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| author | sheaf <sam.derbyshire@gmail.com> | 2022-02-21 16:43:27 +0100 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2022-02-22 16:00:14 -0500 |
| commit | 0b36801f8eec9b9a7cc512135a13eaf89da370a2 (patch) | |
| tree | 8d6cf545d9838c1b23fa0b30f5272b0e4937eb3e /docs | |
| parent | 2b890c89ba5de9bbf91388d7268919d5c7769bbf (diff) | |
| download | haskell-0b36801f8eec9b9a7cc512135a13eaf89da370a2.tar.gz | |
Forbid standalone instances for built-in classes
`check_special_inst_head` includes logic that disallows hand-written
instances for built-in classes such as Typeable, KnownNat
and KnownSymbol.
However, it also allowed standalone deriving declarations. This was
because we do want to allow standalone deriving instances with
Typeable as they are harmless, but we certainly don't want to allow
instances for e.g. KnownNat.
This patch ensures that we don't allow derived instances for
KnownNat, KnownSymbol (and also KnownChar, which was previously
omitted entirely).
Fixes #21087
Diffstat (limited to 'docs')
0 files changed, 0 insertions, 0 deletions