fix corner case in functions (#4488)

fixes #4487

lib/compress.js

@@ -5659,7 +5659,7 @@ merge(Compressor.prototype, {
                             var defun = make_node(AST_Defun, def, def.value);
                             defun.name = make_node(AST_SymbolDefun, def.name, def.name);
                             var name_def = def.name.scope.resolve().def_function(defun.name);
-                            if (old_def) old_def.references.forEach(function(node) {
+                            if (old_def) old_def.forEach(function(node) {
                                 node.name = name_def.name;
                                 node.thedef = name_def;
                                 node.reference({});

test/compress/hoist_vars.js

@@ -134,3 +134,27 @@ issue_2295: {
         }
     }
 }
+
+issue_4487: {
+    options = {
+        functions: true,
+        hoist_vars: true,
+        keep_fnames: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = function f() {
+            var f = console.log(typeof f);
+        };
+        var b = a();
+    }
+    expect: {
+        function a() {
+            var a = console.log(typeof a);
+        }
+        a();
+    }
+    expect_stdout: "undefined"
+}