Rollup merge of #114372 - RalfJung:const-pointer-as-int, r=oli-obk

const validation: point at where we found a pointer but expected an integer

Instead of validation just printing "unable to turn pointer into bytes", make this a regular validation error that says where in the value the bad pointer was found. Also distinguish "expected integer, got pointer" from "expected pointer, got partial pointer or mix of pointers".

To avoid duplicating things too much I refactored the diagnostics for validity a bit, so that "got uninit, expected X" and "got pointer, expected X" can share the "X" part. Also all the errors emitted for validation are now grouped under `const_eval_validation` so that they are in a single group in the ftl file.

r? `@oli-obk`

8 files changed, 280 insertions, 221 deletions

diff --git a/compiler/rustc_const_eval/messages.ftl b/compiler/rustc_const_eval/messages.ftl
index 2905874eec5..0b336109921 100644
--- a/compiler/rustc_const_eval/messages.ftl
+++ b/compiler/rustc_const_eval/messages.ftl
@@ -15,9 +15,6 @@ const_eval_await_non_const =
     cannot convert `{$ty}` into a future in {const_eval_const_context}s
 const_eval_bounds_check_failed =
     indexing out of bounds: the len is {$len} but the index is {$index}
-const_eval_box_to_mut = {$front_matter}: encountered a box pointing to mutable memory in a constant
-const_eval_box_to_static = {$front_matter}: encountered a box pointing to a static variable in a constant
-const_eval_box_to_uninhabited = {$front_matter}: encountered a box pointing to uninhabited type {$ty}
 const_eval_call_nonzero_intrinsic =
     `{$name}` called on 0
 
@@ -41,18 +38,12 @@ const_eval_const_context = {$kind ->
 const_eval_copy_nonoverlapping_overlapping =
     `copy_nonoverlapping` called on overlapping ranges
 
-const_eval_dangling_box_no_provenance = {$front_matter}: encountered a dangling box ({$pointer} has no provenance)
-const_eval_dangling_box_out_of_bounds = {$front_matter}: encountered a dangling box (going beyond the bounds of its allocation)
-const_eval_dangling_box_use_after_free = {$front_matter}: encountered a dangling box (use-after-free)
 const_eval_dangling_int_pointer =
     {$bad_pointer_message}: {$pointer} is a dangling pointer (it has no provenance)
 const_eval_dangling_null_pointer =
     {$bad_pointer_message}: null pointer is a dangling pointer (it has no provenance)
 const_eval_dangling_ptr_in_final = encountered dangling pointer in final constant
 
-const_eval_dangling_ref_no_provenance = {$front_matter}: encountered a dangling reference ({$pointer} has no provenance)
-const_eval_dangling_ref_out_of_bounds = {$front_matter}: encountered a dangling reference (going beyond the bounds of its allocation)
-const_eval_dangling_ref_use_after_free = {$front_matter}: encountered a dangling reference (use-after-free)
 const_eval_dead_local =
     accessing a dead local variable
 const_eval_dealloc_immutable =
@@ -105,7 +96,6 @@ const_eval_error = {$error_kind ->
 const_eval_exact_div_has_remainder =
     exact_div: {$a} cannot be divided by {$b} without remainder
 
-const_eval_expected_non_ptr = {$front_matter}: encountered `{$value}`, but expected plain (non-pointer) bytes
 const_eval_fn_ptr_call =
     function pointers need an RFC before allowed to be called in {const_eval_const_context}s
 const_eval_for_loop_into_iter_non_const =
@@ -156,8 +146,6 @@ const_eval_invalid_align_details =
 
 const_eval_invalid_bool =
     interpreting an invalid 8-bit value as a bool: 0x{$value}
-const_eval_invalid_box_meta = {$front_matter}: encountered invalid box metadata: total size is bigger than largest supported object
-const_eval_invalid_box_slice_meta = {$front_matter}: encountered invalid box metadata: slice is bigger than largest supported object
 const_eval_invalid_char =
     interpreting an invalid 32-bit value as a char: 0x{$value}
 const_eval_invalid_dealloc =
@@ -168,16 +156,12 @@ const_eval_invalid_dealloc =
         *[other] {""}
     }
 
-const_eval_invalid_enum_tag = {$front_matter}: encountered {$value}, but expected a valid enum tag
-const_eval_invalid_fn_ptr = {$front_matter}: encountered {$value}, but expected a function pointer
 const_eval_invalid_function_pointer =
     using {$pointer} as function pointer but it does not point to a function
 const_eval_invalid_meta =
     invalid metadata in wide pointer: total size is bigger than largest supported object
 const_eval_invalid_meta_slice =
     invalid metadata in wide pointer: slice is bigger than largest supported object
-const_eval_invalid_ref_meta = {$front_matter}: encountered invalid reference metadata: total size is bigger than largest supported object
-const_eval_invalid_ref_slice_meta = {$front_matter}: encountered invalid reference metadata: slice is bigger than largest supported object
 const_eval_invalid_str =
     this string is not valid UTF-8: {$err}
 const_eval_invalid_tag =
@@ -189,14 +173,10 @@ const_eval_invalid_uninit_bytes =
     reading memory at {$alloc}{$access}, but memory is uninitialized at {$uninit}, and this operation requires initialized memory
 const_eval_invalid_uninit_bytes_unknown =
     using uninitialized data, but this operation requires initialized memory
-const_eval_invalid_value = constructing invalid value
-const_eval_invalid_value_with_path = constructing invalid value at {$path}
-## The `front_matter`s here refer to either `middle_invalid_value` or `middle_invalid_value_with_path`.
 
 const_eval_invalid_vtable_pointer =
     using {$pointer} as vtable pointer but it does not point to a vtable
 
