fix corner case in conditionals (#5723)

fixes #5722

Author: alexlamsl

lib/compress.js

@@ -11634,10 +11634,14 @@ Compressor.prototype.compress = function(node) {
         });
         self.right = rhs.right;
         if (compressor) {
-            self.left = self.left.transform(compressor);
-        } else if (self.operator == rhs.left.operator) {
-            swap_chain(self.left);
+            var left = self.left.transform(compressor);
+            if (left !== self.left) {
+                self = self.clone();
+                self.left = left;
+            }
+            return self;
         }
+        if (self.operator == rhs.left.operator) swap_chain(self.left);
     }
 
     OPT(AST_Binary, function(self, compressor) {
@@ -11825,7 +11829,7 @@ Compressor.prototype.compress = function(node) {
             // x && (y && z) ---> x && y && z
             // w || (x, y || z) ---> w || (x, y) || z
             var rhs = self.right.tail_node();
-            if (rhs instanceof AST_Binary && self.operator == rhs.operator) swap_chain(self, compressor);
+            if (rhs instanceof AST_Binary && self.operator == rhs.operator) self = swap_chain(self, compressor);
         }
         if (compressor.option("strings") && self.operator == "+") {
             // "foo" + 42 + "" ---> "foo" + 42
@@ -11858,7 +11862,7 @@ Compressor.prototype.compress = function(node) {
                 && (self.left.is_string(compressor) && rhs.is_string(compressor)
                     || rhs.left.is_string(compressor)
                         && (self.left.is_constant() || !rhs.right.has_side_effects(compressor)))) {
-                swap_chain(self, compressor);
+                self = swap_chain(self, compressor);
             }
         }
         if (compressor.option("evaluate")) {

test/compress/conditionals.js

@@ -3068,3 +3068,23 @@ issue_5712: {
     }
     expect_stdout: "PASS"
 }
+
+issue_5722: {
+    options = {
+        conditionals: true,
+        evaluate: true,
+        keep_fnames: true,
+        side_effects: true,
+    }
+    input: {
+        var a = true;
+        a && function f() {
+            return 42;
+        }(a++) ? null + (console.log("PASS") && a++) : "";
+    }
+    expect: {
+        var a = true;
+        a && (void a++, console.log("PASS")) && a++;
+    }
+    expect_stdout: "PASS"
+}