X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=docs%2Fusers_guide%2Fusing.xml;h=06b9ccc315a6ad52eb4f500c3f18fcd2b9439e07;hb=58521c72cec262496dabf5fffb057d25ab17a0f7;hp=fad30ac245558c17c752a0e1622d10647e6c8238;hpb=46f02d59813499ba2aa44e7831e0b69ec6d8f25d;p=ghc-hetmet.git diff --git a/docs/users_guide/using.xml b/docs/users_guide/using.xml index fad30ac..06b9ccc 100644 --- a/docs/users_guide/using.xml +++ b/docs/users_guide/using.xml @@ -844,7 +844,9 @@ ghc -c Foo.hs , , , - , and + , + , + , and . The following flags are simple ways to select standard “packages” of warnings: @@ -858,6 +860,7 @@ ghc -c Foo.hs -W option Provides the standard warnings plus , + , , , , and @@ -876,7 +879,8 @@ ghc -c Foo.hs , , , - , and + , + , and . @@ -988,11 +992,25 @@ foreign import "&f" f :: FunPtr t + : + + + + Causes a warning to be emitted when a datatype + T is exported + with all constructors, i.e. T(..), but is it + just a type synonym. + Also causes a warning to be emitted when a module is + re-exported, but that module exports nothing. + + + + : - Causes a warning to be emitted when a a datatype + Causes a warning to be emitted when a datatype T is imported with all constructors, i.e. T(..), but has been exported abstractly, i.e. T. @@ -1000,6 +1018,20 @@ foreign import "&f" f :: FunPtr t + : + + + + Causes a warning to be emitted when an unlifted type + is bound in a way that looks lazy, e.g. + where (I# x) = .... Use + where !(I# x) = ... instead. This will be an + error, rather than a warning, in GHC 6.14. + + + + + : @@ -1350,6 +1382,56 @@ f "2" = 2 + + : + + + unused do binding, warning + do binding, unused + + Report expressions occuring in do and mdo blocks + that appear to silently throw information away. + For instance do { mapM popInt xs ; return 10 } would report + the first statement in the do block as suspicious, + as it has the type StackM [Int] and not StackM (), but that + [Int] value is not bound to anything. The warning is suppressed by + explicitly mentioning in the source code that your program is throwing something away: + + do { _ <- mapM popInt xs ; return 10 } + + Of course, in this particular situation you can do even better: + + do { mapM_ popInt xs ; return 10 } + + + + + + + : + + + apparently erroneous do binding, warning + do binding, apparently erroneous + + Report expressions occuring in do and mdo blocks + that appear to lack a binding. + For instance do { return (popInt 10) ; return 10 } would report + the first statement in the do block as suspicious, + as it has the type StackM (StackM Int) (which consists of two nested applications + of the same monad constructor), but which is not then "unpacked" by binding the result. + The warning is suppressed by explicitly mentioning in the source code that your program is throwing something away: + + do { _ <- return (popInt 10) ; return 10 } + + For almost all sensible programs this will indicate a bug, and you probably intended to write: + + do { popInt 10 ; return 10 } + + + + + If you're feeling really paranoid, the @@ -1728,7 +1810,9 @@ f "2" = 2 &phases; - + + &shared_libs; + Using Concurrent Haskell Concurrent Haskellusing