Support call methods on functions

Fixes #624

R=jmesserly@google.com

Review URL: https://codereview.chromium.org/2255993002 .

Author: vsmenon

lib/src/compiler/code_generator.dart

@@ -3180,6 +3180,19 @@ class CodeGenerator extends GeneralizingAstVisitor
     if (target == null || isLibraryPrefix(target)) {
       return _emitFunctionCall(node);
     }
+    if (node.methodName.name == 'call') {
+      var targetType = target.staticType;
+      if (targetType is FunctionType) {
+        // Call methods on function types should be handled as regular function
+        // invocations.
+        return _emitFunctionCall(node);
+      }
+      if (targetType.isDartCoreFunction || targetType.isDynamic) {
+        // TODO(vsm): Can a call method take generic type parameters?
+        return _emitDynamicInvoke(node, _visit(target),
+            _visit(node.argumentList) as List<JS.Expression>);
+      }
+    }
 
     return _emitMethodCall(target, node);
   }
@@ -3273,22 +3286,27 @@ class CodeGenerator extends GeneralizingAstVisitor
     return new JS.Call(jsTarget, args);
   }
 
+  JS.Expression _emitDynamicInvoke(
+      InvocationExpression node, JS.Expression fn, List<JS.Expression> args) {
+    var typeArgs = _emitInvokeTypeArguments(node);
+    if (typeArgs != null) {
+      return js.call('dart.dgcall(#, #, #)',
+          [fn, new JS.ArrayInitializer(typeArgs), args]);
+    } else {
+      if (_inWhitelistCode(node, isCall: true)) {
+        return new JS.Call(fn, args);
+      }
+      return js.call('dart.dcall(#, #)', [fn, args]);
+    }
+  }
+
   /// Emits a function call, to a top-level function, local function, or
   /// an expression.
   JS.Expression _emitFunctionCall(InvocationExpression node) {
     var fn = _visit(node.function);
     var args = _visit(node.argumentList) as List<JS.Expression>;
     if (isDynamicInvoke(node.function)) {
-      var typeArgs = _emitInvokeTypeArguments(node);
-      if (typeArgs != null) {
-        return js.call('dart.dgcall(#, #, #)',
-            [fn, new JS.ArrayInitializer(typeArgs), args]);
-      } else {
-        if (_inWhitelistCode(node, isCall: true)) {
-          return new JS.Call(fn, args);
-        }
-        return js.call('dart.dcall(#, #)', [fn, args]);
-      }
+      return _emitDynamicInvoke(node, fn, args);
     } else {
       return new JS.Call(_applyInvokeTypeArguments(fn, node), args);
     }

test/codegen/language/call_function_test.dart

@@ -0,0 +1,39 @@
+// Copyright (c) 2015, 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.
+
+import "package:expect/expect.dart";
+
+Object bar(Object x) { return x; }
+
+Function baz = bar;
+
+dynamic dyn = bar;
+
+class Foo {
+  Object call(Object x) { return 'Foo$x'; }
+}
+
+typedef Object FooType(Object x);
+FooType foo = bar;
+
+void main() {
+  Expect.equals(42, bar.call(42));
+  Expect.equals(42, baz.call(42));
+  Expect.equals(42, foo.call(42));
+  Expect.equals(42, dyn.call(42));
+  Expect.equals(42, bar(42));
+  Expect.equals(42, baz(42));
+  Expect.equals(42, foo(42));
+  Expect.equals(42, dyn(42));
+
+  baz = new Foo();
+  foo = new Foo();
+  dyn = new Foo();
+  Expect.equals('Foo42', baz.call(42));
+  Expect.equals('Foo42', foo.call(42));
+  Expect.equals('Foo42', dyn.call(42));
+  Expect.equals('Foo42', baz(42));
+  Expect.equals('Foo42', foo(42));
+  Expect.equals('Foo42', dyn(42));
+}

test/codegen_expected/varargs.js

@@ -11,12 +11,12 @@ dart_library.library('varargs', null, /* Imports */[
   let dynamicTodynamic = () => (dynamicTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [dart.dynamic])))();
   varargs.varargsTest = function(x, ...others) {
     let args = [1, others];
-    dart.dsend(x, 'call', ...args);
+    dart.dcall(x, ...args);
   };
   dart.fn(varargs.varargsTest, dynamicAnddynamicTodynamic());
   varargs.varargsTest2 = function(x, ...others) {
     let args = [1, others];
-    dart.dsend(x, 'call', ...args);
+    dart.dcall(x, ...args);
   };
   dart.fn(varargs.varargsTest2, dynamicAnddynamicTodynamic());
   src__varargs._Rest = class _Rest extends core.Object {