Commit f0fd72ee authored by Sebastian Graf's avatar Sebastian Graf Committed by Marge Bot

8.10 Release notes for improvements to the pattern-match checker [skip ci]

A little late to the game, but better late than never.
parent 414e2f62
Pipeline #15591 skipped
......@@ -153,6 +153,20 @@ Language
by the right-hand side of ``F2``\'s equation, this now needs ``-XUndecidableInstances``.
The problem is very much akin to its need to detect some functional dependencies.
- The pattern-match coverage checker received a number of improvements wrt.
correctness and performance.
Checking against user-defined COMPLETE pragmas
"just works" now, so that we could move away from the
`complicated procedure for disambiguation <https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html#disambiguating-between-multiple-complete-pragmas>`__
we had in place before.
Previously, the checker performed really badly on some inputs and had no
good story for graceful degradation in these situations. These situations
should occur much less frequently now and degradation happens much more
smoothly, while still producing useful, sound results (see
:ghc-flag:`-fmax-pmcheck-models`).
Compiler
~~~~~~~~
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