fix(go_indexer): fix refs to anonymous members across packages (#5195)

kythe/go/indexer/BUILD

@@ -231,6 +231,12 @@ go_indexer_test(
     srcs = ["testdata/basic/anonymous.go"],
 )
 
+go_indexer_test(
+    name = "anonref_test",
+    srcs = ["testdata/basic/anonref.go"],
+    deps = [":anonymous_test"],
+)
+
 go_indexer_test(
     name = "structinit_test",
     srcs = ["testdata/structinit.go"],

kythe/go/indexer/indexer.go

@@ -588,7 +588,7 @@ func (pi *PackageInfo) newSignature(obj types.Object) (tag, base string) {
 				_, base := pi.newSignature(owner)
 				return tagField, base + "." + t.Name()
 			}
-			return tagField, fmt.Sprintf("[%p].%s", t, t.Name())
+			return tagField, pi.anonSignature(t)
 		} else if owner, ok := pi.owner[t]; ok {
 			_, base := pi.newSignature(owner)
 			return tagParam, base + ":" + t.Name()
@@ -620,7 +620,7 @@ func (pi *PackageInfo) newSignature(obj types.Object) (tag, base string) {
 		}
 
 	case *types.Label:
-		return tagLabel, fmt.Sprintf("[%p].%s", t, t.Name())
+		return tagLabel, pi.anonSignature(t)
 
 	default:
 		log.Panicf("Unexpected object kind: %T", obj)
@@ -638,7 +638,17 @@ func (pi *PackageInfo) newSignature(obj types.Object) (tag, base string) {
 	}
 
 	// Objects in interior (local) scopes, i.e., everything else.
-	return topLevelTag, fmt.Sprintf("[%p].%s", obj, obj.Name())
+	return topLevelTag, pi.anonSignature(obj)
+}
+
+func (pi *PackageInfo) anonSignature(obj types.Object) string {
+	// Use the object's line number and file basename to differentiate the
+	// node while allowing for cross-package references (other parts of the
+	// Position may differ).  This may collide if a source file isn't gofmt'd
+	// and defines multiple anonymous fields with the same name on the same
+	// line, but that's unlikely to happen in practice.
+	pos := pi.FileSet.Position(obj.Pos())
+	return fmt.Sprintf("[%s#%d].%s", filepath.Base(pos.Filename), pos.Line, obj.Name())
 }
 
 // addOwners updates pi.owner from the types in pkg, adding mapping from fields

kythe/go/indexer/testdata/basic/anonref.go

@@ -0,0 +1,9 @@
+package anonref
+
+import (
+	anonymous "kythe/go/indexer/anonymous_test"
+)
+
+//- @Struct ref Struct
+//- @V ref V
+var _ = anonymous.Struct.V

kythe/go/indexer/testdata/basic/anonymous.go

@@ -28,7 +28,9 @@ func f(planx struct {
 	return planx.T
 }
 
-var v = struct {
+//- @Struct defines/binding Struct
+//- Struct.node/kind variable
+var Struct = struct {
 	//- @V defines/binding V
 	//- V.node/kind variable
 	//- V.subkind field
@@ -39,7 +41,7 @@ var v = struct {
 }
 
 //- @V ref V
-var _ = v.V
+var _ = Struct.V
 
 var w struct {
 	//- @X defines/binding X