From c7152b5e6618089c359d8f6c944572997271cfc9 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L." <alexlamsl@gmail.com>
Date: Wed, 31 Jul 2024 17:56:39 +0300
Subject: [PATCH] enhance `comparisons` & `inline` (#5897)

---
 lib/compress.js              | 20 +++++++++---
 test/compress/comparisons.js | 60 ++++++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+), 5 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index 728523652c..a84014c344 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -11065,6 +11065,7 @@ Compressor.prototype.compress = function(node) {
                     var node = make_sequence(self, exprs).optimize(compressor);
                     fn.inlined = save_inlined;
                     node = maintain_this_binding(parent, current, node);
+                    self.inlined_node = node;
                     if (replacing || best_of_expression(node, self) === node) {
                         refs.forEach(function(ref) {
                             ref.scope = exp === fn ? fn.parent_scope : exp.scope;
@@ -11081,6 +11082,12 @@ Compressor.prototype.compress = function(node) {
                             exprs.unshift(self.expression);
                             return make_sequence(self, exprs).drop_side_effect_free(compressor, first_in_statement);
                         };
+                        self.has_side_effects = function(compressor) {
+                            var self = this;
+                            var exprs = self.args.slice();
+                            exprs.unshift(self.expression);
+                            return make_sequence(self, exprs).has_side_effects(compressor);
+                        };
                     }
                 }
                 var arg_used, insert, in_loop, scope;
@@ -12085,15 +12092,18 @@ Compressor.prototype.compress = function(node) {
             // void 0 !== x && null !== x ---> null != x
             // void 0 === x.a || null === x.a ---> null == x.a
             var left = self.left;
+            if (left.inlined_node) left = left.inlined_node;
             if (!(left instanceof AST_Binary)) break;
             if (left.operator != (self.operator == "&&" ? "!==" : "===")) break;
-            if (!(self.right instanceof AST_Binary)) break;
-            if (left.operator != self.right.operator) break;
-            if (is_undefined(left.left, compressor) && self.right.left instanceof AST_Null
-                || left.left instanceof AST_Null && is_undefined(self.right.left, compressor)) {
+            var right = self.right;
+            if (right.inlined_node) right = right.inlined_node;
+            if (!(right instanceof AST_Binary)) break;
+            if (left.operator != right.operator) break;
+            if (is_undefined(left.left, compressor) && right.left instanceof AST_Null
+                || left.left instanceof AST_Null && is_undefined(right.left, compressor)) {
                 var expr = extract_lhs(left.right, compressor);
                 if (!repeatable(compressor, expr)) break;
-                if (!expr.equals(self.right.right)) break;
+                if (!expr.equals(right.right)) break;
                 left.operator = left.operator.slice(0, -1);
                 left.left = make_node(AST_Null, self);
                 return left;
diff --git a/test/compress/comparisons.js b/test/compress/comparisons.js
index 2b43cc4fba..9faf34437c 100644
--- a/test/compress/comparisons.js
+++ b/test/compress/comparisons.js
@@ -517,3 +517,63 @@ nullish_chain: {
         A || B || null == a || C;
     }
 }
+
+nullish_inline: {
+    options = {
+        comparisons: true,
+        inline: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function isNull(a) {
+            return null === a;
+        }
+        function isUndefined(b) {
+            return void 0 === b;
+        }
+        null === c || void 0 === c;
+        isNull(c) || void 0 === c;
+        null === c || isUndefined(c);
+        isNull(c) || isUndefined(c);
+    }
+    expect: {
+        null == c;
+        null == c;
+        null == c;
+        null == c;
+    }
+}
+
+nullish_inline_renamed: {
+    rename = true
+    mangle = {
+        toplevel: true,
+    }
+    options = {
+        comparisons: true,
+        inline: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function isNull(a) {
+            return null === a;
+        }
+        function isUndefined(b) {
+            return void 0 === b;
+        }
+        null === c || void 0 === c;
+        isNull(c) || void 0 === c;
+        null === c || isUndefined(c);
+        isNull(c) || isUndefined(c);
+    }
+    expect: {
+        null == c;
+        null == c;
+        null == c;
+        null == c;
+    }
+}