js_ast: implement rest/spread parsing

lib/src/js/nodes.dart

 // Copyright (c) 2012, 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 js_ast;
 
 abstract class NodeVisitor<T> {
   T visitProgram(Program node);
 
   T visitBlock(Block node);
@@ skipping 22 matching lines @@
   T visitLiteralExpression(LiteralExpression node);
   T visitVariableDeclarationList(VariableDeclarationList node);
   T visitAssignment(Assignment node);
   T visitVariableInitialization(VariableInitialization node);
   T visitConditional(Conditional cond);
   T visitNew(New node);
   T visitCall(Call node);
   T visitBinary(Binary node);
   T visitPrefix(Prefix node);
   T visitPostfix(Postfix node);
+  T visitSpread(Spread node);
 
   T visitIdentifier(Identifier node);
   T visitThis(This node);
   T visitSuper(Super node);
   T visitAccess(PropertyAccess node);
+  T visitRestParameter(RestParameter node);
 
   T visitNamedFunction(NamedFunction node);
   T visitFun(Fun node);
   T visitArrowFun(ArrowFun node);
 
   T visitLiteralBool(LiteralBool node);
   T visitLiteralString(LiteralString node);
   T visitLiteralNumber(LiteralNumber node);
   T visitLiteralNull(LiteralNull node);
 
@@ skipping 72 matching lines @@
     } else {
       return visitExpression(node);
     }
   }
   T visitConditional(Conditional node) => visitExpression(node);
   T visitNew(New node) => visitExpression(node);
   T visitCall(Call node) => visitExpression(node);
   T visitBinary(Binary node) => visitExpression(node);
   T visitPrefix(Prefix node) => visitExpression(node);
   T visitPostfix(Postfix node) => visitExpression(node);
+  T visitSpread(Spread node) => visitPrefix(node);
   T visitAccess(PropertyAccess node) => visitExpression(node);
 
   T visitIdentifier(Identifier node) => visitExpression(node);
   T visitThis(This node) => visitExpression(node);
   T visitSuper(Super node) => visitExpression(node);
 
+  T visitRestParameter(RestParameter node) => visitNode(node);
+
   T visitNamedFunction(NamedFunction node) => visitExpression(node);
   T visitFunctionExpression(FunctionExpression node) => visitExpression(node);
   T visitFun(Fun node) => visitFunctionExpression(node);
   T visitArrowFun(ArrowFun node) => visitFunctionExpression(node);
 
   T visitLiteral(Literal node) => visitExpression(node);
 
   T visitLiteralBool(LiteralBool node) => visitLiteral(node);
   T visitLiteralString(LiteralString node) => visitLiteral(node);
   T visitLiteralNumber(LiteralNumber node) => visitLiteral(node);
@@ skipping 701 matching lines @@
 
   Prefix _clone() => new Prefix(op, argument);
 
   void visitChildren(NodeVisitor visitor) {
     argument.accept(visitor);
   }
 
   int get precedenceLevel => UNARY;
 }
 
+// SpreadElement isn't really a prefix expression, as it can only appear in
+// certain places such as ArgumentList and destructuring, but we pretend
+// it is for simplicity's sake.
+class Spread extends Prefix {
+  Spread(Expression operand) : super('...', operand);
+  int get precedenceLevel => SPREAD;
+
+  accept(NodeVisitor visitor) => visitor.visitSpread(this);
+  Spread _clone() => new Spread(argument);
+}
+
 class Postfix extends Expression {
   final String op;
   final Expression argument;
 
   Postfix(this.op, this.argument);
 
   accept(NodeVisitor visitor) => visitor.visitPostfix(this);
 
   Postfix _clone() => new Postfix(op, argument);
 
   void visitChildren(NodeVisitor visitor) {
     argument.accept(visitor);
   }
 
   int get precedenceLevel => UNARY;
 }
 
-class Identifier extends Expression {
+abstract class Parameter implements Expression {}
+
+class Identifier extends Expression implements Parameter {
   final String name;
   final bool allowRename;
 
   Identifier(this.name, {this.allowRename: true}) {
     assert(_identifierRE.hasMatch(name));
   }
   static RegExp _identifierRE = new RegExp(r'^[A-Za-z_$][A-Za-z_$0-9]*$');
 
   Identifier _clone() =>
       new Identifier(name, allowRename: allowRename);
   accept(NodeVisitor visitor) => visitor.visitIdentifier(this);
   int get precedenceLevel => PRIMARY;
   void visitChildren(NodeVisitor visitor) {}
 }
 
+// This is an expression for convenience in the AST.
+class RestParameter extends Expression implements Parameter {
+  final Identifier parameter;
+
+  RestParameter(this.parameter);
+
+  RestParameter _clone() => new RestParameter(parameter);
+  accept(NodeVisitor visitor) => visitor.visitRestParameter(this);
+  void visitChildren(NodeVisitor visitor) {
+    parameter.accept(visitor);
+  }
+  int get precedenceLevel => SPREAD;
+}
+
 class This extends Expression {
   accept(NodeVisitor visitor) => visitor.visitThis(this);
   This _clone() => new This();
   int get precedenceLevel => PRIMARY;
   void visitChildren(NodeVisitor visitor) {}
 }
 
 // `super` is more restricted in the ES6 spec, but for simplicity we accept
 // it anywhere that `this` is accepted.
 class Super extends Expression {
@@ skipping 14 matching lines @@
   void visitChildren(NodeVisitor visitor) {
     name.accept(visitor);
     function.accept(visitor);
   }
   NamedFunction _clone() => new NamedFunction(name, function);
 
   int get precedenceLevel => CALL;
 }
 
 abstract class FunctionExpression extends Expression {
-  List<Identifier> get params;
+  List<Parameter> get params;
   get body; // Expression or block
 }
 
 class Fun extends FunctionExpression {
-  final List<Identifier> params;
+  final List<Parameter> params;
   final Block body;
   final AsyncModifier asyncModifier;
 
   Fun(this.params, this.body, {this.asyncModifier: const AsyncModifier.sync()});
 
   accept(NodeVisitor visitor) => visitor.visitFun(this);
 
   void visitChildren(NodeVisitor visitor) {
-    for (Identifier param in params) param.accept(visitor);
+    for (Parameter param in params) param.accept(visitor);
     body.accept(visitor);
   }
 
   Fun _clone() => new Fun(params, body, asyncModifier: asyncModifier);
 
   int get precedenceLevel => CALL;
 }
 
 class ArrowFun extends FunctionExpression {
-  final List<Identifier> params;
+  final List<Parameter> params;
   final body; // Expression or Block
 
   ArrowFun(this.params, this.body);
 
   accept(NodeVisitor visitor) => visitor.visitArrowFun(this);
 
   void visitChildren(NodeVisitor visitor) {
-    for (Identifier param in params) param.accept(visitor);
+    for (Parameter param in params) param.accept(visitor);
     body.accept(visitor);
   }
 
   ArrowFun _clone() => new ArrowFun(params, body);
 
   /// Ensure parens always get generated if necessary.
   // TODO(jmesserly): I'm not sure the printer is handling this correctly for
   // function() { ... } either.
   int get precedenceLevel => ASSIGNMENT;
 }
@@ skipping 453 matching lines @@
   final Expression expression;
 
   CommentExpression(this.comment, this.expression);
 
   int get precedenceLevel => PRIMARY;
   accept(NodeVisitor visitor) => visitor.visitCommentExpression(this);
   CommentExpression _clone() => new CommentExpression(comment, expression);
 
   void visitChildren(NodeVisitor visitor) => expression.accept(visitor);
 }