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| author | Richard Eisenberg <rae@cs.brynmawr.edu> | 2018-07-17 00:12:34 -0400 |
|---|---|---|
| committer | Richard Eisenberg <rae@cs.brynmawr.edu> | 2018-08-01 12:12:22 -0400 |
| commit | f8618a9b15177ee8c84771b927cb3583c9cd8408 (patch) | |
| tree | d8abc1b82308735a80721b900372a8eb3e5db56d /testsuite/tests/dependent/should_fail/T15380.stderr | |
| parent | 1df50a0f61f320428f2e6dd07b3c9ce49c4acd31 (diff) | |
| download | haskell-f8618a9b15177ee8c84771b927cb3583c9cd8408.tar.gz | |
Remove the type-checking knot.
Bug #15380 hangs because a knot-tied TyCon ended up in a kind.
Looking at the code in tcInferApps, I'm amazed this hasn't happened
before! I couldn't think of a good way to fix it (with dependent
types, we can't really keep types out of kinds, after all), so
I just went ahead and removed the knot.
This was remarkably easy to do. In tcTyVar, when we find a TcTyCon,
just use it. (Previously, we looked up the knot-tied TyCon and used
that.) Then, during the final zonk, replace TcTyCons with the real,
full-blooded TyCons in the global environment. It's all very easy.
The new bit is explained in the existing
Note [Type checking recursive type and class declarations]
in TcTyClsDecls.
Naturally, I removed various references to the knot and the
zonkTcTypeInKnot (and related) functions. Now, we can print types
during type checking with abandon!
NB: There is a teensy error message regression with this patch,
around the ordering of quantified type variables. This ordering
problem is fixed (I believe) with the patch for #14880. The ordering
affects only internal variables that cannot be instantiated with
any kind of visible type application.
There is also a teensy regression around the printing of types
in TH splices. I think this is really a TH bug and will file
separately.
Test case: dependent/should_fail/T15380
Diffstat (limited to 'testsuite/tests/dependent/should_fail/T15380.stderr')
| -rw-r--r-- | testsuite/tests/dependent/should_fail/T15380.stderr | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/testsuite/tests/dependent/should_fail/T15380.stderr b/testsuite/tests/dependent/should_fail/T15380.stderr new file mode 100644 index 0000000000..9b30078c64 --- /dev/null +++ b/testsuite/tests/dependent/should_fail/T15380.stderr @@ -0,0 +1,6 @@ + +T15380.hs:16:16: error: + • Expecting one more argument to ‘To (M x)’ + Expected a type, but ‘To (M x)’ has kind ‘Rep (M x) -> M x’ + • In the type ‘To (M x)’ + In the type family declaration for ‘MDefault’ |