Rollup merge of #146969 - RalfJung:maybe-null-errors, r=oli-obk

const-eval: better wording for errors involving maybe-null pointers

Fixes https://github.com/rust-lang/rust/issues/146748
r? ``@oli-obk``

1 files changed, 11 insertions, 7 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 9adc3fa4631..5f088fe37e8 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -511,7 +511,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                 CheckInAllocMsg::Dereferenceable, // will anyway be replaced by validity message
             ),
             self.path,
-            Ub(DanglingIntPointer { addr: 0, .. }) => NullPtr { ptr_kind },
+            Ub(DanglingIntPointer { addr: 0, .. }) => NullPtr { ptr_kind, maybe: false },
             Ub(DanglingIntPointer { addr: i, .. }) => DanglingPtrNoProvenance {
                 ptr_kind,
                 // FIXME this says "null pointer" when null but we need translate
@@ -538,8 +538,10 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
         );
         // Make sure this is non-null. We checked dereferenceability above, but if `size` is zero
         // that does not imply non-null.
-        if self.ecx.scalar_may_be_null(Scalar::from_maybe_pointer(place.ptr(), self.ecx))? {
-            throw_validation_failure!(self.path, NullPtr { ptr_kind })
+        let scalar = Scalar::from_maybe_pointer(place.ptr(), self.ecx);
+        if self.ecx.scalar_may_be_null(scalar)? {
+            let maybe = !M::Provenance::OFFSET_IS_ADDR && matches!(scalar, Scalar::Ptr(..));
+            throw_validation_failure!(self.path, NullPtr { ptr_kind, maybe })
         }
         // Do not allow references to uninhabited types.
         if place.layout.is_uninhabited() {
@@ -757,6 +759,11 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                 } else {
                     // Otherwise (for standalone Miri), we have to still check it to be non-null.
                     if self.ecx.scalar_may_be_null(scalar)? {
+                        let maybe =
+                            !M::Provenance::OFFSET_IS_ADDR && matches!(scalar, Scalar::Ptr(..));
+                        // This can't be a "maybe-null" pointer since the check for this being
+                        // a fn ptr at all already ensures that the pointer is inbounds.
+                        assert!(!maybe);
                         throw_validation_failure!(self.path, NullFnPtr);
                     }
                 }
@@ -819,10 +826,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                 if start == 1 && end == max_value {
                     // Only null is the niche. So make sure the ptr is NOT null.
                     if self.ecx.scalar_may_be_null(scalar)? {
-                        throw_validation_failure!(
-                            self.path,
-                            NullablePtrOutOfRange { range: valid_range, max_value }
-                        )
+                        throw_validation_failure!(self.path, NonnullPtrMaybeNull)
                     } else {
                         return interp_ok(());
                     }