cps_ir: Add JS checks, use argument nullability

pkg/compiler/lib/src/tree_ir/tree_ir_builder.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.
 
 library tree_ir_builder;
 
 import '../common.dart';
 import '../constants/values.dart';
 import '../cps_ir/cps_ir_nodes.dart' as cps_ir;
 import '../elements/elements.dart';
@@ skipping 607 matching lines @@
         node.dartType,
         node.target,
         node.selector,
         arguments,
         node.sourceInformation);
   }
 
   visitForeignCode(cps_ir.ForeignCode node) {
     List<Expression> arguments =
         node.arguments.map(getVariableUse).toList(growable: false);
-    if (HasCapturedArguments.check(node.codeTemplate.ast)) {
-      for (Expression arg in arguments) {
-        if (arg is VariableUse) {
-          arg.variable.isCaptured = true;
-        } else {
-          // TODO(asgerf): Avoid capture of 'this'.
-        }
-      }
-    }
+    List<bool> nullableArguments = node.arguments
+        .map((argument) => argument.definition.type.isNullable)
+        .toList(growable: false);
     if (node.codeTemplate.isExpression) {
       return new ForeignExpression(
           node.codeTemplate,
           node.type,
           arguments,
           node.nativeBehavior,
+          nullableArguments,
           node.dependency);
     } else {
       return (Statement next) {
         assert(next is Unreachable); // We are not using the `next` statement.
         return new ForeignStatement(
             node.codeTemplate,
             node.type,
             arguments,
             node.nativeBehavior,
+            nullableArguments,
             node.dependency);
       };
     }
   }
 
   visitNullCheck(cps_ir.NullCheck node) => (Statement next) {
     return new NullCheck(
         condition: getVariableUseOrNull(node.condition),
         value: getVariableUse(node.value),
         selector: node.selector,
@@ skipping 35 matching lines @@
     internalError(CURRENT_ELEMENT_SPANNABLE, 'Unexpected IR node: $node');
   }
 
   visitFunctionDefinition(cps_ir.FunctionDefinition node) {
     unexpectedNode(node);
   }
   visitParameter(cps_ir.Parameter node) => unexpectedNode(node);
   visitContinuation(cps_ir.Continuation node) => unexpectedNode(node);
   visitMutableVariable(cps_ir.MutableVariable node) => unexpectedNode(node);
 }
-
-class HasCapturedArguments extends js.BaseVisitor {
-  static bool check(js.Node node) {
-    HasCapturedArguments visitor = new HasCapturedArguments();
-    node.accept(visitor);
-    return visitor.found;
-  }
-
-  int enclosingFunctions = 0;
-  bool found = false;
-
-  @override
-  visitFun(js.Fun node) {
-    ++enclosingFunctions;
-    node.visitChildren(this);
-    --enclosingFunctions;
-  }
-
-  @override
-  visitInterpolatedNode(js.InterpolatedNode node) {
-    if (enclosingFunctions > 0) {
-      found = true;
-    }
-  }
-}