-const_eval_invalid_vtable_ptr = {$front_matter}: encountered {$value}, but expected a vtable pointer
 
 const_eval_live_drop =
     destructor of `{$dropped_ty}` cannot be evaluated at compile-time
@@ -218,14 +198,13 @@ const_eval_max_num_nodes_in_const = maximum number of nodes exceeded in constant
 const_eval_memory_access_test = memory access failed
 const_eval_memory_exhausted =
     tried to allocate more memory than available to compiler
+
 const_eval_modified_global =
     modifying a static's initial value from another static's initializer
 
 const_eval_mut_deref =
     mutation through a reference is not allowed in {const_eval_const_context}s
 
-const_eval_mutable_ref_in_const = {$front_matter}: encountered mutable reference in a `const`
-const_eval_never_val = {$front_matter}: encountered a value of the never type `!`
 const_eval_non_const_fmt_macro_call =
     cannot call non-const formatting macro in {const_eval_const_context}s
 
@@ -241,10 +220,6 @@ const_eval_noreturn_asm_returned =
 const_eval_not_enough_caller_args =
     calling a function with fewer arguments than it requires
 
-const_eval_null_box = {$front_matter}: encountered a null box
-const_eval_null_fn_ptr = {$front_matter}: encountered a null function pointer
-const_eval_null_ref = {$front_matter}: encountered a null reference
-const_eval_nullable_ptr_out_of_range = {$front_matter}: encountered a potentially null pointer, but expected something that cannot possibly fail to be {$in_range}
 const_eval_nullary_intrinsic_fail =
     could not evaluate nullary intrinsic
 
@@ -257,7 +232,6 @@ const_eval_offset_from_underflow =
 
 const_eval_operator_non_const =
     cannot call non-const operator in {const_eval_const_context}s
-const_eval_out_of_range = {$front_matter}: encountered {$value}, but expected something {$in_range}
 const_eval_overflow =
     overflow executing `{$name}`
 
@@ -287,7 +261,6 @@ const_eval_ptr_as_bytes_1 =
     this code performed an operation that depends on the underlying bytes representing a pointer
 const_eval_ptr_as_bytes_2 =
     the absolute address of a pointer is not known at compile-time, so such operations are not supported
-const_eval_ptr_out_of_range = {$front_matter}: encountered a pointer, but expected something that cannot possibly fail to be {$in_range}
 const_eval_question_branch_non_const =
     `?` cannot determine the branch of `{$ty}` in {const_eval_const_context}s
 
@@ -315,8 +288,8 @@ const_eval_raw_ptr_to_int =
 
 const_eval_read_extern_static =
     cannot read from extern static ({$did})
-const_eval_read_pointer_as_bytes =
-    unable to turn pointer into raw bytes
+const_eval_read_pointer_as_int =
+    unable to turn pointer into integer
 const_eval_realloc_or_alloc_with_offset =
     {$kind ->
         [dealloc] deallocating
@@ -324,9 +297,6 @@ const_eval_realloc_or_alloc_with_offset =
         *[other] {""}
     } {$ptr} which does not point to the beginning of an object
 
-const_eval_ref_to_mut = {$front_matter}: encountered a reference pointing to mutable memory in a constant
-const_eval_ref_to_static = {$front_matter}: encountered a reference pointing to a static variable in a constant
-const_eval_ref_to_uninhabited = {$front_matter}: encountered a reference pointing to uninhabited type {$ty}
 const_eval_remainder_by_zero =
     calculating the remainder with a divisor of zero
 const_eval_remainder_overflow =
@@ -363,8 +333,6 @@ const_eval_transient_mut_borrow_raw = raw mutable references are not allowed in
 
 const_eval_try_block_from_output_non_const =
     `try` block cannot convert `{$ty}` to the result in {const_eval_const_context}s
-const_eval_unaligned_box = {$front_matter}: encountered an unaligned box (required {$required_bytes} byte alignment but found {$found_bytes})
-const_eval_unaligned_ref = {$front_matter}: encountered an unaligned reference (required {$required_bytes} byte alignment but found {$found_bytes})
 const_eval_unallowed_fn_pointer_call = function pointer calls are not allowed in {const_eval_const_context}s
 
 const_eval_unallowed_heap_allocations =
@@ -408,29 +376,14 @@ const_eval_undefined_behavior =
 const_eval_undefined_behavior_note =
     The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
-const_eval_uninhabited_enum_tag = {$front_matter}: encountered an uninhabited enum variant
 const_eval_uninhabited_enum_variant_read =
     read discriminant of an uninhabited enum variant
 const_eval_uninhabited_enum_variant_written =
     writing discriminant of an uninhabited enum variant
-const_eval_uninhabited_val = {$front_matter}: encountered a value of uninhabited type `{$ty}`
-const_eval_uninit = {$front_matter}: encountered uninitialized bytes
-const_eval_uninit_bool = {$front_matter}: encountered uninitialized memory, but expected a boolean
-const_eval_uninit_box = {$front_matter}: encountered uninitialized memory, but expected a box
-const_eval_uninit_char = {$front_matter}: encountered uninitialized memory, but expected a unicode scalar value
-const_eval_uninit_enum_tag = {$front_matter}: encountered uninitialized bytes, but expected a valid enum tag
-const_eval_uninit_float = {$front_matter}: encountered uninitialized memory, but expected a floating point number
-const_eval_uninit_fn_ptr = {$front_matter}: encountered uninitialized memory, but expected a function pointer
-const_eval_uninit_init_scalar = {$front_matter}: encountered uninitialized memory, but expected initialized scalar value
-const_eval_uninit_int = {$front_matter}: encountered uninitialized memory, but expected an integer
-const_eval_uninit_raw_ptr = {$front_matter}: encountered uninitialized memory, but expected a raw pointer
-const_eval_uninit_ref = {$front_matter}: encountered uninitialized memory, but expected a reference
-const_eval_uninit_str = {$front_matter}: encountered uninitialized data in `str`
 const_eval_unreachable = entering unreachable code
 const_eval_unreachable_unwind =
     unwinding past a stack frame that does not allow unwinding
 
