Fix equality between subclasses of Source

pkg/analyzer/lib/src/generated/source_io.dart

Index: pkg/analyzer/lib/src/generated/source_io.dart
diff --git a/pkg/analyzer/lib/src/generated/source_io.dart b/pkg/analyzer/lib/src/generated/source_io.dart
index 491e3ebc5be551eb1b2130952781f190f344f5cd..b7cb0fd5373789875a2b4a022b6f301df7d4c82d 100644
--- a/pkg/analyzer/lib/src/generated/source_io.dart
+++ b/pkg/analyzer/lib/src/generated/source_io.dart
@@ -239,8 +239,14 @@ class FileBasedSource extends Source {
   }
 
   @override
-  bool operator ==(Object object) =>
-      object is FileBasedSource && id == object.id;
+  bool operator ==(Object object) {
+    if (object is FileBasedSource) {
+      return id == object.id;
+    } else if (object is Source) {
+      return uri == object.uri;
+    }
+    return false;
+  }
 
   @override
   bool exists() => file.isFile();