diff options
| author | Simon Peyton Jones <simonpj@microsoft.com> | 2017-03-10 11:46:50 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2017-03-10 16:05:21 +0000 |
| commit | 48d1866e9051e52b80c9c88547bd66d66483f1d5 (patch) | |
| tree | 72047939e1bad05062f7518db97b6c999d32c948 /testsuite/tests/deriving | |
| parent | 7e96526ac2ef5987ecb03217d3d616b6281c1441 (diff) | |
| download | haskell-48d1866e9051e52b80c9c88547bd66d66483f1d5.tar.gz | |
Improve error messages for skolems
In error messages like this
• Couldn't match type ‘c’ with ‘f0 (a -> b)’
‘c’ is a rigid type variable bound by
the type signature for:
f :: ((a -> b) -> b) -> forall c. c -> a
we need to take case both to actually show that 'forall c',
and to make sure that its name lines with the 'c' in the
error message.
This has been shaky for some time, and this commit puts it on solid
ground. See TcRnTypes: Note [SigSkol SkolemInfo]
The main changes are
* SigSkol gets an extra field that records the way in which the
type signature was skolemised.
* The type in SigSkol is now the /un/-skolemised version
* pprSkolemInfo uses the info to make the tidy type line up
nicely
Lots of error message wibbles!
Diffstat (limited to 'testsuite/tests/deriving')
| -rw-r--r-- | testsuite/tests/deriving/should_fail/T5287.stderr | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/testsuite/tests/deriving/should_fail/T5287.stderr b/testsuite/tests/deriving/should_fail/T5287.stderr index 6307c36f24..20ad31dec3 100644 --- a/testsuite/tests/deriving/should_fail/T5287.stderr +++ b/testsuite/tests/deriving/should_fail/T5287.stderr @@ -3,7 +3,7 @@ T5287.hs:6:10: error: • Could not deduce (A a oops0) from the context: A a oops bound by an instance declaration: - A a oops => Read (D a) + forall a oops. A a oops => Read (D a) at T5287.hs:6:10-31 The type variable ‘oops0’ is ambiguous • In the ambiguity check for an instance declaration |