-const_eval_unsafe_cell = {$front_matter}: encountered `UnsafeCell` in a `const`
 const_eval_unsigned_offset_from_overflow =
     `ptr_offset_from_unsigned` called when first pointer has smaller offset than second: {$a_offset} < {$b_offset}
 
@@ -453,8 +406,63 @@ const_eval_unwind_past_top =
 const_eval_upcast_mismatch =
     upcast on a pointer whose vtable does not match its type
 
+## The `front_matter`s here refer to either `const_eval_front_matter_invalid_value` or `const_eval_front_matter_invalid_value_with_path`.
+## (We'd love to sort this differently to make that more clear but tidy won't let us...)
+const_eval_validation_box_to_mut = {$front_matter}: encountered a box pointing to mutable memory in a constant
+const_eval_validation_box_to_static = {$front_matter}: encountered a box pointing to a static variable in a constant
+const_eval_validation_box_to_uninhabited = {$front_matter}: encountered a box pointing to uninhabited type {$ty}
+const_eval_validation_dangling_box_no_provenance = {$front_matter}: encountered a dangling box ({$pointer} has no provenance)
+const_eval_validation_dangling_box_out_of_bounds = {$front_matter}: encountered a dangling box (going beyond the bounds of its allocation)
+const_eval_validation_dangling_box_use_after_free = {$front_matter}: encountered a dangling box (use-after-free)
+const_eval_validation_dangling_ref_no_provenance = {$front_matter}: encountered a dangling reference ({$pointer} has no provenance)
+const_eval_validation_dangling_ref_out_of_bounds = {$front_matter}: encountered a dangling reference (going beyond the bounds of its allocation)
+const_eval_validation_dangling_ref_use_after_free = {$front_matter}: encountered a dangling reference (use-after-free)
+
+const_eval_validation_expected_bool = expected a boolean
+const_eval_validation_expected_box = expected a box
+const_eval_validation_expected_char = expected a unicode scalar value
+const_eval_validation_expected_enum_tag = expected a valid enum tag
+const_eval_validation_expected_float = expected a floating point number
+const_eval_validation_expected_fn_ptr = expected a function pointer
+const_eval_validation_expected_init_scalar = expected initialized scalar value
+const_eval_validation_expected_int = expected an integer
+const_eval_validation_expected_raw_ptr = expected a raw pointer
+const_eval_validation_expected_ref = expected a reference
+const_eval_validation_expected_str = expected a string
+
+const_eval_validation_front_matter_invalid_value = constructing invalid value
+const_eval_validation_front_matter_invalid_value_with_path = constructing invalid value at {$path}
+
 const_eval_validation_invalid_bool = {$front_matter}: encountered {$value}, but expected a boolean
+const_eval_validation_invalid_box_meta = {$front_matter}: encountered invalid box metadata: total size is bigger than largest supported object
+const_eval_validation_invalid_box_slice_meta = {$front_matter}: encountered invalid box metadata: slice is bigger than largest supported object
 const_eval_validation_invalid_char = {$front_matter}: encountered {$value}, but expected a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`)
+
+const_eval_validation_invalid_enum_tag = {$front_matter}: encountered {$value}, but expected a valid enum tag
+const_eval_validation_invalid_fn_ptr = {$front_matter}: encountered {$value}, but expected a function pointer
+const_eval_validation_invalid_ref_meta = {$front_matter}: encountered invalid reference metadata: total size is bigger than largest supported object
+const_eval_validation_invalid_ref_slice_meta = {$front_matter}: encountered invalid reference metadata: slice is bigger than largest supported object
+const_eval_validation_invalid_vtable_ptr = {$front_matter}: encountered {$value}, but expected a vtable pointer
+const_eval_validation_mutable_ref_in_const = {$front_matter}: encountered mutable reference in a `const`
+const_eval_validation_never_val = {$front_matter}: encountered a value of the never type `!`
+const_eval_validation_null_box = {$front_matter}: encountered a null box
+const_eval_validation_null_fn_ptr = {$front_matter}: encountered a null function pointer
+const_eval_validation_null_ref = {$front_matter}: encountered a null reference
+const_eval_validation_nullable_ptr_out_of_range = {$front_matter}: encountered a potentially null pointer, but expected something that cannot possibly fail to be {$in_range}
+const_eval_validation_out_of_range = {$front_matter}: encountered {$value}, but expected something {$in_range}
+const_eval_validation_partial_pointer = {$front_matter}: encountered a partial pointer or a mix of pointers
+const_eval_validation_pointer_as_int = {$front_matter}: encountered a pointer, but {$expected}
+const_eval_validation_ptr_out_of_range = {$front_matter}: encountered a pointer, but expected something that cannot possibly fail to be {$in_range}
+const_eval_validation_ref_to_mut = {$front_matter}: encountered a reference pointing to mutable memory in a constant
+const_eval_validation_ref_to_static = {$front_matter}: encountered a reference pointing to a static variable in a constant
+const_eval_validation_ref_to_uninhabited = {$front_matter}: encountered a reference pointing to uninhabited type {$ty}
+const_eval_validation_unaligned_box = {$front_matter}: encountered an unaligned box (required {$required_bytes} byte alignment but found {$found_bytes})
+const_eval_validation_unaligned_ref = {$front_matter}: encountered an unaligned reference (required {$required_bytes} byte alignment but found {$found_bytes})
+const_eval_validation_uninhabited_enum_variant = {$front_matter}: encountered an uninhabited enum variant
+const_eval_validation_uninhabited_val = {$front_matter}: encountered a value of uninhabited type `{$ty}`
+const_eval_validation_uninit = {$front_matter}: encountered uninitialized memory, but {$expected}
+const_eval_validation_unsafe_cell = {$front_matter}: encountered `UnsafeCell` in a `const`
+
 const_eval_write_to_read_only =
     writing to {$allocation} which is read-only
