From 9bffff6dfc49f32ea1d979609979e9da3c0011f0 Mon Sep 17 00:00:00 2001
From: Brian Wilkerson <brianwilkerson@google.com>
Date: Fri, 1 Nov 2019 21:52:48 +0000
Subject: [PATCH] Fix exception in migration of ?? operator when the right hand
 side is a generic type

Change-Id: Ie372522f9493e2ccea8284f8583b0f43153adbbd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/123884
Reviewed-by: Paul Berry <paulberry@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
---
 pkg/nnbd_migration/lib/src/edge_builder.dart   | 4 +++-
 pkg/nnbd_migration/test/edge_builder_test.dart | 9 +++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/pkg/nnbd_migration/lib/src/edge_builder.dart b/pkg/nnbd_migration/lib/src/edge_builder.dart
index c881f7cbb78..11598f24511 100644
--- a/pkg/nnbd_migration/lib/src/edge_builder.dart
+++ b/pkg/nnbd_migration/lib/src/edge_builder.dart
@@ -378,7 +378,9 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
           rightType = rightOperand.accept(this);
         });
         var ifNullNode = NullabilityNode.forIfNotNull();
-        expressionType = DecoratedType(node.staticType, ifNullNode);
+        expressionType = _decorateUpperOrLowerBound(
+            node, node.staticType, leftType, rightType, true,
+            node: ifNullNode);
         _connect(
             rightType.node, expressionType.node, IfNullOrigin(source, node));
       } finally {
diff --git a/pkg/nnbd_migration/test/edge_builder_test.dart b/pkg/nnbd_migration/test/edge_builder_test.dart
index 20b6a224186..9e3cc4e0a25 100644
--- a/pkg/nnbd_migration/test/edge_builder_test.dart
+++ b/pkg/nnbd_migration/test/edge_builder_test.dart
@@ -1201,6 +1201,15 @@ int f(int i, int j) => i ?? j;
     assertEdge(right, expression, guards: [left], hard: false);
   }
 
+  test_binaryExpression_questionQuestion_genericReturnType() async {
+    await analyze('''
+class C<E> {
+  C<E> operator +(C<E> c) => this;
+}
+C<int> f(C<int> i, C<int> j) => i ?? j;
+''');
+  }
+
   test_binaryExpression_right_dynamic() async {
     await analyze('''
 class C {