fix reduce_vars on AST_Destructuring

fixes #2669

lib/compress.js

@@ -482,6 +482,10 @@ merge(Compressor.prototype, {
         def(AST_Arrow, mark_func_expr);
         def(AST_Assign, function(tw) {
             var node = this;
+            if (node.left instanceof AST_Destructuring) {
+                node.left.walk(suppressor);
+                return;
+            }
             if (node.operator != "=" || !(node.left instanceof AST_SymbolRef)) return;
             var d = node.left.definition();
             if (safe_to_assign(tw, d, node.right)
@@ -705,7 +709,7 @@ merge(Compressor.prototype, {
             var node = this;
             if (node.name instanceof AST_Destructuring) {
                 node.name.walk(suppressor);
-                return true;
+                return;
             }
             var d = node.name.definition();
             if (d.fixed === undefined || safe_to_assign(tw, d, node.value)) {

test/compress/reduce_vars.js

@@ -5446,3 +5446,22 @@ issue_2598: {
     }
     expect_stdout: "true"
 }
+
+issue_2669: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        let foo;
+        console.log(([ foo ] = [ "PASS" ]) && foo);
+    }
+    expect: {
+        let foo;
+        console.log(([ foo ] = [ "PASS" ]) && foo);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}