Improve error report for pattern guards

diff --git a/ghc/compiler/rename/RnBinds.lhs b/ghc/compiler/rename/RnBinds.lhs
index 1ea8f61..7ee82b5 100644 (file)
--- a/ghc/compiler/rename/RnBinds.lhs
+++ b/ghc/compiler/rename/RnBinds.lhs
@@ -604,11 +604,12 @@ rnGRHS ctxt = wrapLocFstM (rnGRHS' ctxt)
 
 rnGRHS' ctxt (GRHS guards rhs)
   = do { opt_GlasgowExts <- doptM Opt_GlasgowExts
-       ; checkM (opt_GlasgowExts || is_standard_guard guards)
-                (addWarn (nonStdGuardErr guards))
-
        ; ((guards', rhs'), fvs) <- rnStmts (PatGuard ctxt) guards $
                                    rnLExpr rhs
+
+       ; checkM (opt_GlasgowExts || is_standard_guard guards')
+                (addWarn (nonStdGuardErr guards'))
+
        ; return (GRHS guards' rhs', fvs) }
   where
        -- Standard Haskell 1.4 guards are just a single boolean
@@ -654,8 +655,7 @@ bindsInHsBootFile mbinds
   = hang (ptext SLIT("Bindings in hs-boot files are not allowed"))
        2 (ppr mbinds)
 
-nonStdGuardErr guard
-  = hang (ptext
-    SLIT("accepting non-standard pattern guards (-fglasgow-exts to suppress this message)")
-    ) 4 (ppr guard)
+nonStdGuardErr guards
+  = hang (ptext SLIT("accepting non-standard pattern guards (-fglasgow-exts to suppress this message)"))
+       4 (interpp'SP guards)
 \end{code}