Merge from rustc

Author: The Miri Conjob Bot

tests/fail/panic/double_panic.stderr

@@ -6,7 +6,6 @@ second
 stack backtrace:
 thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 panic in a destructor during cleanup
-stack backtrace:
 thread caused non-unwinding panic. aborting.
 error: abnormal termination: the program aborted execution
   --> RUSTLIB/std/src/sys/PLATFORM/mod.rs:LL:CC
@@ -19,7 +18,7 @@ LL |     ABORT();
    = note: inside closure at RUSTLIB/std/src/panicking.rs:LL:CC
    = note: inside `std::sys_common::backtrace::__rust_end_short_backtrace::<[closure@std::panicking::begin_panic_handler::{closure#0}], !>` at RUSTLIB/std/src/sys_common/backtrace.rs:LL:CC
    = note: inside `std::panicking::begin_panic_handler` at RUSTLIB/std/src/panicking.rs:LL:CC
-   = note: inside `core::panicking::panic_nounwind` at RUSTLIB/core/src/panicking.rs:LL:CC
+   = note: inside `core::panicking::panic_nounwind_nobacktrace` at RUSTLIB/core/src/panicking.rs:LL:CC
    = note: inside `core::panicking::panic_in_cleanup` at RUSTLIB/core/src/panicking.rs:LL:CC
 note: inside `main`
   --> $DIR/double_panic.rs:LL:CC

tests/pass/function_calls/abi_compat.rs

@@ -0,0 +1,27 @@
+use std::num;
+use std::mem;
+
+fn test_abi_compat<T, U>(t: T, u: U) {
+    fn id<T>(x: T) -> T { x }
+    
+    // This checks ABI compatibility both for arguments and return values,
+    // in both directions.
+    let f: fn(T) -> T = id;
+    let f: fn(U) -> U = unsafe { std::mem::transmute(f) };
+    drop(f(u));
+    
+    let f: fn(U) -> U = id;
+    let f: fn(T) -> T = unsafe { std::mem::transmute(f) };
+    drop(f(t));
+}
+
+fn main() {
+    test_abi_compat(0u32, 'x');
+    test_abi_compat(&0u32, &([true; 4], [0u32; 0]));
+    test_abi_compat(0u32, mem::MaybeUninit::new(0u32));
+    test_abi_compat(42u32, num::NonZeroU32::new(1).unwrap());
+    test_abi_compat(0u32, Some(num::NonZeroU32::new(1).unwrap()));
+    test_abi_compat(0u32, 0i32);
+    // Note that `bool` and `u8` are *not* compatible!
+    // One of them has `arg_ext: Zext`, the other does not.
+}