Allow certain keywords as function param names.

Fixes #69.

CHANGELOG.md

@@ -5,6 +5,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
+## Unreleased
+### Fixed
+ - issue that prevented certain keywords from being used as function parameter names ([#69](https://github.com/rokucommunity/brighterscript/issues/69))
+
 
 ## 0.9.2 - 2020-05-02
 ### Changed

src/parser/Parser.spec.ts

@@ -25,6 +25,12 @@ describe('parser', () => {
     });
 
     describe('parse', () => {
+        it('supports using "interface" as parameter name', () => {
+            expect(parse(`
+                sub main(interface as object)
+                end sub
+            `, ParseMode.BrighterScript).diagnostics[0]?.message).not.to.exist;
+        });
         describe('namespace', () => {
             it('catches namespaces declared not at root level', () => {
                 expect(parse(`

src/parser/Parser.ts

@@ -589,7 +589,7 @@ export class Parser {
     }
 
     private functionParameter(): FunctionParameter {
-        if (!this.check(TokenKind.Identifier)) {
+        if (!this.check(TokenKind.Identifier, ...AllowedLocalIdentifiers)) {
             this.diagnostics.push({
                 ...DiagnosticMessages.expectedParameterNameButFound(this.peek().text),
                 range: this.peek().range
@@ -598,6 +598,9 @@ export class Parser {
         }
 
         let name = this.advance() as Identifier;
+        // force the name into an identifier so the AST makes some sense
+        name.kind = TokenKind.Identifier;
+
         let type: ValueKind = ValueKind.Dynamic;
         let typeToken: Token | undefined;
         let defaultValue;