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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2016-02-08 14:41:08 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2016-02-08 15:08:54 +0000 |
| commit | 43e02d1270701a1043be67f078cf2b1a85047feb (patch) | |
| tree | 26aba405d5ad13a5c9190f960483341e467d530a /compiler/codeGen/CodeGen | |
| parent | 6252b70a2fc61ff90c7abc93d2e9f05cf60ab47e (diff) | |
| download | haskell-43e02d1270701a1043be67f078cf2b1a85047feb.tar.gz | |
Fix a nasty superclass expansion bug
This patch fixes Trac #11523.
* The basic problem was that TcRnTypes.superClassesMightHelp was
returning True of a Derived constraint, and that led to us
expanding Given superclasses, which produced the same Derived
constraint again, and so on infinitely. We really want to do
this only if there are unsolve /Wanted/ contraints!
* On the way I made TcSMonad.getUnsolvedInerts a bit more
discriminating about which Derived equalities it returns;
see Note [Unsolved Derived equalities] in TcSMonad
* Lots of new comments in TcSMonad.
Diffstat (limited to 'compiler/codeGen/CodeGen')
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