improve `mangle` (#2948)

1 files changed, 80 insertions, 64 deletions

diff --git a/lib/scope.js b/lib/scope.js
index 6c883c66..87bfe0d6 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -83,8 +83,9 @@ SymbolDef.prototype = {
             var def;
             if (def = this.redefined()) {
                 this.mangled_name = def.mangled_name || def.name;
-            } else
-                this.mangled_name = s.next_mangled(options, this);
+            } else {
+                this.mangled_name = next_mangled_name(s, options, this);
+            }
             if (this.global && cache) {
                 cache.set(this.name, this.mangled_name);
             }
@@ -168,8 +169,8 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
                 var def = scope.find_variable(node);
                 if (node.thedef !== def) {
                     node.thedef = def;
-                    node.reference(options);
                 }
+                node.reference(options);
             }
         }
         else if (node instanceof AST_SymbolCatch) {
@@ -325,56 +326,59 @@ AST_Scope.DEFMETHOD("def_variable", function(symbol, init){
     return symbol.thedef = def;
 });
 
-function next_mangled(scope, options) {
-    var ext = scope.enclosed;
-    out: while (true) {
-        var m = base54(++scope.cname);
-        if (!is_identifier(m)) continue; // skip over "do"
-
-        // https://github.com/mishoo/UglifyJS2/issues/242 -- do not
-        // shadow a name reserved from mangling.
-        if (member(m, options.reserved)) continue;
-
-        // we must ensure that the mangled name does not shadow a name
-        // from some parent scope that is referenced in this or in
-        // inner scopes.
-        for (var i = ext.length; --i >= 0;) {
-            var sym = ext[i];
-            var name = sym.mangled_name || (sym.unmangleable(options) && sym.name);
-            if (m == name) continue out;
-        }
-        return m;
+function names_in_use(scope, options) {
+    var names = scope.names_in_use;
+    if (!names) {
+        scope.names_in_use = names = Object.create(scope.mangled_names || null);
+        scope.cname_holes = [];
+        scope.enclosed.forEach(function(def) {
+            if (def.unmangleable(options)) names[def.name] = true;
+        });
     }
+    return names;
 }
 
-AST_Scope.DEFMETHOD("next_mangled", function(options){
-    return next_mangled(this, options);
-});
-
-AST_Toplevel.DEFMETHOD("next_mangled", function(options){
-    var name;
-    do {
-        name = next_mangled(this, options);
-    } while (member(name, this.mangled_names));
-    return name;
-});
-
-AST_Function.DEFMETHOD("next_mangled", function(options, def){
+function next_mangled_name(scope, options, def) {
+    var in_use = names_in_use(scope, options);
+    var holes = scope.cname_holes;
+    var names = Object.create(null);
     // #179, #326
     // in Safari strict mode, something like (function x(x){...}) is a syntax error;
     // a function expression's argument cannot shadow the function expression's name
-
-    var tricky_def = def.orig[0] instanceof AST_SymbolFunarg && this.name && this.name.definition();
-
-    // the function's mangled_name is null when keep_fnames is true
-    var tricky_name = tricky_def ? tricky_def.mangled_name || tricky_def.name : null;
-
+    if (scope instanceof AST_Function && scope.name && def.orig[0] instanceof AST_SymbolFunarg) {
+        var tricky_def = scope.name.definition();
+        // the function's mangled_name is null when keep_fnames is true
+        names[tricky_def.mangled_name || tricky_def.name] = true;
+    }
+    var scopes = [ scope ];
+    def.references.forEach(function(sym) {
+        var scope = sym.scope;
+        do {
+            if (scopes.indexOf(scope) < 0) {
+                for (var name in names_in_use(scope, options)) {
+                    names[name] = true;
+                }
+                scopes.push(scope);
+            } else break;
+        } while (scope = scope.parent_scope);
+    });
+    var name;
+    for (var i = 0, len = holes.length; i < len; i++) {
+        name = base54(holes[i]);
+        if (names[name]) continue;
+        holes.splice(i, 1);
+        scope.names_in_use[name] = true;
+        return name;
+    }
     while (true) {
-        var name = next_mangled(this, options);
-        if (!tricky_name || tricky_name != name)
-            return name;
+        name = base54(++scope.cname);
+        if (in_use[name] || !is_identifier(name) || member(name, options.reserved)) continue;
+        if (!names[name]) break;
+        holes.push(scope.cname);
     }
-});
+    scope.names_in_use[name] = true;
+    return name;
+}
 
 AST_Symbol.DEFMETHOD("unmangleable", function(options){
     var def = this.definition();
@@ -419,18 +423,15 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){
     // present (and for AST_SymbolRef-s it'll use the mangled name of
     // the AST_SymbolDeclaration that it points to).
     var lname = -1;
-    var to_mangle = [];
-
-    var mangled_names = this.mangled_names = [];
-    if (options.cache) {
-        this.globals.each(collect);
-        if (options.cache.props) {
-            options.cache.props.each(function(mangled_name) {
-                push_uniq(mangled_names, mangled_name);
-            });
-        }
+
+    if (options.cache && options.cache.props) {
+        var mangled_names = this.mangled_names = Object.create(null);
+        options.cache.props.each(function(mangled_name) {
+            mangled_names[mangled_name] = true;
+        });
     }
 
+    var redefined = [];
     var tw = new TreeWalker(function(node, descend){
         if (node instanceof AST_LabeledStatement) {
             // lname is incremented when we get to the AST_Label
@@ -440,8 +441,12 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){
             return true;        // don't descend again in TreeWalker
         }
         if (node instanceof AST_Scope) {
-            node.variables.each(collect);
-            return;
+            descend();
+            if (options.cache && node instanceof AST_Toplevel) {
+                node.globals.each(mangle);
+            }
+            node.variables.each(mangle);
+            return true;
         }
         if (node instanceof AST_Label) {
             var name;
@@ -449,17 +454,28 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){
             node.mangled_name = name;
             return true;
         }
-        if (!options.ie8 && node instanceof AST_SymbolCatch) {
-            to_mangle.push(node.definition());
-            return;
+        if (!options.ie8 && node instanceof AST_Catch) {
+            var def = node.argname.definition();
+            var redef = def.redefined();
+            if (redef) {
+                redefined.push(def);
+                def.references.forEach(function(ref) {
+                    ref.thedef = redef;
+                    ref.reference(options);
+                    ref.thedef = def;
+                });
+            }
+            descend();
+            if (!redef) mangle(def);
+            return true;
         }
     });
     this.walk(tw);
-    to_mangle.forEach(function(def){ def.mangle(options) });
+    redefined.forEach(mangle);
 
-    function collect(symbol) {
-        if (!member(symbol.name, options.reserved)) {
-            to_mangle.push(symbol);
+    function mangle(def) {
+        if (!member(def.name, options.reserved)) {
+            def.mangle(options);
         }
     }
 });