From 09525c7530fb305c7b60c470ee9bab3510beb8f0 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Tue, 25 Aug 2020 18:26:49 +0100
Subject: fix corner case in `sequences` (#4073)

---
 lib/ast.js      |  5 ++++-
 lib/compress.js | 28 +++++++++++++++++-----------
 2 files changed, 21 insertions(+), 12 deletions(-)

(limited to 'lib')

diff --git a/lib/ast.js b/lib/ast.js
index b6d4ebb7..73f4696a 100644
--- a/lib/ast.js
+++ b/lib/ast.js
@@ -288,10 +288,13 @@ var AST_LabeledStatement = DEFNODE("LabeledStatement", "label", {
             var label = node.label;
             var def = this.label;
             node.walk(new TreeWalker(function(node) {
-                if (node instanceof AST_LoopControl && node.label && node.label.thedef === def) {
+                if (node instanceof AST_LoopControl) {
+                    if (!node.label || node.label.thedef !== def) return;
                     node.label.thedef = label;
                     label.references.push(node);
+                    return true;
                 }
+                if (node instanceof AST_Scope) return true;
             }));
         }
         return node;
diff --git a/lib/compress.js b/lib/compress.js
index 3f0ea219..47445665 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -554,13 +554,6 @@ merge(Compressor.prototype, {
             if (is_arguments(def) && node.property instanceof AST_Number) def.reassigned = true;
         }
 
-        var suppressor = new TreeWalker(function(node) {
-            if (!(node instanceof AST_Symbol)) return;
-            var d = node.definition();
-            if (!d) return;
-            if (node instanceof AST_SymbolRef) push_ref(d, node);
-            d.fixed = false;
-        });
         def(AST_Accessor, function(tw, descend, compressor) {
             push(tw);
             reset_variables(tw, compressor, this);
@@ -740,11 +733,19 @@ merge(Compressor.prototype, {
             return true;
         });
         def(AST_ForIn, function(tw) {
-            this.init.walk(suppressor);
             this.object.walk(tw);
             var saved_loop = tw.in_loop;
             tw.in_loop = this;
             push(tw);
+            var init = this.init;
+            init.walk(tw);
+            if (init instanceof AST_Var) {
+                init = init.definitions[0].name;
+            } else while (init instanceof AST_PropAccess) {
+                init = init.expression.tail_node();
+            }
+            var def = init.definition();
+            if (def) def.fixed = false;
             this.body.walk(tw);
             pop(tw);
             tw.in_loop = saved_loop;
@@ -8521,7 +8522,9 @@ merge(Compressor.prototype, {
             }
         }
         if (is_lhs(compressor.self(), parent)) return self;
-        if (compressor.option("sequences") && compressor.parent().TYPE != "Call") {
+        if (compressor.option("sequences")
+            && parent.TYPE != "Call"
+            && !(parent instanceof AST_ForIn && parent.init === self)) {
             var seq = lift_sequence_in_expression(self, compressor);
             if (seq !== self) return seq.optimize(compressor);
         }
@@ -8632,8 +8635,11 @@ merge(Compressor.prototype, {
                 col: self.start.col
             });
         }
-        if (is_lhs(compressor.self(), compressor.parent())) return self;
-        if (compressor.option("sequences") && compressor.parent().TYPE != "Call") {
+        var parent = compressor.parent();
+        if (is_lhs(compressor.self(), parent)) return self;
+        if (compressor.option("sequences")
+            && parent.TYPE != "Call"
+            && !(parent instanceof AST_ForIn && parent.init === self)) {
             var seq = lift_sequence_in_expression(self, compressor);
             if (seq !== self) return seq.optimize(compressor);
         }
-- 
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