Constrain type annotations with deferred types.

sdk/lib/_internal/compiler/implementation/js/builder.dart

Index: sdk/lib/_internal/compiler/implementation/js/builder.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js/builder.dart b/sdk/lib/_internal/compiler/implementation/js/builder.dart
index ab05952753b919add5299320118378f664d213a3..f7c74e493ea826e60ce068a531cd9dbe68e1e673 100644
--- a/sdk/lib/_internal/compiler/implementation/js/builder.dart
+++ b/sdk/lib/_internal/compiler/implementation/js/builder.dart
@@ -45,6 +45,36 @@ class JsBuilder {
     return call(source, expression);
   }
 
+  /// Creates a litteral js string from [value].
+  LiteralString escapedString(String value) {
+    // Do not escape unicode characters and ' because they are allowed in the
+    // string literal anyway.
+    String escaped =
+        value.replaceAllMapped(new RegExp('\n|"|\\|\0|\b|\t|\v'), (match) {
+      switch (match.group(0)) {
+        case "\n" : return r"\n";
+        case "\\" : return r"\\";
+        case "\"" : return r'\"';
+        case "\0" : return r"\0";
+        case "\b" : return r"\b";
+        case "\t" : return r"\t";
+        case "\f" : return r"\f";
+        case "\v" : return r"\v";
+      }
+    });
+    LiteralString result = string(escaped);
+    // We don't escape ' under the assumption that the string is wrapped
+    // into ". Verify that assumption.
+    assert(result.value.codeUnitAt(0) == '"');
+    return result;
+  }
+
+  /// Creates a litteral js string from [value].
+  ///
+  /// Note that this function only puts quotes around [value]. It does not do
+  /// any escaping, so use only when you can guarantee that [value] does not
+  /// contain newlines or backslashes. For escaping the string use
+  /// [escapedString].
   LiteralString string(String value) => new LiteralString('"$value"');
 
   LiteralNumber number(num value) => new LiteralNumber('$value');