feature: goldstein: keyword-fn: add ability to use "fn" as function name

packages/keyword-fn/fixture/fn-function.gs

@@ -0,0 +1 @@
+function fn() {}

packages/keyword-fn/index.js

@@ -1,4 +1,5 @@
 import {addKeyword, TokenType} from '../operator/index.js';
+import {tokTypes as tt} from 'acorn';
 
 export default function fn(Parser) {
     Parser.acorn.keywordTypes.fn = new TokenType('fn', {
@@ -13,7 +14,9 @@ export default function fn(Parser) {
         }
 
         parseStatement(context, topLevel, exports) {
-            if (this.type === Parser.acorn.keywordTypes.fn)
+            const isParen = this.eat(tt.parenL);
+
+            if (!isParen && this.type === Parser.acorn.keywordTypes.fn)
                 this.type = Parser.acorn.keywordTypes.function;
 
             return super.parseStatement(context, topLevel, exports);
@@ -25,5 +28,15 @@ export default function fn(Parser) {
 
             return super.shouldParseExportStatement();
         }
+
+        checkUnreserved(ref) {
+            const {name} = ref;
+
+            if (name === 'fn')
+                return;
+
+            return super.checkUnreserved(ref);
+        }
     };
 }
+

packages/keyword-fn/index.spec.js

@@ -8,6 +8,11 @@ test('goldstein: keyword: fn', (t) => {
     t.end();
 });
 
+test('goldstein: keyword: fn-function', (t) => {
+    t.noCompile('fn-function');
+    t.end();
+});
+
 test('goldstein: keyword: fn: export', (t) => {
     t.compile('export');
     t.end();