Yeah, it's not strictly necessary that the compiler doesn't emit any parse errors for this sort of thing as long as sufficient caveats are in place, but I guess

Yeah, it's not strictly necessary that the compiler doesn't emit any parse errors for this sort of thing as long as sufficient caveats are in place, but I guess my question is...why? As long as its properly caught as a type error, I don't really see the benefit of making a separate path where it's also a parse error. All else being equal, I feel like having a simpler grammar (e.g. where arrays are indexed by expressions rather than some specific subset of them) is both more flexible and makes the parser simpler; it's not obvious what advantage making something a parser error instead of a type checking error would be.