// digits accepts the sequence { digit | '_' }.
// If base <= 10, digits accepts any decimal digit but records
// the offset (relative to the source start) of a digit >= base
// in *invalid, if *invalid < 0.
// digits returns a bitset describing whether the sequence contained
// digits (bit 0 is set), or separators '_' (bit 1 is set).
func (s *Scanner) digits(base int, invalid *int) (digsep int) {
	if base <= 10 {
		max := rune('0' + base)

		// Don't go inside function literal scopes a second time;
		// they are handled explicitly by funcBody.
		if !scope.isFunc {
			check.usage(scope)
		}
	}
}

// stmtContext is a bitset describing which
// control-flow statements are permissible,
// and provides additional context information
// for better error messages.
type stmtContext uint

const (
	// permissible control-flow statements

		// Don't go inside function literal scopes a second time;
		// they are handled explicitly by funcBody.
		if !scope.isFunc {
			check.usage(scope)
		}
	}
}

// stmtContext is a bitset describing which
// control-flow statements are permissible,
// and provides additional context information
// for better error messages.
type stmtContext uint

const (
	// permissible control-flow statements