Support runtime check of function types.

sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
index c04ff051db9c9ff6222ff049cd3f03351f233e30..fecfb7e685058c2fc0bd28dbdecde6b0308a34dd 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -48,6 +48,13 @@ class ClassBuilder {
   }
 }
 
+// Function signatures used in the generation of runtime type information.
+typedef void FunctionTypeSignatureEmitter(Element method,
+                                          FunctionType methodType);
+// TODO(johnniwinther): Clean up terminology for rti in the emitter.
+typedef void FunctionTypeTestEmitter(FunctionType functionType);
+typedef void SubstitutionEmitter(Element element, {bool emitNull});
+
 /**
  * Generates the code for all used classes in the program. Static fields (even
  * in classes) are ignored, since they can be treated as non-class elements.
@@ -112,11 +119,26 @@ class CodeEmitterTask extends CompilerTask {
   Set<ClassElement> checkedClasses;
 
   /**
-   * Raw Typedef symbols occuring in is-checks and type assertions.  If the
-   * program contains `x is F<int>` and `x is F<bool>` then the TypedefElement
-   * `F` will occur once in [checkedTypedefs].
+   * The set of function types that checked, both explicity through tests of
+   * typedefs and implicitly through type annotations in checked mode.
    */
-  Set<TypedefElement> checkedTypedefs;
+  Set<FunctionType> checkedFunctionTypes;
+
+  Map<ClassElement, Set<FunctionType>> checkedGenericFunctionTypes =
+      new Map<ClassElement, Set<FunctionType>>();
+
+  Set<FunctionType> checkedNonGenericFunctionTypes =
+      new Set<FunctionType>();
+
+  void registerDynamicFunctionTypeCheck(FunctionType functionType) {
+    ClassElement classElement = Types.getClassContext(functionType);
+    if (classElement != null) {
+      checkedGenericFunctionTypes.putIfAbsent(classElement,
+          () => new Set<FunctionType>()).add(functionType);
+    } else {
+      checkedNonGenericFunctionTypes.add(functionType);
+    }
+  }
 
   final bool generateSourceMap;
 
@@ -147,18 +169,20 @@ class CodeEmitterTask extends CompilerTask {
   }
 
   void computeRequiredTypeChecks() {
-    assert(checkedClasses == null && checkedTypedefs == null);
+    assert(checkedClasses == null && checkedFunctionTypes == null);
 
     backend.rti.addImplicitChecks(compiler.codegenWorld,
                                   classesUsingTypeVariableTests);
 
     checkedClasses = new Set<ClassElement>();
-    checkedTypedefs = new Set<TypedefElement>();
+    checkedFunctionTypes = new Set<FunctionType>();
     compiler.codegenWorld.isChecks.forEach((DartType t) {
-      if (t is InterfaceType) {
-        checkedClasses.add(t.element);
-      } else if (t is TypedefType) {
-        checkedTypedefs.add(t.element);
+      if (!t.isMalformed) {
+        if (t is InterfaceType) {
+          checkedClasses.add(t.element);
+        } else if (t is FunctionType) {
+          checkedFunctionTypes.add(t);
+        }
       }
     });
   }
@@ -1319,9 +1343,34 @@ class CodeEmitterTask extends CompilerTask {
       builder.addProperty(namer.operatorIs(other), js('true'));
     }
 
+    void generateIsFunctionTypeTest(FunctionType type) {
+      String operator = namer.operatorIsType(type);
+      builder.addProperty(operator, new jsAst.LiteralBool(true));
+    }
+
+    void generateFunctionTypeSignature(Element method, FunctionType type) {
+      assert(method.isImplementation);
+      String thisAccess = 'this';
+      Node node = method.parseNode(compiler);
+      ClosureClassMap closureData =
+          compiler.closureToClassMapper.closureMappingCache[node];
+      if (closureData != null) {
+        Element thisElement =
+            closureData.freeVariableMapping[closureData.thisElement];
+        if (thisElement != null) {
+          String thisName = backend.namer.getName(thisElement);
+          thisAccess = 'this.$thisName';
+        }
+      }
+      RuntimeTypes rti = backend.rti;
+      String encoding = rti.getSignatureEncoding(type, () => '$thisAccess');
+      String operatorSignature = namer.operatorSignature();
+      builder.addProperty(operatorSignature,
+          new jsAst.LiteralExpression(encoding));
+    }
+
     void generateSubstitution(Element other, {bool emitNull: false}) {
       RuntimeTypes rti = backend.rti;
-      // TODO(karlklose): support typedefs with variables.
       jsAst.Expression expression;
       bool needsNativeCheck = nativeEmitter.requiresNativeIsCheck(other);
       if (other.kind == ElementKind.CLASS) {
@@ -1338,7 +1387,9 @@ class CodeEmitterTask extends CompilerTask {
       }
     }
 
