[project @ 1997-07-05 03:02:04 by sof]

[ghc-hetmet.git] / ghc / compiler / basicTypes / BasicTypes.lhs

diff --git a/ghc/compiler/basicTypes/BasicTypes.lhs b/ghc/compiler/basicTypes/BasicTypes.lhs
index d19f0bd..82a446b 100644 (file)
--- a/ghc/compiler/basicTypes/BasicTypes.lhs
+++ b/ghc/compiler/basicTypes/BasicTypes.lhs
@@ -19,7 +19,7 @@ module BasicTypes(
        SYN_IE(Version), SYN_IE(Arity),
        SYN_IE(Module), moduleString, pprModule,
        Fixity(..), FixityDirection(..),
-       NewOrData(..)
+       NewOrData(..), IfaceFlavour(..)
    ) where
 
 IMP_Ubiq()
@@ -67,6 +67,38 @@ pprModule :: PprStyle -> Module -> Doc
 pprModule sty m = ptext m
 \end{code}
 
+%************************************************************************
+%*                                                                     *
+\subsection[IfaceFlavour]{IfaceFlavour}
+%*                                                                     *
+%************************************************************************
+
+The IfaceFlavour type is used mainly in an imported Name's Provenance
+to say whether the name comes from a regular .hi file, or whether it comes
+from a hand-written .hi-boot file.  This is important, because it has to be 
+propagated.  Suppose
+
+       C.hs imports B
+       B.hs imports A
+       A.hs imports C {-# SOURCE -#} ( f )
+
+Then in A.hi we may mention C.f, in an inlining.  When compiling B we *must not* 
+read C.f's details from C.hi, even if the latter happens to exist from an earlier
+compilation run.  So we use the name "C!f" in A.hi, and when looking for an interface
+file with details of C!f we look in C.hi-boot.  The "!" stuff is recorded in the
+IfaceFlavour in the Name of C.f in A. 
+
+Not particularly beautiful, but it works.
+
+\begin{code}
+data IfaceFlavour = HiFile             -- The interface was read from a standard interface file
+                 | HiBootFile          -- ... or from a handwritten "hi-boot" interface file
+
+instance Text IfaceFlavour where       -- Just used in debug prints of lex tokens
+  showsPrec n HiFile     s = s
+  showsPrec n HiBootFile s = "!" ++ s
+\end{code}
+
 
 %************************************************************************
 %*                                                                     *