From 246d9d4e83e857a26347944ada65fea95ad6381d Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Thu, 9 Nov 2017 20:00:58 +0800
Subject: [PATCH] remove hack in `collapse_vars` (#2457)

fixes #2456
---
 lib/compress.js      |  3 +--
 test/mocha/minify.js | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index 6354197d..e457d808 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1062,7 +1062,7 @@ merge(Compressor.prototype, {
                 var found = false;
                 return statements[stat_index].transform(new TreeTransformer(function(node, descend, in_list) {
                     if (found) return node;
-                    if (node === expr) {
+                    if (node === expr || node.body === expr) {
                         found = true;
                         if (node instanceof AST_VarDef) {
                             drop_decl(node.name.definition());
@@ -1076,7 +1076,6 @@ merge(Compressor.prototype, {
                       case 0: return null;
                       case 1: return node.expressions[0];
                     }
-                    if (node instanceof AST_SimpleStatement && !node.body) return null;
                 }));
             }
 
diff --git a/test/mocha/minify.js b/test/mocha/minify.js
index aed8f915..516541c3 100644
--- a/test/mocha/minify.js
+++ b/test/mocha/minify.js
@@ -297,4 +297,36 @@ describe("minify", function() {
             assert.strictEqual(result.code, "alert({bar:42});");
         });
     });
+
+    describe("collapse_vars", function() {
+        it("Should not produce invalid AST", function() {
+            var code = [
+                "function f(a) {",
+                "    a = x();",
+                "    return a;",
+                "}",
+                "f();",
+            ].join("\n");
+            var ast = Uglify.minify(code, {
+                compress: false,
+                mangle: false,
+                output: {
+                    ast: true
+                },
+            }).ast;
+            assert.strictEqual(ast.TYPE, "Toplevel");
+            assert.strictEqual(ast.body.length, 2);
+            assert.strictEqual(ast.body[0].TYPE, "Defun");
+            assert.strictEqual(ast.body[0].body.length, 2);
+            assert.strictEqual(ast.body[0].body[0].TYPE, "SimpleStatement");
+            var stat = ast.body[0].body[0];
+            Uglify.minify(ast, {
+                compress: {
+                    sequences: false
+                }
+            });
+            assert.ok(stat.body);
+            assert.strictEqual(stat.print_to_string(), "a=x()");
+        });
+    });
 });
-- 
2.34.1