unaligned-raw-deref is always UB

Author: RalfJung

tests/compile-fail/unaligned_pointers/unaligned_ptr_addr_of.rs

@@ -0,0 +1,12 @@
+// This should fail even without validation or Stacked Borrows.
+// compile-flags: -Zmiri-disable-validation -Zmiri-disable-stacked-borrows
+#![feature(raw_ref_macros)]
+use std::ptr;
+
+fn main() {
+    let x = [2u16, 3, 4]; // Make it big enough so we don't get an out-of-bounds error.
+    let x = &x[0] as *const _ as *const u32;
+    // This must fail because alignment is violated: the allocation's base is not sufficiently aligned.
+    // The deref is UB even if we just put the result into a raw pointer.
+    let _x = unsafe { ptr::raw_const!(*x) }; //~ ERROR memory with alignment 2, but alignment 4 is required
+}