Hi,
I think the function you are looking for is reportUnusedNames in
GHC.Rename.Names [1], which calls findUses [2]. You may find the Note
[Tracking unused binding and imports] in GHC.Tc.Types [3] helpful.
Roughly, GHC's renamer traverses the syntax tree to resolve names and
along the way collects sets of defined/used names in tcg_dus. There are
also a set of names used by the typechecker in tcg_keep. After
typechecking, findUses takes the transitive closure of the set of uses
and reportUnusedNames then issues unused-top-binds warnings for all
names defined in the current module that are not in the set.
Hope this helps,
Adam
[1]
https://gitlab.haskell.org/ghc/ghc/-/blob/e1fb56b24e2fe45a6f628f651bfc12b2b9743378/compiler/GHC/Rename/Names.hs#L1579
[2]
https://gitlab.haskell.org/ghc/ghc/-/blob/e1fb56b24e2fe45a6f628f651bfc12b2b9743378/compiler/GHC/Types/Name/Set.hs#L203
[3]
https://gitlab.haskell.org/ghc/ghc/-/blob/e1fb56b24e2fe45a6f628f651bfc12b2b9743378/compiler/GHC/Tc/Types.hs#L710
On 14/03/2023 17:13, Razetime wrote:
This message is related to a feature in the futhark compiler
<https://github.com/diku-dk/futhark/issues/550>, which is a language
with a similar module system.
I am trying to create a tool to detect unused top-level functions in
Futhark, and I have been looking in the ghc codebase to find out how it
does so. So far I have found these areas:
1. warning flag
<https://gitlab.haskell.org/ghc/ghc/-/blob/master/compiler/GHC/Driver/Flags.hs#L556-557>
2. WarnUnusedTopBinds
<https://gitlab.haskell.org/ghc/ghc/-/blob/master/compiler/GHC/Rename/Utils.hs#L355>
The project is a bit too big for my machine to take, so HLS is not
helping me with finding where the computation of unused bindings
(specifically functions) is done.
I would like some help with finding where ghc does this computation, and
maybe some help with the naming conventions of the code.
Thanks in advance.
--
Adam Gundry, Haskell Consultant
Well-Typed LLP, https://www.well-typed.com/
Registered in England & Wales, OC335890
27 Old Gloucester Street, London WC1N 3AX, England
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