dart2js: emit tear-offs in new emitter.

pkg/compiler/lib/src/js_emitter/class_stub_generator.dart

Index: pkg/compiler/lib/src/js_emitter/class_stub_generator.dart
diff --git a/pkg/compiler/lib/src/js_emitter/class_stub_generator.dart b/pkg/compiler/lib/src/js_emitter/class_stub_generator.dart
index d7e1578c9962a0ecc46ba159681e45a0fd10f593..79dbcf607969116f933e64700799161b5a6b3a8a 100644
--- a/pkg/compiler/lib/src/js_emitter/class_stub_generator.dart
+++ b/pkg/compiler/lib/src/js_emitter/class_stub_generator.dart
@@ -112,3 +112,101 @@ class ClassStubGenerator {
     return generatedStubs;
   }
 }
+
+/// 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];
+}