enable `collapse_vars` & `reduce_vars` by default

- fix corner cases in `const` optimisation
- deprecate `/*@const*/`

fixes #1497
closes #1498

2 files changed, 8 insertions, 16 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 95e9c1b3..2bc1c5a5 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -69,8 +69,8 @@ function Compressor(options, false_by_default) {
         hoist_vars    : false,
         if_return     : !false_by_default,
         join_vars     : !false_by_default,
-        collapse_vars : false,
-        reduce_vars   : false,
+        collapse_vars : !false_by_default,
+        reduce_vars   : !false_by_default,
         cascade       : !false_by_default,
         side_effects  : !false_by_default,
         pure_getters  : false,
@@ -1252,7 +1252,7 @@ merge(Compressor.prototype, {
             this._evaluating = true;
             try {
                 var d = this.definition();
-                if ((d.constant || compressor.option("reduce_vars") && !d.modified) && d.init) {
+                if (compressor.option("reduce_vars") && !d.modified && d.init) {
                     if (compressor.option("unsafe")) {
                         if (!HOP(d.init, '_evaluated')) {
                             d.init._evaluated = ev(d.init, compressor);
@@ -3025,9 +3025,11 @@ merge(Compressor.prototype, {
                 return make_node(AST_Infinity, self).transform(compressor);
             }
         }
-        if (compressor.option("evaluate") && !isLHS(self, compressor.parent())) {
+        if (compressor.option("evaluate")
+            && compressor.option("reduce_vars")
+            && !isLHS(self, compressor.parent())) {
             var d = self.definition();
-            if (d && d.constant && d.init && d.init.is_constant(compressor)) {
+            if (d.constant && !d.modified && d.init && d.init.is_constant(compressor)) {
                 var original_as_string = self.print_to_string();
                 var const_node = make_node_from_constant(compressor, d.init.constant_value(compressor), self);
                 var const_node_as_string = const_node.print_to_string();
diff --git a/lib/scope.js b/lib/scope.js
index b0d92d7d..29e4103a 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -97,7 +97,6 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
     var scope = self.parent_scope = null;
     var labels = new Dictionary();
     var defun = null;
-    var last_var_had_const_pragma = false;
     var tw = new TreeWalker(function(node, descend){
         if (options.screw_ie8 && node instanceof AST_Catch) {
             var save_scope = scope;
@@ -154,13 +153,10 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
             // later.
             (node.scope = defun.parent_scope).def_function(node);
         }
-        else if (node instanceof AST_Var) {
-            last_var_had_const_pragma = node.has_const_pragma();
-        }
         else if (node instanceof AST_SymbolVar
                  || node instanceof AST_SymbolConst) {
             var def = defun.def_variable(node);
-            def.constant = node instanceof AST_SymbolConst || last_var_had_const_pragma;
+            def.constant = node instanceof AST_SymbolConst;
             def.init = tw.parent().value;
         }
         else if (node instanceof AST_SymbolCatch) {
@@ -369,12 +365,6 @@ AST_Symbol.DEFMETHOD("global", function(){
     return this.definition().global;
 });
 
-AST_Var.DEFMETHOD("has_const_pragma", function() {
-    var comments_before = this.start && this.start.comments_before;
-    var lastComment = comments_before && comments_before[comments_before.length - 1];
-    return lastComment && /@const\b/.test(lastComment.value);
-});
-
 AST_Toplevel.DEFMETHOD("_default_mangler_options", function(options){
     return defaults(options, {
         except      : [],