From f930d674ca43336aaa85a26b1a2cf4765a469f20 Mon Sep 17 00:00:00 2001
From: Paul Berry <paulberry@google.com>
Date: Sat, 18 May 2019 15:05:26 +0000
Subject: [PATCH] Restore old nullability behavior of
 TypeParameterElement.type.

It doesn't work to make TypeParameterElement.type choose
nullability/non-nullability based on the enclosing library, because
for type parameters of synthetic function types, there is no enclosing
library.

Change-Id: Ic74cc639534e3c03f3c46e7eacfb5655ca74019a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/102981
Auto-Submit: Paul Berry <paulberry@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
---
 .../lib/src/dart/element/element.dart         |  9 ++---
 .../test/src/summary/resynthesize_common.dart | 36 +++++++++++++++++++
 2 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/pkg/analyzer/lib/src/dart/element/element.dart b/pkg/analyzer/lib/src/dart/element/element.dart
index 693953a4f42..3543c8ec192 100644
--- a/pkg/analyzer/lib/src/dart/element/element.dart
+++ b/pkg/analyzer/lib/src/dart/element/element.dart
@@ -9572,10 +9572,11 @@ class TypeParameterElementImpl extends ElementImpl
   }
 
   TypeParameterType get type {
-    return _type ??= new TypeParameterTypeImpl(this,
-        nullabilitySuffix: library.isNonNullableByDefault
-            ? NullabilitySuffix.none
-            : NullabilitySuffix.star);
+    // Note: TypeParameterElement.type has nullability suffix `star` regardless
+    // of whether it appears in a migrated library.  This is because for type
+    // parameters of synthetic function types, the ancestor chain is broken and
+    // we can't find the enclosing library to tell whether it is migrated.
+    return _type ??= new TypeParameterTypeImpl(this);
   }
 
   void set type(TypeParameterType type) {
diff --git a/pkg/analyzer/test/src/summary/resynthesize_common.dart b/pkg/analyzer/test/src/summary/resynthesize_common.dart
index d43701a301e..0861f94e256 100644
--- a/pkg/analyzer/test/src/summary/resynthesize_common.dart
+++ b/pkg/analyzer/test/src/summary/resynthesize_common.dart
@@ -8,9 +8,11 @@ import 'package:analyzer/dart/analysis/declared_variables.dart';
 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/context/context.dart';
 import 'package:analyzer/src/dart/element/element.dart';
+import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/summary/idl.dart';
 import 'package:analyzer/src/summary/resynthesize.dart';
@@ -9438,6 +9440,40 @@ dynamic v;
 ''');
   }
 
+  test_type_param_generic_function_type_nullability_legacy() async {
+    featureSet = disableNnbd;
+    var library = await checkLibrary('''
+T f<T>(T t) {}
+var g = f;
+''');
+    checkElementText(library, '''
+T Function<T>(T) g;
+T f<T>(T t) {}
+''');
+    var g = library.definingCompilationUnit.topLevelVariables[0];
+    var t = (g.type as FunctionType).typeFormals[0];
+    // TypeParameterElement.type has a nullability suffix of `star` regardless
+    // of whether it appears in a migrated library.
+    expect((t.type as TypeImpl).nullabilitySuffix, NullabilitySuffix.star);
+  }
+
+  test_type_param_generic_function_type_nullability_migrated() async {
+    featureSet = enableNnbd;
+    var library = await checkLibrary('''
+T f<T>(T t) {}
+var g = f;
+''');
+    checkElementText(library, '''
+T Function<T>(T) g;
+T f<T>(T t) {}
+''');
+    var g = library.definingCompilationUnit.topLevelVariables[0];
+    var t = (g.type as FunctionType).typeFormals[0];
+    // TypeParameterElement.type has a nullability suffix of `star` regardless
+    // of whether it appears in a migrated library.
+    expect((t.type as TypeImpl).nullabilitySuffix, NullabilitySuffix.star);
+  }
+
   test_type_param_ref_nullability_none() async {
     featureSet = enableNnbd;
     var library = await checkLibrary('''