`ident_str!(...)` macro may not be robust sufficiently.

[jymchng]

sui/external-crates/move/crates/move-core-types/src/identifier.rs

Lines 342 to 343 in 7d006ef

	let is_valid = $crate::identifier::is_valid(s);
	["String is not a valid Move identifier"][!is_valid as usize];

The check using 'out of range' error is not robust as one can easily turn it off by #![allow(conditional_panic)], as shown in this Playground. The program only panics at runtime instead of compile time which is not an expected behavior for ident_str!(...) that is advertised for checking valid identifier at compile time.

I suggest to use a dummy struct with an associated constant that does the assertion of is_valid at compile time like so:

struct _Whatever;
impl _Whatever {
    const IS_VALID: () =
            assert!($crate::is_valid(s), "String is not a valid Move identifier");
    }
_Whatever::IS_VALID;

This is more robust as the macro ident_str expands into {...; _Whatever::IS_VALID; and since _Whatever::IS_VALID is unconditionally evaluated at compile time, this will be a more robust way to check for valid IdentStr at compile time. Playground.