account for exceptions in AST_Assign.left (#2892)

fixes #2891
2018-02-08 03:31:51 +08:00
parent 905325d3e2
commit d66d86f20b
2 changed files with 63 additions and 2 deletions
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2758,8 +2758,13 @@ merge(Compressor.prototype, {
            return any(this.elements, compressor);
        });
        def(AST_Assign, function(compressor){
-            return this.operator != "=" && this.left.may_throw(compressor)
-                || this.right.may_throw(compressor);
+            if (this.right.may_throw(compressor)) return true;
+            if (!compressor.has_directive("use strict")
+                && this.operator == "="
+                && this.left instanceof AST_SymbolRef) {
+                return false;
+            }
+            return this.left.may_throw(compressor);
        });
        def(AST_Binary, function(compressor){
            return this.left.may_throw(compressor)