 const_eval_zst_pointer_out_of_bounds =
diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs
index 8cbc68d9061..3a4e2648b80 100644
--- a/compiler/rustc_const_eval/src/errors.rs
+++ b/compiler/rustc_const_eval/src/errors.rs
@@ -513,7 +513,7 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
             ScalarSizeMismatch(_) => const_eval_scalar_size_mismatch,
             UninhabitedEnumVariantWritten(_) => const_eval_uninhabited_enum_variant_written,
             UninhabitedEnumVariantRead(_) => const_eval_uninhabited_enum_variant_read,
-            Validation(e) => e.diagnostic_message(),
+            ValidationError(e) => e.diagnostic_message(),
             Custom(x) => (x.msg)(),
         }
     }
@@ -587,13 +587,13 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
             InvalidUninitBytes(Some((alloc, info))) => {
                 builder.set_arg("alloc", alloc);
                 builder.set_arg("access", info.access);
-                builder.set_arg("uninit", info.uninit);
+                builder.set_arg("uninit", info.bad);
             }
             ScalarSizeMismatch(info) => {
                 builder.set_arg("target_size", info.target_size);
                 builder.set_arg("data_size", info.data_size);
             }
-            Validation(e) => e.add_args(handler, builder),
+            ValidationError(e) => e.add_args(handler, builder),
             Custom(custom) => {
                 (custom.add_args)(&mut |name, value| {
                     builder.set_arg(name, value);
@@ -608,74 +608,72 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
         use crate::fluent_generated::*;
         use rustc_middle::mir::interpret::ValidationErrorKind::*;
         match self.kind {
-            PtrToUninhabited { ptr_kind: PointerKind::Box, .. } => const_eval_box_to_uninhabited,
-            PtrToUninhabited { ptr_kind: PointerKind::Ref, .. } => const_eval_ref_to_uninhabited,
-
-            PtrToStatic { ptr_kind: PointerKind::Box } => const_eval_box_to_static,
-            PtrToStatic { ptr_kind: PointerKind::Ref } => const_eval_ref_to_static,
-
-            PtrToMut { ptr_kind: PointerKind::Box } => const_eval_box_to_mut,
-            PtrToMut { ptr_kind: PointerKind::Ref } => const_eval_ref_to_mut,
-
-            ExpectedNonPtr { .. } => const_eval_expected_non_ptr,
-            MutableRefInConst => const_eval_mutable_ref_in_const,
-            NullFnPtr => const_eval_null_fn_ptr,
-            NeverVal => const_eval_never_val,
-            NullablePtrOutOfRange { .. } => const_eval_nullable_ptr_out_of_range,
-            PtrOutOfRange { .. } => const_eval_ptr_out_of_range,
-            OutOfRange { .. } => const_eval_out_of_range,
-            UnsafeCell => const_eval_unsafe_cell,
-            UninhabitedVal { .. } => const_eval_uninhabited_val,
-            InvalidEnumTag { .. } => const_eval_invalid_enum_tag,
-            UninhabitedEnumTag => const_eval_uninhabited_enum_tag,
-            UninitEnumTag => const_eval_uninit_enum_tag,
-            UninitStr => const_eval_uninit_str,
-            Uninit { expected: ExpectedKind::Bool } => const_eval_uninit_bool,
-            Uninit { expected: ExpectedKind::Reference } => const_eval_uninit_ref,
-            Uninit { expected: ExpectedKind::Box } => const_eval_uninit_box,
-            Uninit { expected: ExpectedKind::RawPtr } => const_eval_uninit_raw_ptr,
-            Uninit { expected: ExpectedKind::InitScalar } => const_eval_uninit_init_scalar,
-            Uninit { expected: ExpectedKind::Char } => const_eval_uninit_char,
-            Uninit { expected: ExpectedKind::Float } => const_eval_uninit_float,
-            Uninit { expected: ExpectedKind::Int } => const_eval_uninit_int,
-            Uninit { expected: ExpectedKind::FnPtr } => const_eval_uninit_fn_ptr,
-            UninitVal => const_eval_uninit,
-            InvalidVTablePtr { .. } => const_eval_invalid_vtable_ptr,
+            PtrToUninhabited { ptr_kind: PointerKind::Box, .. } => {
+                const_eval_validation_box_to_uninhabited
+            }
+            PtrToUninhabited { ptr_kind: PointerKind::Ref, .. } => {
+                const_eval_validation_ref_to_uninhabited
+            }
+
+            PtrToStatic { ptr_kind: PointerKind::Box } => const_eval_validation_box_to_static,
+            PtrToStatic { ptr_kind: PointerKind::Ref } => const_eval_validation_ref_to_static,
+
+            PtrToMut { ptr_kind: PointerKind::Box } => const_eval_validation_box_to_mut,
+            PtrToMut { ptr_kind: PointerKind::Ref } => const_eval_validation_ref_to_mut,
+
+            PointerAsInt { .. } => const_eval_validation_pointer_as_int,
+            PartialPointer => const_eval_validation_partial_pointer,
+            MutableRefInConst => const_eval_validation_mutable_ref_in_const,
+            NullFnPtr => const_eval_validation_null_fn_ptr,
+            NeverVal => const_eval_validation_never_val,
+            NullablePtrOutOfRange { .. } => const_eval_validation_nullable_ptr_out_of_range,
+            PtrOutOfRange { .. } => const_eval_validation_ptr_out_of_range,
+            OutOfRange { .. } => const_eval_validation_out_of_range,
+            UnsafeCell => const_eval_validation_unsafe_cell,
+            UninhabitedVal { .. } => const_eval_validation_uninhabited_val,
+            InvalidEnumTag { .. } => const_eval_validation_invalid_enum_tag,
+            UninhabitedEnumVariant => const_eval_validation_uninhabited_enum_variant,
+            Uninit { .. } => const_eval_validation_uninit,
+            InvalidVTablePtr { .. } => const_eval_validation_invalid_vtable_ptr,
             InvalidMetaSliceTooLarge { ptr_kind: PointerKind::Box } => {
-                const_eval_invalid_box_slice_meta
+                const_eval_validation_invalid_box_slice_meta
             }
             InvalidMetaSliceTooLarge { ptr_kind: PointerKind::Ref } => {
-                const_eval_invalid_ref_slice_meta
+                const_eval_validation_invalid_ref_slice_meta
             }
 
