diff options
Diffstat (limited to 'compiler/GHC/HsToCore/PmCheck/Oracle.hs')
| -rw-r--r-- | compiler/GHC/HsToCore/PmCheck/Oracle.hs | 21 |
1 files changed, 1 insertions, 20 deletions
diff --git a/compiler/GHC/HsToCore/PmCheck/Oracle.hs b/compiler/GHC/HsToCore/PmCheck/Oracle.hs index 9a3c312a2e..ce02a4cdf9 100644 --- a/compiler/GHC/HsToCore/PmCheck/Oracle.hs +++ b/compiler/GHC/HsToCore/PmCheck/Oracle.hs @@ -166,25 +166,6 @@ mkOneConFull arg_tys con = do -- * Pattern match oracle -{- Note [Recovering from unsatisfiable pattern-matching constraints] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Consider the following code (see #12957 and #15450): - - f :: Int ~ Bool => () - f = case True of { False -> () } - -We want to warn that the pattern-matching in `f` is non-exhaustive. But GHC -used not to do this; in fact, it would warn that the match was /redundant/! -This is because the constraint (Int ~ Bool) in `f` is unsatisfiable, and the -coverage checker deems any matches with unsatisfiable constraint sets to be -unreachable. - -We decide to better than this. When beginning coverage checking, we first -check if the constraints in scope are unsatisfiable, and if so, we start -afresh with an empty set of constraints. This way, we'll get the warnings -that we expect. --} - ------------------------------------- -- * Composable satisfiability checks @@ -1265,7 +1246,7 @@ isTyConTriviallyInhabited tc = elementOfUniqSet tc triviallyInhabitedTyCons {- Note [Checking EmptyCase Expressions] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Empty case expressions are strict on the scrutinee. That is, `case x of {}` -will force argument `x`. Hence, `covCheckMatchGroup` is not sufficient for checking +will force argument `x`. Hence, `covCheckMatches` is not sufficient for checking empty cases, because it assumes that the match is not strict (which is true for all other cases, apart from EmptyCase). This gave rise to #10746. Instead, we do the following: |