Auto merge of #1079 - RalfJung:coercion-error, r=RalfJung

Test diverging closure coercion

Adds a test for #1075. Depends on rust-lang/rust#66827.

Author: bors

rust-version

@@ -1 +1 @@
-f5c81e0a986e4285d3d0fd781a1bd475753eb12c
+4af3ee8ee2a2bc1286b021db7600ba990359cf3f

tests/run-pass/coerce_non_capture_closure_to_fn_ptr.rs

@@ -5,8 +5,10 @@ static FOO: fn() = || { assert_ne!(42, 43) };
 static BAR: fn(i32, i32) = |a, b| { assert_ne!(a, b) };
 
 // use to first make the closure FnOnce() before making it fn()
-fn magic0<R, F: FnOnce() -> R>(f: F) -> F { f }
-fn magic1<T, R, F: FnOnce(T) -> R>(f: F) -> F { f }
+fn force_once0<R, F: FnOnce() -> R>(f: F) -> F { f }
+fn force_once1<T, R, F: FnOnce(T) -> R>(f: F) -> F { f }
+fn force_mut0<R, F: FnMut() -> R>(f: F) -> F { f }
+fn force_mut1<T, R, F: FnMut(T) -> R>(f: F) -> F { f }
 
 fn main() {
     FOO();
@@ -18,19 +20,15 @@ fn main() {
 
     let f: fn() = ||{};
     f();
-    let f = magic0(||{}) as fn();
+    let f = force_once0(||{}) as fn();
+    f();
+    let f = force_mut0(||{}) as fn();
     f();
 
     let g: fn(i32) = |i| assert_eq!(i, 2);
     g(2);
-    let g = magic1(|i| assert_eq!(i, 2)) as fn(i32);
+    let g = force_once1(|i| assert_eq!(i, 2)) as fn(i32);
+    g(2);
+    let g = force_mut1(|i| assert_eq!(i, 2)) as fn(i32);
     g(2);
-
-    // FIXME: This fails with "invalid use of NULL pointer" <https://github.com/rust-lang/miri/issues/1075>
-    //let h: fn() -> ! = || std::process::exit(0);
-    //h();
-    // FIXME: This does not even compile?!? <https://github.com/rust-lang/rust/issues/66738>
-    //let h = magic0(|| std::process::exit(0)) as fn() -> !;
-    //h();
-    // Once these tests pass, they should be in separate files as they terminate the process.
 }

tests/run-pass/issue-miri-1075.rs

@@ -0,0 +1,6 @@
+fn main() {
+    let f: fn() -> ! = || std::process::exit(0);
+    f();
+
+    // FIXME: Also add a test for <https://github.com/rust-lang/rust/issues/66738>, once that is fixed.
+}