magic numbers in token.rs should be static constants

[pnkfelix]

There's a large table of special identifiers and (reserved/strict/etc) keywords in mk_fresh_ident_interners.

There is a note that the indices need to match up with the numbers in special_idents.

In addition, though, there are uses of the numbers in match arms within the code, and there is evidence that the numbers are not being kept up to date.

Why aren't we at least binding the magic numbers to static constants in a single place (presumably near the table in mk_fresh_ident_interners and then referencing those named constants instead?

(Or alternatively, we might have the const expressions in the match arms reference the already present static Ident definitions, e.g. self_.name ... but for that, we would need to support x.y as a const expression.)

(More elaborate discussion available in IRC log: https://botbot.me/mozilla/rust-internals/msg/6710787/ )

[steveklabnik]

Triage: this is still true today.

rust/src/libsyntax/parse/token.rs

Line 475 in a0f86de

fn mk_fresh_ident_interner() -> IdentInterner {