type Importer interface {
	// Import returns the imported package for the given import path.
	// The semantics is like for ImporterFrom.ImportFrom except that
	// dir and mode are ignored (since they are not present).
	Import(path string) (*Package, error)
}

// ImportMode is reserved for future use.
type ImportMode int

// An ImporterFrom resolves import paths to packages; it

type Importer interface {
	// Import returns the imported package for the given import path.
	// The semantics is like for ImporterFrom.ImportFrom except that
	// dir and mode are ignored (since they are not present).
	Import(path string) (*Package, error)
}

// ImportMode is reserved for future use.
type ImportMode int

// An ImporterFrom resolves import paths to packages; it

pkg go/types, method (*Package) SetName(string)
pkg go/types, type ImportMode int
pkg go/types, type ImporterFrom interface { Import, ImportFrom }
pkg go/types, type ImporterFrom interface, Import(string) (*Package, error)
pkg go/types, type ImporterFrom interface, ImportFrom(string, string, ImportMode) (*Package, error)
pkg html/template, func IsTrue(interface{}) (bool, bool)

	} else {
		// ordinary import
		var err error
		if importer := check.conf.Importer; importer == nil {
			err = fmt.Errorf("Config.Importer not installed")
		} else if importerFrom, ok := importer.(ImporterFrom); ok {
			imp, err = importerFrom.ImportFrom(path, dir, 0)
			if imp == nil && err == nil {
				err = fmt.Errorf("Config.Importer.ImportFrom(%s, %s, 0) returned nil but no error", path, dir)
			}
		} else {

	} else {
		// ordinary import
		var err error
		if importer := check.conf.Importer; importer == nil {
			err = fmt.Errorf("Config.Importer not installed")
		} else if importerFrom, ok := importer.(ImporterFrom); ok {
			imp, err = importerFrom.ImportFrom(path, dir, 0)
			if imp == nil && err == nil {
				err = fmt.Errorf("Config.Importer.ImportFrom(%s, %s, 0) returned nil but no error", path, dir)
			}
		} else {

}

// TODO(gri) Once we are certain that typeHash is correct in all situations, use this version of caseTypes instead.
// (Currently it may be possible that different types have identical names and import paths due to ImporterFrom.)
//
// func (check *Checker) caseTypes(x *operand, xtyp *Interface, types []syntax.Expr, seen map[string]syntax.Expr) (T Type) {
// 	var dummy operand
// L:
// 	for _, e := range types {

}

// TODO(gri) Once we are certain that typeHash is correct in all situations, use this version of caseTypes instead.
// (Currently it may be possible that different types have identical names and import paths due to ImporterFrom.)
//
// func (check *Checker) caseTypes(x *operand, xtyp *Interface, types []ast.Expr, seen map[string]ast.Expr) (T Type) {
// 	var dummy operand
// L:
// 	for _, e := range types {