Tweak invalid `fn` header and body parsing#78379

Merged

bors merged 2 commits intorust-lang:masterfrom estebank:fn-signature-parse

Oct 28, 2020

+79-48

Commits on Oct 25, 2020

Rely on regular "expected"/"found" parser error for fn
estebank
committed

Commits on Oct 26, 2020

Tweak invalid fn header and body parsing
estebank
committed