From ad139aa34d79ed34ad70290c48e0a54985ac017f Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Tue, 27 Jun 2017 01:13:00 +0800
Subject: [PATCH] fix `side_effects` on `AST_Expansion` (#2165)

fixes #2163
---
 lib/ast.js                   |  2 +-
 lib/compress.js              |  3 +++
 test/compress/drop-unused.js | 17 +++++++++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/lib/ast.js b/lib/ast.js
index 7668dabf..974d4c1b 100644
--- a/lib/ast.js
+++ b/lib/ast.js
@@ -345,7 +345,7 @@ var AST_Toplevel = DEFNODE("Toplevel", "globals", {
 var AST_Expansion = DEFNODE("Expansion", "expression", {
     $documentation: "An expandible argument, such as ...rest, a splat, such as [1,2,...all], or an expansion in a variable declaration, such as var [first, ...rest] = list",
     $propdoc: {
-        expression: "AST_Symbol the thing to be expanded"
+        expression: "[AST_Node] the thing to be expanded"
     },
     _walk: function(visitor) {
         var self = this;
diff --git a/lib/compress.js b/lib/compress.js
index d2e1e939..f028deee 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2672,6 +2672,9 @@ merge(Compressor.prototype, {
             if (expr) merge_sequence(expressions, expr);
             return make_sequence(this, expressions);
         });
+        def(AST_Expansion, function(compressor, first_in_statement){
+            return this.expression.drop_side_effect_free(compressor, first_in_statement);
+        });
     })(function(node, func){
         node.DEFMETHOD("drop_side_effect_free", func);
     });
diff --git a/test/compress/drop-unused.js b/test/compress/drop-unused.js
index 081df308..0a810470 100644
--- a/test/compress/drop-unused.js
+++ b/test/compress/drop-unused.js
@@ -1409,3 +1409,20 @@ issue_2136_3: {
     expect_stdout: "2"
     node_version: ">=6"
 }
+
+issue_2163: {
+    options = {
+        pure_funcs: [ "pure" ],
+        side_effects: true,
+    }
+    input: {
+        var c;
+        /*@__PURE__*/f(...a);
+        pure(b, ...c);
+    }
+    expect: {
+        var c;
+        a;
+        b;
+    }
+}