Fix #5378, stack overflow on large files (#5380)

lib/coffeescript/nodes.js

@@ -723,7 +723,7 @@
       // better not to generate them in the first place, but for now, clean up
       // obvious double-parentheses.
       compileNode(o) {
-        var fragments, parts;
+        var fragments, functionKeyword;
         o.indent = o.bare ? '' : TAB;
         o.level = LEVEL_TOP;
         o.compiling = true;
@@ -732,15 +732,8 @@
         if (o.bare) {
           return fragments;
         }
-        parts = [];
-        parts.push(this.makeCode('('));
-        if (this.isAsync) {
-          parts.push(this.makeCode('async '));
-        }
-        parts.push(this.makeCode('function() {\n'));
-        parts.push(...fragments);
-        parts.push(this.makeCode('\n}).call(this);\n'));
-        return [].concat(...parts);
+        functionKeyword = `${this.isAsync ? 'async ' : ''}function`;
+        return [].concat(this.makeCode(`(${functionKeyword}() {\n`), fragments, this.makeCode("\n}).call(this);\n"));
       }
 
       initializeScope(o) {

src/nodes.coffee

@@ -528,13 +528,8 @@ exports.Root = class Root extends Base
     @initializeScope o
     fragments = @body.compileRoot o
     return fragments if o.bare
-    parts = []
-    parts.push @makeCode '('
-    parts.push @makeCode 'async ' if @isAsync
-    parts.push @makeCode 'function() {\n'
-    parts.push ...fragments
-    parts.push @makeCode '\n}).call(this);\n'
-    [].concat ...parts
+    functionKeyword = "#{if @isAsync then 'async ' else ''}function"
+    [].concat @makeCode("(#{functionKeyword}() {\n"), fragments, @makeCode("\n}).call(this);\n")
 
   initializeScope: (o) ->
     o.scope = new Scope null, @body, null, o.referencedVars ? []