Add minifying renamer to the JS printer so locals are called z0, z1, z2, etc.

lib/compiler/implementation/js/printer.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.
 
 class Printer implements NodeVisitor {
   final bool shouldCompressOutput;
   leg.Compiler compiler;
   leg.CodeBuffer outBuffer;
   int indentLevel = 0;
   bool inForInit = false;
   bool atStatementBegin = false;
   final DanglingElseVisitor danglingElseVisitor;
+  Renamer _renamer;

[floitsch, 2012/10/09 13:45:43]

no need to make it private.

[erikcorry, 2012/10/09 20:15:51]

Done.

 
   Printer(leg.Compiler compiler)
       : shouldCompressOutput = compiler.enableMinification,
         this.compiler = compiler,
         outBuffer = new leg.CodeBuffer(),
-        danglingElseVisitor = new DanglingElseVisitor(compiler);
+        danglingElseVisitor = new DanglingElseVisitor(compiler) {
+    _renamer = shouldCompressOutput ? new MinifyRenamer() : new DummyRenamer();
+  }
 
   void spaceOut() {
     if (!shouldCompressOutput) out(" ");
   }
   void lineOut() {
     if (!shouldCompressOutput) out("\n");
   }
 
   String lastAddedString = null;
   int get lastCharCode {
@@ skipping 316 matching lines @@
   }
 
   void functionOut(Fun fun, Node name) {
     out("function");
     if (name != null) {
       out(" ");
       // Name must be a [Decl]. Therefore only test for primary expressions.
       visitNestedExpression(name, PRIMARY,
                             newInForInit: false, newAtStatementBegin: false);
     }
+    _renamer.enterScope();
     out("(");
     if (fun.params != null) {
       visitCommaSeparated(fun.params, PRIMARY,
                           newInForInit: false, newAtStatementBegin: false);
     }
     out(")");
     blockBody(fun.body, needsSeparation: false, needsNewline: false);
+    _renamer.leaveScope();
   }
 
   visitFunctionDeclaration(FunctionDeclaration declaration) {
     indent();
     functionOut(declaration.function, declaration.name);
     lineOut();
   }
 
   visitNestedExpression(Expression node, int requiredPrecedence,
                         [bool newInForInit, bool newAtStatementBegin]) {
@@ skipping 217 matching lines @@
   }
 
   visitPostfix(Postfix postfix) {
     visitNestedExpression(postfix.argument, LEFT_HAND_SIDE,
                           newInForInit: inForInit,
                           newAtStatementBegin: atStatementBegin);
     out(postfix.op);
   }
 
   visitVariableUse(VariableUse ref) {
-    out(ref.name);
+    var newName = _renamer.getName(ref.name);

[floitsch, 2012/10/09 13:45:43]

FYI: I think it can currently happen that the name contains a ".". For example
"isolate.foo".
This is however correctly handled by your code.

[erikcorry, 2012/10/09 20:15:51]

ok

+    out(newName);

[floitsch, 2012/10/09 13:45:43]

out(renamer.getName(ref.name)) ?

[erikcorry, 2012/10/09 20:15:51]

Done.

   }
 
   visitThis(This node) {
     out("this");
   }
 
   visitVariableDeclaration(VariableDeclaration decl) {
-    out(decl.name);
+    var newName = _renamer.declareName(decl.name);
+    out(newName);
   }
 
   visitParameter(Parameter param) {
-    out(param.name);
+    var newName = _renamer.declareName(param.name);
+    out(newName);
   }
 
   bool isDigit(int charCode) {
     return charCodes.$0 <= charCode && charCode <= charCodes.$9;
   }
 
   bool isValidJavaScriptId(String field) {
     if (field.length < 3) return false;
     // Ignore the leading and trailing string-delimiter.
     for (int i = 1; i < field.length - 1; i++) {
@@ skipping 196 matching lines @@
   bool visitExpression(Expression node) => false;
 }
 
 
 leg.CodeBuffer prettyPrint(Node node,
                            leg.Compiler compiler) {
   Printer printer = new Printer(compiler);
   printer.visit(node);
   return printer.outBuffer;
 }
+
+
+abstract class Renamer {

[floitsch, 2012/10/09 13:45:43]

Missing enterScope, leaveScope.

