miri: add test for overlapping typed_swap

Author: RalfJung

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -649,7 +649,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         let kind = MemoryKind::Stack;
         let temp = self.allocate(left.layout, kind)?;
         self.copy_op(&left, &temp)?;
-        self.copy_op(&right, &left)?;
+        self.copy_op(&right, &left)?; // this checks that they are non-overlapping
         self.copy_op(&temp, &right)?;
         self.deallocate_ptr(temp.ptr(), None, kind)?;
         interp_ok(())

src/tools/miri/tests/fail/intrinsics/typed-swap-overlap.rs

@@ -0,0 +1,13 @@
+#![feature(core_intrinsics)]
+#![feature(rustc_attrs)]
+
+use std::intrinsics::typed_swap;
+use std::ptr::addr_of_mut;
+
+fn main() {
+    let mut a = [0_u8; 100];
+    unsafe {
+        let a = addr_of_mut!(a);
+        typed_swap(a, a); //~ERROR: called on overlapping ranges
+    }
+}

src/tools/miri/tests/fail/intrinsics/typed-swap-overlap.stderr

@@ -0,0 +1,15 @@
+error: Undefined Behavior: `copy_nonoverlapping` called on overlapping ranges
+  --> tests/fail/intrinsics/typed-swap-overlap.rs:LL:CC
+   |
+LL |         typed_swap(a, a);
+   |         ^^^^^^^^^^^^^^^^ `copy_nonoverlapping` called on overlapping ranges
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE:
+   = note: inside `main` at tests/fail/intrinsics/typed-swap-overlap.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+