ensure that -Zmiri-check-number-validity detects integers with provenance

Author: RalfJung

tests/compile-fail/ptr_integer_array_transmute.rs

@@ -0,0 +1,6 @@
+// compile-flags: -Zmiri-check-number-validity
+
+fn main() {
+    let r = &mut 42;
+    let _i: [usize; 1] = unsafe { std::mem::transmute(r) }; //~ ERROR encountered a pointer, but expected plain (non-pointer) bytes
+}

tests/compile-fail/ptr_integer_transmute.rs

@@ -0,0 +1,6 @@
+// compile-flags: -Zmiri-check-number-validity
+
+fn main() {
+    let r = &mut 42;
+    let _i: usize = unsafe { std::mem::transmute(r) }; //~ ERROR expected initialized plain (non-pointer) bytes
+}