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authorRichard Eisenberg <rae@richarde.dev>2022-02-18 23:29:52 +0100
committerMarge Bot <ben+marge-bot@smart-cactus.org>2022-02-23 08:16:07 -0500
commita599abbad939820c666ced00ae9eb33706a4f360 (patch)
tree7b3811972a50da9e81018056cdcdeef158bc22e3 /testsuite/tests/polykinds
parent558c7d554b9724abfaa2bcc1f42050e67b36a988 (diff)
downloadhaskell-a599abbad939820c666ced00ae9eb33706a4f360.tar.gz
Kill derived constraints
Co-authored by: Sam Derbyshire Previously, GHC had three flavours of constraint: Wanted, Given, and Derived. This removes Derived constraints. Though serving a number of purposes, the most important role of Derived constraints was to enable better error messages. This job has been taken over by the new RewriterSets, as explained in Note [Wanteds rewrite wanteds] in GHC.Tc.Types.Constraint. Other knock-on effects: - Various new Notes as I learned about under-described bits of GHC - A reshuffling around the AST for implicit-parameter bindings, with better integration with TTG. - Various improvements around fundeps. These were caused by the fact that, previously, fundep constraints were all Derived, and Derived constraints would get dropped. Thus, an unsolved Derived didn't stop compilation. Without Derived, this is no longer possible, and so we have to be considerably more careful around fundeps. - A nice little refactoring in GHC.Tc.Errors to center the work on a new datatype called ErrorItem. Constraints are converted into ErrorItems at the start of processing, and this allows for a little preprocessing before the main classification. - This commit also cleans up the behavior in generalisation around functional dependencies. Now, if a variable is determined by functional dependencies, it will not be quantified. This change is user facing, but it should trim down GHC's strange behavior around fundeps. - Previously, reportWanteds did quite a bit of work, even on an empty WantedConstraints. This commit adds a fast path. - Now, GHC will unconditionally re-simplify constraints during quantification. See Note [Unconditionally resimplify constraints when quantifying], in GHC.Tc.Solver. Close #18398. Close #18406. Solve the fundep-related non-confluence in #18851. Close #19131. Close #19137. Close #20922. Close #20668. Close #19665. ------------------------- Metric Decrease: LargeRecord T9872b T9872b_defer T9872d TcPlugin_RewritePerf -------------------------
Diffstat (limited to 'testsuite/tests/polykinds')
-rw-r--r--testsuite/tests/polykinds/T14172.stderr8
-rw-r--r--testsuite/tests/polykinds/T9017.stderr4
2 files changed, 7 insertions, 5 deletions
diff --git a/testsuite/tests/polykinds/T14172.stderr b/testsuite/tests/polykinds/T14172.stderr
index 2ad319592c..b4eb6302d0 100644
--- a/testsuite/tests/polykinds/T14172.stderr
+++ b/testsuite/tests/polykinds/T14172.stderr
@@ -11,9 +11,11 @@ T14172.hs:7:46: error:
In the type ‘(a -> f b) -> g a -> f (h _)’
T14172.hs:8:19: error:
- • Couldn't match type ‘h’ with ‘Compose f'0 g'0’
- arising from a use of ‘_Wrapping’
- ‘h’ is a rigid type variable bound by
+ • Couldn't match type ‘a’ with ‘g'1 a'0’
+ Expected: (f'0 a -> f (f'0 b)) -> g a -> f (h a')
+ Actual: (Unwrapped (Compose f'0 g'1 a'0) -> f (Unwrapped (h a')))
+ -> Compose f'0 g'1 a'0 -> f (h a')
+ ‘a’ is a rigid type variable bound by
the inferred type of
traverseCompose :: (a -> f b) -> g a -> f (h a')
at T14172.hs:7:1-47
diff --git a/testsuite/tests/polykinds/T9017.stderr b/testsuite/tests/polykinds/T9017.stderr
index 2070ea667e..ca6a4b564d 100644
--- a/testsuite/tests/polykinds/T9017.stderr
+++ b/testsuite/tests/polykinds/T9017.stderr
@@ -1,12 +1,12 @@
T9017.hs:8:7: error:
- • Couldn't match kind ‘k1’ with ‘*’
+ • Couldn't match kind ‘k2’ with ‘*’
When matching types
a0 :: * -> * -> *
a :: k1 -> k2 -> *
Expected: a b (m b)
Actual: a0 b0 (m0 b0)
- ‘k1’ is a rigid type variable bound by
+ ‘k2’ is a rigid type variable bound by
the type signature for:
foo :: forall {k1} {k2} (a :: k1 -> k2 -> *) (b :: k1)
(m :: k1 -> k2).