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| author | Iavor S. Diatchki <diatchki@galois.com> | 2015-03-07 10:37:31 -0600 |
|---|---|---|
| committer | Austin Seipp <austin@well-typed.com> | 2015-03-07 10:38:30 -0600 |
| commit | b359c886cd7578ed083bcedcea05d315ecaeeb54 (patch) | |
| tree | bb1959149dde78d29614966131841a77fa38bbab /testsuite/tests/polykinds/T8132.stderr | |
| parent | 479523f3c37894d63352f1718e06696f3ed63143 (diff) | |
| download | haskell-b359c886cd7578ed083bcedcea05d315ecaeeb54.tar.gz | |
Custom `Typeable` solver, that keeps track of kinds.
Summary:
This implements the new `Typeable` solver: when GHC sees `Typeable` constraints
it solves them on the spot.
The current implementation creates `TyCon` representations on the spot.
Pro: No overhead at all in code that does not use `Typeable`
Cons: Code that uses `Typeable` may create multipe `TyCon` represntations.
We have discussed an implementation where representations of `TyCons` are
computed once, in the module, where a datatype is declared. This would
lead to more code being generated: for a promotable datatype we need to
generate `2 + number_of_data_cons` type-constructro representations,
and we have to do that for all programs, even ones that do not intend to
use typeable.
I added code to emit warning whenevar `deriving Typeable` is encountered---
the idea being that this is not needed anymore, and shold be fixed.
Also, we allow `instance Typeable T` in .hs-boot files, but they result
in a warning, and are ignored. This last one was to avoid breaking exisitng
code, and should become an error, eventually.
Test Plan:
1. GHC can compile itself.
2. I compiled a number of large libraries, including `lens`.
- I had to make some small changes:
`unordered-containers` uses internals of `TypeReps`, so I had to do a 1 line fix
- `lens` needed one instance changed, due to a poly-kinded `Typeble` instance
3. I also run some code that uses `syb` to traverse a largish datastrucutre.
I didn't notice any signifiant performance difference between the 7.8.3 version,
and this implementation.
Reviewers: simonpj, simonmar, austin, hvr
Reviewed By: austin, hvr
Subscribers: thomie
Differential Revision: https://phabricator.haskell.org/D652
GHC Trac Issues: #9858
Diffstat (limited to 'testsuite/tests/polykinds/T8132.stderr')
| -rw-r--r-- | testsuite/tests/polykinds/T8132.stderr | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/testsuite/tests/polykinds/T8132.stderr b/testsuite/tests/polykinds/T8132.stderr index 6c567de60a..e4c46591c3 100644 --- a/testsuite/tests/polykinds/T8132.stderr +++ b/testsuite/tests/polykinds/T8132.stderr @@ -1,5 +1,3 @@ T8132.hs:6:10: - Typeable instances can only be derived - Try ‘deriving instance Typeable K’ - (requires StandaloneDeriving) + Class `Typeable` does not support user-specified instances. |