-            InvalidMetaTooLarge { ptr_kind: PointerKind::Box } => const_eval_invalid_box_meta,
-            InvalidMetaTooLarge { ptr_kind: PointerKind::Ref } => const_eval_invalid_ref_meta,
-            UnalignedPtr { ptr_kind: PointerKind::Ref, .. } => const_eval_unaligned_ref,
-            UnalignedPtr { ptr_kind: PointerKind::Box, .. } => const_eval_unaligned_box,
+            InvalidMetaTooLarge { ptr_kind: PointerKind::Box } => {
+                const_eval_validation_invalid_box_meta
+            }
+            InvalidMetaTooLarge { ptr_kind: PointerKind::Ref } => {
+                const_eval_validation_invalid_ref_meta
+            }
+            UnalignedPtr { ptr_kind: PointerKind::Ref, .. } => const_eval_validation_unaligned_ref,
+            UnalignedPtr { ptr_kind: PointerKind::Box, .. } => const_eval_validation_unaligned_box,
 
-            NullPtr { ptr_kind: PointerKind::Box } => const_eval_null_box,
-            NullPtr { ptr_kind: PointerKind::Ref } => const_eval_null_ref,
+            NullPtr { ptr_kind: PointerKind::Box } => const_eval_validation_null_box,
+            NullPtr { ptr_kind: PointerKind::Ref } => const_eval_validation_null_ref,
             DanglingPtrNoProvenance { ptr_kind: PointerKind::Box, .. } => {
-                const_eval_dangling_box_no_provenance
+                const_eval_validation_dangling_box_no_provenance
             }
             DanglingPtrNoProvenance { ptr_kind: PointerKind::Ref, .. } => {
-                const_eval_dangling_ref_no_provenance
+                const_eval_validation_dangling_ref_no_provenance
             }
             DanglingPtrOutOfBounds { ptr_kind: PointerKind::Box } => {
-                const_eval_dangling_box_out_of_bounds
+                const_eval_validation_dangling_box_out_of_bounds
             }
             DanglingPtrOutOfBounds { ptr_kind: PointerKind::Ref } => {
-                const_eval_dangling_ref_out_of_bounds
+                const_eval_validation_dangling_ref_out_of_bounds
             }
             DanglingPtrUseAfterFree { ptr_kind: PointerKind::Box } => {
-                const_eval_dangling_box_use_after_free
+                const_eval_validation_dangling_box_use_after_free
             }
             DanglingPtrUseAfterFree { ptr_kind: PointerKind::Ref } => {
-                const_eval_dangling_ref_use_after_free
+                const_eval_validation_dangling_ref_use_after_free
             }
             InvalidBool { .. } => const_eval_validation_invalid_bool,
             InvalidChar { .. } => const_eval_validation_invalid_char,
-            InvalidFnPtr { .. } => const_eval_invalid_fn_ptr,
+            InvalidFnPtr { .. } => const_eval_validation_invalid_fn_ptr,
         }
     }
 
@@ -683,13 +681,21 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
         use crate::fluent_generated as fluent;
         use rustc_middle::mir::interpret::ValidationErrorKind::*;
 
+        if let PointerAsInt { .. } | PartialPointer = self.kind {
+            err.help(fluent::const_eval_ptr_as_bytes_1);
+            err.help(fluent::const_eval_ptr_as_bytes_2);
+        }
+
         let message = if let Some(path) = self.path {
             handler.eagerly_translate_to_string(
-                fluent::const_eval_invalid_value_with_path,
+                fluent::const_eval_validation_front_matter_invalid_value_with_path,
                 [("path".into(), DiagnosticArgValue::Str(path.into()))].iter().map(|(a, b)| (a, b)),
             )
         } else {
-            handler.eagerly_translate_to_string(fluent::const_eval_invalid_value, [].into_iter())
+            handler.eagerly_translate_to_string(
+                fluent::const_eval_validation_front_matter_invalid_value,
+                [].into_iter(),
+            )
         };
 
