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GHC 10.0.0.20260917 · lts/ghc-10.0.x · 77a8662 · 2026-10-31

Moduleghc-tcplugins-extra-0.5Haskell2010

GHC.TcPluginM.Extra

Cpp

Contents

Create new constraints
Creating evidence
Lookup
Trace state of the plugin
Substitutions

Synopsis

value newWanted
value newGiven
value evByFiatWithDependencies
value evByFiat
value lookupModule
value lookupName
value tracePlugin
value flattenGivens
value mkSubst
value mkSubst'
value substType
value substCt

Packageghc-tcplugins-extra-0.5
Exports12
LanguageHaskell2010
LicenceBSD-2-Clause
SourcePlugin.hs

Create new constraints

valuenewWanted :: CtLoc -> PredType -> TcPluginM CtEvidence

Create a new Wanted constraint with the given CtLoc.

valuenewGiven

Create a new [G]iven constraint, with the supplied evidence. This must not be invoked from tcPluginInit or tcPluginStop, or it will panic.

Creating evidence

valueevByFiatWithDependencies

:: String
Name the coercion should have
-> [Coercion]
The set of all the in-scope coercion that the proof makes use of.
-> Type
The LHS of the equivalence relation (~)
-> Type
The RHS of the equivalence relation (~)
-> EvTerm

The EvTerm equivalent for Unsafe.unsafeCoerce

valueevByFiat

:: String
Name the coercion should have
-> Type
The LHS of the equivalence relation (~)
-> Type
The RHS of the equivalence relation (~)
-> EvTerm

Deprecated. evByFiat creates proofs that can lead to unsoundness, use evByFiatWithDependencies instead. See also https://gitlab.haskell.org/ghc/ghc/-/merge_requests/12037

The EvTerm equivalent for Unsafe.unsafeCoerce

Lookup

valuelookupModule

:: ModuleName
Name of the module
-> FastString
Name of the package containing the module. NOTE: This value is ignored on ghc>=8.0.
-> TcPluginM Module

Find a module

valuelookupName :: Module -> OccName -> TcPluginM Name

Find a Name in a Module given an OccName

Trace state of the plugin

valuetracePlugin :: String -> TcPlugin -> TcPlugin

Print out extra information about the initialisation, stop, and every run of the plugin when -ddump-tc-trace is enabled.

Substitutions

valueflattenGivens :: [Ct] -> [Ct]

Flattens evidence of constraints by substituting each others equalities.

NB: Should only be used on [G]iven constraints!

NB: Doesn't flatten under binders

valuemkSubst :: Ct -> Maybe ((TcTyVar, TcType), Ct)

Create simple substitution from type equalities

valuemkSubst' :: [Ct] -> [((TcTyVar, TcType), Ct)]

Create flattened substitutions from type equalities, i.e. the substitutions have been applied to each others right hand sides.

valuesubstType :: [(TcTyVar, TcType)] -> TcType -> TcType

Apply substitutions in Types

NB: Doesn't substitute under binders

valuesubstCt :: [(TcTyVar, TcType)] -> Ct -> Ct

Apply substitution in the evidence of Cts