Better error message on failed type parse

[sezna]

Currently just throws "expected literal" which is very wrong #111 could help

---

petr/petr-parse/src/parse_to_ast.rs

Lines 230 to 235 in 6c2873b

	// TODO: Better error message on failed type parse
	// Currently just throws "expected literal" which is very wrong
	// https://github.com/ch-systems/petr/issues/111
	// ^^ could help
	// parse constant literal types, which are just literals

---

This issue was generated by todo-issue based on a TODO comment in 6c2873b. It's been assigned to @sezna because they committed the code.