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| author | Jakob Bruenker <jakob.bruenker@gmail.com> | 2022-03-21 00:14:25 +0100 |
|---|---|---|
| committer | Jakob Bruenker <jakob.bruenker@gmail.com> | 2022-03-31 17:45:37 +0200 |
| commit | a9c0c69b42657d39f26ab822241900ba0f308dc3 (patch) | |
| tree | fd59a5e49146ee436e04137b313d8e4178c2bed0 /compiler/GHC/HsToCore/Match.hs | |
| parent | dda46e2da13268c239db3290720b014cef00c01d (diff) | |
| download | haskell-wip/T20768.tar.gz | |
Implement \cases (Proposal 302)wip/T20768
This commit implements proposal 302: \cases - Multi-way lambda
expressions.
This adds a new expression heralded by \cases, which works exactly like
\case, but can match multiple apats instead of a single pat.
Updates submodule haddock to support the ITlcases token.
Closes #20768
Diffstat (limited to 'compiler/GHC/HsToCore/Match.hs')
| -rw-r--r-- | compiler/GHC/HsToCore/Match.hs | 37 |
1 files changed, 27 insertions, 10 deletions
diff --git a/compiler/GHC/HsToCore/Match.hs b/compiler/GHC/HsToCore/Match.hs index 8fcb150329..5c45d9b705 100644 --- a/compiler/GHC/HsToCore/Match.hs +++ b/compiler/GHC/HsToCore/Match.hs @@ -708,15 +708,32 @@ Call @match@ with all of this information! \end{enumerate} -} +-- Note [matchWrapper scrutinees] +-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +-- There are three possible cases for matchWrapper's scrutinees argument: +-- +-- 1. Nothing Used for FunBind, HsLam, HsLamcase, where there is no explicit scrutinee +-- The MatchGroup may have matchGroupArity of 0 or more. Examples: +-- f p1 q1 = ... -- matchGroupArity 2 +-- f p2 q2 = ... +-- +-- \cases | g1 -> ... -- matchGroupArity 0 +-- | g2 -> ... +-- +-- 2. Just [e] Used for HsCase, RecordUpd; exactly one scrutinee +-- The MatchGroup has matchGroupArity of exactly 1. Example: +-- case e of p1 -> e1 -- matchGroupArity 1 +-- p2 -> e2 +-- +-- 3. Just es Used for HsCmdLamCase; zero or more scrutinees +-- The MatchGroup has matchGroupArity of (length es). Example: +-- \cases p1 q1 -> returnA -< ... -- matchGroupArity 2 +-- p2 q2 -> ... + matchWrapper :: HsMatchContext GhcRn -- ^ For shadowing warning messages - -> Maybe (LHsExpr GhcTc) -- ^ Scrutinee. (Just scrut) for a case expr - -- case scrut of { p1 -> e1 ... } - -- (and in this case the MatchGroup will - -- have all singleton patterns) - -- Nothing for a function definition - -- f p1 q1 = ... -- No "scrutinee" - -- f p2 q2 = ... -- in this case + -> Maybe [LHsExpr GhcTc] -- ^ Scrutinee(s) + -- see Note [matchWrapper scrutinees] -> MatchGroup GhcTc (LHsExpr GhcTc) -- ^ Matches being desugared -> DsM ([Id], CoreExpr) -- ^ Results (usually passed to 'match') @@ -744,7 +761,7 @@ one pattern, and match simply only accepts one pattern. JJQC 30-Nov-1997 -} -matchWrapper ctxt mb_scr (MG { mg_alts = L _ matches +matchWrapper ctxt scrs (MG { mg_alts = L _ matches , mg_ext = MatchGroupTc arg_tys rhs_ty , mg_origin = origin }) = do { dflags <- getDynFlags @@ -762,7 +779,7 @@ matchWrapper ctxt mb_scr (MG { mg_alts = L _ matches -- @rhss_nablas@ is a flat list of covered Nablas for each RHS. -- Each Match will split off one Nablas for its RHSs from this. ; matches_nablas <- if isMatchContextPmChecked dflags origin ctxt - then addHsScrutTmCs mb_scr new_vars $ + then addHsScrutTmCs (concat scrs) new_vars $ -- See Note [Long-distance information] pmcMatches (DsMatchContext ctxt locn) new_vars matches else pure (initNablasMatches matches) @@ -872,7 +889,7 @@ matchSinglePatVar var mb_scrut ctx pat ty match_result ; locn <- getSrcSpanDs -- Pattern match check warnings ; when (isMatchContextPmChecked dflags FromSource ctx) $ - addCoreScrutTmCs mb_scrut [var] $ + addCoreScrutTmCs (maybeToList mb_scrut) [var] $ pmcPatBind (DsMatchContext ctx locn) var (unLoc pat) ; let eqn_info = EqnInfo { eqn_pats = [unLoc (decideBangHood dflags pat)] |