handle overlapped variable definitions (#1691)

Process variable definitions with or without assigned values against:
- `arguments`
- named function arguments
- multiple definitions within same scope

Essentially demote variable declarations with no value assignments.

Also fixed invalid use of `AST_VarDef` over `arguments` - should use a member of `AST_SymbolDeclaration` instead.

1 files changed, 12 insertions, 5 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 83486b61..590015ff 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -260,7 +260,7 @@ merge(Compressor.prototype, {
                 if (node instanceof AST_SymbolRef) {
                     var d = node.definition();
                     d.references.push(node);
-                    if (!d.fixed || !is_safe(d)
+                    if (d.fixed === undefined || !is_safe(d)
                         || is_modified(node, 0, d.fixed instanceof AST_Lambda)) {
                         d.fixed = false;
                     }
@@ -270,10 +270,10 @@ merge(Compressor.prototype, {
                 }
                 if (node instanceof AST_VarDef) {
                     var d = node.name.definition();
-                    if (d.fixed === undefined) {
-                        d.fixed = node.value || make_node(AST_Undefined, node);
+                    if (d.fixed == null) {
+                        d.fixed = node.value;
                         mark_as_safe(d);
-                    } else {
+                    } else if (node.value) {
                         d.fixed = false;
                     }
                 }
@@ -357,7 +357,14 @@ merge(Compressor.prototype, {
 
         function is_safe(def) {
             for (var i = safe_ids.length, id = def.id; --i >= 0;) {
-                if (safe_ids[i][id]) return true;
+                if (safe_ids[i][id]) {
+                    if (def.fixed == null) {
+                        var orig = def.orig[0];
+                        if (orig instanceof AST_SymbolFunarg || orig.name == "arguments") return false;
+                        def.fixed = make_node(AST_Undefined, orig);
+                    }
+                    return true;
+                }
             }
         }