drop assignment in `AST_VarDef.value` (#2522)

fixes #2516

1 files changed, 28 insertions, 31 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 22415f4d..b51fdfc7 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1088,6 +1088,7 @@ merge(Compressor.prototype, {
             function get_lhs(expr) {
                 if (expr instanceof AST_VarDef) {
                     var def = expr.name.definition();
+                    if (!member(expr.name, def.orig)) return;
                     var declared = def.orig.length - def.eliminated;
                     var referenced = def.references.length - def.replaced;
                     if (declared > 1 && !(expr.name instanceof AST_SymbolFunarg)
@@ -2434,47 +2435,18 @@ merge(Compressor.prototype, {
                 });
                 return true;
             }
-            var sym;
-            if (scope === self
-                && (sym = assign_as_unused(node)) instanceof AST_SymbolRef
-                && self.variables.get(sym.name) === sym.definition()) {
-                if (node instanceof AST_Assign) node.right.walk(tw);
-                return true;
-            }
-            if (node instanceof AST_SymbolRef) {
-                var node_def = node.definition();
-                if (!(node_def.id in in_use_ids)) {
-                    in_use_ids[node_def.id] = true;
-                    in_use.push(node_def);
-                }
-                return true;
-            }
-            if (node instanceof AST_Scope) {
-                var save_scope = scope;
-                scope = node;
-                descend();
-                scope = save_scope;
-                return true;
-            }
+            return scan_ref_scoped(node, descend);
         });
         self.walk(tw);
         // pass 2: for every used symbol we need to walk its
         // initialization code to figure out if it uses other
         // symbols (that may not be in_use).
+        tw = new TreeWalker(scan_ref_scoped);
         for (var i = 0; i < in_use.length; ++i) {
             in_use[i].orig.forEach(function(decl){
                 // undeclared globals will be instanceof AST_SymbolRef
                 var init = initializations.get(decl.name);
                 if (init) init.forEach(function(init){
-                    var tw = new TreeWalker(function(node){
-                        if (node instanceof AST_SymbolRef) {
-                            var node_def = node.definition();
-                            if (!(node_def.id in in_use_ids)) {
-                                in_use_ids[node_def.id] = true;
-                                in_use.push(node_def);
-                            }
-                        }
-                    });
                     init.walk(tw);
                 });
             });
@@ -2663,6 +2635,31 @@ merge(Compressor.prototype, {
             }
         );
         self.transform(tt);
+
+        function scan_ref_scoped(node, descend) {
+            var sym;
+            if (scope === self
+                && (sym = assign_as_unused(node)) instanceof AST_SymbolRef
+                && self.variables.get(sym.name) === sym.definition()) {
+                if (node instanceof AST_Assign) node.right.walk(tw);
+                return true;
+            }
+            if (node instanceof AST_SymbolRef) {
+                var node_def = node.definition();
+                if (!(node_def.id in in_use_ids)) {
+                    in_use_ids[node_def.id] = true;
+                    in_use.push(node_def);
+                }
+                return true;
+            }
+            if (node instanceof AST_Scope) {
+                var save_scope = scope;
+                scope = node;
+                descend();
+                scope = save_scope;
+                return true;
+            }
+        }
     });
 
     AST_Scope.DEFMETHOD("hoist_declarations", function(compressor){