         err.set_arg("front_matter", message);
@@ -729,8 +735,24 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
             PtrToUninhabited { ty, .. } | UninhabitedVal { ty } => {
                 err.set_arg("ty", ty);
             }
-            ExpectedNonPtr { value }
-            | InvalidEnumTag { value }
+            PointerAsInt { expected } | Uninit { expected } => {
+                let msg = match expected {
+                    ExpectedKind::Reference => fluent::const_eval_validation_expected_ref,
+                    ExpectedKind::Box => fluent::const_eval_validation_expected_box,
+                    ExpectedKind::RawPtr => fluent::const_eval_validation_expected_raw_ptr,
+                    ExpectedKind::InitScalar => fluent::const_eval_validation_expected_init_scalar,
+                    ExpectedKind::Bool => fluent::const_eval_validation_expected_bool,
+                    ExpectedKind::Char => fluent::const_eval_validation_expected_char,
+                    ExpectedKind::Float => fluent::const_eval_validation_expected_float,
+                    ExpectedKind::Int => fluent::const_eval_validation_expected_int,
+                    ExpectedKind::FnPtr => fluent::const_eval_validation_expected_fn_ptr,
+                    ExpectedKind::EnumTag => fluent::const_eval_validation_expected_enum_tag,
+                    ExpectedKind::Str => fluent::const_eval_validation_expected_str,
+                };
+                let msg = handler.eagerly_translate_to_string(msg, [].into_iter());
+                err.set_arg("expected", msg);
+            }
+            InvalidEnumTag { value }
             | InvalidVTablePtr { value }
             | InvalidBool { value }
             | InvalidChar { value }
@@ -758,15 +780,12 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
             | NullFnPtr
             | NeverVal
             | UnsafeCell
-            | UninitEnumTag
-            | UninitStr
-            | Uninit { .. }
-            | UninitVal
             | InvalidMetaSliceTooLarge { .. }
             | InvalidMetaTooLarge { .. }
             | DanglingPtrUseAfterFree { .. }
             | DanglingPtrOutOfBounds { .. }
-            | UninhabitedEnumTag => {}
+            | UninhabitedEnumVariant
+            | PartialPointer => {}
         }
     }
 }
@@ -776,9 +795,9 @@ impl ReportErrorExt for UnsupportedOpInfo {
         use crate::fluent_generated::*;
         match self {
             UnsupportedOpInfo::Unsupported(s) => s.clone().into(),
-            UnsupportedOpInfo::PartialPointerOverwrite(_) => const_eval_partial_pointer_overwrite,
-            UnsupportedOpInfo::PartialPointerCopy(_) => const_eval_partial_pointer_copy,
-            UnsupportedOpInfo::ReadPointerAsBytes => const_eval_read_pointer_as_bytes,
+            UnsupportedOpInfo::OverwritePartialPointer(_) => const_eval_partial_pointer_overwrite,
+            UnsupportedOpInfo::ReadPartialPointer(_) => const_eval_partial_pointer_copy,
+            UnsupportedOpInfo::ReadPointerAsInt(_) => const_eval_read_pointer_as_int,
             UnsupportedOpInfo::ThreadLocalStatic(_) => const_eval_thread_local_static,
             UnsupportedOpInfo::ReadExternStatic(_) => const_eval_read_extern_static,
         }
@@ -787,13 +806,16 @@ impl ReportErrorExt for UnsupportedOpInfo {
         use crate::fluent_generated::*;
 
         use UnsupportedOpInfo::*;
-        if let ReadPointerAsBytes | PartialPointerOverwrite(_) | PartialPointerCopy(_) = self {
+        if let ReadPointerAsInt(_) | OverwritePartialPointer(_) | ReadPartialPointer(_) = self {
             builder.help(const_eval_ptr_as_bytes_1);
             builder.help(const_eval_ptr_as_bytes_2);
         }
         match self {
-            Unsupported(_) | ReadPointerAsBytes => {}
-            PartialPointerOverwrite(ptr) | PartialPointerCopy(ptr) => {
+            // `ReadPointerAsInt(Some(info))` is never printed anyway, it only serves as an error to
+            // be further processed by validity checking which then turns it into something nice to
+            // print. So it's not worth the effort of having diagnostics that can print the `info`.
+            Unsupported(_) | ReadPointerAsInt(_) => {}
+            OverwritePartialPointer(ptr) | ReadPartialPointer(ptr) => {
                 builder.set_arg("ptr", ptr);
             }
             ThreadLocalStatic(did) | ReadExternStatic(did) => {
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index ff22d3d2d5a..d3f05af1c72 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -25,13 +25,17 @@ use rustc_target::abi::{
 
 use std::hash::Hash;
 
-// for the validation errors
-use super::UndefinedBehaviorInfo::*;
 use super::{
     AllocId, CheckInAllocMsg, GlobalAlloc, ImmTy, Immediate, InterpCx, InterpResult, MPlaceTy,
     Machine, MemPlaceMeta, OpTy, Pointer, Projectable, Scalar, ValueVisitor,
 };
 
+// for the validation errors
+use super::InterpError::UndefinedBehavior as Ub;
+use super::InterpError::Unsupported as Unsup;
+use super::UndefinedBehaviorInfo::*;
+use super::UnsupportedOpInfo::*;
+
 macro_rules! throw_validation_failure {
     ($where:expr, $kind: expr) => {{
         let where_ = &$where;
@@ -43,7 +47,7 @@ macro_rules! throw_validation_failure {
             None
         };
 
-        throw_ub!(Validation(ValidationErrorInfo { path, kind: $kind }))
+        throw_ub!(ValidationError(ValidationErrorInfo { path, kind: $kind }))
     }};
 }
 
