Agda-2.5.4.1.20181026: A dependently typed functional programming language and proof assistant

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LanguageHaskell2010

Agda.TypeChecking.MetaVars.Occurs

Contents

Description

The occurs check for unification. Does pruning on the fly.

When hitting a meta variable:

  • Compute flex/rigid for its arguments.
  • Compare to allowed variables.
  • Mark arguments with rigid occurrences of disallowed variables for deletion.
  • Attempt to delete marked arguments.
  • We don't need to check for success, we can just continue occurs checking.
Synopsis

Documentation

initOccursCheck :: MetaVariable -> TCM () Source #

Set the names of definitions to be looked at to the defs in the current mutual block.

defNeedsChecking :: QName -> TCM Bool Source #

Is a def in the list of stuff to be checked?

tallyDef :: QName -> TCM () Source #

Remove a def from the list of defs to be looked at.

data OccursCtx Source #

Constructors

Flex

We are in arguments of a meta.

Rigid

We are not in arguments of a meta but a bound var.

StronglyRigid

We are at the start or in the arguments of a constructor.

Irrel

We are in an irrelevant argument.

weakly :: OccursCtx -> OccursCtx Source #

Leave the strongly rigid position.

type Vars = ([Nat], [Nat], [Nat]) Source #

Distinguish relevant, irrelevant and nonstrict variables in occurs check.

class Occurs t where Source #

Extended occurs check.

Minimal complete definition

occurs, metaOccurs

Methods

occurs :: UnfoldStrategy -> OccursCtx -> MetaId -> Vars -> t -> TCM t Source #

metaOccurs :: MetaId -> t -> TCM () Source #

Instances
Occurs QName Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Occurs Clause Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Occurs LevelAtom Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Occurs PlusLevel Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Occurs Level Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Occurs Sort Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Occurs Type Source # 
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Defined in Agda.TypeChecking.MetaVars.Occurs

Occurs Term Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Occurs Defn Source # 
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Defined in Agda.TypeChecking.MetaVars.Occurs

Occurs a => Occurs [a] Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

occurs :: UnfoldStrategy -> OccursCtx -> MetaId -> Vars -> [a] -> TCM [a] Source #

metaOccurs :: MetaId -> [a] -> TCM () Source #

Occurs a => Occurs (Maybe a) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Occurs a => Occurs (Dom a) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

occurs :: UnfoldStrategy -> OccursCtx -> MetaId -> Vars -> Dom a -> TCM (Dom a) Source #

metaOccurs :: MetaId -> Dom a -> TCM () Source #

Occurs a => Occurs (Arg a) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

occurs :: UnfoldStrategy -> OccursCtx -> MetaId -> Vars -> Arg a -> TCM (Arg a) Source #

metaOccurs :: MetaId -> Arg a -> TCM () Source #

(Occurs a, Subst t a) => Occurs (Abs a) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

occurs :: UnfoldStrategy -> OccursCtx -> MetaId -> Vars -> Abs a -> TCM (Abs a) Source #

metaOccurs :: MetaId -> Abs a -> TCM () Source #

Occurs a => Occurs (Elim' a) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

(Occurs a, Occurs b) => Occurs (a, b) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

occurs :: UnfoldStrategy -> OccursCtx -> MetaId -> Vars -> (a, b) -> TCM (a, b) Source #

metaOccurs :: MetaId -> (a, b) -> TCM () Source #

occursCheck :: (Occurs a, InstantiateFull a, PrettyTCM a) => MetaId -> Vars -> a -> TCM a Source #

When assigning m xs := v, check that m does not occur in v and that the free variables of v are contained in xs.

Getting rid of flexible occurrences

prune :: MetaId -> Args -> [Nat] -> TCM PruneResult Source #

prune m' vs xs attempts to remove all arguments from vs whose free variables are not contained in xs. If successful, m' is solved by the new, pruned meta variable and we return True else False.

Issue 1147: If any of the meta args vs is matchable, e.g., is a constructor term, we cannot prune, because the offending variables could be removed by reduction for a suitable instantiation of the meta variable.

hasBadRigid :: [Nat] -> Term -> ExceptT () TCM Bool Source #

hasBadRigid xs v = Just True iff one of the rigid variables in v is not in xs. Actually we can only prune if a bad variable is in the head. See issue 458. Or in a non-eliminateable position (see succeed/PruningNonMillerPattern).

hasBadRigid xs v = Nothing means that we cannot prune at all as one of the meta args is matchable. (See issue 1147.)

isNeutral :: MonadTCM tcm => Blocked t -> QName -> Elims -> tcm Bool Source #

Check whether a term Def f es is finally stuck. Currently, we give only a crude approximation.

rigidVarsNotContainedIn :: (MonadTCM tcm, FoldRigid a) => a -> [Nat] -> tcm Bool Source #

Check whether any of the variables (given as de Bruijn indices) occurs *definitely* in the term in a rigid position. Reduces the term successively to remove variables in dead subterms. This fixes issue 1386.

class FoldRigid a where Source #

Collect the *definitely* rigid variables in a monoid. We need to successively reduce the expression to do this.

Minimal complete definition

foldRigid

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> a -> TCM m Source #

Instances
FoldRigid LevelAtom Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> LevelAtom -> TCM m Source #

FoldRigid PlusLevel Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> PlusLevel -> TCM m Source #

FoldRigid Level Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> Level -> TCM m Source #

FoldRigid Sort Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> Sort -> TCM m Source #

FoldRigid Type Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> Type -> TCM m Source #

FoldRigid Term Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> Term -> TCM m Source #

FoldRigid a => FoldRigid [a] Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> [a] -> TCM m Source #

FoldRigid a => FoldRigid (Dom a) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> Dom a -> TCM m Source #

FoldRigid a => FoldRigid (Arg a) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> Arg a -> TCM m Source #

(Subst t a, FoldRigid a) => FoldRigid (Abs a) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> Abs a -> TCM m Source #

FoldRigid a => FoldRigid (Elim' a) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> Elim' a -> TCM m Source #

(FoldRigid a, FoldRigid b) => FoldRigid (a, b) Source # 
Instance details

Defined in Agda.TypeChecking.MetaVars.Occurs

Methods

foldRigid :: Monoid (TCM m) => (Nat -> TCM m) -> (a, b) -> TCM m Source #

data PruneResult Source #

Constructors

NothingToPrune

the kill list is empty or only Falses

PrunedNothing

there is no possible kill (because of type dep.)

PrunedSomething

managed to kill some args in the list

PrunedEverything

all prescribed kills where performed

killArgs :: [Bool] -> MetaId -> TCM PruneResult Source #

killArgs [k1,...,kn] X prunes argument i from metavar X if ki==True. Pruning is carried out whenever > 0 arguments can be pruned.

killedType :: [(Dom (ArgName, Type), Bool)] -> Type -> TCM ([Arg Bool], Type) Source #

killedType [((x1,a1),k1)..((xn,an),kn)] b = ([k'1..k'n],t') (ignoring Dom). Let t' = (xs:as) -> b. Invariant: k'i == True iff ki == True and pruning the ith argument from type b is possible without creating unbound variables. t' is type t after pruning all k'i==True.

performKill Source #

Arguments

:: [Arg Bool]

Arguments to old meta var in left to right order with Bool indicating whether they can be pruned.

-> MetaId

The old meta var to receive pruning.

-> Type

The pruned type of the new meta var.

-> TCM () 

Instantiate a meta variable with a new one that only takes the arguments which are not pruneable.