Fix an ICE when attempting to transmute an uninhabited type

1 files changed, 13 insertions, 3 deletions

diff --git a/src/librustc_codegen_llvm/mir/block.rs b/src/librustc_codegen_llvm/mir/block.rs
index 556baeba39e..bc5819791fa 100644
--- a/src/librustc_codegen_llvm/mir/block.rs
+++ b/src/librustc_codegen_llvm/mir/block.rs
@@ -428,9 +428,19 @@ impl<'a, 'tcx> FunctionCx<'a, 'tcx> {
                 let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 
                 if intrinsic == Some("transmute") {
-                    let &(ref dest, target) = destination.as_ref().unwrap();
-                    self.codegen_transmute(&bx, &args[0], dest);
-                    funclet_br(self, bx, target);
+                    if let Some(destination_ref) = destination.as_ref() {
+                        let &(ref dest, target) = destination_ref;
+                        self.trans_transmute(&bx, &args[0], dest);
+                        funclet_br(self, bx, target);
+                    } else {
+                        // If we are trying to transmute to an uninhabited type,
+                        // it is likely there is no allotted destination. In fact,
+                        // transmuting to an uninhabited type is UB, which means
+                        // we can do what we like. Here, we declare that transmuting
+                        // into an uninhabited type is impossible, so anything following
+                        // it must be unreachable.
+                        bx.unreachable();
+                    }
                     return;
                 }