TyCons represent type constructors. Type constructors are introduced by things such as:

1) Data declarations: data Foo = ... creates the Foo type constructor of kind *

2) Type synonyms: type Foo = ... creates the Foo type constructor

3) Newtypes: newtype Foo a = MkFoo ... creates the Foo type constructor of kind * -> *

4) Class declarations: class Foo where creates the Foo type constructor of kind *

This data type also encodes a number of primitive, built in type constructors such as those for function and tuple types.

Names of the fields in an algebraic record type

Represents right-hand-sides of TyCons for algebraic types

Both type classes as well as family instances imply implicit type constructors. These implicit type constructors refer to their parent structure (ie, the class or family from which they derive) using a type of the following form. We use TyConParent for both algebraic and synonym types, but the variant ClassTyCon will only be used by algebraic TyCons.

Extract those DataCons that we are able to learn about. Note that visibility in this sense does not correspond to visibility in the context of any particular user program!

Information pertaining to the expansion of a type synonym (type)

This is the making of an algebraic TyCon. Notably, you have to pass in the generic (in the -XGenerics sense) information about the type constructor - you can get hold of it easily (see Generics module)

Simpler specialization of mkAlgTyCon for classes

Given the name of the function type constructor and it's kind, create the corresponding TyCon. It is reccomended to use funTyCon if you want this functionality

Create an unlifted primitive TyCon, such as Int#

Kind constructors

Create a lifted primitive TyCon such as RealWorld

Create a type synonym TyCon

Create a type family TyCon

Create a promoted data constructor TyCon Somewhat dodgily, we give it the same Name as the data constructor itself; when we pretty-print the TyCon we add a quote; see the Outputable TyCon instance

Create a promoted type constructor TyCon Somewhat dodgily, we give it the same Name as the type constructor itself

Returns True if the supplied TyCon resulted from either a data or newtype declaration

Is this TyCon that for a class instance?

Is this TyCon that for a data family instance?

Does this TyCon represent something that cannot be defined in Haskell?

Does this TyCon represent a tuple?

NB: when compiling Data.Tuple, the tycons won't reply True to isTupleTyCon, because they are built as AlgTyCons. However they get spat into the interface file as tuple tycons, so I don't think it matters.

Is this the TyCon for an unboxed tuple?

Is this the TyCon for a boxed tuple?

Is this a TyCon representing a regular H98 type synonym (type)?

Is this a PromotedDataCon?

Is this a PromotedTyCon?

Retrieves the promoted DataCon if this is a PromotedDataCon;

Retrieves the promoted TyCon if this is a PromotedTyCon;

Returns True for data types that are definitely represented by heap-allocated constructors. These are scrutinised by Core-level case expressions, and they get info tables allocated for them.

Generally, the function will be true for all data types and false for newtypes, unboxed tuples and type family TyCons. But it is not guaranteed to return True in all cases that it could.

NB: for a data type family, only the instance TyCons get an info table. The family declaration TyCon does not

Is this an algebraic TyCon which is just an enumeration of values?

Is this TyCon that for a newtype

Test if the TyCon is algebraic but abstract (invisible data constructors)

Is this a TyCon, synonym or otherwise, that defines a family?

Is this a TyCon, synonym or otherwise, that defines a family with instances?

Is this a synonym TyCon that can have may have further instances appear?

Is this a synonym TyCon that can have may have further instances appear?

Is this TyCon unlifted (i.e. cannot contain bottom)? Note that this can only be true for primitive and unboxed-tuple TyCons

Is this an algebraic TyCon declared with the GADT syntax?

isDistinctTyCon is true of TyCons that are equal only to themselves, even via coercions (except for unsafeCoerce). This excludes newtypes, type functions, type synonyms. It relates directly to the FC consistency story: If the axioms are consistent, and co : S tys ~ T tys, and S,T are "distinct" TyCons, then S=T. Cf Note [Pruning dead case alternatives] in Unify

isInjectiveTyCon is true of TyCons for which this property holds (where X is the role passed in): If (T a1 b1 c1) ~X (T a2 b2 c2), then (a1 ~X1 a2), (b1 ~X2 b2), and (c1 ~X3 c2) (where X1, X2, and X3, are the roles given by tyConRolesX tc X) See also Note [Decomposing equalities] in TcCanonical

isGenerativeTyCon is true of TyCons for which this property holds (where X is the role passed in): If (T tys ~X t), then (t's head ~X T). See also Note [Decomposing equalities] in TcCanonical

Is this an AlgTyConRhs of a TyCon that is generative and injective with respect to representational equality?

