From a5fdefe45ad1aeade840beaecfbf9063f1bf3d65 Mon Sep 17 00:00:00 2001
From: bjorn3 <bjorn3@users.noreply.github.com>
Date: Sun, 24 Feb 2019 17:38:31 +0100
Subject: [PATCH] Fix trans_get_discriminant for uninhabited types

---
 src/base.rs |  2 +-
 src/trap.rs | 11 ++++++++---
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/base.rs b/src/base.rs
index 32299aeb68cd..7aeae5509334 100644
--- a/src/base.rs
+++ b/src/base.rs
@@ -739,7 +739,7 @@ pub fn trans_get_discriminant<'a, 'tcx: 'a>(
     let layout = place.layout();
 
     if layout.abi == layout::Abi::Uninhabited {
-        trap_unreachable(&mut fx.bcx);
+        return trap_unreachable_ret_value(fx, dest_layout);
     }
     match layout.variants {
         layout::Variants::Single { index } => {
diff --git a/src/trap.rs b/src/trap.rs
index d94a852153e4..d76e2728aeac 100644
--- a/src/trap.rs
+++ b/src/trap.rs
@@ -1,6 +1,4 @@
-use cranelift::prelude::*;
-
-use cranelift::codegen::ir::TrapCode;
+use crate::prelude::*;
 
 /// Trap code: user0
 pub fn trap_panic(bcx: &mut FunctionBuilder) {
@@ -11,3 +9,10 @@ pub fn trap_panic(bcx: &mut FunctionBuilder) {
 pub fn trap_unreachable(bcx: &mut FunctionBuilder) {
     bcx.ins().trap(TrapCode::User(!0));
 }
+
+pub fn trap_unreachable_ret_value<'tcx>(fx: &mut FunctionCx<'_, 'tcx, impl cranelift_module::Backend>, dest_layout: TyLayout<'tcx>) -> CValue<'tcx> {
+    let true_ = fx.bcx.ins().iconst(types::I32, 1);
+    fx.bcx.ins().trapnz(true_, TrapCode::User(!0));
+    let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);
+    CValue::ByRef(zero, dest_layout)
+}