-    generateIsTestsOn(classElement, generateIsTest, generateSubstitution);
+    generateIsTestsOn(classElement, generateIsTest,
+        generateIsFunctionTypeTest, generateFunctionTypeSignature,
+        generateSubstitution);
   }
 
   void emitRuntimeTypeSupport(CodeBuffer buffer) {
@@ -1358,6 +1409,17 @@ class CodeEmitterTask extends CompilerTask {
         }
       };
     }
+
+    void addSignature(FunctionType type) {
+      String encoding = rti.getTypeEncoding(type);
+      buffer.add('${namer.signatureName(type)}$_=${_}$encoding$N');
+    }
+
+    checkedNonGenericFunctionTypes.forEach(addSignature);
+
+    checkedGenericFunctionTypes.forEach((_, Set<FunctionType> functionTypes) {
+      functionTypes.forEach(addSignature);
+    });
   }
 
   /**
@@ -1489,12 +1551,14 @@ class CodeEmitterTask extends CompilerTask {
     DartType type = member.computeType(compiler);
     // TODO(ahe): Generate a dynamic type error here.
     if (type.element.isErroneous()) return;
-    FunctionElement helperElement
-        = backend.getCheckedModeHelper(type, typeCast: false);
+    type = type.unalias(compiler);
+    CheckedModeHelper helper =
+        backend.getCheckedModeHelper(type, typeCast: false);
+    FunctionElement helperElement = helper.getElement(compiler);
     String helperName = namer.isolateAccess(helperElement);
     List<jsAst.Expression> arguments = <jsAst.Expression>[js('v')];
     if (helperElement.computeSignature(compiler).parameterCount != 1) {
-      arguments.add(js.string(namer.operatorIs(type.element)));
+      arguments.add(js.string(namer.operatorIsType(type)));
     }
 
     String setterName = namer.setterNameFromAccessorName(accessorName);
@@ -1735,14 +1799,27 @@ class CodeEmitterTask extends CompilerTask {
     return _selectorRank(selector1) - _selectorRank(selector2);
   }
 
-  Iterable<Element> getTypedefChecksOn(DartType type) {
-    bool isSubtype(TypedefElement typedef) {
-      FunctionType typedefType =
-          typedef.computeType(compiler).unalias(compiler);
-      return compiler.types.isSubtype(type, typedefType);
+  /**
+   * Returns a mapping containing all checked function types for which [type]
+   * can be a subtype. A function type is mapped to [:true:] if [type] is
+   * statically known to be a subtype of it and to [:false:] if [type] might
+   * be a subtype, provided with the right type arguments.
+   */
+  // TODO(johnniwinther): Change to return a mapping from function types to
+  // a set of variable points and use this to detect statically/dynamically
+  // known subtype relations.
+  Map<FunctionType, bool> getFunctionTypeChecksOn(DartType type) {
+    Map<FunctionType, bool> functionTypeMap =
+        new LinkedHashMap<FunctionType, bool>();
+    for (FunctionType functionType in checkedFunctionTypes) {
+      if (compiler.types.isSubtype(type, functionType)) {
+        functionTypeMap[functionType] = true;
+      } else if (compiler.types.isPotentialSubtype(type, functionType)) {
+        functionTypeMap[functionType] = false;
+      }
     }
-    return checkedTypedefs.where(isSubtype).toList()
-        ..sort(Elements.compareByPosition);
+    // TODO(johnniwinther): Ensure stable ordering of the keys.
+    return functionTypeMap;
   }
 
