Moduleghc-lib-parser-9.14.1.20251220GHC2021

GHC.HsToCore.Pmc.Types

Types used through-out pattern match checking. This module is mostly there to be imported from GHC.HsToCore.Types. The exposed API is that of GHC.HsToCore.Pmc.

These types model the paper Lower Your Guards: A Compositional Pattern-Match Coverage Checker".

15 types
5 values

Packageghc-lib-parser-9.14.1.20251220
Exports20
LanguageGHC2021
LicenceBSD-3-Clause
SourceTypes.hs

LYG syntax

0 declarations

Guard language

newtypenewtype SrcInfo

Means by which we identify a source construct for later pretty-printing in a warning message. SDoc for the equation to show, Located for the location.

Constructors

SrcInfo (Located SDoc)

Instances1Outputable

Outputable SrcInfoDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types

datadata PmGrd

A very simple language for pattern guards. Let bindings, bang patterns, and matching variables against flat constructor patterns. The LYG guard language.

Constructors

PmCon
PmCon x K dicts args corresponds to a K dicts args <- x guard. The args are bound in this construct, the x is just a use. For the arguments' meaning see GHC.Hs.Pat.ConPatOut.
- pm_id :: !Id
- pm_con_con :: !PmAltCon
- pm_con_tvs :: ![TyVar]
- pm_con_dicts :: ![EvVar]
- pm_con_args :: ![Id]
PmBang
PmBang x corresponds to a seq x True guard. If the extra SrcInfo is present, the bang guard came from a source bang pattern, in which case we might want to report it as redundant. See Note [Dead bang patterns] in GHC.HsToCore.Pmc.Check.
- pm_id :: !Id
- _pm_loc :: !Maybe SrcInfo
PmLet
PmLet x expr corresponds to a let x = expr guard. This actually binds x.
- pm_id :: !Id
- _pm_let_expr :: !CoreExpr

Instances1Outputable

Outputable PmGrdDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types
Should not be user-facing.

datadata GrdDag

A series-parallel graph of PmGrds, so very nearly a guard tree, if it weren't for or-patterns/GdAlt! The implicit "source" corresponds to "before the match" and the implicit "sink" corresponds to "after a successful match".

GdEnd is a GrdDag that always matches.
GdOne is a GrdDag that matches iff its PmGrd matches.
GdSeq g1 g2 corresponds to matching guards g1 and then g2 if matching g1 succeeded. Example: The Haskell guard | x > 1, x < 10 = ... will test x > 1 before x < 10, failing if either test fails.
GdAlt g1 g2 is far less common than GdSeq and corresponds to matching an or-pattern (LT; EQ), succeeding if the match variable matches either LT or EQ. See Note [Implementation of OrPatterns] for a larger example.

Instances1Outputable

Outputable GrdDagDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types
Format LYG guards as | True <- x, let x = 42, !z

valueconsGrdDag :: PmGrd -> GrdDag -> GrdDag

Sequentially compose a PmGrd in front of a GrdDag.

valuegdSeq :: GrdDag -> GrdDag -> GrdDag

Sequentially compose two GrdDags. A smart constructor for GdSeq that eliminates GdEnds.

valuesequencePmGrds :: [PmGrd] -> GrdDag

Sequentially compose a list of PmGrds into a GrdDag.

valuesequenceGrdDags :: [GrdDag] -> GrdDag

Sequentially compose a list of GrdDags.

valuealternativesGrdDags :: NonEmpty GrdDag -> GrdDag

Parallel composition of a list of GrdDags. Needs a non-empty list as GdAlt does not have a neutral element.

Guard tree language

newtypenewtype PmMatchGroup p

A guard tree denoting MatchGroup.

Constructors

PmMatchGroup (NonEmpty (PmMatch p))

Instances1Outputable

Outputable p => Outputable (PmMatchGroup p)Defined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types

datadata PmMatch p

A guard tree denoting Match: A payload describing the pats and a bunch of GRHS.

Constructors

PmMatch
- pm_pats :: !p
- pm_grhss :: !PmGRHSs p

Instances1Outputable

Outputable p => Outputable (PmMatch p)Defined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types

datadata PmGRHSs p

A guard tree denoting GRHSs: A bunch of PmLet guards for local bindings from the GRHSss where clauses and the actual list of GRHS. See Note [Long-distance information for HsLocalBinds] in GHC.HsToCore.Pmc.Desugar.

Constructors

PmGRHSs
- pgs_lcls :: !p
- pgs_grhss :: !NonEmpty (PmGRHS p)

Instances1Outputable

Outputable p => Outputable (PmGRHSs p)Defined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types

datadata PmGRHS p

A guard tree denoting GRHS: A payload describing the grds and a SrcInfo useful for printing out in warnings messages.

Constructors

PmGRHS
- pg_grds :: !p
- pg_rhs :: !SrcInfo

Instances1Outputable

Outputable p => Outputable (PmGRHS p)Defined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types

newtypenewtype PmPatBind p

A guard tree denoting a pattern binding.

Constructors

PmPatBind (PmGRHS p)

Instances1Outputable

Outputable p => Outputable (PmPatBind p)Defined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types

newtypenewtype PmEmptyCase

A guard tree denoting an -XEmptyCase.

Constructors

PmEmptyCase
- pe_var :: Id

Instances1Outputable

Outputable PmEmptyCaseDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types

datadata PmRecSel v

Constructors

PmRecSel
- pr_arg_var :: v
- pr_arg :: CoreExpr
- pr_cons :: [ConLike]

Coverage Checking types

3 declarations

datadata RedSets

Redundancy sets, used to determine redundancy of RHSs and bang patterns (later digested into a CIRB).

Constructors

RedSets
- rs_cov :: !Nablas
  The Covered set; the set of values reaching a particular program point.
- rs_div :: !Nablas
  The Diverging set; empty if no match can lead to divergence. If it wasn't empty, we have to turn redundancy warnings into inaccessibility warnings for any subclauses.
- rs_bangs :: !OrdList (Nablas, SrcInfo)
  If any of the Nablas is empty, the corresponding SrcInfo pin-points a bang pattern in source that is redundant. See Note [Dead bang patterns].

Instances1Outputable

Outputable RedSetsDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types

datadata Precision

Approximate Precise

Instances5Eq, Show, Semigroup, Monoid, Outputable

Eq PrecisionDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types
Show PrecisionDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types
Semigroup PrecisionDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types
Monoid PrecisionDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types
Outputable PrecisionDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types

datadata CheckResult a

Pattern-match coverage check result

Constructors

CheckResult
- cr_ret :: !a
  A hole for redundancy info and covered sets.
- cr_uncov :: !Nablas
  The set of uncovered values falling out at the bottom. (for -Wincomplete-patterns, but also important state for the algorithm)
- cr_approx :: !Precision
  A flag saying whether we ran into the maxPmCheckModels limit for the purpose of suggesting to crank it up in the warning message. Writer state.

Instances2Functor, Outputable

Functor CheckResultDefined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types
Outputable a => Outputable (CheckResult a)Defined in ghc-lib-parser-9.14.1.20251220 · GHC.HsToCore.Pmc.Types

Pre and post coverage checking synonyms

2 declarations

typetype Pre = GrdDag

Used as tree payload pre-checking. The LYG guards to check.

typetype Post = RedSets

Used as tree payload post-checking. The redundancy info we elaborated.

Normalised refinement types

0 declarations

module GHC.HsToCore.Pmc.Solver.Types