fix corner case in reduce_vars (#4944)

fixes #4943

lib/compress.js

@@ -1194,11 +1194,20 @@ merge(Compressor.prototype, {
         def(AST_SymbolRef, function(tw, descend, compressor) {
             var d = this.definition();
             push_ref(d, this);
-            if (d.references.length == 1
-                && !d.fixed
-                && d.orig[0] instanceof AST_SymbolDefun) {
+            if (d.references.length == 1 && !d.fixed && d.orig[0] instanceof AST_SymbolDefun) {
                 tw.loop_ids[d.id] = tw.in_loop;
             }
+            var recursive = recursive_ref(tw, d);
+            if (recursive) recursive.enclosed.forEach(function(def) {
+                if (d === def) return;
+                if (def.scope === recursive) return;
+                var assigns = def.fixed && def.fixed.assigns;
+                if (!assigns) return;
+                if (assigns[assigns.length - 1] instanceof AST_VarDef) return;
+                var safe = tw.safe_ids[def.id];
+                if (!safe) return;
+                safe.assign = true;
+            });
             if (d.fixed === false) {
                 var redef = d.redefined();
                 if (redef && cross_scope(d.scope, this.scope)) redef.single_use = false;
@@ -1207,7 +1216,6 @@ merge(Compressor.prototype, {
             } else if (d.fixed) {
                 if (this.in_arg && d.orig[0] instanceof AST_SymbolLambda) this.fixed = d.scope;
                 var value = this.fixed_value();
-                var recursive = recursive_ref(tw, d);
                 if (recursive) {
                     d.recursive_refs++;
                 } else if (value && ref_once(compressor, d)) {
@@ -1228,9 +1236,7 @@ merge(Compressor.prototype, {
                         d.fixed = false;
                     }
                 }
-                if (d.fixed && tw.loop_ids[d.id] !== tw.in_loop) {
-                    d.cross_loop = true;
-                }
+                if (d.fixed && tw.loop_ids[d.id] !== tw.in_loop) d.cross_loop = true;
                 mark_escaped(tw, d, this.scope, this, value, 0, 1);
             }
             if (!this.fixed) this.fixed = d.fixed;

test/compress/reduce_vars.js

@@ -7662,3 +7662,63 @@ issue_4937: {
     }
     expect_stdout: "PASS"
 }
+
+issue_4943_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a, b = 1;
+        (function f() {
+            a = "foo";
+            b-- && f();
+            console.log(a);
+            a = "bar";
+        })();
+    }
+    expect: {
+        var a, b = 1;
+        (function f() {
+            a = "foo";
+            b-- && f();
+            console.log(a);
+            a = "bar";
+        })();
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+}
+
+issue_4943_2: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a, b = 1;
+        (function f() {
+            a = "foo";
+            b-- && f();
+            console.log(a);
+            a = "bar";
+        })();
+    }
+    expect: {
+        var a, b = 1;
+        (function f() {
+            a = "foo";
+            b-- && f();
+            console.log(a);
+            a = "bar";
+        })();
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+}