These macros are intended to be used in build phases.
More precisely, (assoc-ref %build-inputs "input") can be
replaced by #$(this-package-input "input") or #+(this-package-native-input
"native-input") as appropriate.

* guix/packages.scm
  (package-input, package-native-input): New (unexported) procedures.
  (this-package-input, this-package-native-input): New macros.
---
 guix/packages.scm  | 29 +++++++++++++++++++++++++++++
 tests/packages.scm | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)