func (a *Alias) String() string { return TypeString(a, nil) }

// Underlying returns the [underlying type] of the alias type a, which is the
// underlying type of the aliased type. Underlying types are never Named,
// TypeParam, or Alias types.
//
// [underlying type]: https://go.dev/ref/spec#Underlying_types.
func (a *Alias) Underlying() Type { return unalias(a).Underlying() }

// Origin returns the generic Alias type of which a is an instance.

	if ok, _ := x.assignableTo(check, T, cause); ok {
		return true
	}

	origT := T
	V := Unalias(x.typ)
	T = Unalias(T)
	Vu := under(V)
	Tu := under(T)
	Vp, _ := V.(*TypeParam)
	Tp, _ := T.(*TypeParam)

	// "V and T have identical underlying types if tags are ignored
	// and V and T are not type parameters"
	if IdenticalIgnoreTags(Vu, Tu) && Vp == nil && Tp == nil {
		return true
	}

func (a *Alias) String() string { return TypeString(a, nil) }

// Underlying returns the [underlying type] of the alias type a, which is the
// underlying type of the aliased type. Underlying types are never Named,
// TypeParam, or Alias types.
//
// [underlying type]: https://go.dev/ref/spec#Underlying_types.
func (a *Alias) Underlying() Type { return unalias(a).Underlying() }

// Origin returns the generic Alias type of which a is an instance.

	if ok, _ := x.assignableTo(check, T, cause); ok {
		return true
	}

	origT := T
	V := Unalias(x.typ)
	T = Unalias(T)
	Vu := under(V)
	Tu := under(T)
	Vp, _ := V.(*TypeParam)
	Tp, _ := T.(*TypeParam)

	// "V and T have identical underlying types if tags are ignored
	// and V and T are not type parameters"
	if IdenticalIgnoreTags(Vu, Tu) && Vp == nil && Tp == nil {
		return true
	}

// so we could depend on it from other packages without
// introducing an import cycle.)
type Type interface {
	// Underlying returns the underlying type of a type.
	// Underlying types are never Named, TypeParam, or Alias types.
	//
	// See https://go.dev/ref/spec#Underlying_types.
	Underlying() Type

	// String returns a string representation of a type.
	String() string
}

	origT := T
	V := Unalias(x.typ)
	T = Unalias(T)

	// x's type is identical to T
	if Identical(V, T) {
		return true, 0
	}

	Vu := under(V)
	Tu := under(T)
	Vp, _ := V.(*TypeParam)
	Tp, _ := T.(*TypeParam)

	// x is an untyped value representable by a value of type T.
	if isUntyped(Vu) {
		assert(Vp == nil)
		if Tp != nil {
			// T is a type parameter: x is assignable to T if it is

	// bounds is a slice of typeInfos corresponding to the underlying
	// bounds of the element's type parameters.
	bounds []typeInfo

	// tparams is a slice of the constructed TypeParams for the element.
	tparams []*types.TypeParam

	// derived is a slice of types derived from tparams, which may be
	// instantiated while reading the current element.
	derived      []derivedInfo
	derivedTypes []types.Type // lazily instantiated from derived
}

			w.tpSubscripts = tpSubscripts
			buf.WriteByte('[')
			for i, x := range a {
				if i > 0 {
					buf.WriteString(", ")
				}
				w.typ(x)
			}
			buf.WriteByte(']')
			arg = buf.String()
		case []*TypeParam:
			var buf bytes.Buffer
			w := newTypeWriter(&buf, qf)
			w.tpSubscripts = tpSubscripts
			buf.WriteByte('[')
			for i, x := range a {
				if i > 0 {
					buf.WriteString(", ")
				}
				w.typ(x)
			}

			w.tpSubscripts = tpSubscripts
			buf.WriteByte('[')
			for i, x := range a {
				if i > 0 {
					buf.WriteString(", ")
				}
				w.typ(x)
			}
			buf.WriteByte(']')
			arg = buf.String()
		case []*TypeParam:
			var buf bytes.Buffer
			w := newTypeWriter(&buf, qf)
			w.tpSubscripts = tpSubscripts
			buf.WriteByte('[')
			for i, x := range a {
				if i > 0 {
					buf.WriteString(", ")
				}
				w.typ(x)
			}

		} else if w.ctxt == nil && t.TypeParams().Len() != 0 { // For type hashing, don't need to format the TypeParams
			// parameterized type
			w.tParamList(t.TypeParams().list())
		}

	case *TypeParam:
		if t.obj == nil {
			w.error("unnamed type parameter")
			break
		}
		if i := tparamIndex(w.tparams.list(), t); i >= 0 {
			// The names of type parameters that are declared by the type being