[commit: ghc] master: Fail nicely when encountering an invalid bang annotation (#7210) (62da65a)

[Paolo Capriotti]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/62da65a6ba728603b0ee4dab31cd9d59123f3135

>---------------------------------------------------------------

commit 62da65a6ba728603b0ee4dab31cd9d59123f3135
Author: Patrick Palka <patrick at parcs.ath.cx>
Date:   Mon Sep 3 10:27:26 2012 -0400

    Fail nicely when encountering an invalid bang annotation (#7210)

>---------------------------------------------------------------

 compiler/typecheck/TcHsType.lhs |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/compiler/typecheck/TcHsType.lhs b/compiler/typecheck/TcHsType.lhs
index d0e89bb..1f61e37 100644
--- a/compiler/typecheck/TcHsType.lhs
+++ b/compiler/typecheck/TcHsType.lhs
@@ -321,7 +321,11 @@ tc_hs_type :: HsType Name -> ExpKind -> TcM TcType
 tc_hs_type (HsParTy ty)        exp_kind = tc_lhs_type ty exp_kind
 tc_hs_type (HsDocTy ty _)      exp_kind = tc_lhs_type ty exp_kind
 tc_hs_type (HsQuasiQuoteTy {}) _ = panic "tc_hs_type: qq"	-- Eliminated by renamer
-tc_hs_type (HsBangTy {})       _ = panic "tc_hs_type: bang"   -- Unwrapped by con decls
+tc_hs_type ty@(HsBangTy {})    _
+    -- While top-level bangs at this point are eliminated (eg !(Maybe Int)),
+    -- other kinds of bangs are not (eg ((!Maybe) Int)). These kinds of
+    -- bangs are invalid, so fail. (#7210)
+    = failWithTc (ptext (sLit "Unexpected strictness annotation:") <+> ppr ty)
 tc_hs_type (HsRecTy _)         _ = panic "tc_hs_type: record" -- Unwrapped by con decls
       -- Record types (which only show up temporarily in constructor 
       -- signatures) should have been removed by now