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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2012-05-02 15:44:14 +0100 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2012-05-02 15:44:14 +0100 |
| commit | ac230c5ef652e27f61d954281ae6a3195e1f9970 (patch) | |
| tree | 4cd59d3ca670916f64bcfe9c0c3f72f21a272e42 /compiler/specialise/Specialise.lhs | |
| parent | b04c0beb951b2e69f76f724a4e72b98c896b468a (diff) | |
| download | haskell-ac230c5ef652e27f61d954281ae6a3195e1f9970.tar.gz | |
Allow cases with empty alterantives
This patch allows, for the first time, case expressions with an empty
list of alternatives. Max suggested the idea, and Trac #6067 showed
that it is really quite important.
So I've implemented the idea, fixing #6067. Main changes
* See Note [Empty case alternatives] in CoreSyn
* Various foldr1's become foldrs
* IfaceCase does not record the type of the alternatives.
I added IfaceECase for empty-alternative cases.
* Core Lint does not complain about empty cases
* MkCore.castBottomExpr constructs an empty-alternative case
expression (case e of ty {})
* CoreToStg converts '(case e of {})' to just 'e'
Diffstat (limited to 'compiler/specialise/Specialise.lhs')
| -rw-r--r-- | compiler/specialise/Specialise.lhs | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/compiler/specialise/Specialise.lhs b/compiler/specialise/Specialise.lhs index 321deb866a..6c80f8fbde 100644 --- a/compiler/specialise/Specialise.lhs +++ b/compiler/specialise/Specialise.lhs @@ -1037,12 +1037,12 @@ specCalls subst rules_for_me calls_for_me fn rhs = WARN( notNull calls_for_me, ptext (sLit "Missed specialisation opportunity for") <+> ppr fn $$ _trace_doc ) -- Note [Specialisation shape] - -- pprTrace "specDefn: none" (ppr fn $$ ppr calls_for_me) $ + -- pprTrace "specDefn: none" (ppr fn <+> ppr calls_for_me) $ return ([], [], emptyUDs) where - _trace_doc = vcat [ ppr rhs_tyvars, ppr n_tyvars - , ppr rhs_ids, ppr n_dicts - , ppr (idInlineActivation fn) ] + _trace_doc = sep [ ppr rhs_tyvars, ppr n_tyvars + , ppr rhs_ids, ppr n_dicts + , ppr (idInlineActivation fn) ] fn_type = idType fn fn_arity = idArity fn |