[floitsch, 2012/10/09 13:45:43]

I would call this class 'Namer'. Otherwise it implies that it renames, which it
doesn't always do.

[erikcorry, 2012/10/09 20:15:51]

Done.

[erikcorry, 2012/10/09 20:15:51]

Done and the member variable was also renamed to match.

+  String getName(String oldName);
+  String declareName(String oldName);
+}
+
+
+class DummyRenamer implements Renamer {

[floitsch, 2012/10/09 13:45:43]

Don't like "Dummy". Maybe "PassThroughNamer", "OriginalNamer", "NoMinifyNamer",
"VerboseNamer", "SimpleNamer", ...

[ngeoffray, 2012/10/09 13:53:42]

IdentityNamer?

[floitsch, 2012/10/09 13:55:35]

yeah. That's actually the one I was looking for. thanks.

[erikcorry, 2012/10/09 20:15:51]

Done.

+  String getName(String oldName) => oldName;
+  String declareName(String oldName) => oldName;
+  void enterScope() {}
+  void leaveScope() {}
+}
+
+
+class MinifyRenamer implements Renamer {
+  MinifyRenamer() : _maps = [], _name_number_stack = [], _name_number = 0;

[ngeoffray, 2012/10/09 13:53:42]

_name_number -> _nameNumber
_name_number_stack -> _nameNumberStack

[ngeoffray, 2012/10/09 13:53:42]

You could type these lists:
_maps = <Map<String, String>[], _nameNumberStack = <int>[]

[erikcorry, 2012/10/09 20:15:51]

Done.

[erikcorry, 2012/10/09 20:15:51]

I'd rather not.

+
+  void enterScope() {
+    _maps.add(new Map<String, String>());
+    _name_number_stack.add(_name_number);

[floitsch, 2012/10/09 13:45:43]

_nameNumberStack

[erikcorry, 2012/10/09 20:15:51]

Done.

+  }
+
+  void leaveScope() {
+    _maps.removeLast();
+    _name_number = _name_number_stack.removeLast();
+  }
+
+  String getName(String oldName) {
+    for (int i = _maps.length - 1; i >= 0; i--) {
+      var map = _maps[i];

[floitsch, 2012/10/09 13:45:43]

Personally I would prefer having a type here, but style-guide says it's ok, and
I understand that "Map<String, String>" is long.

[erikcorry, 2012/10/09 20:15:51]

I'd rather not.

+      if (map.containsKey(oldName)) return map[oldName];

[floitsch, 2012/10/09 13:45:43]

String replacement = map[oldName];
if (replacement !== null) return replacement;

[erikcorry, 2012/10/09 20:15:51]

Done.

+    }
+    return oldName;
+  }
+
+  Strint declareName(String oldName) {
+    if (_maps.length == 0) return oldName;
+    var newName = "z${_name_number++}";
+    _maps.last()[oldName] = newName;
+    return newName;
+  }
+
+  List<Map<String, String>> _maps;

[floitsch, 2012/10/09 13:45:43]

We usually have locals on the top of the class.

[floitsch, 2012/10/09 13:45:43]

No need to make the fields private.

[floitsch, 2012/10/09 13:45:43]

make the maps field final.

[erikcorry, 2012/10/09 20:15:51]

Done.

[erikcorry, 2012/10/09 20:15:51]

Done.

[erikcorry, 2012/10/09 20:15:51]

Done.

+  List<int> _name_number_stack;

[floitsch, 2012/10/09 13:45:43]

make nameNumberStack final.

[erikcorry, 2012/10/09 20:15:51]

Done.

+  int _name_number;
+}