3 files changed, 13 insertions, 11 deletions

diff --git a/lib/ast.js b/lib/ast.js
index ecaecc5b..0605fb8c 100644
--- a/lib/ast.js
+++ b/lib/ast.js
@@ -569,6 +569,10 @@ var AST_Function = DEFNODE("Function", "inlined", {
     },
 }, AST_Lambda);
 
+function is_defun(node) {
+    return node instanceof AST_AsyncDefun || node instanceof AST_Defun;
+}
+
 var AST_AsyncDefun = DEFNODE("AsyncDefun", null, {
     $documentation: "An asynchronous function definition",
     _validate: function() {
diff --git a/lib/compress.js b/lib/compress.js
index 09b27635..be38304a 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -5115,7 +5115,7 @@ merge(Compressor.prototype, {
             }
             if (node === self) return;
             if (scope === self) {
-                if (node instanceof AST_AsyncDefun || node instanceof AST_Defun) {
+                if (is_defun(node)) {
                     var def = node.name.definition();
                     if (!drop_funcs && !(def.id in in_use_ids)) {
                         in_use_ids[def.id] = true;
@@ -5266,7 +5266,7 @@ merge(Compressor.prototype, {
             if (node instanceof AST_Call) calls_to_drop_args.push(node);
             if (scope !== self) return;
             if (node instanceof AST_Lambda) {
-                if (drop_funcs && node !== self && (node instanceof AST_AsyncDefun || node instanceof AST_Defun)) {
+                if (drop_funcs && node !== self && is_defun(node)) {
                     var def = node.name.definition();
                     if (!(def.id in in_use_ids)) {
                         log(node.name, "Dropping unused function {name}");
@@ -7826,7 +7826,7 @@ merge(Compressor.prototype, {
                         in_order = null;
                         return;
                     }
-                    if (def.init instanceof AST_AsyncDefun || def.init instanceof AST_Defun) return abort = true;
+                    if (is_defun(def.init)) return abort = true;
                     if (is_lhs(node, this.parent())) return abort = true;
                     var index = resolve_index(def);
                     if (!(begin < index)) begin = index;
@@ -7877,7 +7877,7 @@ merge(Compressor.prototype, {
         function can_inject_vars(defined, used, safe_to_inject) {
             for (var i = 0; i < fn.body.length; i++) {
                 var stat = fn.body[i];
-                if (stat instanceof AST_AsyncDefun || stat instanceof AST_Defun) {
+                if (is_defun(stat)) {
                     if (!safe_to_inject || var_exists(used, stat.name.name)) return false;
                     if (!all(stat.enclosed, function(def) {
                         return def.scope === stat || !defined[def.name];
@@ -7925,9 +7925,7 @@ merge(Compressor.prototype, {
                 fn.walk(new TreeWalker(function(node) {
                     if (found) return true;
                     if (node instanceof AST_Scope && node !== fn) {
-                        if (node instanceof AST_AsyncDefun || node instanceof AST_Defun) {
-                            if (node.name.name == "await") found = true;
-                        }
+                        if (is_defun(node) && node.name.name == "await") found = true;
                         return true;
                     }
                     if (node instanceof AST_Symbol && node.name == "await" && node !== fn.name) return found = true;
@@ -8027,7 +8025,7 @@ merge(Compressor.prototype, {
             flatten_vars(decls, expressions);
             expressions.push(value);
             var args = fn.body.filter(function(stat) {
-                if (stat instanceof AST_AsyncDefun || stat instanceof AST_Defun) {
+                if (is_defun(stat)) {
                     var def = stat.name.definition();
                     scope.functions.set(def.name, def);
                     scope.variables.set(def.name, def);
diff --git a/lib/scope.js b/lib/scope.js
index c1bbc086..6c521bcc 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -112,7 +112,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
     var next_def_id = 0;
     var scope = self.parent_scope = null;
     var tw = new TreeWalker(function(node, descend) {
-        if (node instanceof AST_AsyncDefun || node instanceof AST_Defun) {
+        if (is_defun(node)) {
             node.name.walk(tw);
             walk_scope(function() {
                 node.argnames.forEach(function(argname) {
@@ -397,7 +397,7 @@ AST_BlockScope.DEFMETHOD("find_variable", function(name) {
 
 AST_BlockScope.DEFMETHOD("def_function", function(symbol, init) {
     var def = this.def_variable(symbol, init);
-    if (!def.init || def.init instanceof AST_Defun) def.init = init;
+    if (!def.init || is_defun(def.init)) def.init = init;
     this.functions.set(symbol.name, def);
     return def;
 });
@@ -406,7 +406,7 @@ AST_BlockScope.DEFMETHOD("def_variable", function(symbol, init) {
     var def = this.variables.get(symbol.name);
     if (def) {
         def.orig.push(symbol);
-        if (def.init instanceof AST_Function) def.init = init;
+        if (is_function(def.init)) def.init = init;
     } else {
         def = this.make_def(symbol, init);
         this.variables.set(symbol.name, def);