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| author | Vladislav Zavialov <vlad.z.4096@gmail.com> | 2021-11-17 23:57:15 +0300 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-11-18 14:45:20 -0500 |
| commit | 12d023d1b4706665645cc0783dd1ae67625357a3 (patch) | |
| tree | e570489aa694be6bd915b78efa63526a59094e44 /testsuite | |
| parent | f55ae1803ef0eea3f99243be5dc1bd41eeb69048 (diff) | |
| download | haskell-12d023d1b4706665645cc0783dd1ae67625357a3.tar.gz | |
testsuite: check for FlexibleContexts in T17563
The purpose of testsuite/tests/typecheck/should_fail/T17563.hs is to
make sure we do validity checking on quantified constraints.
In particular, see the following functions in GHC.Tc.Validity:
* check_quant_pred
* check_pred_help
* check_class_pred
The original bug report used a~b constraints as an example of a
constraint that requires validity checking. But with GHC Proposal #371,
equality constraints no longer require GADTs or TypeFamilies; instead,
they require TypeOperators, which are checked earlier in the pipeline,
in the renamer.
Rather than simply remove this test, we change the example to use
another extension: FlexibleContexts. Since we decide whether a
constraint requires this extension in check_class_pred, the regression
test continues to exercise the relevant code path.
Diffstat (limited to 'testsuite')
| -rw-r--r-- | testsuite/tests/typecheck/should_fail/T17563.hs | 6 | ||||
| -rw-r--r-- | testsuite/tests/typecheck/should_fail/T17563.stderr | 11 |
2 files changed, 9 insertions, 8 deletions
diff --git a/testsuite/tests/typecheck/should_fail/T17563.hs b/testsuite/tests/typecheck/should_fail/T17563.hs index 565cd9f59e..2017db4877 100644 --- a/testsuite/tests/typecheck/should_fail/T17563.hs +++ b/testsuite/tests/typecheck/should_fail/T17563.hs @@ -3,5 +3,7 @@ module T17563 where -blah :: (forall a. a b ~ a c) => b -> c -blah = undefined +data T a b + +blah :: (forall x. Num (T a x)) => T a b +blah = 0 diff --git a/testsuite/tests/typecheck/should_fail/T17563.stderr b/testsuite/tests/typecheck/should_fail/T17563.stderr index 8900a41470..08c077fb7c 100644 --- a/testsuite/tests/typecheck/should_fail/T17563.stderr +++ b/testsuite/tests/typecheck/should_fail/T17563.stderr @@ -1,7 +1,6 @@ -T17563.hs:6:9: error: - • Illegal equational constraint a b ~ a c - • In the quantified constraint ‘forall (a :: * -> *). a b ~ a c’ - In the type signature: blah :: (forall a. a b ~ a c) => b -> c - Suggested fix: - Enable any of the following extensions: GADTs, TypeFamilies +T17563.hs:8:9: error: + • Non type-variable argument in the constraint: Num (T a x) + • In the quantified constraint ‘forall x. Num (T a x)’ + In the type signature: blah :: (forall x. Num (T a x)) => T a b + Suggested fix: Perhaps you intended to use FlexibleContexts |