diff options
Diffstat (limited to 'compiler/rename')
| -rw-r--r-- | compiler/rename/RnPat.lhs | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/compiler/rename/RnPat.lhs b/compiler/rename/RnPat.lhs index c3b40fe0f2..9738585aa4 100644 --- a/compiler/rename/RnPat.lhs +++ b/compiler/rename/RnPat.lhs @@ -121,10 +121,26 @@ wrapSrcSpanCps fn (L loc a) lookupConCps :: Located RdrName -> CpsRn (Located Name) lookupConCps con_rdr = CpsRn (\k -> do { con_name <- lookupLocatedOccRn con_rdr - ; (r, fvs) <- k con_name - ; return (r, fvs `plusFV` unitFV (unLoc con_name)) }) + ; k con_name }) + -- We do not add the constructor name to the free vars + -- See Note [Patterns are not uses] \end{code} +Note [Patterns are not uses] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider + module Foo( f, g ) where + data T = T1 | T2 + + f T1 = True + f T2 = False + + g _ = T1 + +Arguaby we should report T2 as unused, even though it appears in a +pattern, because it never occurs in a constructed position. See +Trac #7336. + %********************************************************* %* * Name makers |