Upgrade opaque pointer-related failures to panics

This way, users who encounter them in the wild will be more strongly encouraged
to report it on the issue tracker.

src/SAWScript/Crucible/LLVM/Builtins.hs

@@ -2238,7 +2238,11 @@ constructExpandedSetupValue cc sc loc t =
     Crucible.X86_FP80Type{} -> failUnsupportedType "X86_FP80"
     -- See https://github.com/GaloisInc/saw-script/issues/1879 for why it is
     -- tricky to support opaque pointers here.
-    Crucible.PtrOpaqueType  -> failUnsupportedType "PtrOpaque"
+    Crucible.PtrOpaqueType  ->
+      panic "SAWScript.Crucible.LLVM.Builtins.constructExpandedSetupValue"
+            [ "llvm_fresh_expanded_val does not support opaque pointers"
+            , "Please report this at: https://github.com/GaloisInc/saw-script/issues/1879"
+            ]
   where failUnsupportedType tyName = throwCrucibleSetup loc $ unwords
           ["llvm_fresh_expanded_var: " ++ tyName ++ " not supported"]
 

src/SAWScript/Crucible/LLVM/Skeleton.hs

@@ -39,6 +39,8 @@ import qualified Data.Set as Set
 import qualified Text.LLVM as LLVM
 import qualified Text.LLVM.DebugUtils as LLVM
 
+import SAWScript.Panic (panic)
+
 --------------------------------------------------------------------------------
 -- ** Skeletons
 
@@ -101,10 +103,11 @@ parseType (LLVM.PtrTo t) = pure $ TypeSkeleton t True [SizeGuess 1 True "default
 -- It is unclear how to combine opaque pointers with type skeletons due to the
 -- lack of a pointee type. For now, we simply fail if we encounter one
 -- (see #1877).
-parseType LLVM.PtrOpaque = fail $ unlines
-  [ "Skeleton generation does not support opaque pointers."
-  , "You should report this issue at: https://github.com/GaloisInc/saw-script/issues/1877"
-  ]
+parseType LLVM.PtrOpaque =
+  panic "SAWScript.Crucible.LLVM.Skeleton.parseType"
+        [ "Skeleton generation does not support opaque pointers"
+        , "Please report this at: https://github.com/GaloisInc/saw-script/issues/1877"
+        ]
 parseType (LLVM.Array i t) = pure $ TypeSkeleton t True
   [ SizeGuess (fromIntegral i) True $ "default guess of size " <> Text.pack (show i)
   ]