Add basic checks for well-formedness of `fn`/`fn_mut` lang items#86246

Merged

bors merged 2 commits intorust-lang:masterfrom FabianWolff:issue-83471

Sep 25, 2021

+180-6

Commits on Sep 24, 2021

Add basic checks for well-formedness of fn/fn_mut lang items
FabianWolff
committed
Make error message for malformed fn/fn_mut lang item more specific
FabianWolff
committed