ghc-7.6.1.20121125: The GHC API

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CoreSubst

Contents

Synopsis

Main data types

data Subst Source

A substitution environment, containing both Id and TyVar substitutions.

Some invariants apply to how you use the substitution:

  1. The in-scope set contains at least those Ids and TyVars that will be in scope after applying the substitution to a term. Precisely, the in-scope set must be a superset of the free vars of the substitution range that might possibly clash with locally-bound variables in the thing being substituted in.
  2. You may apply the substitution only once

There are various ways of setting up the in-scope set such that the first of these invariants hold:

  • Arrange that the in-scope set really is all the things in scope
  • Arrange that it's the free vars of the range of the substitution
  • Make it empty, if you know that all the free vars of the substitution are fresh, and hence can't possibly clash

Instances

type TvSubstEnv = TyVarEnv TypeSource

A substitition of Types for TyVars and Kinds for KindVars

type IdSubstEnv = IdEnv CoreExprSource

An environment for substituting for Ids

data InScopeSet Source

A set of variables that are in scope at some point

Substituting into expressions and related types

deShadowBinds :: CoreProgram -> CoreProgramSource

De-shadowing the program is sometimes a useful pre-pass. It can be done simply by running over the bindings with an empty substitution, becuase substitution returns a result that has no-shadowing guaranteed.

(Actually, within a single type there might still be shadowing, because substTy is a no-op for the empty substitution, but that's probably OK.)

Aug 09
This function is not used in GHC at the moment, but seems so short and simple that I'm going to leave it here

substSpec :: Subst -> Id -> SpecInfo -> SpecInfoSource

Substitutes for the Ids within the WorkerInfo given the new function Id

substExprSC :: SDoc -> Subst -> CoreExpr -> CoreExprSource

Apply a substititon to an entire CoreExpr. Rememeber, you may only apply the substitution once: see CoreSubst

Do *not* attempt to short-cut in the case of an empty substitution! See Note [Extending the Subst]

substBind :: Subst -> CoreBind -> (Subst, CoreBind)Source

Apply a substititon to an entire CoreBind, additionally returning an updated Subst that should be used by subsequent substitutons.

substBindSC :: Subst -> CoreBind -> (Subst, CoreBind)Source

Apply a substititon to an entire CoreBind, additionally returning an updated Subst that should be used by subsequent substitutons.

substUnfolding :: Subst -> Unfolding -> UnfoldingSource

Substitutes for the Ids within an unfolding

substUnfoldingSC :: Subst -> Unfolding -> UnfoldingSource

Substitutes for the Ids within an unfolding

lookupIdSubst :: SDoc -> Subst -> Id -> CoreExprSource

Find the substitution for an Id in the Subst

lookupTvSubst :: Subst -> TyVar -> TypeSource

Find the substitution for a TyVar in the Subst

lookupCvSubst :: Subst -> CoVar -> CoercionSource

Find the coercion substitution for a CoVar in the Subst

Operations on substitutions

mkOpenSubst :: InScopeSet -> [(Var, CoreArg)] -> SubstSource

Simultaneously substitute for a bunch of variables No left-right shadowing ie the substitution for (x y. e) a1 a2 so neither x nor y scope over a1 a2

substInScope :: Subst -> InScopeSetSource

Find the in-scope set: see CoreSubst

extendIdSubst :: Subst -> Id -> CoreExpr -> SubstSource

Add a substitution for an Id to the Subst: you must ensure that the in-scope set is such that the CoreSubst is true after extending the substitution like this

extendIdSubstList :: Subst -> [(Id, CoreExpr)] -> SubstSource

Adds multiple Id substitutions to the Subst: see also extendIdSubst

extendTvSubst :: Subst -> TyVar -> Type -> SubstSource

Add a substitution for a TyVar to the Subst: you must ensure that the in-scope set is such that the CoreSubst is true after extending the substitution like this

extendTvSubstList :: Subst -> [(TyVar, Type)] -> SubstSource

Adds multiple TyVar substitutions to the Subst: see also extendTvSubst

extendCvSubst :: Subst -> CoVar -> Coercion -> SubstSource

Add a substitution from a CoVar to a Coercion to the Subst: you must ensure that the in-scope set is such that the CoreSubst is true after extending the substitution like this

extendCvSubstList :: Subst -> [(CoVar, Coercion)] -> SubstSource

Adds multiple CoVar -> Coercion substitutions to the Subst: see also extendCvSubst

extendSubst :: Subst -> Var -> CoreArg -> SubstSource

Add a substitution appropriate to the thing being substituted (whether an expression, type, or coercion). See also extendIdSubst, extendTvSubst, and extendCvSubst.

extendSubstList :: Subst -> [(Var, CoreArg)] -> SubstSource

Add a substitution as appropriate to each of the terms being substituted (whether expressions, types, or coercions). See also extendSubst.

zapSubstEnv :: Subst -> SubstSource

Remove all substitutions for Ids and Vars that might have been built up while preserving the in-scope set

addInScopeSet :: Subst -> VarSet -> SubstSource

Add the Var to the in-scope set, but do not remove any existing substitutions for it

extendInScope :: Subst -> Var -> SubstSource

Add the Var to the in-scope set: as a side effect, and remove any existing substitutions for it

extendInScopeList :: Subst -> [Var] -> SubstSource

Add the Vars to the in-scope set: see also extendInScope

extendInScopeIds :: Subst -> [Id] -> SubstSource

Optimized version of extendInScopeList that can be used if you are certain all the things being added are Ids and hence none are TyVars or CoVars

Substituting and cloning binders

substBndr :: Subst -> Var -> (Subst, Var)Source

Substitutes a Var for another one according to the Subst given, returning the result and an updated Subst that should be used by subsequent substitutons. IdInfo is preserved by this process, although it is substituted into appropriately.

substBndrs :: Subst -> [Var] -> (Subst, [Var])Source

Applies substBndr to a number of Vars, accumulating a new Subst left-to-right

substRecBndrs :: Subst -> [Id] -> (Subst, [Id])Source

Substitute in a mutually recursive group of Ids

cloneIdBndr :: Subst -> UniqSupply -> Id -> (Subst, Id)Source

Very similar to substBndr, but it always allocates a new Unique for each variable in its output. It substitutes the IdInfo though.

cloneIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])Source

Applies cloneIdBndr to a number of Ids, accumulating a final substitution from left to right

cloneRecIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])Source

Clone a mutually recursive group of Ids

Simple expression optimiser

simpleOptExprWith :: Subst -> InExpr -> OutExprSource

exprIsConApp_maybe :: IdUnfoldingFun -> CoreExpr -> Maybe (DataCon, [Type], [CoreExpr])Source

Returns Just (dc, [t1..tk], [x1..xn]) if the argument expression is a *saturated* constructor application of the form dc t1..tk x1 .. xn, where t1..tk are the *universally-qantified* type args of dc