From 43bcc5945ef9776f36c73825043934d774b76dc4 Mon Sep 17 00:00:00 2001
From: Jennifer Messerly <jmesserly@google.com>
Date: Fri, 4 Nov 2016 17:37:13 -0700
Subject: [PATCH] fix #27766, allow implicit casts from dynamic to composite
 types

R=leafp@google.com

Review URL: https://codereview.chromium.org/2477093002 .
---
 CHANGELOG.md                                        | 13 +++++++++++++
 pkg/analyzer/lib/src/task/strong/checker.dart       |  2 +-
 pkg/analyzer/test/src/task/strong/checker_test.dart |  4 ++--
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a9e4b6f04a3..2f5b2389d15 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,19 @@ Patch release, resolves one issue:
 
 * Dartium: Fixes a bug that caused crashes.  No issue filed
 
+### Strong Mode
+
+* It is no longer a warning when casting from dynamic to a composite type
+    (SDK issue [27766](https://github.com/dart-lang/sdk/issues/27766)).
+
+    ```dart
+    main() {
+      dynamic obj = <int>[1, 2, 3];
+      // This is now allowed without a warning.
+      List<int> list = obj;
+    }
+    ```
+
 ## 1.20.0 - 2016-10-11
 
 ### Dart VM
diff --git a/pkg/analyzer/lib/src/task/strong/checker.dart b/pkg/analyzer/lib/src/task/strong/checker.dart
index e8c80c0a34f..4e2a092523c 100644
--- a/pkg/analyzer/lib/src/task/strong/checker.dart
+++ b/pkg/analyzer/lib/src/task/strong/checker.dart
@@ -1107,7 +1107,7 @@ class CodeChecker extends RecursiveAstVisitor {
         downCastComposite =
             typeArgs.isEmpty || typeArgs.any((t) => t.isDynamic);
       } else {
-        downCastComposite = true;
+        downCastComposite = !from.isDynamic;
       }
     }
 
diff --git a/pkg/analyzer/test/src/task/strong/checker_test.dart b/pkg/analyzer/test/src/task/strong/checker_test.dart
index 53d1bea19e0..6c22865f630 100644
--- a/pkg/analyzer/test/src/task/strong/checker_test.dart
+++ b/pkg/analyzer/test/src/task/strong/checker_test.dart
@@ -988,7 +988,7 @@ Stream<int> bar4() async* { yield /*error:YIELD_OF_INVALID_TYPE*/new Stream<int>
 
 baz1() async* { yield* /*info:DYNAMIC_CAST*/x; }
 Stream baz2() async* { yield* /*info:DYNAMIC_CAST*/x; }
-Stream<int> baz3() async* { yield* /*warning:DOWN_CAST_COMPOSITE*/x; }
+Stream<int> baz3() async* { yield* /*info:DYNAMIC_CAST*/x; }
 Stream<int> baz4() async* { yield* new Stream<int>(); }
 Stream<int> baz5() async* { yield* /*info:INFERRED_TYPE_ALLOCATION*/new Stream(); }
 ''');
@@ -1005,7 +1005,7 @@ Iterable<int> bar4() sync* { yield /*error:YIELD_OF_INVALID_TYPE*/bar3(); }
 
 baz1() sync* { yield* /*info:DYNAMIC_CAST*/x; }
 Iterable baz2() sync* { yield* /*info:DYNAMIC_CAST*/x; }
-Iterable<int> baz3() sync* { yield* /*warning:DOWN_CAST_COMPOSITE*/x; }
+Iterable<int> baz3() sync* { yield* /*info:DYNAMIC_CAST*/x; }
 Iterable<int> baz4() sync* { yield* bar3(); }
 Iterable<int> baz5() sync* { yield* /*info:INFERRED_TYPE_ALLOCATION*/new List(); }
 ''');