imports       []*PkgName                  // list of imported packages
	dotImportMap  map[dotImportKey]*PkgName   // maps dot-imported objects to the package they were dot-imported through
	recvTParamMap map[*syntax.Name]*TypeParam // maps blank receiver type parameters to their type
	brokenAliases map[*TypeName]bool          // set of aliases with broken (not yet determined) types
	unionTypeSets map[*Union]*_TypeSet        // computed type sets for union types

		//
		// TODO(adonovan): unfortunately, Alias nodes
		// (GODEBUG=gotypesalias=1) don't entirely resolve
		// problems with cycles. For example, in
		// GOROOT/test/typeparam/issue50259.go,
		//
		// 	type T[_ any] struct{}
		// 	type A T[B]
		// 	type B = T[A]
		//
		// TypeName A has Type Named during checking, but by
		// the time the unified export data is written out,

		//
		// TODO(adonovan): unfortunately, Alias nodes
		// (GODEBUG=gotypesalias=1) don't entirely resolve
		// problems with cycles. For example, in
		// GOROOT/test/typeparam/issue50259.go,
		//
		// 	type T[_ any] struct{}
		// 	type A T[B]
		// 	type B = T[A]
		//
		// TypeName A has Type Named during checking, but by
		// the time the unified export data is written out,

// applyTypeFunc returns nil.
// If x is not a type parameter, the result is f(x).
func (check *Checker) applyTypeFunc(f func(Type) Type, x *operand, id builtinId) Type {
	if tp, _ := Unalias(x.typ).(*TypeParam); tp != nil {
		// Test if t satisfies the requirements for the argument
		// type and collect possible result types at the same time.
		var terms []*Term
		if !tp.is(func(t *term) bool {
			if t == nil {

// applyTypeFunc returns nil.
// If x is not a type parameter, the result is f(x).
func (check *Checker) applyTypeFunc(f func(Type) Type, x *operand, id builtinId) Type {
	if tp, _ := Unalias(x.typ).(*TypeParam); tp != nil {
		// Test if t satisfies the requirements for the argument
		// type and collect possible result types at the same time.
		var terms []*Term
		if !tp.is(func(t *term) bool {
			if t == nil {

	// dirs are the directories to look for *.go files in.
	// TODO(bradfitz): just use all directories?
	dirs = []string{".", "ken", "chan", "interface", "syntax", "dwarf", "fixedbugs", "codegen", "runtime", "abi", "typeparam", "typeparam/mdempsky", "arenas"}
)

// Test is the main entrypoint that runs tests in the GOROOT/test directory.
//
// Each .go file test case in GOROOT/test is registered as a subtest with a

		err.addf(nopos, "want %s", check.typesSummary(varTypes(params), sig.variadic))
		err.report()
		return
	}

	// collect type parameters of callee and generic function arguments
	var tparams []*TypeParam

	// collect type parameters of callee
	n := sig.TypeParams().Len()
	if n > 0 {
		if !check.allowVersion(call.Pos(), go1_18) {
			if iexpr, _ := call.Fun.(*syntax.IndexExpr); iexpr != nil {

		err.addf(noposn, "want %s", check.typesSummary(varTypes(params), sig.variadic))
		err.report()
		return
	}

	// collect type parameters of callee and generic function arguments
	var tparams []*TypeParam

	// collect type parameters of callee
	n := sig.TypeParams().Len()
	if n > 0 {
		if !check.allowVersion(call, go1_18) {
			switch call.Fun.(type) {
			case *ast.IndexExpr, *ast.IndexListExpr:

// If typ is a type parameter, underIs returns the result of typ.underIs(f).
// Otherwise, underIs returns the result of f(under(typ)).
func underIs(typ Type, f func(Type) bool) bool {
	typ = Unalias(typ)
	if tpar, _ := typ.(*TypeParam); tpar != nil {
		return tpar.underIs(f)
	}
	return f(under(typ))
}

// The unary expression e may be nil. It's passed in for better error messages only.

		{"(*TypeName).String", Method, 5},
		{"(*TypeName).Type", Method, 5},
		{"(*TypeParam).Constraint", Method, 18},
		{"(*TypeParam).Index", Method, 18},
		{"(*TypeParam).Obj", Method, 18},
		{"(*TypeParam).SetConstraint", Method, 18},
		{"(*TypeParam).String", Method, 18},
		{"(*TypeParam).Underlying", Method, 18},
		{"(*TypeParamList).At", Method, 18},
		{"(*TypeParamList).Len", Method, 18},