   /**
@@ -1754,7 +1831,9 @@ class CodeEmitterTask extends CompilerTask {
    */
   void generateIsTestsOn(ClassElement cls,
                          void emitIsTest(Element element),
-                         void emitSubstitution(Element element, {emitNull})) {
+                         FunctionTypeTestEmitter emitIsFunctionTypeTest,
+                         FunctionTypeSignatureEmitter emitFunctionTypeSignature,
+                         SubstitutionEmitter emitSubstitution) {
     if (checkedClasses.contains(cls)) {
       emitIsTest(cls);
       emitSubstitution(cls);
@@ -1777,7 +1856,7 @@ class CodeEmitterTask extends CompilerTask {
       Set<ClassElement> emitted = new Set<ClassElement>();
       // TODO(karlklose): move the computation of these checks to
       // RuntimeTypeInformation.
-      if (backend.needsRti(cls)) {
+      if (backend.classNeedsRti(cls)) {
         emitSubstitution(superclass, emitNull: true);
         emitted.add(superclass);
       }
@@ -1805,7 +1884,7 @@ class CodeEmitterTask extends CompilerTask {
     // A class that defines a [:call:] method implicitly implements
     // [Function] and needs checks for all typedefs that are used in is-checks.
     if (checkedClasses.contains(compiler.functionClass) ||
-        !checkedTypedefs.isEmpty) {
+        !checkedFunctionTypes.isEmpty) {
       Element call = cls.lookupLocalMember(Compiler.CALL_OPERATOR_NAME);
       if (call == null) {
         // If [cls] is a closure, it has a synthetic call operator method.
@@ -1816,8 +1895,12 @@ class CodeEmitterTask extends CompilerTask {
                                   emitIsTest,
                                   emitSubstitution,
                                   generated);
-        getTypedefChecksOn(call.computeType(compiler)).forEach(emitIsTest);
-      }
+        FunctionType callType = call.computeType(compiler);
+        Map<FunctionType, bool> functionTypeChecks =
+            getFunctionTypeChecksOn(callType);
+        generateFunctionTypeTests(call, callType, functionTypeChecks,
+            emitFunctionTypeSignature, emitIsFunctionTypeTest);
+     }
     }
 
     for (DartType interfaceType in cls.interfaces) {
@@ -1831,7 +1914,7 @@ class CodeEmitterTask extends CompilerTask {
    */
   void generateInterfacesIsTests(ClassElement cls,
                                  void emitIsTest(ClassElement element),
-                                 void emitSubstitution(ClassElement element),
+                                 SubstitutionEmitter emitSubstitution,
                                  Set<Element> alreadyGenerated) {
     void tryEmitTest(ClassElement check) {
       if (!alreadyGenerated.contains(check) && checkedClasses.contains(check)) {
@@ -1859,6 +1942,45 @@ class CodeEmitterTask extends CompilerTask {
     }
   }
 
+  static const int MAX_FUNCTION_TYPE_PREDICATES = 10;
+
+  /**
+   * Generates function type checks on [method] with type [methodType] against
+   * the function type checks in [functionTypeChecks].
+   */
+  void generateFunctionTypeTests(
+      Element method,
+      FunctionType methodType,
+      Map<FunctionType, bool> functionTypeChecks,
+      FunctionTypeSignatureEmitter emitFunctionTypeSignature,
+      FunctionTypeTestEmitter emitIsFunctionTypeTest) {
+    bool hasDynamicFunctionTypeCheck = false;
+    int neededPredicates = 0;
+    functionTypeChecks.forEach((FunctionType functionType, bool knownSubtype) {
+      if (!knownSubtype) {
+        registerDynamicFunctionTypeCheck(functionType);
+        hasDynamicFunctionTypeCheck = true;
+      } else {
+        neededPredicates++;
+      }
+    });
+    bool alwaysUseSignature = false;
+    if (hasDynamicFunctionTypeCheck ||
+        neededPredicates > MAX_FUNCTION_TYPE_PREDICATES) {
+      emitFunctionTypeSignature(method, methodType);
+      alwaysUseSignature = true;
+    }
+    functionTypeChecks.forEach((FunctionType functionType, bool knownSubtype) {
+      if (knownSubtype) {
+        if (alwaysUseSignature) {
+          registerDynamicFunctionTypeCheck(functionType);
+        } else {
+          emitIsFunctionTypeTest(functionType);
+        }
+      }
+    });
+  }
+
   /**
    * Return a function that returns true if its argument is a class
    * that needs to be emitted.
@@ -2021,12 +2143,6 @@ class CodeEmitterTask extends CompilerTask {
 
       addParameterStubs(callElement, closureBuilder.addProperty);
 
-      DartType type = element.computeType(compiler);
-      getTypedefChecksOn(type).forEach((Element typedef) {
-        String operator = namer.operatorIs(typedef);
-        closureBuilder.addProperty(operator, js('true'));
-      });
-
       // TODO(ngeoffray): Cache common base classes for closures, bound
       // closures, and static closures that have common type checks.
       boundClosures.add(
@@ -2034,6 +2150,28 @@ class CodeEmitterTask extends CompilerTask {
               closureBuilder.toObjectInitializer()));
 
