Rollup merge of #35883 - durka:gh35849, r=eddyb

typeck: use NoExpectation to check return type of diverging fn

Fixes #35849.

Thanks @eddyb.

Author: eddyb

src/librustc_typeck/check/mod.rs

@@ -708,7 +708,12 @@ fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
 
     inherited.tables.borrow_mut().liberated_fn_sigs.insert(fn_id, fn_sig);
 
-    fcx.check_block_with_expected(body, ExpectHasType(fcx.ret_ty));
+    let expected = if fcx.ret_ty.is_never() {
+        NoExpectation
+    } else {
+        ExpectHasType(fcx.ret_ty)
+    };
+    fcx.check_block_with_expected(body, expected);
 
     fcx
 }

src/test/run-pass/diverging-fn-tail-35849.rs

@@ -0,0 +1,18 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn _assert_sizeof() -> ! {
+    unsafe {
+        ::std::mem::transmute::<f64, [u8; 8]>(panic!())
+    }
+}
+
+fn main() { }
+