@@ -85,16 +89,16 @@ macro_rules! try_validation {
             Ok(x) => x,
             // We catch the error and turn it into a validation failure. We are okay with
             // allocation here as this can only slow down builds that fail anyway.
-            Err(e) => match e.into_parts() {
+            Err(e) => match e.kind() {
                 $(
-                    (InterpError::UndefinedBehavior($($p)|+), _) =>
+                    $($p)|+ =>
                        throw_validation_failure!(
                             $where,
                             $kind
                         )
                 ),+,
                 #[allow(unreachable_patterns)]
-                (e, rest) => Err::<!, _>($crate::interpret::InterpErrorInfo::from_parts(e, rest))?,
+                _ => Err::<!, _>(e)?,
             }
         }
     }};
@@ -294,7 +298,13 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
         Ok(try_validation!(
             self.ecx.read_immediate(op),
             self.path,
-            InvalidUninitBytes(None) => Uninit { expected }
+            Ub(InvalidUninitBytes(None)) =>
+                Uninit { expected },
+            // The `Unsup` cases can only occur during CTFE
+            Unsup(ReadPointerAsInt(_)) =>
+                PointerAsInt { expected },
+            Unsup(ReadPartialPointer(_)) =>
+                PartialPointer,
         ))
     }
 
@@ -319,8 +329,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 let (_ty, _trait) = try_validation!(
                     self.ecx.get_ptr_vtable(vtable),
                     self.path,
-                    DanglingIntPointer(..) |
-                    InvalidVTablePointer(..) => InvalidVTablePtr { value: format!("{vtable}") }
+                    Ub(DanglingIntPointer(..) | InvalidVTablePointer(..)) =>
+                        InvalidVTablePtr { value: format!("{vtable}") }
                 );
                 // FIXME: check if the type/trait match what ty::Dynamic says?
             }
@@ -356,7 +366,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
         let size_and_align = try_validation!(
             self.ecx.size_and_align_of_mplace(&place),
             self.path,
-            InvalidMeta(msg) => match msg {
+            Ub(InvalidMeta(msg)) => match msg {
                 InvalidMetaKind::SliceTooBig => InvalidMetaSliceTooLarge { ptr_kind },
                 InvalidMetaKind::TooBig => InvalidMetaTooLarge { ptr_kind },
             }
@@ -375,23 +385,23 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 CheckInAllocMsg::InboundsTest, // will anyway be replaced by validity message
             ),
             self.path,
-            AlignmentCheckFailed { required, has } => UnalignedPtr {
+            Ub(AlignmentCheckFailed { required, has }) => UnalignedPtr {
                 ptr_kind,
                 required_bytes: required.bytes(),
                 found_bytes: has.bytes()
             },
-            DanglingIntPointer(0, _) => NullPtr { ptr_kind },
-            DanglingIntPointer(i, _) => DanglingPtrNoProvenance {
+            Ub(DanglingIntPointer(0, _)) => NullPtr { ptr_kind },
+            Ub(DanglingIntPointer(i, _)) => DanglingPtrNoProvenance {
                 ptr_kind,
                 // FIXME this says "null pointer" when null but we need translate
-                pointer: format!("{}", Pointer::<Option<AllocId>>::from_addr_invalid(i))
+                pointer: format!("{}", Pointer::<Option<AllocId>>::from_addr_invalid(*i))
             },
-            PointerOutOfBounds { .. } => DanglingPtrOutOfBounds {
+            Ub(PointerOutOfBounds { .. }) => DanglingPtrOutOfBounds {
                 ptr_kind
             },
             // This cannot happen during const-eval (because interning already detects
             // dangling pointers), but it can happen in Miri.
-            PointerUseAfterFree(..) => DanglingPtrUseAfterFree {
+            Ub(PointerUseAfterFree(..)) => DanglingPtrUseAfterFree {
                 ptr_kind,
             },
         );
@@ -477,7 +487,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 try_validation!(
                     value.to_bool(),
                     self.path,
-                    InvalidBool(..) => ValidationErrorKind::InvalidBool {
+                    Ub(InvalidBool(..)) => ValidationErrorKind::InvalidBool {
                         value: format!("{value:x}"),
                     }
                 );
@@ -488,7 +498,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 try_validation!(
                     value.to_char(),
                     self.path,
-                    InvalidChar(..) => ValidationErrorKind::InvalidChar {
+                    Ub(InvalidChar(..)) => ValidationErrorKind::InvalidChar {
                         value: format!("{value:x}"),
                     }
                 );
@@ -497,7 +507,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
             ty::Float(_) | ty::Int(_) | ty::Uint(_) => {
                 // NOTE: Keep this in sync with the array optimization for int/float
                 // types below!
-                let value = self.read_scalar(
+                self.read_scalar(
                     value,
                     if matches!(ty.kind(), ty::Float(..)) {
                         ExpectedKind::Float
@@ -505,14 +515,6 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                         ExpectedKind::Int
                     },
                 )?;
-                // As a special exception we *do* match on a `Scalar` here, since we truly want
-                // to know its underlying representation (and *not* cast it to an integer).
-                if matches!(value, Scalar::Ptr(..)) {
-                    throw_validation_failure!(
-                        self.path,
-                        ExpectedNonPtr { value: format!("{value:x}") }
-                    )
-                }
                 Ok(true)
             }
             ty::RawPtr(..) => {
@@ -546,10 +548,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                     let _fn = try_validation!(
                         self.ecx.get_ptr_fn(ptr),
                         self.path,
-                        DanglingIntPointer(..) |
-                        InvalidFunctionPointer(..) => InvalidFnPtr {
-                            value: format!("{ptr}"),
-                        },
+                        Ub(DanglingIntPointer(..) | InvalidFunctionPointer(..)) =>
+                            InvalidFnPtr { value: format!("{ptr}") },
                     );
                     // FIXME: Check if the signature matches
                 } else {
@@ -657,11 +657,12 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
             Ok(try_validation!(
                 this.ecx.read_discriminant(op),
                 this.path,
-                InvalidTag(val) => InvalidEnumTag {
+                Ub(InvalidTag(val)) => InvalidEnumTag {
                     value: format!("{val:x}"),
                 },
-                UninhabitedEnumVariantRead(_) => UninhabitedEnumTag,
-                InvalidUninitBytes(None) => UninitEnumTag,
+                Ub(UninhabitedEnumVariantRead(_)) => UninhabitedEnumVariant,
+                // Uninit / bad provenance are not possible since the field was already previously
+                // checked at its integer type.
             ))
         })
     }
@@ -740,7 +741,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
                 try_validation!(
                     self.ecx.read_bytes_ptr_strip_provenance(mplace.ptr, Size::from_bytes(len)),
                     self.path,
-                    InvalidUninitBytes(..) => { UninitStr },
+                    Ub(InvalidUninitBytes(..)) => Uninit { expected: ExpectedKind::Str },
+                    Unsup(ReadPointerAsInt(_)) => PointerAsInt { expected: ExpectedKind::Str }
                 );
             }
             ty::Array(tys, ..) | ty::Slice(tys)
@@ -752,6 +754,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
                 if matches!(tys.kind(), ty::Int(..) | ty::Uint(..) | ty::Float(..))
                 =>
             {
+                let expected = if tys.is_integral() { ExpectedKind::Int } else { ExpectedKind::Float };
                 // Optimized handling for arrays of integer/float type.
 
