When calling `to_string()` on an identifier, the returned string will
have an `r#` prefix if the original identifer was a raw identifier. This
prefix needs to be removed if the identifier is interpolated into
another identifier (e.g. `__some_prefix__r#other_ident`) in order for
the new identifier to be valid.
This issue was previously masked due to the fact that the relevant test
uses `r#i32`. It's possible to use `i32` as a normal (non-raw) ident -
due to a bug in rustc, this means that the user-supplied `r#` prefix
will be lost when calling `to_string()`. This bug will eventually be
fixed, causing `to_string()` to start returning `r#i32` instead of
`i32`.
This commit strips the `r#` prefix (if present) from an identifier
before using it to construct a new identifier. The relevant test is
updated to use `r#match`, which actually requires the `r#` prefix to be
a valid identifier. This causes the test to fail without this patch on
current versions of Rust.
Sunli
Aaron Hill
Koxiaet