Are we able to extract informationa TyVar to class argument list mappping from a given TyCon?

Is this a recursive TyCon?

Identifies implicit tycons that, in particular, do not go into interface files (because they are implicitly reconstructed when the interface is read).

Note that:

• Associated families are implicit, as they are re-constructed from the class declaration in which they reside, and
• Family instances are not implicit as they represent the instance body (similar to a dfun does that for a class instance).

Name of the constructor

Kind of this TyCon (full kind, not just the return kind)

A Unique of this TyCon. Invariant: identical to Unique of Name stored in tyConName field.

The kind and type variables used in the type constructor. Invariant: length tyvars = arity Precisely, this list scopes over:

1. The algTcStupidTheta
2. The cached types in algTyConRhs.NewTyCon
3. The family instance types if present

Note that it does not scope over the data constructors.

The C type that should be used for this type when using the FFI and CAPI

As tyConDataCons_maybe, but returns the empty list of constructors if no constructors could be found

Determine the DataCons originating from the given TyCon, if the TyCon is the sort that can have any constructors (note: this does not include abstract algebraic types)

If the given TyCon has a single data constructor, i.e. it is a data type with one alternative, a tuple type or a newtype then that constructor is returned. If the TyCon has more than one constructor, or represents a primitive or function type constructor then Nothing is returned. In any other case, the function panics

Determine the number of value constructors a TyCon has. Panics if the TyCon is not algebraic or a tuple

Find the "stupid theta" of the TyCon. A "stupid theta" is the context to the left of an algebraic type declaration, e.g. Eq a in the declaration data Eq a => T a ...

Number of arguments this TyCon must receive to be considered saturated (including implicit kind variables)

Get the list of roles for the type parameters of a TyCon

If this TyCon is that for a class instance, return the class it is for. Otherwise returns Nothing

If this TyCon is that of a family instance, return the family in question and the instance types. Otherwise, return Nothing

If this TyCon is that of a family instance, return a TyCon which represents a coercion identifying the representation type with the type instance family. Otherwise, return Nothing

Extract the TyVars bound by a vanilla type synonym and the corresponding (unsubstituted) right hand side.

Extract the information pertaining to the right hand side of a type synonym (type) declaration.

Extract the flavour of a type family (with all the extra information that it carries)

Extract an AlgTyConRhs with information about data constructors from an algebraic or tuple TyCon. Panics for any other sort of TyCon

Extract the bound type variables and type expansion of a type synonym TyCon. Panics if the TyCon is not a synonym

The number of type parameters that need to be passed to a newtype to resolve it. May be less than in the definition if it can be eta-contracted.

Extract the bound type variables and type expansion of an eta-contracted type synonym TyCon. Panics if the TyCon is not a synonym

Take a TyCon apart into the TyVars it scopes over, the Type it expands into, and (possibly) a coercion from the representation type to the newtype. Returns Nothing if this is not possible.

Extract the boxity of the given TyCon, if it is a TupleTyCon. Panics otherwise

Extract the TupleSort of the given TyCon, if it is a TupleTyCon. Panics otherwise

Extract the arity of the given TyCon, if it is a TupleTyCon. Panics otherwise

Used to create the view Core has on TyCons. We expand not only closed synonyms like tcExpandTyCon_maybe, but also non-recursive newtypes

Used to create the view the typechecker has on TyCons. We expand (closed) synonyms only, cf. coreExpandTyCon_maybe

Used to create the view the typechecker has on TyCons. We expand (closed) synonyms only, cf. coreExpandTyCon_maybe

Make an algebraic TyCon abstract. Panics if the supplied TyCon is not algebraic

Extracts the newtype coercion from such a TyCon, which can be used to construct something with the newtypes type from its representation type (right hand side). If the supplied TyCon is not a newtype, returns Nothing

A PrimRep is an abstraction of a type. It contains information that the code generator needs in order to pass arguments, return results, and store values of this type.

Find the primitive representation of a TyCon

Find the size of a PrimRep, in words