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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2018-07-04 15:17:54 +0100 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2018-07-05 10:44:23 +0100 |
| commit | 45f44e2c9d5db2f25c52abb402f197c20579400f (patch) | |
| tree | f2d09ea5cfa5d0c414e9bff8592595081d2610aa /testsuite/tests/partial-sigs | |
| parent | 14dfdf6a0a3364e2d3ae6f6839ef65bb24df4ebf (diff) | |
| download | haskell-45f44e2c9d5db2f25c52abb402f197c20579400f.tar.gz | |
Refactor validity checking for constraints
There are several changes here.
* TcInteract has gotten too big, so I moved all the class-instance
matching out of TcInteract into a new module ClsInst. It parallels
the FamInst module.
The main export of ClsInst is matchGlobalInst.
This now works in TcM not TcS.
* A big reason to make matchGlobalInst work in TcM is that we can
then use it from TcValidity.checkSimplifiableClassConstraint.
That extends checkSimplifiableClassConstraint to work uniformly
for built-in instances, which means that we now get a warning
if we have givens (Typeable x, KnownNat n); see Trac #15322.
* This change also made me refactor LookupInstResult, in particular
by adding the InstanceWhat field. I also changed the name of the
type to ClsInstResult.
Then instead of matchGlobalInst reporting a staging error (which is
inappropriate for the call from TcValidity), we can do so in
TcInteract.checkInstanceOK.
* In TcValidity, we now check quantified constraints for termination.
For example, this signature should be rejected:
f :: (forall a. Eq (m a) => Eq (m a)) => blah
as discussed in Trac #15316. The main change here is that
TcValidity.check_pred_help now uses classifyPredType, and has a
case for ForAllPred which it didn't before.
This had knock-on refactoring effects in TcValidity.
Diffstat (limited to 'testsuite/tests/partial-sigs')
| -rw-r--r-- | testsuite/tests/partial-sigs/should_compile/SomethingShowable.stderr | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/testsuite/tests/partial-sigs/should_compile/SomethingShowable.stderr b/testsuite/tests/partial-sigs/should_compile/SomethingShowable.stderr index 4b72ec4520..262b76d60a 100644 --- a/testsuite/tests/partial-sigs/should_compile/SomethingShowable.stderr +++ b/testsuite/tests/partial-sigs/should_compile/SomethingShowable.stderr @@ -7,8 +7,8 @@ Dependent packages: [base-4.12.0.0, ghc-prim-0.5.3, integer-gmp-1.0.2.0] SomethingShowable.hs:5:1: warning: [-Wsimplifiable-class-constraints (in -Wdefault)] - • The constraint ‘Show Bool’ matches an instance declaration - instance Show Bool -- Defined in ‘GHC.Show’ + • The constraint ‘Show Bool’ matches + instance Show Bool -- Defined in ‘GHC.Show’ This makes type inference for inner bindings fragile; either use MonoLocalBinds, or simplify it using the instance • When checking the inferred type |