Warning generated by hscpp code have unhelpful file names

I've started seeing this when compiling cabal with 7.8.3:

[64 of 80] Compiling Distribution.Simple.GHC ( Distribution/Simple/GHC.hs, dist/build/Distribution/Simple/GHC.o )

/var/folders/00/0__yr000h01000cxqpysvccm0019bv/T/ghc43003_0/ghc43003_30.hscpp:270:1: Warning:
    The import of ‘LibraryName’
    from module ‘Distribution.Simple.LocalBuildInfo’ is redundant

/var/folders/00/0__yr000h01000cxqpysvccm0019bv/T/ghc43003_0/ghc43003_30.hscpp:308:1: Warning:
    The import of ‘Language’
    from module ‘Language.Haskell.Extension’ is redundant

/var/folders/00/0__yr000h01000cxqpysvccm0019bv/T/ghc43003_0/ghc43003_30.hscpp:318:1: Warning:
    The import of ‘getTemporaryDirectory, getDirectoryContents’
    from module ‘System.Directory’ is redundant

/var/folders/00/0__yr000h01000cxqpysvccm0019bv/T/ghc43003_0/ghc43003_30.hscpp:325:1: Warning:
    The import of ‘System.IO’ is redundant
      except perhaps to import instances from ‘System.IO’
    To import instances alone, use: import System.IO()

/var/folders/00/0__yr000h01000cxqpysvccm0019bv/T/ghc43003_0/ghc43003_30.hscpp:1092:5: Warning:
    Pattern match(es) are non-exhaustive
    In an equation for ‘supportRPaths’: Patterns not matched: Ghcjs
[65 of 80] Compiling Distribution.Simple.GHCJS ( Distribution/Simple/GHCJS.hs, dist/build/Distribution/Simple/GHCJS.o )

The /var/folders/00/0__yr000h01000cxqpysvccm0019bv/T/ghc43003_0/ghc43003_30.hscpp file name isn't really helpful. I haven't seen this before so I'm guessing this is a regression.

Trac metadata

Trac field	Value
Version	7.8.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Driver
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown/Multiple
Architecture