If ghci runs out of labels, panic

diff --git a/compiler/ghci/ByteCodeGen.lhs b/compiler/ghci/ByteCodeGen.lhs
index 4ec8043..d92e7f8 100644 (file)
--- a/compiler/ghci/ByteCodeGen.lhs
+++ b/compiler/ghci/ByteCodeGen.lhs
@@ -1534,7 +1534,10 @@ recordItblMallocBc a
 
 getLabelBc :: BcM Word16
 getLabelBc
-  = BcM $ \st -> return (st{nextlabel = 1 + nextlabel st}, nextlabel st)
+  = BcM $ \st -> do let nl = nextlabel st
+                    when (nl == maxBound) $
+                        panic "getLabelBc: Ran out of labels"
+                    return (st{nextlabel = nl + 1}, nl)
 
 getLabelsBc :: Word16 -> BcM [Word16]
 getLabelsBc n