Redo "Use an explicit 'this' parameter instead of 'This' nodes."

pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
index 614845e7bcd39927a9d612064424fec060f30974..d75cbbe48ec6441eaa1793e22e07d4215d8841b9 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
@@ -219,10 +219,25 @@ class IrBuilderDelimitedState {
   final ExecutableElement currentElement;
 
   final ir.Continuation returnContinuation = new ir.Continuation.retrn();
+  ir.Parameter _thisParameter;
+  ir.Parameter enclosingMethodThisParameter;
 
   final List<ir.Definition> functionParameters = <ir.Definition>[];
 
   IrBuilderDelimitedState(this.constantSystem, this.currentElement);
+
+  ir.Parameter get thisParameter => _thisParameter;
+  void set thisParameter(ir.Parameter value) {
+    assert(_thisParameter == null);
+    _thisParameter = value;
+  }
+}
+
+class ThisParameterLocal implements Local {
+  final ExecutableElement executableContext;
+  ThisParameterLocal(this.executableContext);
+  String get name => 'this';
+  toString() => 'ThisParameterLocal($executableContext)';
 }
 
 /// A factory for building the cps IR.
@@ -296,6 +311,7 @@ abstract class IrBuilder {
   /// Add the given function parameter to the IR, and bind it in the environment
   /// or put it in its box, if necessary.
   void _createFunctionParameter(ParameterElement parameterElement);
+  void _createThisParameter();
 
   /// Creates an access to the receiver from the current (or enclosing) method.
   ///
@@ -387,8 +403,11 @@ abstract class IrBuilder {
 
   /// Construct a builder for an inner function.
   IrBuilder makeInnerFunctionBuilder(ExecutableElement currentElement) {
+    IrBuilderDelimitedState innerState =
+        new IrBuilderDelimitedState(state.constantSystem, currentElement)
+          ..enclosingMethodThisParameter = state.enclosingMethodThisParameter;
     return _makeInstance()
-        ..state = new IrBuilderDelimitedState(state.constantSystem, currentElement)
+        ..state = innerState
         ..environment = new Environment.empty();
   }
 
@@ -402,6 +421,7 @@ abstract class IrBuilder {
   List<ir.Primitive> buildFunctionHeader(Iterable<ParameterElement> parameters,
                                         {ClosureScope closureScope,
                                          ClosureEnvironment env}) {
+    _createThisParameter();
     _enterClosureEnvironment(env);
     _enterScope(closureScope);
     parameters.forEach(_createFunctionParameter);
@@ -658,11 +678,11 @@ abstract class IrBuilder {
           message: "Local constants for abstract method $element: "
                    "${state.localConstants}"));
       return new ir.FunctionDefinition.abstract(
-                element, state.functionParameters, defaults);
+          element, state.thisParameter, state.functionParameters, defaults);
     } else {
       ir.RunnableBody body = makeRunnableBody();
       return new ir.FunctionDefinition(
-          element, state.functionParameters, body,
+          element, state.thisParameter, state.functionParameters, body,
           state.localConstants, defaults);
     }
   }
@@ -686,7 +706,7 @@ abstract class IrBuilder {
     FunctionElement element = state.currentElement;
     ir.RunnableBody body = makeRunnableBody();
     return new ir.ConstructorDefinition(
-        element, state.functionParameters, body, initializers,
+        element, state.thisParameter, state.functionParameters, body, initializers,
         state.localConstants, defaults);
   }
 
@@ -1147,13 +1167,17 @@ abstract class IrBuilder {
     bodyBuilder.add(new ir.LetCont(currentInvoked,
         new ir.InvokeMethod(iterator, new Selector.getter("current", null),
             currentInvoked, emptyArguments)));
+    // TODO(sra): Does this cover all cases? The general setter case include
+    // super.
     if (Elements.isLocal(variableElement)) {
       bodyBuilder.buildLocalSet(variableElement, currentValue);
-    } else if (Elements.isStaticOrTopLevel(variableElement)) {
+    } else if (Elements.isStaticOrTopLevel(variableElement) ||
+               Elements.isErroneous(variableElement)) {
       bodyBuilder.buildStaticSet(
           variableElement, variableSelector, currentValue);
     } else {
       ir.Primitive receiver = bodyBuilder.buildThis();
+      assert(receiver != null);
       bodyBuilder.buildDynamicSet(receiver, variableSelector, currentValue);
     }
 
@@ -2037,6 +2061,26 @@ class DartIrBuilder extends IrBuilder {
     }
   }
 
+  void _createThisParameter() {
+    void create() {
+      ir.Parameter thisParameter =
+          new ir.Parameter(new ThisParameterLocal(state.currentElement));
+      state.thisParameter = thisParameter;
+      state.enclosingMethodThisParameter = thisParameter;
+    }
+    if (state.currentElement.isLocal) return;
+    if (state.currentElement.isStatic) return;
+    if (state.currentElement.isGenerativeConstructor) {
+      create();
+      return;
+    }
+    if (state.currentElement.isStatic) return;
+    if (state.currentElement.isInstanceMember) {
+      create();
+      return;
+    }
+  }
+
   void declareLocalVariable(LocalVariableElement variableElement,
                             {ir.Primitive initialValue}) {
     assert(isOpen);
@@ -2095,7 +2139,9 @@ class DartIrBuilder extends IrBuilder {
     return value;
   }
 
-  ir.Primitive buildThis() => addPrimitive(new ir.This());
+  ir.Primitive buildThis() {
+    return state.enclosingMethodThisParameter;
+  }
 
   ir.Primitive buildSuperInvocation(Element target,
                                     Selector selector,
@@ -2142,7 +2188,7 @@ class JsIrBuilder extends IrBuilder {
     if (env == null) return;
 
     // Obtain a reference to the function object (this).
-    ir.Primitive thisPrim = addPrimitive(new ir.This());
+    ir.Parameter thisPrim = state.thisParameter;
 
     // Obtain access to the free variables.
     env.freeVariables.forEach((Local local, ClosureLocation location) {
@@ -2203,6 +2249,13 @@ class JsIrBuilder extends IrBuilder {
     }
   }
 
+  void _createThisParameter() {
+    if (Elements.isStaticOrTopLevel(state.currentElement)) return;
+    if (state.currentElement.isLocal) return;
+    state.thisParameter =
+        new ir.Parameter(new ThisParameterLocal(state.currentElement));
+  }
+
   void declareLocalVariable(LocalElement variableElement,
                             {ir.Primitive initialValue}) {
     assert(isOpen);
@@ -2306,7 +2359,7 @@ class JsIrBuilder extends IrBuilder {
 
   ir.Primitive buildThis() {
     if (jsState.receiver != null) return jsState.receiver;
-    return addPrimitive(new ir.This());
+    return state.thisParameter;
   }
 
   ir.Primitive buildSuperInvocation(Element target,
@@ -2348,6 +2401,7 @@ class JsIrBuilder extends IrBuilder {
   /// instead of being created in the header.
   void buildConstructorBodyHeader(Iterable<Local> parameters,
                                   ClosureScope closureScope) {
+    _createThisParameter();
     for (Local param in parameters) {
       ir.Parameter parameter = createLocalParameter(param);
       state.functionParameters.add(parameter);