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 {

// 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 {

func (check *Checker) newAliasInstance(pos syntax.Pos, orig *Alias, targs []Type, ctxt *Context) *Alias {
	assert(len(targs) > 0)
	obj := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil)
	rhs := check.subst(pos, orig.fromRHS, makeSubstMap(orig.TypeParams().list(), targs), nil, ctxt)
	res := check.newAlias(obj, rhs)
	res.orig = orig
	res.tparams = orig.tparams
	res.targs = newTypeList(targs)
	return res
}

func (a *Alias) cleanup() {

func (check *Checker) newAliasInstance(pos token.Pos, orig *Alias, targs []Type, ctxt *Context) *Alias {
	assert(len(targs) > 0)
	obj := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil)
	rhs := check.subst(pos, orig.fromRHS, makeSubstMap(orig.TypeParams().list(), targs), nil, ctxt)
	res := check.newAlias(obj, rhs)
	res.orig = orig
	res.tparams = orig.tparams
	res.targs = newTypeList(targs)
	return res
}

func (a *Alias) cleanup() {

			return Typ[Invalid]
		}
		if tparams.Len() == 0 {
			return orig // nothing to do (minor optimization)
		}
		sig := check.subst(pos, orig, makeSubstMap(tparams.list(), targs), nil, ctxt).(*Signature)
		// If the signature doesn't use its type parameters, subst
		// will not make a copy. In that case, make a copy now (so
		// we can set tparams to nil w/o causing side-effects).

	//           (which only happens in case of an error) and then avoid doing
	//           the substitution (which always happens).
	if params.Len() > 0 {
		smap := makeSubstMap(tparams, targs)
		params = check.subst(nopos, params, smap, nil, check.context()).(*Tuple)
	}

	// Unify parameter and argument types for generic parameters with typed arguments

			return Typ[Invalid]
		}
		if tparams.Len() == 0 {
			return orig // nothing to do (minor optimization)
		}
		sig := check.subst(pos, orig, makeSubstMap(tparams.list(), targs), nil, ctxt).(*Signature)
		// If the signature doesn't use its type parameters, subst
		// will not make a copy. In that case, make a copy now (so
		// we can set tparams to nil w/o causing side-effects).

	//           (which only happens in case of an error) and then avoid doing
	//           the substitution (which always happens).
	if params.Len() > 0 {
		smap := makeSubstMap(tparams, targs)
		params = check.subst(nopos, params, smap, nil, check.context()).(*Tuple)
	}

	// Unify parameter and argument types for generic parameters with typed arguments

	// and type parameters. This check is necessary in the presence of invalid
	// code.
	if origSig.RecvTypeParams().Len() == t.inst.targs.Len() {
		smap := makeSubstMap(origSig.RecvTypeParams().list(), t.inst.targs.list())
		var ctxt *Context
		if check != nil {
			ctxt = check.context()
		}
		sig = check.subst(origm.pos, origSig, smap, t, ctxt).(*Signature)
	}

	// and type parameters. This check is necessary in the presence of invalid
	// code.
	if origSig.RecvTypeParams().Len() == t.inst.targs.Len() {
		smap := makeSubstMap(origSig.RecvTypeParams().list(), t.inst.targs.list())
		var ctxt *Context
		if check != nil {
			ctxt = check.context()
		}
		sig = check.subst(origm.pos, origSig, smap, t, ctxt).(*Signature)
	}