}
	if f.Type != nil {
		return f.Type.Pos()
	}
	return token.NoPos
}

func (f *Field) End() token.Pos {
	if f.Tag != nil {
		return f.Tag.End()
	}
	if f.Type != nil {
		return f.Type.End()
	}
	if len(f.Names) > 0 {
		return f.Names[len(f.Names)-1].End()
	}
	return token.NoPos
}

// A FieldList represents a list of Fields, enclosed by parentheses,

			for i, xtparam := range xtparams {
				ybound := check.subst(nopos, ytparams[i].bound, smap, nil, ctxt)
				if !c.identical(xtparam.bound, ybound, p) {
					return false
				}
			}

			yparams = check.subst(nopos, y.params, smap, nil, ctxt).(*Tuple)
			yresults = check.subst(nopos, y.results, smap, nil, ctxt).(*Tuple)
		}

		return x.variadic == y.variadic &&

			"package equivalentinterfaces; type T[P any] int",
			"T", []Type{
				NewInterfaceType([]*Func{NewFunc(nopos, nil, "M", emptySignature)}, nil),
			},
			"T", []Type{
				NewInterfaceType(
					nil,
					[]Type{
						NewInterfaceType([]*Func{NewFunc(nopos, nil, "M", emptySignature)}, nil),
					},
				),
			},
			true,
		},
		{
			// int|string is equivalent to string|int

	{new(ast.Expr), new(notASTExpr), false},
	{new(*notAnExpr), new(notASTExpr), true},
}

type notAnExpr struct{}

func (notAnExpr) Pos() token.Pos { return token.NoPos }
func (notAnExpr) End() token.Pos { return token.NoPos }
func (notAnExpr) exprNode()      {}

type notASTExpr interface {
	Pos() token.Pos
	End() token.Pos
	exprNode()
}

func TestImplements(t *testing.T) {

			"package equivalentinterfaces; type T[P any] int",
			"T", []Type{
				NewInterfaceType([]*Func{NewFunc(nopos, nil, "M", emptySignature)}, nil),
			},
			"T", []Type{
				NewInterfaceType(
					nil,
					[]Type{
						NewInterfaceType([]*Func{NewFunc(nopos, nil, "M", emptySignature)}, nil),
					},
				),
			},
			true,
		},
		{
			// int|string is equivalent to string|int

			for i, xtparam := range xtparams {
				ybound := check.subst(nopos, ytparams[i].bound, smap, nil, ctxt)
				if !c.identical(xtparam.bound, ybound, p) {
					return false
				}
			}

			yparams = check.subst(nopos, y.params, smap, nil, ctxt).(*Tuple)
			yresults = check.subst(nopos, y.results, smap, nil, ctxt).(*Tuple)
		}

		return x.variadic == y.variadic &&

	//
	// TODO(adonovan): now that each declaration has the correct
	// scopePos, there should be no need for scope squashing.
	// Audit to ensure all lookups honor scopePos and simplify.
	scope := NewScope(check.scope, nopos, nopos, "function body (temp. scope)")
	scopePos := ftyp.End() // all parameters' scopes start after the signature
	recvList, _ := check.collectParams(scope, recvPar, false, scopePos)

func CheckExpr(fset *token.FileSet, pkg *Package, pos token.Pos, expr ast.Expr, info *Info) (err error) {
	// determine scope
	var scope *Scope
	if pkg == nil {
		scope = Universe
		pos = nopos
	} else if !pos.IsValid() {
		scope = pkg.scope
	} else {
		// The package scope extent (position information) may be
		// incorrect (files spread across a wide range of fset

// to that directive. A position base in turn contains the position at which it
// was introduced in the current file.
type Pos struct {
	base *PosBase
	lico
}

// NoPos is a valid unknown position.
var NoPos Pos

// MakePos creates a new Pos value with the given base, and (file-absolute)
// line and column.
func MakePos(base *PosBase, line, col uint) Pos {
	return Pos{base, makeLico(line, col)}
}

var runtimePkg = func() *types2.Package {
	var nopos syntax.Pos
	pkg := types2.NewPackage("runtime", "runtime")
	anyType := types2.Universe.Lookup("any").Type()
	intType := types2.Universe.Lookup("int").Type()

	// func deferrangefunc() unsafe.Pointer
	obj := types2.NewFunc(nopos, pkg, "deferrangefunc", types2.NewSignatureType(nil, nil, nil, nil, types2.NewTuple(types2.NewParam(nopos, pkg, "extra", anyType)), false))