Function parseFor

src/parser/syntaxes/statements.ts:292–360

* ```abnf * For = ForRange / ForTimes * ForRange = "for" "(" "let" IDENT ["=" Expr] "," Expr ")" BlockOrStatement * / "for" "let" IDENT ["=" Expr] "," Expr BlockOrStatement * ForTimes = "for" "(" Expr ")" BlockOrStatement * / "for" Expr BlockOrStatement * ```

(s: ITokenStream)

 * ```
*/
function parseFor(s: ITokenStream): Ast.For {
	const startPos = s.getPos();
	let hasParen = false;

	s.expect(TokenKind.ForKeyword);
	s.next();

	if (s.is(TokenKind.OpenParen)) {
		hasParen = true;
		s.next();
	}

	if (s.is(TokenKind.LetKeyword)) {
		// range syntax
		s.next();

		const identPos = s.getPos();

		s.expect(TokenKind.Identifier);
		const name = s.getTokenValue();
		s.next();

		let _from: Ast.Expression;
		if (s.is(TokenKind.Eq)) {
			s.next();
			_from = parseExpr(s, false);
		} else {
			_from = NODE('num', { value: 0 }, identPos, identPos);
		}

		if (s.is(TokenKind.Comma)) {
			s.next();
		} else {
			throw new AiScriptSyntaxError('separator expected', s.getPos());
		}

		const to = parseExpr(s, false);

		if (hasParen) {
			s.expect(TokenKind.CloseParen);
			s.next();
		}

		const body = parseBlockOrStatement(s);

		return NODE('for', {
			var: name,
			from: _from,
			to,
			for: body,
		}, startPos, s.getPos());
	} else {
		// times syntax

		const times = parseExpr(s, false);

		if (hasParen) {
			s.expect(TokenKind.CloseParen);