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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2015-12-22 14:33:35 +0100 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2015-12-22 14:34:36 +0100 |
| commit | f40e122b7709c11d4ad20fd5cb26bf719235dbf1 (patch) | |
| tree | a335cef2c5f5ff1a1a0f6dc57aef45937c18d864 /compiler/basicTypes/PatSyn.hs | |
| parent | 29928f29d53cfc7aceb7e8ab81967f784cf06159 (diff) | |
| download | haskell-f40e122b7709c11d4ad20fd5cb26bf719235dbf1.tar.gz | |
Fix typechecking for pattern synonym signatures
Various tickets have revealed bad shortcomings in the typechecking of
pattern type synonyms. Discussed a lot in (the latter part of)
Trac #11224.
This patch fixes the most complex issues:
- Both parser and renamer now treat pattern synonyms as an
ordinary LHsSigType. Nothing special. Hooray.
- tcPatSynSig (now in TcPatSyn) typechecks the signature, and
decomposes it into its pieces.
See Note [Pattern synonym signatures]
- tcCheckPatSyn has had a lot of refactoring.
See Note [Checking against a pattern signature]
The result is a lot tidier and more comprehensible.
Plus, it actually works!
NB: this patch doesn't actually address the precise
target of #11224, namely "inlining pattern synonym
does not preserve semantics". That's an unrelated
bug, with a separate patch.
ToDo: better documentation in the user manual
Test Plan: Validate
Reviewers: austin, hvr, goldfire
Subscribers: goldfire, mpickering, thomie, simonpj
Differential Revision: https://phabricator.haskell.org/D1685
GHC Trac Issues: #11224
Diffstat (limited to 'compiler/basicTypes/PatSyn.hs')
| -rw-r--r-- | compiler/basicTypes/PatSyn.hs | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/compiler/basicTypes/PatSyn.hs b/compiler/basicTypes/PatSyn.hs index b7aff18534..c35bcf3e13 100644 --- a/compiler/basicTypes/PatSyn.hs +++ b/compiler/basicTypes/PatSyn.hs @@ -159,8 +159,8 @@ so pattern P has type with the following typeclass constraints: - provides: (Show (Maybe t), Ord b) requires: (Eq t, Num t) + provides: (Show (Maybe t), Ord b) In this case, the fields of MkPatSyn will be set as follows: |