1 files changed, 61 insertions, 43 deletions
diff --git a/compiler/GHC/Types/SourceFile.hs b/compiler/GHC/Types/SourceFile.hs
index 7a1898a51e..0d04a194de 100644
--- a/compiler/GHC/Types/SourceFile.hs
+++ b/compiler/GHC/Types/SourceFile.hs
@@ -1,8 +1,11 @@
+{-# LANGUAGE PatternSynonyms #-}
+
 module GHC.Types.SourceFile
-   ( HscSource(..)
+   ( HscSource(HsBootFile, HsigFile, ..)
+   , HsBootOrSig(..)
    , hscSourceToIsBoot
    , isHsBootOrSig
-   , isHsigFile
+   , isHsBootFile, isHsigFile
    , hscSourceString
    )
 where
@@ -11,45 +14,57 @@ import GHC.Prelude
 import GHC.Utils.Binary
 import GHC.Unit.Types
 
--- Note [HscSource types]
--- ~~~~~~~~~~~~~~~~~~~~~~
--- There are three types of source file for Haskell code:
---
---      * HsSrcFile is an ordinary hs file which contains code,
---
---      * HsBootFile is an hs-boot file, which is used to break
---        recursive module imports (there will always be an
---        HsSrcFile associated with it), and
---
---      * HsigFile is an hsig file, which contains only type
---        signatures and is used to specify signatures for
---        modules.
---
--- Syntactically, hs-boot files and hsig files are quite similar: they
--- only include type signatures and must be associated with an
--- actual HsSrcFile.  isHsBootOrSig allows us to abstract over code
--- which is indifferent to which.  However, there are some important
--- differences, mostly owing to the fact that hsigs are proper
--- modules (you `import Sig` directly) whereas HsBootFiles are
--- temporary placeholders (you `import {-# SOURCE #-} Mod).
--- When we finish compiling the true implementation of an hs-boot,
--- we replace the HomeModInfo with the real HsSrcFile.  An HsigFile, on the
--- other hand, is never replaced (in particular, we *cannot* use the
--- HomeModInfo of the original HsSrcFile backing the signature, since it
--- will export too many symbols.)
---
--- Additionally, while HsSrcFile is the only Haskell file
--- which has *code*, we do generate .o files for HsigFile, because
--- this is how the recompilation checker figures out if a file
--- needs to be recompiled.  These are fake object files which
--- should NOT be linked against.
+{- Note [HscSource types]
+~~~~~~~~~~~~~~~~~~~~~~~~~
+There are three types of source file for Haskell code:
+
+     * HsSrcFile is an ordinary hs file which contains code,
+
+     * HsBootFile is an hs-boot file, which is used to break
+       recursive module imports (there will always be an
+       HsSrcFile associated with it), and
+
+     * HsigFile is an hsig file, which contains only type
+       signatures and is used to specify signatures for
+       modules.
+
+Syntactically, hs-boot files and hsig files are quite similar: they
+only include type signatures and must be associated with an
+actual HsSrcFile.  isHsBootOrSig allows us to abstract over code
+which is indifferent to which.  However, there are some important
+differences, mostly owing to the fact that hsigs are proper
+modules (you `import Sig` directly) whereas HsBootFiles are
+temporary placeholders (you `import {-# SOURCE #-} Mod).
+When we finish compiling the true implementation of an hs-boot,
+we replace the HomeModInfo with the real HsSrcFile.  An HsigFile, on the
+other hand, is never replaced (in particular, we *cannot* use the
+HomeModInfo of the original HsSrcFile backing the signature, since it
+will export too many symbols.)
+
+Additionally, while HsSrcFile is the only Haskell file
+which has *code*, we do generate .o files for HsigFile, because
+this is how the recompilation checker figures out if a file
+needs to be recompiled.  These are fake object files which
+should NOT be linked against.
+-}
+
+data HsBootOrSig
+  = HsBoot -- ^ .hs-boot file
+  | Hsig   -- ^ .hsig file
+   deriving (Eq, Ord, Show)
 
 data HscSource
-   = HsSrcFile  -- ^ .hs file
-   | HsBootFile -- ^ .hs-boot file
-   | HsigFile   -- ^ .hsig file
+   -- | .hs file
+   = HsSrcFile
+   -- | .hs-boot or .hsig file
+   | HsBootOrSig !HsBootOrSig
    deriving (Eq, Ord, Show)
 
+{-# COMPLETE HsSrcFile, HsBootFile, HsigFile #-}
+pattern HsBootFile, HsigFile :: HscSource
+pattern HsBootFile = HsBootOrSig HsBoot
+pattern HsigFile   = HsBootOrSig Hsig
+
 -- | Tests if an 'HscSource' is a boot file, primarily for constructing elements
 -- of 'BuildModule'. We conflate signatures and modules because they are bound
 -- in the same namespace; only boot interfaces can be disambiguated with
@@ -70,15 +85,18 @@ instance Binary HscSource where
             _ -> return HsigFile
 
 hscSourceString :: HscSource -> String
-hscSourceString HsSrcFile   = ""
-hscSourceString HsBootFile  = "[boot]"
-hscSourceString HsigFile    = "[sig]"
+hscSourceString HsSrcFile  = ""
+hscSourceString HsBootFile = "[boot]"
+hscSourceString HsigFile   = "[sig]"
 
 -- See Note [HscSource types]
 isHsBootOrSig :: HscSource -> Bool
-isHsBootOrSig HsBootFile = True
-isHsBootOrSig HsigFile   = True
-isHsBootOrSig _          = False
+isHsBootOrSig (HsBootOrSig _) = True
+isHsBootOrSig HsSrcFile       = False
+
+isHsBootFile :: HscSource -> Bool
+isHsBootFile HsBootFile = True
+isHsBootFile _          = False
 
 isHsigFile :: HscSource -> Bool
 isHsigFile HsigFile = True