Build new IR for functions returning a constant

sdk/lib/_internal/compiler/implementation/ir/ir_nodes.dart

+// Copyright (c) 2013, 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.
+
+// IrNodes are kept in a separate library to have precise control over their
+// dependencies on other parts of the system
+library ir_nodes;
+
+import '../dart2jslib.dart' show Constant;
+
+abstract class IrNode {
+  final int offset;
+  const IrNode(this.offset);
+  accept(IrNodesVisitor visitor);
+}
+
+/**
+ * The singleton instance of this class never ends up in the final IR, it is
+ * just used as a return value in the [IrNodeBuilderVisitor] for non-expressions
+ * such as [:visitBlock:].
+ *
+ * TODO(lry): use [:null:] instead?
+ */
+class IrNoValue extends IrNode {
+  const IrNoValue() : super(0);
+  accept(IrNodesVisitor visitor) => throw "NoValue.accept()";
+}
+
+class IrFunction extends IrNode {
+  // Non-final for now because the node is created early, allowing [IrReturn]
+  // nodes in the body to refer to it.
+  List<IrNode> statements;

[karlklose, 2013/11/06 09:11:28]

The field 'statements' can be final, you only need to add elements later.

[lukas, 2013/11/06 11:36:08]

Done.

+  IrFunction(int offset, this.statements) : super(offset);
+  accept(IrNodesVisitor visitor) => visitor.visitIrFunction(this);
+
+  bool hasBody() => statements.isNotEmpty;
+}
+
+class IrReturn extends IrNode {
+  final IrFunction function;

[karlklose, 2013/11/06 09:11:28]

If the primary way of dealing with the IR is to use visitors, this information
can always be held in the context, so  you could remove it from the node.

[lukas, 2013/11/06 11:36:08]

OK, removed for now, we'll see how to encode returns.

+  final IrNode value;
+  IrReturn(int offset, this.function, this.value) : super(offset);
+  accept(IrNodesVisitor visitor) => visitor.visitIrReturn(this);
+}
+
+class IrConstant extends IrNode {
+  final Constant value;
+  IrConstant(int offset, this.value) : super(offset);
+  accept(IrNodesVisitor visitor) => visitor.visitIrConstant(this);
+}
+
+
+abstract class IrNodesVisitor<T> {
+  T visitIrFunction(IrFunction node);
+  T visitIrReturn(IrReturn node);
+  T visitIrConstant(IrConstant node);
+}