const: make ptr.is_null() stop execution on ambiguity

2 files changed, 39 insertions, 0 deletions

diff --git a/tests/ui/consts/const-ptr-is-null.rs b/tests/ui/consts/const-ptr-is-null.rs
new file mode 100644
index 00000000000..82c293c0ad6
--- /dev/null
+++ b/tests/ui/consts/const-ptr-is-null.rs
@@ -0,0 +1,20 @@
+#![feature(const_ptr_is_null)]
+use std::ptr;
+
+const IS_NULL: () = {
+    assert!(ptr::null::<u8>().is_null());
+};
+const IS_NOT_NULL: () = {
+    assert!(!ptr::null::<u8>().wrapping_add(1).is_null());
+};
+
+const MAYBE_NULL: () = {
+    let x = 15;
+    let ptr = &x as *const i32;
+    // This one is still unambiguous...
+    assert!(!ptr.is_null());
+    // but once we shift outside the allocation, we might become null.
+    assert!(!ptr.wrapping_sub(512).is_null()); //~inside `MAYBE_NULL`
+};
+
+fn main() {}
diff --git a/tests/ui/consts/const-ptr-is-null.stderr b/tests/ui/consts/const-ptr-is-null.stderr
new file mode 100644
index 00000000000..20e44a1401f
--- /dev/null
+++ b/tests/ui/consts/const-ptr-is-null.stderr
@@ -0,0 +1,19 @@
+error[E0080]: evaluation of constant value failed
+  --> $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
+   |
+   = note: the evaluated program panicked at 'null-ness of this pointer cannot be determined in const context', $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
+   |
+note: inside `std::ptr::const_ptr::<impl *const T>::is_null::const_impl`
+  --> $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
+note: inside `std::ptr::const_ptr::<impl *const i32>::is_null`
+  --> $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
+note: inside `MAYBE_NULL`
+  --> $DIR/const-ptr-is-null.rs:17:14
+   |
+LL |     assert!(!ptr.wrapping_sub(512).is_null());
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.