.Var) {
-
 	// If this is the declaring package, check that the struct
 	// declaration is free of field conflicts, and field/method
 	// conflicts.

gopls/internal/test/marker/testdata/rename/issue67069.txt

@@ -0,0 +1,54 @@
+This test verifies spurious pkgname conflicts.
+Issue golang/go#67069.
+
+-- go.mod --
+module example
+go 1.19
+
+-- aa/a.go --
+package aa
+
+var cc int //@rename("cc", "aa", CToA)
+const C = 0
+const D = 0
+
+-- aa/a_test.go --
+package aa_test
+
+import "example/aa"
+
+var _ = aa.C //@rename("aa", "bb", AToB)
+-- @CToA/aa/a.go --
+@@ -3 +3 @@
+-var cc int //@rename("cc", "aa", CToA)
++var aa int //@rename("cc", "aa", CToA)
+-- @AToB/aa/a_test.go --
+@@ -3 +3 @@
+-import "example/aa"
++import bb "example/aa"
+@@ -5 +5 @@
+-var _ = aa.C //@rename("aa", "bb", AToB)
++var _ = bb.C //@rename("aa", "bb", AToB)
+-- bb/b.go --
+package bb
+
+import "example/aa"
+
+var _ = aa.C
+var bb int //@renameerr("bb", "aa", errImportConflict)
+
+-- @errImportConflict --
+bb/b.go:6:5: renaming this var "bb" to "aa" would conflict
+bb/b.go:3:8:	with this imported package name
+-- aa/a_internal_test.go --
+package aa
+
+var _ = D //@rename("D", "aa", DToA)
+-- @DToA/aa/a_internal_test.go --
+@@ -3 +3 @@
+-var _ = D //@rename("D", "aa", DToA)
++var _ = aa //@rename("D", "aa", DToA)
+-- @DToA/aa/a.go --
+@@ -5 +5 @@
+-const D = 0
++const aa = 0