Using "ITstring !FastString" in Lexer.x goes wrong (internal error: stg_ap_v_ret)

With this patch:

hunk ./compiler/parser/Lexer.x 535
+#if __GLASGOW_HASKELL__ >= 609
+  | ITstring     !FastString
+#else
hunk ./compiler/parser/Lexer.x 539
+#endif

something goes wrong. The first sign, when validating, is that timeout is broken:

timeout: internal error: stg_ap_v_ret
    (GHC version 6.9.20080902 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

If you use the python timeout program instead then you find a few tests fail, e.g.:

testsuite/tests/ghc-regress/codeGen/should_run$ '/home/ian/ghc/darcs/st2/ghc/stage2-inplace/ghc' -fforce-recomp -dcore-lint -dcmm-lint -Dx86_64_unknown_linux  -dno-debug-output -o cg052 cg052.hs -O -fasm -funbox-strict-fields
testsuite/tests/ghc-regress/codeGen/should_run$ ./cg052 
ok
cg052: internal error: stg_ap_v_ret
    (GHC version 6.9.20080902 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
zsh: abort      ./cg052

I'm not sure what's going on, but it seems to be repeatable.

Trac metadata

Trac field	Value
Version	6.8.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Unknown