Issue 29360. Fix type name resolution for GenericTypeAliasElement.

pkg/analyzer/lib/src/dart/element/element.dart

Index: pkg/analyzer/lib/src/dart/element/element.dart
diff --git a/pkg/analyzer/lib/src/dart/element/element.dart b/pkg/analyzer/lib/src/dart/element/element.dart
index 58e3d96b370a3d5bf567f3bcc023871e9f67d4dc..e3c4ed967a0de4559113ed62602df9f953501576 100644
--- a/pkg/analyzer/lib/src/dart/element/element.dart
+++ b/pkg/analyzer/lib/src/dart/element/element.dart
@@ -5236,6 +5236,10 @@ class GenericTypeAliasElementImpl extends ElementImpl
    * `dynamic` will be used in place of each of the type arguments.
    */
   FunctionType typeAfterSubstitution(List<DartType> typeArguments) {
+    GenericFunctionTypeElement function = this.function;
+    if (function == null) {
+      return null;
+    }
     FunctionType functionType = function.type;
     List<TypeParameterElement> parameterElements = typeParameters;
     List<DartType> parameterTypes =