src/vs/editor/contrib/snippet/snippetParser.ts/SnippetParser/_accept
class SnippetParser:	private _accept(type: TokenType, value?: boolean): boolean | string {
		if (type === undefined || this._token.type === type) {
			let ret = !value ? true : this._scanner.tokenText(this._token);
			this._token = this._scanner.next();
			return ret;
		}
		return false;
	}