dart2js: Move parameterStub generation to parameter_stub_generator and add parameter stubs to model.

pkg/compiler/lib/src/js_emitter/parameter_stub_generator.dart

+// 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.
+
+part of dart2js.js_emitter;
+
+class ParameterStubGenerator {
+  final Namer namer;
+  final Compiler compiler;
+  final JavaScriptBackend backend;
+
+  ParameterStubGenerator(this.compiler, this.namer, this.backend);
+
+  Emitter get emitter => backend.emitter.emitter;
+  CodeEmitterTask get emitterTask => backend.emitter;
+
+  bool needsSuperGetter(FunctionElement element) =>
+    compiler.codegenWorld.methodsNeedingSuperGetter.contains(element);
+
+  /**
+   * Generate stubs to handle invocation of methods with optional
+   * arguments.
+   *
+   * A method like [: foo([x]) :] may be invoked by the following
+   * calls: [: foo(), foo(1), foo(x: 1) :]. See the sources of this
+   * function for detailed examples.
+   */
+  jsAst.Expression generateParameterStub(FunctionElement member,
+                                         Selector selector) {
+    FunctionSignature parameters = member.functionSignature;
+    int positionalArgumentCount = selector.positionalArgumentCount;
+    if (positionalArgumentCount == parameters.parameterCount) {
+      assert(selector.namedArgumentCount == 0);
+      return null;
+    }
+    if (parameters.optionalParametersAreNamed
+        && selector.namedArgumentCount == parameters.optionalParameterCount) {
+      // If the selector has the same number of named arguments as the element,
+      // we don't need to add a stub. The call site will hit the method
+      // directly.
+      return null;
+    }
+    JavaScriptConstantCompiler handler = backend.constants;
+    List<String> names = selector.getOrderedNamedArguments();
+
+    String invocationName = namer.invocationName(selector);
+
+    bool isInterceptedMethod = backend.isInterceptedMethod(member);
+
+    // If the method is intercepted, we need to also pass the actual receiver.
+    int extraArgumentCount = isInterceptedMethod ? 1 : 0;
+    // Use '$receiver' to avoid clashes with other parameter names. Using
+    // '$receiver' works because [:namer.safeName:] used for getting parameter
+    // names never returns a name beginning with a single '$'.
+    String receiverArgumentName = r'$receiver';
+
+    // The parameters that this stub takes.
+    List<jsAst.Parameter> parametersBuffer =
+        new List<jsAst.Parameter>(selector.argumentCount + extraArgumentCount);
+    // The arguments that will be passed to the real method.
+    List<jsAst.Expression> argumentsBuffer =
+        new List<jsAst.Expression>(
+            parameters.parameterCount + extraArgumentCount);
+
+    int count = 0;
+    if (isInterceptedMethod) {
+      count++;
+      parametersBuffer[0] = new jsAst.Parameter(receiverArgumentName);
+      argumentsBuffer[0] = js('#', receiverArgumentName);
+    }
+
+    int optionalParameterStart = positionalArgumentCount + extraArgumentCount;
+    // Includes extra receiver argument when using interceptor convention
+    int indexOfLastOptionalArgumentInParameters = optionalParameterStart - 1;
+
+    int parameterIndex = 0;
+    parameters.orderedForEachParameter((ParameterElement element) {
+      String jsName = backend.namer.safeName(element.name);
+      assert(jsName != receiverArgumentName);
+      if (count < optionalParameterStart) {
+        parametersBuffer[count] = new jsAst.Parameter(jsName);
+        argumentsBuffer[count] = js('#', jsName);
+      } else {
+        int index = names.indexOf(element.name);
+        if (index != -1) {
+          indexOfLastOptionalArgumentInParameters = count;
+          // The order of the named arguments is not the same as the
+          // one in the real method (which is in Dart source order).
+          argumentsBuffer[count] = js('#', jsName);
+          parametersBuffer[optionalParameterStart + index] =
+              new jsAst.Parameter(jsName);
+        } else {
+          ConstantExpression constant = handler.getConstantForVariable(element);
+          if (constant == null) {
+            argumentsBuffer[count] =
+                emitter.constantReference(new NullConstantValue());
+          } else {
+            ConstantValue value = constant.value;
+            if (!value.isNull) {
+              // If the value is the null constant, we should not pass it
+              // down to the native method.
+              indexOfLastOptionalArgumentInParameters = count;
+            }
+            argumentsBuffer[count] = emitter.constantReference(value);
+          }
+        }
+      }
+      count++;
+    });
+
+    var body;  // List or jsAst.Statement.
+    if (member.hasFixedBackendName) {
+      body = emitterTask.nativeEmitter.generateParameterStubStatements(
+          member, isInterceptedMethod, invocationName,
+          parametersBuffer, argumentsBuffer,
+          indexOfLastOptionalArgumentInParameters);
+    } else if (member.isInstanceMember) {
+      if (needsSuperGetter(member)) {
+        ClassElement superClass = member.enclosingClass;
+        String methodName = namer.getNameOfInstanceMember(member);
+        // When redirecting, we must ensure that we don't end up in a subclass.
+        // We thus can't just invoke `this.foo$1.call(filledInArguments)`.
+        // Instead we need to call the statically resolved target.
