Partial fix for call methods #542

lib/src/compiler/code_generator.dart

Index: lib/src/compiler/code_generator.dart
diff --git a/lib/src/compiler/code_generator.dart b/lib/src/compiler/code_generator.dart
index d0bdf2043190b9a91a642c7f84ea0751b1be688b..4c723483646594d53e5e30d8a04999bf77258898 100644
--- a/lib/src/compiler/code_generator.dart
+++ b/lib/src/compiler/code_generator.dart
@@ -701,6 +701,10 @@ class CodeGenerator extends GeneralizingAstVisitor
     var fields = <FieldDeclaration>[];
     var staticFields = <FieldDeclaration>[];
     var methods = <MethodDeclaration>[];
+
+    // The "call" method or getter, if one exists. This can also be
+    // "noSuchMethod" method, because nSM could implement "call".
+    ExecutableElement callMethod;
     for (var member in node.members) {
       if (member is ConstructorDeclaration) {
         ctors.add(member);
@@ -708,6 +712,16 @@ class CodeGenerator extends GeneralizingAstVisitor
         (member.isStatic ? staticFields : fields).add(member);
       } else if (member is MethodDeclaration) {
         methods.add(member);
+        var name = member.name.name;
+        if (name == 'call' && !member.isSetter) {
+          callMethod = member.element;
+        } else if (name == 'noSuchMethod' &&
+            !member.isGetter &&
+            !member.isSetter &&
+            // Exclude SDK because we know they don't use nSM to implement call.
+            !classElem.library.source.isInSystemLibrary) {
+          callMethod ??= member.element;
+        }
       }
     }
 
@@ -738,7 +752,7 @@ class CodeGenerator extends GeneralizingAstVisitor
     _emitSuperHelperSymbols(_superHelperSymbols, body);
 
     // Emit the class, e.g. `core.Object = class Object { ... }`
-    _defineClass(classElem, className, classExpr, body);
+    _defineClass(classElem, className, classExpr, callMethod, body);
 
     // Emit things that come after the ES6 `class ... { ... }`.
     var jsPeerName = _getJSPeerName(classElem);
@@ -746,7 +760,7 @@ class CodeGenerator extends GeneralizingAstVisitor
 
     _emitClassTypeTests(classElem, className, body);
 
-    _defineNamedConstructors(ctors, body, className);
+    _defineNamedConstructors(ctors, body, className, callMethod);
     _emitVirtualFieldSymbols(virtualFieldSymbols, body);
     _emitClassSignature(methods, classElem, ctors, extensions, className, body);
     _defineExtensionMembers(extensions, className, body);
@@ -764,6 +778,45 @@ class CodeGenerator extends GeneralizingAstVisitor
     return _statement(body);
   }
 
+  /// Emits code to support a class with a "call" method and an unnamed
+  /// constructor.
+  ///
+  /// This ensures instances created by the unnamed constructor are functions.
+  /// Named constructors are handled elsewhere, see [_defineNamedConstructors].
+  JS.Expression _emitCallableClass(JS.ClassExpression classExpr,
+      ConstructorElement unnamedCtor, ExecutableElement callMethod) {
+    var ctor = new JS.NamedFunction(
+        classExpr.name, _emitCallableClassConstructor(unnamedCtor, callMethod));
+
+    // Name the constructor function the same as the class.
+    return js.call('dart.callableClass(#, #)', [ctor, classExpr]);
+  }
+
+  JS.Fun _emitCallableClassConstructor(
+      ConstructorElement ctor, ExecutableElement callMethod) {
+    bool dynamicCall = false;
+    if (callMethod is PropertyAccessorElement) {
+      assert(callMethod.isGetter);
+      dynamicCall = callMethod.returnType is! FunctionType;

[vsm, 2016/06/15 19:52:26]

Do we need a dcall here if one of the param types is dynamic?  _isDynamicCall in
the analyzer checker does this.

[Jennifer Messerly, 2016/06/15 20:16:51]

I don't think so. Those dcalls will be handled by the caller:

    typedef F(x);
    F f = new C();
    f(42); // dcall here


Actually, now that I think about this, I'm not sure what case will use this ...
I was thinking about test cases like:

    class C {
       get call => ...;
    }
    Int2Int f = new C();

... but that will fail at runtime to cast to Int2Int. And if we replace with
Function (or dynamic):

    class C {
       Function get call => ...;
    }
    Function f = new C();
    f();

... then it should be a caller side dcall. Same with the noSuchMethod case. We
will not allow you to assign it anywhere a typed function is expected, so only
the typed path needs to be supported.

Yeah, I'll revert the "dynamicCall" support. And change "callMethod" back to
"isCallable"...

+    } else if (callMethod.name == 'noSuchMethod') {
+      dynamicCall = true;
+    }
+
+    var callCall =
+        dynamicCall ? 'dart.dcall(self, args)' : 'self.call.apply(self, args)';
+    return js.call(
+        r'''function (...args) {
+          const self = this;
+          function call(...args) {
+            return #;
+          }
+          call.__proto__ = this.__proto__;
+          call.#.apply(call, args);
+          return call;
+        }''',
+        [js.call(callCall), _constructorName(ctor)]);
+  }
+
   void _emitClassTypeTests(ClassElement classElem, JS.Expression className,
       List<JS.Statement> body) {
     if (classElem == objectClass) {
@@ -978,12 +1031,26 @@ class CodeGenerator extends GeneralizingAstVisitor
     }
   }
 
-  void _defineClass(ClassElement classElem, JS.Expression className,
-      JS.ClassExpression classExpr, List<JS.Statement> body) {
+  void _defineClass(
+      ClassElement classElem,
+      JS.Expression className,
+      JS.ClassExpression classExpr,
+      ExecutableElement callMethod,
+      List<JS.Statement> body) {
+    JS.Expression callableClass;
+    if (callMethod != null && classElem.unnamedConstructor != null) {
+      callableClass = _emitCallableClass(
+          classExpr, classElem.unnamedConstructor, callMethod);
+    }
+
     if (classElem.typeParameters.isNotEmpty) {
-      body.add(new JS.ClassDeclaration(classExpr));
+      if (callableClass != null) {
+        body.add(js.statement('const # = #;', [classExpr.name, callableClass]));
+      } else {
+        body.add(new JS.ClassDeclaration(classExpr));
+      }
     } else {
-      body.add(js.statement('# = #;', [className, classExpr]));
+      body.add(js.statement('# = #;', [className, callableClass ?? classExpr]));
     }
   }
 
@@ -1400,12 +1467,23 @@ class CodeGenerator extends GeneralizingAstVisitor
     }
   }
 
-  void _defineNamedConstructors(List<ConstructorDeclaration> ctors,
-      List<JS.Statement> body, JS.Expression className) {
+  void _defineNamedConstructors(
+      List<ConstructorDeclaration> ctors,
+      List<JS.Statement> body,
+      JS.Expression className,
+      ExecutableElement callMethod) {
+    var code = callMethod != null
+        ? 'dart.defineNamedConstructorCallable(#, #, #);'
+        : 'dart.defineNamedConstructor(#, #)';
+
     for (ConstructorDeclaration member in ctors) {
       if (member.name != null && member.factoryKeyword == null) {
-        body.add(js.statement('dart.defineNamedConstructor(#, #);',
-            [className, _constructorName(member.element)]));
+        var args = [className, _constructorName(member.element)];
+        if (callMethod != null) {
+          args.add(_emitCallableClassConstructor(member.element, callMethod));
+        }
+
+        body.add(js.statement(code, args));
       }
     }
   }