enable collapsing within AST_Definitions

lib/compress.js

@@ -647,30 +647,41 @@ merge(Compressor.prototype, {
             for (var stat_index = statements.length; --stat_index >= 0;) {
                 var stat = statements[stat_index];
 
-                // The variable definition must precede a statement.
+                var var_names_seen = Object.create(null);
-                if (stat_index <= 0) break;
-                var prev_stat_index = stat_index - 1;
-                var prev_stat = statements[prev_stat_index];
-                if (!(prev_stat instanceof AST_Definitions)) continue;
-                var var_defs = prev_stat.definitions;
-                if (var_defs == null) continue;
-
-                var var_names_seen = {};
                 var side_effects_encountered = false;
                 var lvalues_encountered = false;
-                var lvalues = {};
+                var lvalues = Object.create(null);
+                var prev_stat_index, var_defs, var_defs_index;
 
                 // Scan variable definitions from right to left.
-                for (var var_defs_index = var_defs.length; --var_defs_index >= 0;) {
+                if (stat instanceof AST_Definitions) {
+                    prev_stat_index = stat_index;
+                    var_defs = stat.definitions;
+                    for (var_defs_index = var_defs.length - 1; --var_defs_index >= 0;) {
+                        if (collapse(var_defs[var_defs_index + 1])) break;
+                    }
+                } else if (stat_index > 0) {
+                    // The variable definition must precede a statement.
+                    prev_stat_index = stat_index - 1;
+                    var prev_stat = statements[prev_stat_index];
+                    if (!(prev_stat instanceof AST_Definitions)) continue;
+                    var_defs = prev_stat.definitions;
+                    for (var_defs_index = var_defs.length; --var_defs_index >= 0;) {
+                        if (collapse(stat)) break;
+                    }
+                }
+            }
 
-                    // Obtain var declaration and var name with basic sanity check.
+            return statements;
+
+            function collapse(stat) {
                 var var_decl = var_defs[var_defs_index];
-                    if (var_decl.value == null) break;
+                if (var_decl.value == null) return true;
                 var var_name = var_decl.name.name;
-                    if (!var_name || !var_name.length) break;
+                if (!var_name || !var_name.length) return true;
 
                 // Bail if we've seen a var definition of same name before.
-                    if (var_name in var_names_seen) break;
+                if (var_name in var_names_seen) return true;
                 var_names_seen[var_name] = true;
 
                 // Only interested in cases with just one reference to the variable.
@@ -678,12 +689,12 @@ merge(Compressor.prototype, {
                 if (def.references.length !== 1
                     || var_name == "arguments" || (!toplevel && def.global)) {
                     side_effects_encountered = true;
-                        continue;
+                    return;
                 }
                 var ref = def.references[0];
 
                 // Don't replace ref if eval() or with statement in scope.
-                    if (ref.scope.uses_eval || ref.scope.uses_with) break;
+                if (ref.scope.uses_eval || ref.scope.uses_with) return true;
 
                 // Constant single use vars can be replaced in any scope.
                 if (var_decl.value.is_constant()) {
@@ -694,20 +705,20 @@ merge(Compressor.prototype, {
                             return node;
                         }
                         if (node === ref)
-                                return replace_var(node, parent, true);
+                            return replace_var(var_decl, node, parent, true);
                     });
                     stat.transform(ctt);
-                        continue;
+                    return;
                 }
 
                 // Restrict var replacement to constants if side effects encountered.
-                    if (side_effects_encountered |= lvalues_encountered) continue;
+                if (side_effects_encountered |= lvalues_encountered) return;
 
                 var value_has_side_effects = var_decl.value.has_side_effects(compressor);
                 // Non-constant single use vars can only be replaced in same scope.
                 if (ref.scope !== scope) {
                     side_effects_encountered |= value_has_side_effects;
-                        continue;
+                    return;
                 }
 
                 // Detect lvalues in var value.
@@ -754,7 +765,7 @@ merge(Compressor.prototype, {
                     function postorder(node) {
                         if (unwind) return node;
                         if (node === ref)
-                                return unwind = true, replace_var(node, tt.parent(), false);
+                            return unwind = true, replace_var(var_decl, node, tt.parent(), false);
                         if (side_effects_encountered |= node.has_side_effects(compressor))
                             return unwind = true, node;
                         if (lvalues_encountered && node instanceof AST_SymbolRef && node.name in lvalues) {
@@ -765,14 +776,12 @@ merge(Compressor.prototype, {
                 );
                 stat.transform(tt);
             }
-            }
-
-            return statements;
 
             function is_lvalue(node, parent) {
                 return node instanceof AST_SymbolRef && is_lhs(node, parent);
             }
-            function replace_var(node, parent, is_constant) {
+
+            function replace_var(var_decl, node, parent, is_constant) {
                 if (is_lvalue(node, parent)) return node;
 
                 // Remove var definition and return its value to the TreeTransformer to replace.
@@ -789,7 +798,7 @@ merge(Compressor.prototype, {
 
                 compressor.info("Collapsing {type} {name} [{file}:{line},{col}]", {
                     type: is_constant ? "constant" : "variable",
-                    name: var_name,
+                    name: var_decl.name.name,
                     file: node.start.file,
                     line: node.start.line,
                     col: node.start.col
@@ -1737,6 +1746,7 @@ merge(Compressor.prototype, {
         def(AST_SymbolRef, function(compressor){
             return this.undeclared();
         });
+        def(AST_SymbolDeclaration, return_false);
         def(AST_Object, function(compressor){
             return any(this.properties, compressor);
         });

test/compress/collapse_vars.js

@@ -667,7 +667,7 @@ collapse_vars_lvalues: {
         function f4(x) { var a = (x -= 3); return x + a; }
         function f5(x) { var w = e1(), v = e2(), c = v = --x; return (w = x) - c; }
         function f6(x) { var w = e1(), v = e2(); return (v = --x) - (w = x); }
-        function f7(x) { var w = e1(), v = e2(), c = v - x; return (w = x) - c; }
+        function f7(x) { var w = e1(), c = e2() - x; return (w = x) - c; }
         function f8(x) { var w = e1(), v = e2(); return (w = x) - (v - x); }
         function f9(x) { var w = e1(); return e2() - x - (w = x); }
     }
@@ -699,7 +699,7 @@ collapse_vars_lvalues_drop_assign: {
         function f4(x) { var a = (x -= 3); return x + a; }
         function f5(x) { var v = (e1(), e2()), c = v = --x; return x - c; }
         function f6(x) { e1(), e2(); return --x - x; }
-        function f7(x) { var v = (e1(), e2()), c = v - x; return x - c; }
+        function f7(x) { var c = (e1(), e2() - x); return x - c; }
         function f8(x) { var v = (e1(), e2()); return x - (v - x); }
         function f9(x) { e1(); return e2() - x - x; }
     }