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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2016-01-22 16:34:18 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2016-01-25 11:32:25 +0000 |
| commit | ff21795a0b9253e811a45626d5686e981ed07f82 (patch) | |
| tree | 62224ed16e322bd7fb13424d9331243decb96712 /testsuite/tests/polykinds | |
| parent | fd6dd41c67f3bd23bbf074357219cfd251eb53d6 (diff) | |
| download | haskell-ff21795a0b9253e811a45626d5686e981ed07f82.tar.gz | |
Special-case implicit params in superclass expansion
This issue came up in Trac #11480, and is documented in
Note [When superclasses help] in TcRnTypes.
We were getting a spurious warning
T11480.hs:1:1: warning:
solveWanteds: too many iterations (limit = 4)
The fix is easy. A bit of refactoring along the way.
The original bug report in Trac #11480 appears to work
fine in HEAD and the 8.0 branch but I added a regression
test in this commit as well.
Diffstat (limited to 'testsuite/tests/polykinds')
| -rw-r--r-- | testsuite/tests/polykinds/T11480a.hs | 26 | ||||
| -rw-r--r-- | testsuite/tests/polykinds/all.T | 1 |
2 files changed, 27 insertions, 0 deletions
diff --git a/testsuite/tests/polykinds/T11480a.hs b/testsuite/tests/polykinds/T11480a.hs new file mode 100644 index 0000000000..3d17168082 --- /dev/null +++ b/testsuite/tests/polykinds/T11480a.hs @@ -0,0 +1,26 @@ +{-# language KindSignatures, PolyKinds, TypeFamilies, + NoImplicitPrelude, FlexibleContexts, + MultiParamTypeClasses, GADTs, + ConstraintKinds, FlexibleInstances, + FunctionalDependencies, UndecidableSuperClasses #-} + +module T11480a where + +import GHC.Types (Constraint) +import qualified Prelude + +data Nat (c :: i -> i -> *) (d :: j -> j -> *) (f :: i -> j) (g :: i -> j) + +class Functor p (Nat p (->)) p => Category (p :: i -> i -> *) + +class (Category dom, Category cod) + => Functor (dom :: i -> i -> *) (cod :: j -> j -> *) (f :: i -> j) + | f -> dom cod + +instance (Category c, Category d) => Category (Nat c d) +instance (Category c, Category d) => Functor (Nat c d) (Nat (Nat c d) (->)) (Nat c d) +instance (Category c, Category d) => Functor (Nat c d) (->) (Nat c d f) + +instance Category (->) +instance Functor (->) (->) ((->) e) +instance Functor (->) (Nat (->) (->)) (->) diff --git a/testsuite/tests/polykinds/all.T b/testsuite/tests/polykinds/all.T index f1f25cecc4..69c5ba0790 100644 --- a/testsuite/tests/polykinds/all.T +++ b/testsuite/tests/polykinds/all.T @@ -134,3 +134,4 @@ test('T11278', normal, compile, ['']) test('T11255', normal, compile, ['']) test('T11459', normal, compile_fail, ['']) test('T11466', normal, compile_fail, ['']) +test('T11480a', normal, compile, ['']) |