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authorSebastian Graf <sebastian.graf@kit.edu>2020-01-27 14:18:04 +0100
committerBen Gamari <ben@smart-cactus.org>2020-02-06 17:23:17 -0500
commit4f3db327a1b30bd77368948ba87a84ba9ce34dca (patch)
tree8d3699dc1b5ddb1496d06c389397e61b366e1c63
parentac08f13fbc8adff4ff792228994f8feb3b59b6f3 (diff)
downloadhaskell-4f3db327a1b30bd77368948ba87a84ba9ce34dca.tar.gz
8.10 Release notes for improvements to the pattern-match checker
A little late to the game, but better late than never. (cherry picked from commit 873e7847bab694d2a00bfafa1e66b6642ea3c04c)
-rw-r--r--docs/users_guide/8.10.1-notes.rst14
1 files changed, 14 insertions, 0 deletions
diff --git a/docs/users_guide/8.10.1-notes.rst b/docs/users_guide/8.10.1-notes.rst
index 836508d030..c580443093 100644
--- a/docs/users_guide/8.10.1-notes.rst
+++ b/docs/users_guide/8.10.1-notes.rst
@@ -159,6 +159,20 @@ Language
by the right-hand side of ``F2``\'s equation, this now needs :ghc-flag:`-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
~~~~~~~~