suppress function substitution across loops

lib/compress.js

@@ -324,9 +324,8 @@ merge(Compressor.prototype, {
                                     || value.is_constant_expression(node.scope);
                             } else {
                                 d.single_use = d.scope === node.scope
-                                    && loop_ids[d.id] === in_loop
                                     && value.is_constant_expression();
-                                }
+                            }
                         } else {
                             d.single_use = false;
                         }
@@ -384,6 +383,7 @@ merge(Compressor.prototype, {
                         d.fixed = false;
                     } else {
                         d.fixed = node;
+                        loop_ids[d.id] = in_loop;
                         mark(d, true);
                         if (ref_once(d)) {
                             d.single_use = d.scope === d.references[0].scope
@@ -577,7 +577,11 @@ merge(Compressor.prototype, {
         }
 
         function ref_once(def) {
-            return unused && !def.scope.uses_eval && !def.scope.uses_with && def.references.length == 1;
+            return unused
+                && !def.scope.uses_eval
+                && !def.scope.uses_with
+                && def.references.length == 1
+                && loop_ids[def.id] === in_loop;
         }
 
         function is_immutable(value) {

test/compress/reduce_vars.js

@@ -1123,11 +1123,12 @@ toplevel_on_loops_1: {
         while (x);
     }
     expect: {
+        function bar() {
+            console.log("bar:", --x);
+        }
         var x = 3;
         do
-            (function() {
+            bar();
-                console.log("bar:", --x);
-            })();
         while (x);
     }
     expect_stdout: true
@@ -1180,9 +1181,10 @@ toplevel_on_loops_2: {
         while (x);
     }
     expect: {
-        for (;;) (function() {
+        function bar() {
             console.log("bar:");
-        })();
+        }
+        for (;;) bar();
     }
 }
 
@@ -3920,3 +3922,70 @@ issue_2450_3: {
     }
     expect_stdout: "true"
 }
+
+issue_2450_4: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a;
+        function f(b) {
+            console.log(a === b);
+            a = b;
+        }
+        function g() {}
+        for (var i = 3; --i >= 0;)
+            f(g);
+    }
+    expect: {
+        var a;
+        function f(b) {
+            console.log(a === b);
+            a = b;
+        }
+        function g() {}
+        for (var i = 3; --i >= 0;)
+            f(g);
+    }
+    expect_stdout: [
+        "false",
+        "true",
+        "true",
+    ]
+}
+
+issue_2450_5: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a;
+        function f(b) {
+            console.log(a === b);
+            a = b;
+        }
+        function g() {}
+        [1, 2, 3].forEach(function() {
+            f(g);
+        });
+    }
+    expect: {
+        var a;
+        function g() {}
+        [1, 2, 3].forEach(function() {
+            (function(b) {
+                console.log(a === b);
+                a = b;
+            })(g);
+        });
+    }
+    expect_stdout: [
+        "false",
+        "true",
+        "true",
+    ]
+}