Auto merge of #42578 - estebank:recover-binop, r=nikomatsakis

Auto merge of #42578 - estebank:recover-binop, r=nikomatsakis

Learn to parse `a as usize < b`

Parsing `a as usize > b` always works, but `a as usize < b` was a
parsing error because the parser would think the `<` started a generic
type argument for `usize`. The parser now attempts to parse as before,
and if a DiagnosticError is returned, try to parse again as a type with
no generic arguments. If this fails, return the original
`DiagnosticError`.

Fix #22644.