dart2js: Refactoring, documentation, and a few bugfixes in Namer class.

pkg/compiler/lib/src/js_backend/minify_namer.dart

Index: pkg/compiler/lib/src/js_backend/minify_namer.dart
diff --git a/pkg/compiler/lib/src/js_backend/minify_namer.dart b/pkg/compiler/lib/src/js_backend/minify_namer.dart
index 4641afdd5fe6fd5cbfe1bb187b86c03eb3060a83..579429e82259688f042e27cd3e17a3d79707d9be 100644
--- a/pkg/compiler/lib/src/js_backend/minify_namer.dart
+++ b/pkg/compiler/lib/src/js_backend/minify_namer.dart
@@ -26,14 +26,18 @@ class MinifyNamer extends Namer {
 
   _FieldNamingRegistry fieldRegistry;
 
-  // You can pass an invalid identifier to this and unlike its non-minifying
-  // counterpart it will never return the proposedName as the new fresh name.
+  /// You can pass an invalid identifier to this and unlike its non-minifying
+  /// counterpart it will never return the proposedName as the new fresh name.
+  ///
+  /// [sanitizeForNatives] and [sanitizeForAnnotations] are ignored because the
+  /// minified names will always avoid clashing with annotated names or natives.
   String getFreshName(String proposedName,
                       Set<String> usedNames,
                       Map<String, String> suggestedNames,
-                      {bool ensureSafe: true}) {
-    var freshName;
-    var suggestion = suggestedNames[proposedName];
+                      {bool sanitizeForNatives: false,
+                       bool sanitizeForAnnotations: false}) {
+    String freshName;
+    String suggestion = suggestedNames[proposedName];
     if (suggestion != null && !usedNames.contains(suggestion)) {
       freshName = suggestion;
     } else {
@@ -44,18 +48,20 @@ class MinifyNamer extends Namer {
     return freshName;
   }
 
-  String getClosureVariableName(String name, int id) {
+  String getClosureVariableName(String _, int id) {
     if (id < ALPHABET_CHARACTERS) {
       return new String.fromCharCodes([_letterNumber(id)]);
     }
-    return "${getMappedInstanceName('closure')}_$id";
+    // Fall back to a slightly longer name.
+    String basename = _disambiguateMember(null, 'closure');
+    return '${basename}_$id';
   }
 
   // From issue 7554.  These should not be used on objects (as instance
   // variables) because they clash with names from the DOM. However, it is
   // OK to use them as fields, as we only access fields directly if we know
   // the receiver type.
-  static const _reservedNativeProperties = const <String>[
+  static const List<String> _reservedNativeProperties = const <String>[
       'Q', 'a', 'b', 'c', 'd', 'e', 'f', 'r', 'x', 'y', 'z',
       // 2-letter:
       'ch', 'cx', 'cy', 'db', 'dx', 'dy', 'fr', 'fx', 'fy', 'go', 'id', 'k1',
@@ -80,9 +86,11 @@ class MinifyNamer extends Namer {
       'Text', 'time', 'type', 'view', 'warn', 'wrap', 'ZERO'];
 
   void reserveBackendNames() {
-    for (var name in _reservedNativeProperties) {
+    for (String name in _reservedNativeProperties) {
       if (name.length < 2) {
-        instanceNameMap[name] = name;
+        // Ensure the 1-letter names are disambiguated to the same name.
+        String disambiguatedName = name;
+        reservePublicMemberName(name, disambiguatedName);
       }
       usedInstanceNames.add(name);
       // Getter and setter names are autogenerated by prepending 'g' and 's' to
@@ -166,12 +174,12 @@ class MinifyNamer extends Namer {
     // in a predictable order determined by the proposed name.  This is in order
     // to make the renamer stable: small changes in the input should nornally
     // result in relatively small changes in the output.
-    for (var n = 1; n <= 3; n++) {
+    for (int n = 1; n <= 3; n++) {
       int h = hash;
       while (h > 10) {
-        var codes = <int>[_letterNumber(h)];
+        List<int> codes = <int>[_letterNumber(h)];
         int h2 = h ~/ ALPHABET_CHARACTERS;
-        for (var i = 1; i < n; i++) {
+        for (int i = 1; i < n; i++) {
           codes.add(_alphaNumericNumber(h2));
           h2 ~/= ALPHANUMERIC_CHARACTERS;
         }
@@ -213,9 +221,9 @@ class MinifyNamer extends Namer {
   /// If we can't find a hash based name in the three-letter space, then base
   /// the name on a letter and a counter.
   String _badName(int hash, Set<String> usedNames) {
-    var startLetter = new String.fromCharCodes([_letterNumber(hash)]);
-    var name;
-    var i = 0;
+    String startLetter = new String.fromCharCodes([_letterNumber(hash)]);
+    String name;
+    int i = 0;
     do {
       name = "$startLetter${i++}";
     } while (usedNames.contains(name));
@@ -291,8 +299,7 @@ class _FieldNamingRegistry {
         nameStore.add(MinifyNamer._reservedNativeProperties[count]);
       } else {
         nameStore.add(namer.getFreshName("field$count",
-            namer.usedInstanceNames, namer.suggestedInstanceNames,
-            ensureSafe: true));
+            namer.usedInstanceNames, namer.suggestedInstanceNames));
       }
     }
 
@@ -422,7 +429,7 @@ class _MixinFieldNamingScope extends _FieldNamingScope {
     : super.inherit(container, superScope, registry);
 
   String _nextName() {
-    var proposed = super._nextName();
+    String proposed = super._nextName();
     return proposed + r'$';
   }
 }