Compress conditional assignments where all possible outcomes are equivalant and condition has no side effects

lib/compress.js

@@ -2321,6 +2321,13 @@ merge(Compressor.prototype, {
                 alternative: alternative
             });
         }
+        // x=y?1:1 --> x=1
+        if (!self.condition.has_side_effects(compressor)
+            && consequent instanceof AST_Constant
+            && alternative instanceof AST_Constant
+            && consequent.equivalent_to(alternative)) {
+            return make_node_from_constant(compressor, consequent.value, self);
+        }
         return self;
     });