dart2js: Use frequency of occurence to sort metadata indices.

pkg/js_ast/lib/src/nodes.dart

Index: pkg/js_ast/lib/src/nodes.dart
diff --git a/pkg/js_ast/lib/src/nodes.dart b/pkg/js_ast/lib/src/nodes.dart
index 7c8293e8d9e5ae5896583167499a28236375793f..5b71db99826efee3db2570cf3b1a7af963e27aec 100644
--- a/pkg/js_ast/lib/src/nodes.dart
+++ b/pkg/js_ast/lib/src/nodes.dart
@@ -49,11 +49,17 @@ abstract class NodeVisitor<T> {
   T visitNamedFunction(NamedFunction node);
   T visitFun(Fun node);
 
+  T visitTokenExpression(TokenExpression node);
+  T visitTokenNumber(TokenNumber node);
+  T visitTokenString(TokenString node);
+
   T visitLiteralBool(LiteralBool node);
   T visitLiteralString(LiteralString node);
   T visitLiteralNumber(LiteralNumber node);
   T visitLiteralNull(LiteralNull node);
 
+  T visitStringConcatenation(StringConcatenation node);
+
   T visitArrayInitializer(ArrayInitializer node);
   T visitArrayHole(ArrayHole node);
   T visitObjectInitializer(ObjectInitializer node);
@@ -139,6 +145,12 @@ class BaseVisitor<T> implements NodeVisitor<T> {
   T visitNamedFunction(NamedFunction node) => visitExpression(node);
   T visitFun(Fun node) => visitExpression(node);
 
+  T visitToken(Token node) => visitExpression(node);
+
+  T visitTokenExpression(TokenExpression node) => visitExpression(node);
+  T visitTokenNumber(TokenNumber node) => visitToken(node);
+  T visitTokenString(TokenString node) => visitToken(node);
+
   T visitLiteral(Literal node) => visitExpression(node);
 
   T visitLiteralBool(LiteralBool node) => visitLiteral(node);
@@ -146,6 +158,8 @@ class BaseVisitor<T> implements NodeVisitor<T> {
   T visitLiteralNumber(LiteralNumber node) => visitLiteral(node);
   T visitLiteralNull(LiteralNull node) => visitLiteral(node);
 
+  T visitStringConcatenation(StringConcatenation node) => visitLiteral(node);
+
   T visitArrayInitializer(ArrayInitializer node) => visitExpression(node);
   T visitArrayHole(ArrayHole node) => visitExpression(node);
   T visitObjectInitializer(ObjectInitializer node) => visitExpression(node);
@@ -916,6 +930,30 @@ class PropertyAccess extends Expression {
   int get precedenceLevel => CALL;
 }
 
+abstract class Token extends Literal {

[sra1, 2015/05/27 19:38:51]

These are abstract classes that are overridden.
Describe how they should be used.

I think 'DeferredToken' and 'DeferredNumberToken' etc would be a better names. 
'Late' would be an acceptable synonym for 'Deferred'

[herhut, 2015/06/09 11:10:00]

Well, this is only one use (the current use) of the Token interface. Once could
also use it to insert a blob into the AST without telling what it really is.
Just as an example. But I am fine with the renaming if you want to narrow the
scope.

+  void visitChildren(NodeVisitor visitor) {}
+
+  Token _clone() => this;
+}
+
+abstract class TokenNumber extends Token {
+  accept(NodeVisitor visitor) => visitor.visitTokenNumber(this);
+
+  int get value;
+}
+
+abstract class TokenString extends Token {
+  accept(NodeVisitor visitor) => visitor.visitTokenString(this);
+
+  String get value;
+}
+
+abstract class TokenExpression extends Token {

[sra1, 2015/05/27 19:38:51]

What is a TokenExpression?
DeferredExpression?

[herhut, 2015/06/09 11:10:00]

Done.

+  accept(NodeVisitor visitor) => visitor.visitTokenExpression(this);
+
+  Expression get value;

[sra1, 2015/05/27 19:38:51]

What is the precedence?
PRIMARY is almost certainly wrong.

[herhut, 2015/06/09 11:10:00]

It actually was correct for the current usage but I have changed Token to extend
Expression, so now any class that implements TokenExpression will have to supply
a precedence.

+}
+
 abstract class Literal extends Expression {
   void visitChildren(NodeVisitor visitor) {}
 
@@ -946,7 +984,7 @@ class LiteralString extends Literal {
    * Constructs a LiteralString from a string value.
    *
    * The constructor does not add the required quotes.  If [value] is not
-   * surrounded by quotes and property escaped, the resulting object is invalid
+   * surrounded by quotes and properly escaped, the resulting object is invalid
    * as a JS value.
    *
    * TODO(sra): Introduce variants for known valid strings that don't allocate a
@@ -958,6 +996,25 @@ class LiteralString extends Literal {
   LiteralString _clone() => new LiteralString(value);
 }
 
+class StringConcatenation extends Literal {
+  final List<Literal> parts;
+
+  /**
+   * Constructs a StringConcatenation from a list of Literal elements.
+   * The constructor does not add surrounding quotes to the resulting
+   * concatenated string.
+   */
+  StringConcatenation(this.parts);
+
+  accept(NodeVisitor visitor) => visitor.visitStringConcatenation(this);
+
+  void visitChildren(NodeVisitor visitor) {
+    for (Literal part in parts) part.accept(visitor);
+  }
+
+  StringConcatenation _clone() => new StringConcatenation(this.parts);
+}
+
 class LiteralNumber extends Literal {
   final String value;  // Must be a valid JavaScript number literal.
 
@@ -1161,7 +1218,6 @@ class Await extends Expression {
   accept(NodeVisitor visitor) => visitor.visitAwait(this);
   void visitChildren(NodeVisitor visitor) => expression.accept(visitor);
   Await _clone() => new Await(expression);
-
 }
 
 /**