Rollup merge of #45880 - arielb1:never-coerce, r=nikomatsakis

make coercions to `!` in unreachable code a hard error

This was added to cover up a lazy extra semicolon in #35849, but does
not actually make sense. This is removed as a part of the stabilization
of `never_type`.

src/test/compile-fail/coerce-to-bang-cast.rs

@@ -12,8 +12,11 @@
 
 fn foo(x: usize, y: !, z: usize) { }
 
+#[deny(coerce_never)]
 fn cast_a() {
     let y = {return; 22} as !;
+    //~^ ERROR cannot coerce `i32` to !
+    //~| hard error
 }
 
 fn cast_b() {

src/test/compile-fail/coerce-to-bang.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 #![feature(never_type)]
+#![deny(coerce_never)]
 
 fn foo(x: usize, y: !, z: usize) { }
 
@@ -17,6 +18,8 @@ fn call_foo_a() {
     // the coercion to `!`, but within same expression. Not clear that
     // these are the rules we want.
     foo(return, 22, 44);
+    //~^ ERROR cannot coerce `{integer}` to !
+    //~| hard error
 }
 
 fn call_foo_b() {
@@ -36,6 +39,8 @@ fn call_foo_d() {
     let b = 22;
     let c = 44;
     foo(a, b, c); // ... and hence a reference to `a` is expected to diverge.
+    //~^ ERROR cannot coerce `{integer}` to !
+    //~| hard error
 }
 
 fn call_foo_e() {
@@ -75,6 +80,8 @@ fn tuple_a() {
 fn tuple_b() {
     // Divergence happens before coercion: OK
     let x: (usize, !, usize) = (return, 44, 66);
+    //~^ ERROR cannot coerce `{integer}` to !
+    //~| hard error
 }
 
 fn tuple_c() {

src/test/compile-fail/diverging-fn-tail-35849.rs

@@ -8,9 +8,13 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-fn _converge() -> ! {
-    42 //~ ERROR mismatched types
+#[deny(coerce_never)]
+fn assert_sizeof() -> ! {
+    unsafe {
+        ::std::mem::transmute::<f64, [u8; 8]>(panic!())
+            //~^ ERROR cannot coerce `[u8; 8]` to !
+            //~| hard error
+    }
 }
 
 fn main() { }
-