Support tearoffs in the new emitter.

pkg/compiler/lib/src/js_emitter/class_stub_generator.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 dart2js.js_emitter;
 
 class ClassStubGenerator {
   final Namer namer;
   final Compiler compiler;
   final JavaScriptBackend backend;
@@ skipping 169 matching lines @@
     jsAst.Expression function;
     if (backend.isInterceptedName(selector.name)) {
       function = js(r'function($receiver, #) { return # }',
                               [parameterNames, expression]);
     } else {
       function = js(r'function(#) { return # }', [parameterNames, expression]);
     }
     return new StubMethod(name, function);
   }
 }
+
+/// Creates two JavaScript functions: `tearOffGetter` and `tearOff`.
+///
+/// `tearOffGetter` is internal and only used by `tearOff`.
+///
+/// `tearOff` takes the following arguments:
+///   * `funcs`: a list of functions. These are the functions representing the
+///    member that is torn off. There can be more than one, since a member
+///    can have several stubs.
+///    Each function must have the `$callName` property set.
+///   * `reflectionInfo`: contains reflective information, and the function
+///    type. TODO(floitsch): point to where this is specified.
+///   * `isStatic`.
+///   * `name`.
+///   * `isIntercepted.
+List<jsAst.Statement> buildTearOffCode(JavaScriptBackend backend) {
+  Namer namer = backend.namer;
+  Compiler compiler = backend.compiler;
+
+  Element closureFromTearOff = backend.findHelper('closureFromTearOff');
+  String tearOffAccessText;
+  jsAst.Expression tearOffAccessExpression;
+  String tearOffGlobalObjectName;
+  String tearOffGlobalObject;
+  if (closureFromTearOff != null) {
+    // We need both the AST that references [closureFromTearOff] and a string
+    // for the NoCsp version that constructs a function.
+    tearOffAccessExpression =
+        backend.emitter.staticFunctionAccess(closureFromTearOff);
+    tearOffAccessText =
+        jsAst.prettyPrint(tearOffAccessExpression, compiler).getText();
+    tearOffGlobalObjectName = tearOffGlobalObject =
+        namer.globalObjectFor(closureFromTearOff);
+  } else {
+    // Default values for mocked-up test libraries.
+    tearOffAccessText =
+        r'''function() { throw 'Helper \'closureFromTearOff\' missing.' }''';
+    tearOffAccessExpression = js(tearOffAccessText);
+    tearOffGlobalObjectName = 'MissingHelperFunction';
+    tearOffGlobalObject = '($tearOffAccessText())';
+  }
+
+  jsAst.Statement tearOffGetter;
+  if (!compiler.useContentSecurityPolicy) {
+    // This template is uncached because it is constructed from code fragments
+    // that can change from compilation to compilation.  Some of these could be
+    // avoided, except for the string literals that contain the compiled access
+    // path to 'closureFromTearOff'.
+    tearOffGetter = js.uncachedStatementTemplate('''
+function tearOffGetter(funcs, reflectionInfo, name, isIntercepted) {
+  return isIntercepted
+      ? new Function("funcs", "reflectionInfo", "name",
+                     "$tearOffGlobalObjectName", "c",
+          "return function tearOff_" + name + (functionCounter++) + "(x) {" +
+            "if (c === null) c = $tearOffAccessText(" +
+                "this, funcs, reflectionInfo, false, [x], name);" +
+                "return new c(this, funcs[0], x, name);" +
+                "}")(funcs, reflectionInfo, name, $tearOffGlobalObject, null)
+      : new Function("funcs", "reflectionInfo", "name",
+                     "$tearOffGlobalObjectName", "c",
+          "return function tearOff_" + name + (functionCounter++)+ "() {" +
+            "if (c === null) c = $tearOffAccessText(" +
+                "this, funcs, reflectionInfo, false, [], name);" +
+                "return new c(this, funcs[0], null, name);" +
+                "}")(funcs, reflectionInfo, name, $tearOffGlobalObject, null);
+}''').instantiate([]);
+  } else {
+    tearOffGetter = js.statement('''
+      function tearOffGetter(funcs, reflectionInfo, name, isIntercepted) {
+        var cache = null;
+        return isIntercepted
+            ? function(x) {
+                if (cache === null) cache = #(
+                    this, funcs, reflectionInfo, false, [x], name);
+                return new cache(this, funcs[0], x, name);
+              }
+            : function() {
+                if (cache === null) cache = #(
+                    this, funcs, reflectionInfo, false, [], name);
+                return new cache(this, funcs[0], null, name);
+              };
+      }''', [tearOffAccessExpression, tearOffAccessExpression]);
+  }
+
+  jsAst.Statement tearOff = js.statement('''
+    function tearOff(funcs, reflectionInfo, isStatic, name, isIntercepted) {
+      var cache;
+      return isStatic
+          ? function() {
+              if (cache === void 0) cache = #tearOff(
+                  this, funcs, reflectionInfo, true, [], name).prototype;
+              return cache;
+            }
+          : tearOffGetter(funcs, reflectionInfo, name, isIntercepted);
+    }''',  {'tearOff': tearOffAccessExpression});
+
+  return <jsAst.Statement>[tearOffGetter, tearOff];
+}