Fix issue 19424

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

Index: pkg/analyzer/lib/src/generated/resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/resolver.dart b/pkg/analyzer/lib/src/generated/resolver.dart
index aeaa9727d6cf9fa8e9abada540a80bfe19e84b8f..4ae165e44ca83c2cb1adf050a28a48ac716c0297 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -7923,6 +7923,15 @@ class LibraryImportScope extends Scope {
   }
 
   @override
+  Source getSource(AstNode node) {
+    Source source = super.getSource(node);
+    if (source == null) {
+      source = _definingLibrary.definingCompilationUnit.source;
+    }
+    return source;
+  }
+
+  @override
   Element internalLookup(Identifier identifier, String name, LibraryElement referencingLibrary) {
     Element foundElement = localLookup(name, referencingLibrary);
     if (foundElement != null) {