       staticGetters[element] = closureClassElement;
+
+      void emitFunctionTypeSignature(Element method, FunctionType methodType) {
+        RuntimeTypes rti = backend.rti;
+        // [:() => null:] is dummy encoding of [this] which is never needed for
+        // the encoding of the type of the static [method].
+        String encoding = rti.getSignatureEncoding(methodType, () => 'null');
+        String operatorSignature = namer.operatorSignature();
+        // TODO(johnniwinther): Make MiniJsParser support function expressions.
+        closureBuilder.addProperty(operatorSignature,
+            new jsAst.LiteralExpression(encoding));
+      }
+
+      void emitIsFunctionTypeTest(FunctionType functionType) {
+        String operator = namer.operatorIsType(functionType);
+        closureBuilder.addProperty(operator, js('true'));
+      }
+
+      FunctionType methodType = element.computeType(compiler);
+      Map<FunctionType, bool> functionTypeChecks =
+          getFunctionTypeChecksOn(methodType);
+      generateFunctionTypeTests(element, methodType, functionTypeChecks,
+          emitFunctionTypeSignature, emitIsFunctionTypeTest);
     }
   }
 
@@ -2091,12 +2229,14 @@ class CodeEmitterTask extends CompilerTask {
       fieldNames.add(namer.getName(field));
     });
 
-    Iterable<Element> typedefChecks =
-        getTypedefChecksOn(member.computeType(compiler));
-    bool hasTypedefChecks = !typedefChecks.isEmpty;
+    DartType memberType = member.computeType(compiler);
+    Map<FunctionType, bool> functionTypeChecks =
+        getFunctionTypeChecksOn(memberType);
+    bool hasFunctionTypeChecks = !functionTypeChecks.isEmpty;
 
-    bool canBeShared = !hasOptionalParameters && !hasTypedefChecks;
+    bool canBeShared = !hasOptionalParameters && !hasFunctionTypeChecks;
 
+    ClassElement classElement = member.getEnclosingClass();
     String closureClass = canBeShared ? cache[parameterCount] : null;
     if (closureClass == null) {
       // Either the class was not cached yet, or there are optional parameters.
@@ -2152,10 +2292,23 @@ class CodeEmitterTask extends CompilerTask {
       boundClosureBuilder.addProperty(invocationName, fun);
 
       addParameterStubs(callElement, boundClosureBuilder.addProperty);
-      typedefChecks.forEach((Element typedef) {
-        String operator = namer.operatorIs(typedef);
-        boundClosureBuilder.addProperty(operator, js('true'));
-      });
+
+      void emitFunctionTypeSignature(Element method, FunctionType methodType) {
+        String encoding = backend.rti.getSignatureEncoding(
+            methodType, () => 'this.${fieldNames[0]}');
+        String operatorSignature = namer.operatorSignature();
+        boundClosureBuilder.addProperty(operatorSignature,
+            new jsAst.LiteralExpression(encoding));
+      }
+
+      void emitIsFunctionTypeTest(FunctionType functionType) {
+        String operator = namer.operatorIsType(functionType);
+        boundClosureBuilder.addProperty(operator,
+            new jsAst.LiteralBool(true));
+      }
+
+      generateFunctionTypeTests(member, memberType, functionTypeChecks,
+          emitFunctionTypeSignature, emitIsFunctionTypeTest);
 
       boundClosures.add(
           js('$classesCollector.$mangledName = #',
@@ -2187,8 +2340,7 @@ class CodeEmitterTask extends CompilerTask {
     }
 
     jsAst.Expression getterFunction = js.fun(
-        parameters,
-        js.return_(js(closureClass).newWith(arguments)));
+        parameters, js.return_(js(closureClass).newWith(arguments)));
 
     defineStub(getterName, getterFunction);
   }
@@ -2228,7 +2380,6 @@ class CodeEmitterTask extends CompilerTask {
     // identical stubs for each we track untyped selectors which already have
     // stubs.
     Set<Selector> generatedSelectors = new Set<Selector>();
-
     for (Selector selector in selectors) {
       if (selector.applies(member, compiler)) {
         selector = selector.asUntyped;
@@ -2833,6 +2984,15 @@ if (typeof document !== "undefined" && document.readyState !== "complete") {
         rti.getClassesUsedInSubstitutions(backend, requiredChecks);
     addClassesWithSuperclasses(classesUsedInSubstitutions);
 
+    // 3c. Add classes that contain checked generic function types. These are
+    //     needed to store the signature encoding.
+    for (FunctionType type in checkedFunctionTypes) {
+      ClassElement contextClass = Types.getClassContext(type);
+      if (contextClass != null) {
+        neededClasses.add(contextClass);
+      }
+    }
+
     // 4. Finally, sort the classes.
     List<ClassElement> sortedClasses = Elements.sortedByPosition(neededClasses);