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 d014da84d46ff6cc79e20af2c967da923399e495..d3e391f8327d5f24eb4e3aeb30d36e5509473537 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -108,7 +108,23 @@ 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;
 
@@ -139,17 +155,17 @@ class CodeEmitterTask extends CompilerTask {
   }
 
   void computeRequiredTypeChecks() {
-    assert(checkedClasses == null && checkedTypedefs == null);
+    assert(checkedClasses == null && checkedFunctionTypes == null);
 
     compiler.codegenWorld.addImplicitChecks(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);
+      } else if (t is FunctionType) {
+        checkedFunctionTypes.add(t);
       }
     });
   }
@@ -974,6 +990,19 @@ class CodeEmitterTask extends CompilerTask {
       builder.addProperty(namer.operatorIs(other), code);
     }
 
+    void generateIsFunctionTypeTest(FunctionType type) {
+      builder.addProperty(namer.operatorIsFunctionType(type),
+          new jsAst.LiteralBool(true));
+    }
+
+    void generateFunctionTypeSignature(FunctionType type) {
+      RuntimeTypeInformation rti = backend.rti;
+      String encoding = rti.getTypeEncoding(type, alwaysGenerateFunction: true);
+      String operatorSignature = namer.operatorSignature();
+      builder.addProperty(operatorSignature,
+          new jsAst.LiteralExpression(encoding));
+    }
+
     void generateSubstitution(Element other, {bool emitNull: false}) {
       RuntimeTypeInformation rti = backend.rti;
       // TODO(karlklose): support typedefs with variables.
@@ -996,7 +1025,9 @@ class CodeEmitterTask extends CompilerTask {
       }
     }
 
-    generateIsTestsOn(classElement, generateIsTest, generateSubstitution);
+    generateIsTestsOn(classElement, generateIsTest,
+        generateIsFunctionTypeTest, generateFunctionTypeSignature,
+        generateSubstitution);
 
     if (identical(classElement, compiler.objectClass)
         && compiler.enabledNoSuchMethod) {
@@ -1054,6 +1085,19 @@ 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');
+          }
+        });
   }
 
   void visitNativeMixins(ClassElement classElement,
@@ -1389,14 +1433,26 @@ 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;
   }
 
   /**
@@ -1408,6 +1464,8 @@ class CodeEmitterTask extends CompilerTask {
    */
   void generateIsTestsOn(ClassElement cls,
                          void emitIsTest(Element element),
+                         void emitIsFunctionTypeTest(FunctionType type),
+                         void emitFunctionTypeSignature(FunctionType type),
                          void emitSubstitution(Element element, {emitNull})) {
     if (checkedClasses.contains(cls)) {
       emitIsTest(cls);
@@ -1459,7 +1517,7 @@ 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) {
       FunctionElement call = cls.lookupLocalMember(Compiler.CALL_OPERATOR_NAME);
       if (call == null) {
         // If [cls] is a closure, it has a synthetic call operator method.
@@ -1470,7 +1528,21 @@ class CodeEmitterTask extends CompilerTask {
                                   emitIsTest,
                                   emitSubstitution,
                                   generated);
-        getTypedefChecksOn(call.computeType(compiler)).forEach(emitIsTest);
+        FunctionType callType = call.computeType(compiler);
+        Map<FunctionType,bool> functionTypeChecks =
+            getFunctionTypeChecksOn(callType);
+        bool hasDynamicFunctionTypeCheck = false;
+        functionTypeChecks.forEach((FunctionType functionType,
+                                    bool knownSubtype) {
+          emitIsFunctionTypeTest(functionType);
+          if (!knownSubtype) {
+            registerDynamicFunctionTypeCheck(functionType);
+            hasDynamicFunctionTypeCheck = true;
+          }
+        });
+        if (hasDynamicFunctionTypeCheck) {
+          emitFunctionTypeSignature(callType);
+        }
       }
     }
 
