diff options
| author | Richard Eisenberg <rae@cs.brynmawr.edu> | 2018-10-28 16:06:17 -0400 |
|---|---|---|
| committer | Richard Eisenberg <rae@cs.brynmawr.edu> | 2018-10-28 23:17:47 -0400 |
| commit | 4427315a65b25db22e1754d41b43dd4b782b022f (patch) | |
| tree | 345b7293b2db9a4db36447fe469ebcc066b9a8f1 /compiler/typecheck/TcHsSyn.hs | |
| parent | 5e45ad10ffca1ad175b10f6ef3327e1ed8ba25f3 (diff) | |
| download | haskell-4427315a65b25db22e1754d41b43dd4b782b022f.tar.gz | |
Fix #15787 by squashing a coercion hole.
In type-incorrect code, we can sometimes let a coercion
hole make it through the zonker. If this coercion hole then
ends up in the environment (e.g., in the type of a data
constructor), then it causes trouble later.
This patch avoids trouble by substituting the coercion hole
for its representative CoVar. Really, any coercion would do,
but the CoVar was very handy.
test case: polykinds/T15787
Diffstat (limited to 'compiler/typecheck/TcHsSyn.hs')
| -rw-r--r-- | compiler/typecheck/TcHsSyn.hs | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/compiler/typecheck/TcHsSyn.hs b/compiler/typecheck/TcHsSyn.hs index f5fedc9d51..99e2172c5b 100644 --- a/compiler/typecheck/TcHsSyn.hs +++ b/compiler/typecheck/TcHsSyn.hs @@ -1810,7 +1810,9 @@ zonkCoHole env hole@(CoercionHole { ch_ref = ref, ch_co_var = cv }) , text "Type-correct unfilled coercion hole" <+> ppr hole ) ; cv' <- zonkCoVar cv - ; return $ mkHoleCo (hole { ch_co_var = cv' }) } } + ; return $ mkCoVarCo cv' } } + -- This will be an out-of-scope variable, but keeping + -- this as a coercion hole led to #15787 zonk_tycomapper :: TyCoMapper ZonkEnv TcM zonk_tycomapper = TyCoMapper |