Documentation
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Index ¶
- Variables
- func CoreType(T types.Type) types.Type
- func InterfaceTermSet(iface *types.Interface) ([]*types.Term, error)
- func NormalTerms(typ types.Type) ([]*types.Term, error)
- func StructuralTerms(tparam *types.TypeParam) ([]*types.Term, error)
- func UnionTermSet(union *types.Union) ([]*types.Term, error)
Constants ¶
This section is empty.
Variables ¶
var ErrEmptyTypeSet = errors.New("empty type set")
var ErrNilType = errors.New("nil type")
var ErrUnreachable = errors.New("unreachable")
Functions ¶
func CoreType ¶
CoreType returns the core type of T or nil if T does not have a core type.
See https://go.dev/ref/spec#Core_types for the definition of a core type.
func InterfaceTermSet ¶
InterfaceTermSet computes the normalized terms for a constraint interface, returning an error if the term set cannot be computed or is empty. In the latter case, the error will be ErrEmptyTypeSet.
See the documentation of StructuralTerms for more information on normalization.
func NormalTerms ¶
NormalTerms returns a slice of terms representing the normalized structural type restrictions of a type, if any.
For all types other than *types.TypeParam, *types.Interface, and *types.Union, this is just a single term with Tilde() == false and Type() == typ. For *types.TypeParam, *types.Interface, and *types.Union, see below.
Structural type restrictions of a type parameter are created via non-interface types embedded in its constraint interface (directly, or via a chain of interface embeddings). For example, in the declaration type T[P interface{~int; m()}] int the structural restriction of the type parameter P is ~int.
With interface embedding and unions, the specification of structural type restrictions may be arbitrarily complex. For example, consider the following:
type A interface{ ~string|~[]byte }
type B interface{ int|string }
type C interface { ~string|~int }
type T[P interface{ A|B; C }] int
In this example, the structural type restriction of P is ~string|int: A|B expands to ~string|~[]byte|int|string, which reduces to ~string|~[]byte|int, which when intersected with C (~string|~int) yields ~string|int.
NormalTerms computes these expansions and reductions, producing a "normalized" form of the embeddings. A structural restriction is normalized if it is a single union containing no interface terms, and is minimal in the sense that removing any term changes the set of types satisfying the constraint. It is left as a proof for the reader that, modulo sorting, there is exactly one such normalized form.
Because the minimal representation always takes this form, NormalTerms returns a slice of tilde terms corresponding to the terms of the union in the normalized structural restriction. An error is returned if the type is invalid, exceeds complexity bounds, or has an empty type set. In the latter case, NormalTerms returns ErrEmptyTypeSet.
NormalTerms makes no guarantees about the order of terms, except that it is deterministic.
func StructuralTerms ¶
StructuralTerms returns a slice of terms representing the normalized structural type restrictions of a type parameter, if any.
Structural type restrictions of a type parameter are created via non-interface types embedded in its constraint interface (directly, or via a chain of interface embeddings). For example, in the declaration
type T[P interface{~int; m()}] int
the structural restriction of the type parameter P is ~int.
With interface embedding and unions, the specification of structural type restrictions may be arbitrarily complex. For example, consider the following:
type A interface{ ~string|~[]byte }
type B interface{ int|string }
type C interface { ~string|~int }
type T[P interface{ A|B; C }] int
In this example, the structural type restriction of P is ~string|int: A|B expands to ~string|~[]byte|int|string, which reduces to ~string|~[]byte|int, which when intersected with C (~string|~int) yields ~string|int.
StructuralTerms computes these expansions and reductions, producing a "normalized" form of the embeddings. A structural restriction is normalized if it is a single union containing no interface terms, and is minimal in the sense that removing any term changes the set of types satisfying the constraint. It is left as a proof for the reader that, modulo sorting, there is exactly one such normalized form.
Because the minimal representation always takes this form, StructuralTerms returns a slice of tilde terms corresponding to the terms of the union in the normalized structural restriction. An error is returned if the constraint interface is invalid, exceeds complexity bounds, or has an empty type set. In the latter case, StructuralTerms returns ErrEmptyTypeSet.
StructuralTerms makes no guarantees about the order of terms, except that it is deterministic.
func UnionTermSet ¶
UnionTermSet computes the normalized terms for a union, returning an error if the term set cannot be computed or is empty. In the latter case, the error will be ErrEmptyTypeSet.
See the documentation of StructuralTerms for more information on normalization.
Types ¶
This section is empty.
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