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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2014-05-02 12:09:52 +0100 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2014-05-05 09:12:15 +0100 |
| commit | 9f3e39d5f8686e511ffca406a6e056dec4095e53 (patch) | |
| tree | 6f8330a048ed9352f049ef8be341d83f1902630f /compiler/rename | |
| parent | f0fcc41d755876a1b02d1c7c79f57515059f6417 (diff) | |
| download | haskell-9f3e39d5f8686e511ffca406a6e056dec4095e53.tar.gz | |
Fix over-zealous unused-import warning
See Note [Un-warnable import decls] in RnNames.
Fixes Trac #9061.
Diffstat (limited to 'compiler/rename')
| -rw-r--r-- | compiler/rename/RnNames.lhs | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/compiler/rename/RnNames.lhs b/compiler/rename/RnNames.lhs index 7f6a840295..678eb73395 100644 --- a/compiler/rename/RnNames.lhs +++ b/compiler/rename/RnNames.lhs @@ -1301,7 +1301,7 @@ type ImportDeclUsage warnUnusedImportDecls :: TcGblEnv -> RnM () warnUnusedImportDecls gbl_env = do { uses <- readMutVar (tcg_used_rdrnames gbl_env) - ; let imports = filter explicit_import (tcg_rn_imports gbl_env) + ; let imports = filterOut un_warnable_import (tcg_rn_imports gbl_env) rdr_env = tcg_rdr_env gbl_env ; let usage :: [ImportDeclUsage] @@ -1315,11 +1315,27 @@ warnUnusedImportDecls gbl_env ; whenGOptM Opt_D_dump_minimal_imports $ printMinimalImports usage } where - explicit_import (L _ decl) = not (ideclImplicit decl) - -- Filter out the implicit Prelude import - -- which we do not want to bleat about + un_warnable_import (L _ decl) -- See Note [Un-warnable import decls] + | ideclImplicit decl + = True + | Just (True, hides) <- ideclHiding decl + , not (null hides) + , pRELUDE_NAME == unLoc (ideclName decl) + = True + | otherwise + = False \end{code} +Note [Un-warnable import decls] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +We do not warn about the implicit import of Prelude, since the user can't remove it + +We do not warn about + import Prelude hiding( x, y ) +because even if nothing else from Prelude is used, it may be essential to hide +x,y to avoid name-shadowing warnings. Example (Trac #9061) + import Prelude hiding( log ) + f x = log where log = () Note [The ImportMap] ~~~~~~~~~~~~~~~~~~~~ |