Restrict what symbols can be used in #[diagnostic::on_unimplemented]
format strings
#118495
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This commit restricts what symbols can be used in a format string for any option of the
diagnostic::on_unimplemented
attribute. We previously allowed all the ad-hoc options supported by the internal#[rustc_on_unimplemented]
attribute. For the stable attribute we only want to support generic parameter names and{Self}
as parameters. For any other parameter an warning is emitted and the parameter is replaced by the literal parameter string, so for example{integer}
turns into{integer}
. This follows the general design of attributes in the#[diagnostic]
attribute namespace, that any syntax "error" is treated as warning and subsequently ignored.r? @compiler-errors