Function parseIf

src/parser/syntaxes/expressions.ts:378–408

* ```abnf * If = "if" Expr BlockOrStatement *("elif" Expr BlockOrStatement) ["else" BlockOrStatement] * ```

(s: ITokenStream)

 * ```
*/
function parseIf(s: ITokenStream): Ast.If {
	const startPos = s.getPos();

	s.expect(TokenKind.IfKeyword);
	s.next();
	const cond = parseExpr(s, false);
	const then = parseBlockOrStatement(s);

	if (s.is(TokenKind.NewLine) && [TokenKind.ElifKeyword, TokenKind.ElseKeyword].includes(s.lookahead(1).kind)) {
		s.next();
	}

	const elseif: Ast.If['elseif'] = [];
	while (s.is(TokenKind.ElifKeyword)) {
		s.next();
		const elifCond = parseExpr(s, false);
		const elifThen = parseBlockOrStatement(s);
		if (s.is(TokenKind.NewLine) && [TokenKind.ElifKeyword, TokenKind.ElseKeyword].includes(s.lookahead(1).kind)) {
			s.next();
		}
		elseif.push({ cond: elifCond, then: elifThen });
	}

	let _else = undefined;
	if (s.is(TokenKind.ElseKeyword)) {
		s.next();
		_else = parseBlockOrStatement(s);
	}

	return NODE('if', { cond, then, elseif, else: _else }, startPos, s.getPos());
}

/**
 * ```abnf