Commit 4283feaa authored by Committed by Marge Bot
Introduce and use DerivClauseTys (#18662)
This switches `deriv_clause_tys` so that instead of using a list of `LHsSigType`s to represent the types in a `deriving` clause, it now uses a sum type. `DctSingle` represents a `deriving` clause with no enclosing parentheses, while `DctMulti` represents a clause with enclosing parentheses. This makes pretty-printing easier and avoids confusion between `HsParTy` and the enclosing parentheses in `deriving` clauses, which are different semantically. Fixes #18662.