Function parseFnDef

src/parser/syntaxes/statements.ts:152–194

* ```abnf * FnDef = "@" IDENT [TypeParams] Params [":" Type] Block * ```

(s: ITokenStream)

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

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

	s.expect(TokenKind.Identifier);
	const nameStartPos = s.getPos();
	const name = s.getTokenValue();
	s.next();
	const dest = NODE('identifier', { name }, nameStartPos, s.getPos());

	let typeParams: Ast.TypeParam[];
	if (s.is(TokenKind.Lt)) {
		typeParams = parseTypeParams(s);
	} else {
		typeParams = [];
	}

	const params = parseParams(s);

	let type: Ast.TypeSource | undefined;
	if (s.is(TokenKind.Colon)) {
		s.next();
		type = parseType(s);
	}

	const body = parseBlock(s);

	const endPos = s.getPos();

	return NODE('def', {
		dest,
		expr: NODE('fn', {
			typeParams,
			params: params,
			retType: type,
			children: body,
		}, startPos, endPos),
		mut: false,
		attr: [],
	}, startPos, endPos);
}

/**
 * ```abnf