gotools/internal/typeparams/coretype.go

// 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 CoreType(T types.Type) types.Type { … }

// 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 NormalTerms(typ types.Type) ([]*types.Term, error) { … }

// Deref returns the type of the variable pointed to by t,
// if t's core type is a pointer; otherwise it returns t.
//
// Do not assume that Deref(T)==T implies T is not a pointer:
// consider "type T *T", for example.
//
// TODO(adonovan): ideally this would live in typesinternal, but that
// creates an import cycle. Move there when we melt this package down.
func Deref(t types.Type) types.Type { … }

// MustDeref returns the type of the variable pointed to by t.
// It panics if t's core type is not a pointer.
//
// TODO(adonovan): ideally this would live in typesinternal, but that
// creates an import cycle. Move there when we melt this package down.
func MustDeref(t types.Type) types.Type { … }