@@ -1653,12 +1725,28 @@ class CodeEmitterTask extends CompilerTask {
       // in case it is used in spawnFunction.
       String fieldName = namer.STATIC_CLOSURE_NAME_NAME;
       buffer.write('$fieldAccess.$fieldName$_=$_"$staticName"$N');
-      getTypedefChecksOn(element.computeType(compiler)).forEach(
-        (Element typedef) {
-          String operator = namer.operatorIs(typedef);
-          buffer.write('$fieldAccess.$operator$_=${_}true$N');
+      FunctionType elementType = element.computeType(compiler);
+      Map<FunctionType,bool> functionTypeChecks =
+          getFunctionTypeChecksOn(elementType);
+      bool hasDynamicFunctionTypeCheck = false;
+      functionTypeChecks.forEach((FunctionType functionType,
+                                  bool knownSubtype) {
+        String operator = namer.operatorIsFunctionType(functionType);
+        buffer.write('$fieldAccess.$operator$_=${_}true$N');
+        if (!knownSubtype) {
+          TypeVariableType typeVariable = functionType.typeVariableOccurrence;
+          registerDynamicFunctionTypeCheck(functionType);
+          hasDynamicFunctionTypeCheck = true;
         }
-      );
+      });
+      if (hasDynamicFunctionTypeCheck) {
+        RuntimeTypeInformation rti = backend.rti;
+        String encoding = rti.getTypeEncoding(elementType,
+            alwaysGenerateFunction: true);
+        String operatorSignature = namer.operatorSignature();
+        buffer.add('$fieldAccess.$operatorSignature$_=${_}$encoding$N');
+      }
+
     }
   }
 
@@ -1719,12 +1807,14 @@ class CodeEmitterTask extends CompilerTask {
         : inInterceptor ? const ['self', 'target', 'receiver']
                         : const ['self', 'target'];
 
-    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.
@@ -1781,10 +1871,24 @@ class CodeEmitterTask extends CompilerTask {
       boundClosureBuilder.addProperty(invocationName, fun);
 
       addParameterStubs(callElement, boundClosureBuilder.addProperty);
-      typedefChecks.forEach((Element typedef) {
-        String operator = namer.operatorIs(typedef);
+      bool hasDynamicFunctionTypeCheck = false;
+      functionTypeChecks.forEach((FunctionType functionType,
+                                  bool knownSubtype) {
+        String operator = namer.operatorIsFunctionType(functionType);
         boundClosureBuilder.addProperty(operator, new jsAst.LiteralBool(true));
+        if (!knownSubtype) {
+          registerDynamicFunctionTypeCheck(functionType);
+          hasDynamicFunctionTypeCheck = true;
+        }
       });
+      if (hasDynamicFunctionTypeCheck) {
+        RuntimeTypeInformation rti = backend.rti;
+        String encoding = rti.getTypeEncoding(memberType,
+            alwaysGenerateFunction: true);
+        String operatorSignature = namer.operatorSignature();
+        boundClosureBuilder.addProperty(operatorSignature,
+            new jsAst.LiteralExpression(encoding));
+      }
 
       boundClosures.add(
           js[classesCollector][mangledName].assign(
@@ -1811,14 +1915,34 @@ class CodeEmitterTask extends CompilerTask {
       arguments.add(js[extraArg]);
     }
 
+    jsAst.Expression newClosure = js[closureClass].newWith(arguments);
     jsAst.Expression getterFunction = js.fun(
         parameters,
-        js.return_(js[closureClass].newWith(arguments)));
+        forwardRuntimeTypeInfo(newClosure, memberType, classElement));
 
     defineStub(getterName, getterFunction);
   }
 
   /**
+   * Wraps the [newExpression] of a closure with code for setting the runtime
+   * type information if needed.
+   */
+  forwardRuntimeTypeInfo(jsAst.Expression newExpression,
+                         DartType memberType,
+                         ClassElement thisClass) {
+    if (compiler.world.needsRti(thisClass) &&
+        memberType.containsTypeVariables) {
+      String forwardRuntimeTypeInfo =
+          namer.isolateAccess(backend.getForwardRuntimeTypeInfo());
+      String substitution = namer.substitutionName(thisClass);
+      return js.return_(new jsAst.Call(js[forwardRuntimeTypeInfo],
+          [newExpression, js['this.$substitution'], js['this']]));
+    } else {
+      return js.return_(newExpression);
+    }
+  }
+
+  /**
    * Documentation wanted -- johnniwinther
    *
    * Invariant: [member] must be a declaration element.
@@ -1853,7 +1977,7 @@ 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;