[PATCH 0/3] Add '-Wunused-module'

[Ludovic Courtès]

Hello Guilers!

Following a discussion started at the Guix Days and continued online¹,
it seems we could benefit from a compiler warning for unused modules,
and this is what this patch does.

The new ‘-Wunused-module’ warning is enabled at ‘-W2’ only.  The main
reason for not enabling it at ‘-W1’ is that in the case of modules used
at macro-expansion time only, such as (srfi srfi-26), it cannot
determine whether a module is definitely unused.  In this case, the
compiler reports the module as “possibly unused”, and it is up to the
programmer to check that claim.

Currently we cannot do any better because warnings operate at the
tree-il, after macro expansion, and there’s nothing indicating whether a
piece of code results from macro expansion.

There’s also the rare case of modules imported for their side effects,
not for their bindings, and that should be kept even if seemingly
“unused”.  One example might be the use of (rnrs bytevectors) in (rnrs
io ports).  But again, that’s super unusual.

Anyway, it’s pretty useful already and has allowed me to trim imports in
Guile modules.

Thoughts?

Ludo’.

¹ https://lists.gnu.org/archive/html/guix-devel/2023-02/msg00028.html

Ludovic Courtès (3):
  Add -Wunused-module.
  Add 'record-case' to '.dir-locals.el'.
  Remove unnecessary module imports.

 .dir-locals.el                         |   1 +
 NEWS                                   |  17 +++
 module/ice-9/copy-tree.scm             |   1 -
 module/ice-9/eval-string.scm           |   1 -
 module/ice-9/getopt-long.scm           |   1 -
 module/ice-9/poll.scm                  |   1 -
 module/ice-9/popen.scm                 |   1 -
 module/ice-9/sandbox.scm               |   1 -
 module/ice-9/threads.scm               |   1 -
 module/language/tree-il/analyze.scm    | 138 +++++++++++++++++++++++-
 module/language/tree-il/fix-letrec.scm |   4 -
 module/sxml/apply-templates.scm        |   2 -
 module/sxml/simple.scm                 |   1 -
 module/system/base/message.scm         |  11 +-
 module/system/base/types.scm           |   1 -
 module/system/repl/command.scm         |   3 -
 module/system/repl/common.scm          |   2 -
 module/system/repl/coop-server.scm     |   1 -
 module/system/repl/debug.scm           |   6 --
 module/system/repl/error-handling.scm  |   1 -
 module/system/repl/repl.scm            |   4 -
 module/system/repl/server.scm          |   1 -
 module/system/vm/assembler.scm         |   2 -
 module/system/vm/disassembler.scm      |   2 -
 module/system/vm/dwarf.scm             |   2 -
 module/system/vm/elf.scm               |   2 -
 module/system/vm/frame.scm             |   2 -
 module/system/vm/inspect.scm           |   5 -
 module/system/vm/linker.scm            |   2 -
 module/system/vm/program.scm           |   1 -
 module/system/vm/trace.scm             |   3 -
 module/system/vm/trap-state.scm        |   1 -
 module/system/vm/traps.scm             |   2 -
 module/system/xref.scm                 |   1 -
 module/texinfo/indexing.scm            |   1 -
 module/texinfo/plain-text.scm          |   3 -
 module/texinfo/reflection.scm          |   2 -
 module/texinfo/string-utils.scm        |   2 -
 module/web/client.scm                  |   3 -
 module/web/http.scm                    |   2 -
 module/web/request.scm                 |   1 -
 module/web/response.scm                |   2 -
 test-suite/tests/tree-il.test          | 141 ++++++++++++++++++++++++-
 43 files changed, 305 insertions(+), 77 deletions(-)


base-commit: 9d339ea1a95c3b2d04a88aa6b116f997349fc4f4
-- 
2.39.1