X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=docs%2Fusers_guide%2Fseparate_compilation.xml;h=01748ae9261d66c1ca023a2287210b8b77042b25;hb=76c799aeabde8d961416255a6f0f95601d1b159c;hp=1bdb0c5344d716cf7ef2410950a16c8f1d514c0c;hpb=f8697474dee10b95bd7cb576a26ce8116aee261b;p=ghc-hetmet.git diff --git a/docs/users_guide/separate_compilation.xml b/docs/users_guide/separate_compilation.xml index 1bdb0c5..01748ae 100644 --- a/docs/users_guide/separate_compilation.xml +++ b/docs/users_guide/separate_compilation.xml @@ -1169,7 +1169,8 @@ just in case they contain an instance declaration that matters to M. This would be a disaster in practice, so GHC tries to be clever. In particular, if an instance declaration is in the same module as the definition -of any type or class mentioned in the head of the instance declaration, then +of any type or class mentioned in the head of the instance declaration +(the part after the “=>”; see ), then GHC has to visit that interface file anyway. Example: module A where @@ -1208,7 +1209,7 @@ functional dependency: class E x y | y -> x where ... Then in some importing module M, the constraint (E a Int) should be "improved" by setting -a = Int, even though there is no explicit mention +a = T, even though there is no explicit mention of T in M. These considerations lead to the following definition of an orphan module: @@ -1232,7 +1233,7 @@ These considerations lead to the following definition of an orphan module: - Only the instance head (the part after the “=>”) + Only the instance head counts. In the example above, it is not good enough for C's declaration to be in module A; it must be the declaration of D or T. @@ -1246,7 +1247,13 @@ These considerations lead to the following definition of an orphan module: -GHC will warn you if you are creating an orphan module, if you add `-fwarn-orphan-modules`. +If you use the flag , GHC will warn you +if you are creating an orphan module. +Like any warning, you can switch the warning off with , +and +will make the compilation fail if the warning is issued. + + You can identify an orphan module by looking in its interface file, M.hi, using the mode. If there is a [orphan module] on the