{new(mapError), new(error), true},
	{new(*mapError), new(error), 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()
}

type mapError map[string]string

type missingKeyAction int

const (
	mapInvalid   missingKeyAction = iota // Return an invalid reflect.Value.
	mapZeroValue                         // Return the zero value for the map element.
	mapError                             // Error out
)

type option struct {
	missingKey missingKeyAction
}

// Option sets options for the template. Options are described by