"No variables matched as repeating at this depth" is checked late

[mark-i-m]

For example, the following compiles, but an error message is issued when the macro is used: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=491ff00e42a73bdcda9c8da783050097

(and likewise for all the other errors in that file)

[mark-i-m]

The code that issues this error is in syntax::ext::tt:transcribe::transcribe()

[estebank]

Cc #35853

[mark-i-m]

Closing in favor of #61053