// This file implements type parameter substitution.

package types

import (
	"go/token"
)

type substMap map[*TypeParam]Type

// makeSubstMap creates a new substitution map mapping tpars[i] to targs[i].
// If targs[i] is nil, tpars[i] is not substituted.
func makeSubstMap(tpars []*TypeParam, targs []Type) substMap {
	assert(len(tpars) == len(targs))
	proj := make(substMap, len(tpars))
	for i, tpar := range tpars {

package types2

import (
	"cmd/compile/internal/syntax"
)

type substMap map[*TypeParam]Type

// makeSubstMap creates a new substitution map mapping tpars[i] to targs[i].
// If targs[i] is nil, tpars[i] is not substituted.
func makeSubstMap(tpars []*TypeParam, targs []Type) substMap {
	assert(len(tpars) == len(targs))
	proj := make(substMap, len(tpars))
	for i, tpar := range tpars {

		u.setHandle(x, hy)
	}
	return true
}

// asBoundTypeParam returns x.(*TypeParam) if x is a type parameter recorded with u.
// Otherwise, the result is nil.
func (u *unifier) asBoundTypeParam(x Type) *TypeParam {
	if x, _ := Unalias(x).(*TypeParam); x != nil {
		if _, found := u.handles[x]; found {
			return x
		}
	}
	return nil
}

// type set. In the latter case, StructuralTerms returns ErrEmptyTypeSet.
//
// StructuralTerms makes no guarantees about the order of terms, except that it
// is deterministic.
func StructuralTerms(tparam *types.TypeParam) ([]*types.Term, error) {
	constraint := tparam.Constraint()
	if constraint == nil {
		return nil, fmt.Errorf("%s has nil constraint", tparam)
	}
	iface, _ := constraint.Underlying().(*types.Interface)
	if iface == nil {

		u.setHandle(x, hy)
	}
	return true
}

// asBoundTypeParam returns x.(*TypeParam) if x is a type parameter recorded with u.
// Otherwise, the result is nil.
func (u *unifier) asBoundTypeParam(x Type) *TypeParam {
	if x, _ := Unalias(x).(*TypeParam); x != nil {
		if _, found := u.handles[x]; found {
			return x
		}
	}
	return nil
}

// identical element types), the single underlying type is the restricted
// channel type if the restrictions are always the same, or nil otherwise.
func coreType(t Type) Type {
	t = Unalias(t)
	tpar, _ := t.(*TypeParam)
	if tpar == nil {
		return under(t)
	}

	var su Type
	if tpar.underIs(func(u Type) bool {
		if u == nil {
			return false
		}
		if su != nil {
			u = match(su, u)
			if u == nil {

// 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

// identical element types), the single underlying type is the restricted
// channel type if the restrictions are always the same, or nil otherwise.
func coreType(t Type) Type {
	t = Unalias(t)
	tpar, _ := t.(*TypeParam)
	if tpar == nil {
		return under(t)
	}

	var su Type
	if tpar.underIs(func(u Type) bool {
		if u == nil {
			return false
		}
		if su != nil {
			u = match(su, u)
			if u == nil {

package types

// A Type represents a type of Go.
// All types implement the Type interface.
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

// by obtaining it from the internals of the gcexportdata decoder.
func importMap(imports []*types.Package) map[string]*types.Package {
	objects := make(map[types.Object]bool)
	typs := make(map[types.Type]bool) // Named and TypeParam
	packages := make(map[string]*types.Package)

	var addObj func(obj types.Object)
	var addType func(T types.Type)

	addObj = func(obj types.Object) {
		if !objects[obj] {
			objects[obj] = true