diff options
Diffstat (limited to 'compiler/GHC/Core/Lint.hs')
| -rw-r--r-- | compiler/GHC/Core/Lint.hs | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/compiler/GHC/Core/Lint.hs b/compiler/GHC/Core/Lint.hs index 6fcd8aca96..0511a4004d 100644 --- a/compiler/GHC/Core/Lint.hs +++ b/compiler/GHC/Core/Lint.hs @@ -667,8 +667,8 @@ lintLetBind top_lvl rec_flag binder rhs rhs_ty -- exceeds idArity, but that is an unnecessary complication, see -- Note [idArity varies independently of dmdTypeDepth] in GHC.Core.Opt.DmdAnal - -- Check that the binder's arity is within the bounds imposed by - -- the type and the strictness signature. See Note [exprArity invariant] + -- Check that the binder's arity is within the bounds imposed by the type + -- and the strictness signature. See Note [Arity invariants for bindings] -- and Note [Trimming arity] ; checkL (typeArity (idType binder) >= idArity binder) @@ -677,6 +677,7 @@ lintLetBind top_lvl rec_flag binder rhs rhs_ty ppr (typeArity (idType binder)) <> colon <+> ppr binder) + -- See Note [Check arity on bottoming functions] ; case splitDmdSig (idDmdSig binder) of (demands, result_info) | isDeadEndDiv result_info -> checkL (demands `lengthAtLeast` idArity binder) @@ -761,6 +762,12 @@ lintIdUnfolding _ _ _ -- to exponential behaviour; c.f. GHC.Core.FVs.idUnfoldingVars {- +Note [Check arity on bottoming functions] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +If a function has a strictness signature like [S]b, it claims to +return bottom when applied to one argument. So its arity should not +be greater than 1! We check this claim in Lint. + Note [Checking for INLINE loop breakers] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ It's very suspicious if a strong loop breaker is marked INLINE. |