drop property assignment to constants (#2612)

1 files changed, 13 insertions, 2 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 52c30964..735b4d2d 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1708,6 +1708,11 @@ merge(Compressor.prototype, {
             return this.consequent._dot_throw(compressor)
                 || this.alternative._dot_throw(compressor);
         })
+        def(AST_Dot, function(compressor) {
+            if (!is_strict(compressor)) return false;
+            if (this.expression instanceof AST_Function && this.property == "prototype") return false;
+            return true;
+        });
         def(AST_Sequence, function(compressor) {
             return this.tail_node()._dot_throw(compressor);
         });
@@ -3184,8 +3189,14 @@ merge(Compressor.prototype, {
             }
         });
         def(AST_Assign, function(compressor){
-            this.write_only = !this.left.has_side_effects(compressor);
-            return this;
+            var left = this.left;
+            if (left.has_side_effects(compressor)) return this;
+            this.write_only = true;
+            while (left instanceof AST_PropAccess) {
+                left = left.expression;
+            }
+            if (left instanceof AST_Symbol) return this;
+            return this.right.drop_side_effect_free(compressor);
         });
         def(AST_Conditional, function(compressor){
             var consequent = this.consequent.drop_side_effect_free(compressor);