Documentation

If UndecidableInstances is turned on, it checks whether any type class or type family instances needs UndecidableInstances in the module.

Checks whether any type class or type family instances needs UndecidableInstances in the module.

If the type class instance requires UndecidableInstances, it adds the occurence with location of the instance.

Decides whether a type class instance requires UndecidableInstances.

If the type class instance requires UndecidableInstances, it adds the occurence with location of the instance.

Decides whether a family instance requires UndecidableInstances. If it is a data family instance, it does not need the extension.

Checks a declaration whether it needs UndecidableInstances. (If the extension is turned on)

Checks a declaration whether it needs UndecidableInstances. If a lookup is not successful, it keeps the extension.

Checks a class declaration whether it has a type function in its context, or a closed type family declaration needs UndecidableInstances. For more information on the family check, see checkFamInstRhs. May fail on lookup.

We need to check declarations because we want to avoid checking type family instances

Checks an instance rule in declaration We need to check declarations because we want to avoid checking type family instances

Checks and instance head in an instance rule

Collects the type arguments in an instance declaration Type arguments are the the types that the class is being instantiated with

Checks a Type whether it contains any DeclHeads that amy need TypeOperators

Checks an Assertion whether it contains any DeclHeads that amy need TypeOperators

Checks an InstanceHEad whether it contains any DeclHeads that amy need TypeOperators

Checks a Decl whether it contains any DeclHeads that amy need TypeOperators We check Decls to avoid getting multiple occurences of the same DeclHead (e.g. we would check it with and without parentheses)

Checks whether any name's corresponding type in the module contains a type equality.

Checks an operator for syntactic evidence of a ~ b type equality if TypeFamilies or GADTs is turned on.

Checks a declaration if TypeFamilies is turned on.

Checks a class element if TypeFamilies is turned on.

Checks an instance body if TypeFamilies is turned on.

Checks whether a given name's has a type equality operator in it. If the type lookup fails, it returns Nothing. If given a type variable, it returns False.

Decides whether a class or instance declaration needs MultiParamTypeClasses Also handles the NullaryTypeClasses case

Decides whether an instance declaration needs MultiParamTypeClasses Also handles the NullaryTypeClasses case

Checks a GADT-style constructor if GADTSyntax is turned on. Sometimes GADTSyntax is sufficient and GADTs is not even needed.

Checks a data constructor declaration if GADTs or ExistentialQuantification is turned on. This function is responsible for checking ExistentialQuantification as well. (there is no separate checker for that extension)

Checks whether a GADTs-style constructor declaration requires GADTs. If all data constructors are vanilla Haskell 98 data constructors , then only GADTSyntax is needed. If any constructor's lookup fails , we add MissingInformation.

Extracts the name from a ConDecl, and checks whether it is a vanilla data constructor. Ifthe lookup fails, adds MissingInformation.

Checks whether all type class applications in a type synonym rhs (that has kind Constraint) have only type variable heads. Returns False if a lookup inside is not succesful. If it isn't applied to a type that has kind Constraint, it may give false positive results.

We need to check declarations because we want to avoid checking type family instances

Checks every single type argument in an instance declaration If the class being instantiated could not have been looked up, it keeps FlexibleInstances

Checks a type argument of class whether it needs FlexibleInstances First checks the structure of the type argument opaquely Then, for type synonyms, it checks whether their GHC representation itself needs the extension.

Might find false positive occurences for phantom types: > type Phantom a b = [a] > instance C (Phantom a a) > instance C (Phantom a Int)

Checks a type argument of class whether it has only (distinct) type variable arguments.

Checks whether a GHC.Type is an application, and has only (distinct) type variable arguments Logic from TcValidity.tcInstHeadTyAppAllTyVars

A local helper function from TcValidity

A local helper function from TcValidity

Returns the preprocessed source code. If it is not present, it returns an empty string.

Check a DeclHead for ConstrainedClassMethods. Adds the extension if it is needed or the lookup fails.

Helper function for chkCCMDeclHead. True = Lookup is succesful and ConstrainedClassMethods is needed False = Lookup is succesful, but CCM is not needed, or the argument is not a class DeclHead fails = Lookup is unsuccesful (either name or type lookup)

Decides whether a class really needs the ConstrainedClassMethods extension A class needs CCM iff at least one of its class methods has a constraint with a non-empty type variable set, that contains only class type variables.