Alternative fix for the js-interop crash.

pkg/compiler/lib/src/native/behavior.dart

 // Copyright (c) 2014, 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.
 
 part of native;
 
 /// This class is a temporary work-around until we get a more powerful DartType.
 class SpecialType {
   final String name;
   const SpecialType._(this.name);
@@ skipping 627 matching lines @@
         resolver,
         isBuiltin: false,
         validTags: const ['returns', 'creates']);
 
     return behavior;
   }
 
   static NativeBehavior ofMethod(FunctionElement method,  Compiler compiler) {
     FunctionType type = method.computeType(compiler.resolution);
     var behavior = new NativeBehavior();
-    behavior.typesReturned.add(type.returnType);
+    var returnType = type.returnType;
+    bool isInterop = compiler.backend.isJsInterop(method);
+    // Note: For dart:html and other internal libraries we maintain, we can
+    // trust the return type and use it to limit what we enqueue. We have to
+    // be more conservative about JS interop types and assume they can return
+    // anything (unless the user provides the experimental flag to trust the
+    // type of js-interop APIs). We do restrict the allocation effects and say
+    // that interop calls create only interop types (which may be unsound if
+    // an interop call returns a DOM type and declares a dynamic return type,
+    // but otherwise we would include a lot of code by default).
+    // TODO(sigmund,sra): consider doing something better for numeric types.
+    behavior.typesReturned.add(
+        !isInterop || compiler.trustJSInteropTypeAnnotations ? returnType
+        : const DynamicType());
     if (!type.returnType.isVoid) {
       // Declared types are nullable.
       behavior.typesReturned.add(compiler.coreTypes.nullType);
     }
-    behavior._capture(type, compiler.resolution);
+    behavior._capture(type, compiler.resolution,
+        isInterop: isInterop, compiler: compiler);
 
     // TODO(sra): Optional arguments are currently missing from the
     // DartType. This should be fixed so the following work-around can be
     // removed.
     method.functionSignature.forEachOptionalParameter(
         (ParameterElement parameter) {
           behavior._escape(parameter.type, compiler.resolution);
         });
 
     behavior._overrideWithAnnotations(method, compiler);
     return behavior;
   }
 
   static NativeBehavior ofFieldLoad(MemberElement field, Compiler compiler) {
     Resolution resolution = compiler.resolution;
     DartType type = field.computeType(resolution);
     var behavior = new NativeBehavior();
-    behavior.typesReturned.add(type);
+    bool isInterop = compiler.backend.isJsInterop(field);
+    // TODO(sigmund,sra): consider doing something better for numeric types.
+    behavior.typesReturned.add(
+        !isInterop || compiler.trustJSInteropTypeAnnotations ? type
+        : const DynamicType());
     // Declared types are nullable.
     behavior.typesReturned.add(resolution.coreTypes.nullType);
-    behavior._capture(type, resolution);
+    behavior._capture(type, resolution,
+        isInterop: isInterop, compiler: compiler);
     behavior._overrideWithAnnotations(field, compiler);
     return behavior;
   }
 
   static NativeBehavior ofFieldStore(MemberElement field, Compiler compiler) {
     Resolution resolution = compiler.resolution;
     DartType type = field.computeType(resolution);
     var behavior = new NativeBehavior();
     behavior._escape(type, resolution);
     // We don't override the default behaviour - the annotations apply to
@@ skipping 73 matching lines @@
       _escape(functionType.returnType, resolution);
       for (DartType parameter in functionType.parameterTypes) {
         _capture(parameter, resolution);
       }
     }
   }
 
   /// Models the behavior of Dart code receiving instances and methods of [type]
   /// from native code.  We usually start the analysis by capturing a native
   /// method that has been used.
-  void _capture(DartType type, Resolution resolution) {
+  ///
+  /// We assume that JS-interop APIs cannot instantiate Dart types or
+  /// non-JSInterop native types.
+  void _capture(DartType type, Resolution resolution,
+      {bool isInterop: false, Compiler compiler}) {
     type.computeUnaliased(resolution);
     type = type.unaliased;
     if (type is FunctionType) {
       FunctionType functionType = type;
-      _capture(functionType.returnType, resolution);
+      _capture(functionType.returnType, resolution,
+          isInterop: isInterop, compiler: compiler);
       for (DartType parameter in functionType.parameterTypes) {
         _escape(parameter, resolution);
       }
     } else {
-      typesInstantiated.add(type);
+      DartType instantiated = null;
+      JavaScriptBackend backend = compiler?.backend;
+      if (!isInterop) {
+        typesInstantiated.add(type);
+      } else {
+        if (type.element != null && backend.isNative(type.element)) {
+          // Any declared native or interop type (isNative implies isJsInterop)
+          // is assumed to be allocated.
+          typesInstantiated.add(type);
+        }
+
+        if (!compiler.trustJSInteropTypeAnnotations ||
+          type.isDynamic || type.isObject) {
+          // By saying that only JS-interop types can be created, we prevent
+          // pulling in every other native type (e.g. all of dart:html) when a
+          // JS interop API returns dynamic or when we don't trust the type
+          // annotations. This means that to some degree we still use the return
+          // type to decide whether to include native types, even if we don't
+          // trust the type annotation.
+          typesInstantiated.add(
+              backend.helpers.jsJavaScriptObjectClass.thisType);
+        } else {
+          // Otherwise, when the declared type is a Dart type, we do not
+          // register an allocation because we assume it cannot be instantiated
+          // from within the JS-interop code. It must have escaped from another
+          // API.
+        }
+      }
     }
   }
 
   static dynamic _parseType(
       String typeString,
       Parsing parsing,
       lookup(name),
       locationNodeOrElement) {
     DiagnosticReporter reporter = parsing.reporter;
     if (typeString == '=Object') return SpecialType.JsObject;
@@ skipping 21 matching lines @@
         MessageKind.GENERIC,
         {'text': "Type '$typeString' not found."});
     return const DynamicType();
   }
 
   static _errorNode(locationNodeOrElement, Parsing parsing) {
     if (locationNodeOrElement is Node) return locationNodeOrElement;
     return locationNodeOrElement.parseNode(parsing);
   }
 }