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 841c0a88fed00aee9a2760345450609dc7b2014a..876b619b02a70d3cfbf5cb43deab05012a71b5a4 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -112,7 +112,23 @@ class CodeEmitterTask extends CompilerTask {
    * program contains `x is F<int>` and `x is F<bool>` then the TypedefElement
    * `F` will occur once in [checkedTypedefs].
    */
-  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;
 
@@ -143,18 +159,19 @@ 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) {
+      assert(!t.isMalformed);
       if (t is InterfaceType) {
         checkedClasses.add(t.element);
-      } else if (t is TypedefType) {
-        checkedTypedefs.add(t.element);
+      } else if (t is FunctionType) {
+        checkedFunctionTypes.add(t);
       }
     });
   }
@@ -1236,6 +1253,32 @@ 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.
@@ -1255,7 +1298,9 @@ class CodeEmitterTask extends CompilerTask {
       }
     }
 
-    generateIsTestsOn(classElement, generateIsTest, generateSubstitution);
+    generateIsTestsOn(classElement, generateIsTest,
+        generateIsFunctionTypeTest, generateFunctionTypeSignature,
+        generateSubstitution);
   }
 
   void emitRuntimeTypeSupport(CodeBuffer buffer) {
@@ -1275,6 +1320,19 @@ class CodeEmitterTask extends CompilerTask {
         }
       };
     }
+
+    checkedNonGenericFunctionTypes.forEach((FunctionType type) {
+      String encoding = rti.getTypeEncoding(type);
+      buffer.add('${namer.signatureName(type)}$_=${_}$encoding$N');
+    });
+
+    checkedGenericFunctionTypes.forEach(
+        (ClassElement cls, Set<FunctionType> functionTypes) {
+          for (FunctionType type in functionTypes) {
+            String encoding = rti.getTypeEncoding(type);
+            buffer.add('${namer.signatureName(type)}$_=${_}$encoding$N');
+          }
+        });
   }
 
   /**
@@ -1406,12 +1464,13 @@ 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);
+    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);
@@ -1624,14 +1683,26 @@ 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.
+   */
+  // 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;
   }
 
   /**
@@ -1643,6 +1714,8 @@ class CodeEmitterTask extends CompilerTask {
    */
   void generateIsTestsOn(ClassElement cls,
                          void emitIsTest(Element element),
+                         void emitIsFunctionTypeTest(FunctionType type),
+                         void emitFunctionTypeSignature(Element method, FunctionType type),
                          void emitSubstitution(Element element, {emitNull})) {
     if (checkedClasses.contains(cls)) {
       emitIsTest(cls);
@@ -1694,7 +1767,7 @@ 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.
@@ -1705,8 +1778,10 @@ class CodeEmitterTask extends CompilerTask {
                                   emitIsTest,
                                   emitSubstitution,
                                   generated);
-        getTypedefChecksOn(call.computeType(compiler)).forEach(emitIsTest);
-      }
+        FunctionType callType = call.computeType(compiler);
+        generateFunctionTypeTests(call, callType,
+            emitFunctionTypeSignature, emitIsFunctionTypeTest);
+     }
     }
 
     for (DartType interfaceType in cls.interfaces) {
@@ -1748,6 +1823,53 @@ class CodeEmitterTask extends CompilerTask {
     }
   }
 
+  void generateFunctionTypeTests(
+      Element method,
+      FunctionType methodType,
+      void emitFunctionTypeSignature(Element method, FunctionType methodType),
+      void emitIsFunctionTypeTest(FunctionType functionType)) {
+    Map<FunctionType, bool> functionTypeChecks =
+        getFunctionTypeChecksOn(methodType);
+    generateFunctionTypeTestsInternal(method, methodType, functionTypeChecks,
+        emitFunctionTypeSignature, emitIsFunctionTypeTest);
+  }
+
+  const int MAX_FUNCTION_TYPE_PREDICATES = 10;
+
+  void generateFunctionTypeTestsInternal(
+      Element method,
+      FunctionType methodType,
+      Map<FunctionType, bool> functionTypeChecks,
+      void emitFunctionTypeSignature(Element method, FunctionType methodType),
+      void emitIsFunctionTypeTest(FunctionType functionType)) {
+    bool hasDynamicFunctionTypeCheck = false;
+    int neededPredicates = 0;
+    functionTypeChecks.forEach((FunctionType functionType, bool knownSubtype) {
+      if (!knownSubtype) {
+        registerDynamicFunctionTypeCheck(functionType);
+        hasDynamicFunctionTypeCheck = true;
+      } else {
+        neededPredicates++;
+      }
+    });
+    bool hasSignature = false;
+    if (hasDynamicFunctionTypeCheck ||
+        neededPredicates > MAX_FUNCTION_TYPE_PREDICATES) {
+      emitFunctionTypeSignature(method, methodType);
+      hasSignature = true;
+    }
+    functionTypeChecks.forEach((FunctionType functionType,
+        bool knownSubtype) {
+      if (knownSubtype || !hasDynamicFunctionTypeCheck) {
+        if (hasSignature) {
+          registerDynamicFunctionTypeCheck(functionType);
+        } else {
+          emitIsFunctionTypeTest(functionType);
+        }
+      }
+    });
+  }
+
   /**
    * Return a function that returns true if its argument is a class
    * that needs to be emitted.
@@ -1908,12 +2030,6 @@ 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(
@@ -1921,6 +2037,23 @@ class CodeEmitterTask extends CompilerTask {
               closureBuilder.toObjectInitializer()));
 
       staticGetters[element] = closureClassElement;
+
+      void emitFunctionTypeSignature(Element method, FunctionType methodType) {
+        RuntimeTypes rti = backend.rti;
+        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'));
+      }
+
+      generateFunctionTypeTests(element, element.computeType(compiler),
+          emitFunctionTypeSignature, emitIsFunctionTypeTest);
     }
   }
 
@@ -1978,12 +2111,14 @@ 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.
@@ -2039,10 +2174,24 @@ 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) {
+        RuntimeTypes rti = backend.rti;
+        String encoding = 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));
+      }
+
+      generateFunctionTypeTestsInternal(member, memberType, functionTypeChecks,
+          emitFunctionTypeSignature, emitIsFunctionTypeTest);
 
       boundClosures.add(
           js('$classesCollector.$mangledName = #',
@@ -2073,9 +2222,9 @@ class CodeEmitterTask extends CompilerTask {
       arguments.add(new jsAst.LiteralNull());
     }
 
+    jsAst.Expression newClosure = js(closureClass).newWith(arguments);
     jsAst.Expression getterFunction = js.fun(
-        parameters,
-        js.return_(js(closureClass).newWith(arguments)));
+        parameters, js.return_(newClosure));
 
     defineStub(getterName, getterFunction);
   }
@@ -2115,7 +2264,7 @@ class CodeEmitterTask extends CompilerTask {
     // identical stubs for each we track untyped selectors which already have
     // stubs.
     Set<Selector> generatedSelectors = new Set<Selector>();
-
+    DartType memberType = member.computeType(compiler);
     for (Selector selector in selectors) {
       if (selector.applies(member, compiler)) {
         selector = selector.asUntyped;