Better casting of for-in loops.

pkg/analyzer/test/src/task/strong/checker_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // TODO(jmesserly): this file needs to be refactored, it's a port from
 // package:dev_compiler's tests
 /// General type checking tests
 library analyzer.test.src.task.strong.checker_test;
 
 import 'package:unittest/unittest.dart';
@@ skipping 69 matching lines @@
         do {} while (/*warning:NON_BOOL_CONDITION*/i);
 
         for (;b;) {}
         for (;/*info:DYNAMIC_CAST*/dyn;) {}
         for (;/*info:DOWN_CAST_IMPLICIT*/obj;) {}
         for (;/*warning:NON_BOOL_CONDITION*/i;) {}
       }
     ''');
   });
 
+  test('for-in casts supertype sequence to iterable', () {
+    checkFile('''
+      main() {
+        dynamic d;
+        for (var i in /*info:DYNAMIC_CAST*/d) {}
+
+        Object o;
+        for (var i in /*info:DOWN_CAST_IMPLICIT*/o) {}
+      }
+    ''');
+  });
+
+  test('await for-in casts supertype sequence to stream', () {
+    checkFile('''
+      main() async {
+        dynamic d;
+        await for (var i in /*info:DYNAMIC_CAST*/d) {}
+
+        Object o;
+        await for (var i in /*info:DOWN_CAST_IMPLICIT*/o) {}
+      }
+    ''');
+  });
+
+  test('for-in casts iterable element to variable', () {
+    checkFile('''
+      main() {
+        // Don't choke if sequence is not iterable.
+        for (var i in /*warning:FOR_IN_OF_INVALID_TYPE*/1234) {}
+
+        // Dynamic cast.
+        for (String /*info:DYNAMIC_CAST*/s in <dynamic>[]) {}
+
+        // Identity cast.
+        for (String s in <String>[]) {}
+
+        // Untyped.
+        for (var s in <String>[]) {}
+
+        // Downcast.
+        for (int /*info:DOWN_CAST_IMPLICIT*/i in <num>[]) {}
+      }
+    ''');
+  });
+
+  test('await for-in casts stream element to variable', () {
+    checkFile('''
+      import 'dart:async';
+      main() async {
+        // Don't choke if sequence is not stream.
+        await for (var i in /*warning:FOR_IN_OF_INVALID_TYPE*/1234) {}
+
+        // Dynamic cast.
+        await for (String /*info:DYNAMIC_CAST*/s in new Stream<dynamic>()) {}
+
+        // Identity cast.
+        await for (String s in new Stream<String>()) {}
+
+        // Untyped.
+        await for (var s in new Stream<String>()) {}
+
+        // Downcast.
+        await for (int /*info:DOWN_CAST_IMPLICIT*/i in new Stream<num>()) {}
+      }
+    ''');
+  });
+
   test('dynamic invocation', () {
     checkFile('''
       class A {
         dynamic call(dynamic x) => x;
       }
       class B extends A {
         int call(int x) => x;
         double col(double x) => x;
       }
       void main() {
@@ skipping 2806 matching lines @@
 
         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> baz4() sync* { yield* bar3(); }
         Iterable<int> baz5() sync* { yield* /*info:INFERRED_TYPE_ALLOCATION*/new List(); }
     ''');
     });
   });
 }