+        //   `<class>.prototype.bar$1.call(this, argument0, ...)`.
+        body = js.statement(
+            'return #.#.call(this, #);',
+            [backend.emitter.prototypeAccess(superClass,
+                                             hasBeenInstantiated: true),
+             methodName,
+             argumentsBuffer]);
+      } else {
+        body = js.statement(
+            'return this.#(#);',
+            [namer.getNameOfInstanceMember(member), argumentsBuffer]);
+      }
+    } else {
+      body = js.statement('return #(#)',
+          [emitter.staticFunctionAccess(member), argumentsBuffer]);
+    }
+
+    jsAst.Fun function = js('function(#) { #; }', [parametersBuffer, body]);
+
+    return function;
+  }
+
+  Map<Selector, jsAst.Expression> generateParameterStubs(FunctionElement member,
+                                          [bool canTearOff = false]) {
+    Map<Selector, jsAst.Expression> generatedStubs
+        = <Selector, jsAst.Expression>{};
+
+    if (member.enclosingElement.isClosure) {
+      ClosureClassElement cls = member.enclosingElement;
+      if (cls.supertype.element == backend.boundClosureClass) {
+        compiler.internalError(cls.methodElement, 'Bound closure1.');
+      }
+      if (cls.methodElement.isInstanceMember) {
+        compiler.internalError(cls.methodElement, 'Bound closure2.');
+      }
+    }
+
+    // We fill the lists depending on the selector. For example,
+    // take method foo:
+    //    foo(a, b, {c, d});
+    //
+    // We may have multiple ways of calling foo:
+    // (1) foo(1, 2);
+    // (2) foo(1, 2, c: 3);
+    // (3) foo(1, 2, d: 4);
+    // (4) foo(1, 2, c: 3, d: 4);
+    // (5) foo(1, 2, d: 4, c: 3);
+    //
+    // What we generate at the call sites are:
+    // (1) foo$2(1, 2);
+    // (2) foo$3$c(1, 2, 3);
+    // (3) foo$3$d(1, 2, 4);
+    // (4) foo$4$c$d(1, 2, 3, 4);
+    // (5) foo$4$c$d(1, 2, 3, 4);
+    //
+    // The stubs we generate are (expressed in Dart):
+    // (1) foo$2(a, b) => foo$4$c$d(a, b, null, null)
+    // (2) foo$3$c(a, b, c) => foo$4$c$d(a, b, c, null);
+    // (3) foo$3$d(a, b, d) => foo$4$c$d(a, b, null, d);
+    // (4) No stub generated, call is direct.
+    // (5) No stub generated, call is direct.
+    //
+    // We need to pay attention if this stub is for a function that has been
+    // invoked from a subclass. Then we cannot just redirect, since that
+    // would invoke the methods of the subclass. We have to compile to:
+    // (1) foo$2(a, b) => MyClass.foo$4$c$d.call(this, a, b, null, null)
+    // (2) foo$3$c(a, b, c) => MyClass.foo$4$c$d(this, a, b, c, null);
+    // (3) foo$3$d(a, b, d) => MyClass.foo$4$c$d(this, a, b, null, d);
+
+    Set<Selector> selectors = member.isInstanceMember
+        ? compiler.codegenWorld.invokedNames[member.name]
+        : null; // No stubs needed for static methods.
+
+    /// Returns all closure call selectors renamed to match this member.
+    Set<Selector> callSelectorsAsNamed() {
+      if (!canTearOff) return null;
+      Set<Selector> callSelectors = compiler.codegenWorld.invokedNames[
+          namer.closureInvocationSelectorName];
+      if (callSelectors == null) return null;
+      return callSelectors.map((Selector callSelector) {
+        return new Selector.call(
+            member.name, member.library,
+            callSelector.argumentCount, callSelector.namedArguments);
+      }).toSet();
+    }
+    if (selectors == null) {
+      selectors = callSelectorsAsNamed();
+      if (selectors == null) return generatedStubs;
+    } else {
+      Set<Selector> callSelectors = callSelectorsAsNamed();
+      if (callSelectors != null) {
+        selectors = selectors.union(callSelectors);
+      }
+    }
+    Set<Selector> untypedSelectors = new Set<Selector>();
+    if (selectors != null) {
+      for (Selector selector in selectors) {
+        if (!selector.appliesUnnamed(member, compiler.world)) continue;
+        if (untypedSelectors.add(selector.asUntyped)) {
+          jsAst.Expression stub = generateParameterStub(member, selector);
+          if (stub != null) {
+            generatedStubs[selector] = stub;
+          }
+        }
+      }
+    }
+    if (canTearOff) {
+      selectors = compiler.codegenWorld.invokedNames[
+          namer.closureInvocationSelectorName];
+      if (selectors != null) {
+        for (Selector selector in selectors) {
+          selector = new Selector.call(
+              member.name, member.library,
+              selector.argumentCount, selector.namedArguments);
+          if (!selector.appliesUnnamed(member, compiler.world)) continue;
+          if (untypedSelectors.add(selector)) {
+            jsAst.Expression stub = generateParameterStub(member, selector);
+            if (stub != null) {
+              generatedStubs[selector] = stub;
+            }
+          }
+        }
+      }
+    }
+    return generatedStubs;
+  }
+}