                 // This is the length of the array/slice.
@@ -770,7 +773,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
                     Left(mplace) => mplace,
                     Right(imm) => match *imm {
                         Immediate::Uninit =>
-                            throw_validation_failure!(self.path, UninitVal),
+                            throw_validation_failure!(self.path, Uninit { expected }),
                         Immediate::Scalar(..) | Immediate::ScalarPair(..) =>
                             bug!("arrays/slices can never have Scalar/ScalarPair layout"),
                     }
@@ -796,17 +799,21 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
                         // For some errors we might be able to provide extra information.
                         // (This custom logic does not fit the `try_validation!` macro.)
                         match err.kind() {
-                            err_ub!(InvalidUninitBytes(Some((_alloc_id, access)))) => {
+                            Ub(InvalidUninitBytes(Some((_alloc_id, access)))) | Unsup(ReadPointerAsInt(Some((_alloc_id, access)))) => {
                                 // Some byte was uninitialized, determine which
                                 // element that byte belongs to so we can
                                 // provide an index.
                                 let i = usize::try_from(
-                                    access.uninit.start.bytes() / layout.size.bytes(),
+                                    access.bad.start.bytes() / layout.size.bytes(),
                                 )
                                 .unwrap();
                                 self.path.push(PathElem::ArrayElem(i));
 
-                                throw_validation_failure!(self.path, UninitVal)
+                                if matches!(err.kind(), Ub(InvalidUninitBytes(_))) {
+                                    throw_validation_failure!(self.path, Uninit { expected })
+                                } else {
+                                    throw_validation_failure!(self.path, PointerAsInt { expected })
+                                }
                             }
 
                             // Propagate upwards (that will also check for unexpected errors).
@@ -892,17 +899,22 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // Run it.
         match visitor.visit_value(&op) {
             Ok(()) => Ok(()),
-            // Pass through validation failures.
-            Err(err) if matches!(err.kind(), err_ub!(Validation { .. })) => Err(err),
-            // Complain about any other kind of UB error -- those are bad because we'd like to
+            // Pass through validation failures and "invalid program" issues.
+            Err(err)
+                if matches!(
+                    err.kind(),
+                    err_ub!(ValidationError { .. }) | InterpError::InvalidProgram(_)
+                ) =>
+            {
+                Err(err)
+            }
+            // Complain about any other kind of error -- those are bad because we'd like to
             // report them in a way that shows *where* in the value the issue lies.
-            Err(err) if matches!(err.kind(), InterpError::UndefinedBehavior(_)) => {
+            Err(err) => {
                 let (err, backtrace) = err.into_parts();
                 backtrace.print_backtrace();
                 bug!("Unexpected Undefined Behavior error during validation: {err:?}");
             }
-            // Pass through everything else.
-            Err(err) => Err(err),
         }
     }
 
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index c1cb2f2e497..2567170f39a 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -18,9 +18,9 @@ use rustc_span::DUMMY_SP;
 use rustc_target::abi::{Align, HasDataLayout, Size};
 
 use super::{
-    read_target_uint, write_target_uint, AllocId, InterpError, InterpResult, Pointer, Provenance,
-    ResourceExhaustionInfo, Scalar, ScalarSizeMismatch, UndefinedBehaviorInfo, UninitBytesAccess,
-    UnsupportedOpInfo,
+    read_target_uint, write_target_uint, AllocId, BadBytesAccess, InterpError, InterpResult,
+    Pointer, PointerArithmetic, Provenance, ResourceExhaustionInfo, Scalar, ScalarSizeMismatch,
+    UndefinedBehaviorInfo, UnsupportedOpInfo,
 };
 use crate::ty;
 use init_mask::*;
@@ -173,13 +173,13 @@ pub enum AllocError {
     /// A scalar had the wrong size.
     ScalarSizeMismatch(ScalarSizeMismatch),
     /// Encountered a pointer where we needed raw bytes.
-    ReadPointerAsBytes,
+    ReadPointerAsInt(Option<BadBytesAccess>),
     /// Partially overwriting a pointer.
-    PartialPointerOverwrite(Size),
+    OverwritePartialPointer(Size),
     /// Partially copying a pointer.
-    PartialPointerCopy(Size),
+    ReadPartialPointer(Size),
     /// Using uninitialized data where it is not allowed.
-    InvalidUninitBytes(Option<UninitBytesAccess>),
+    InvalidUninitBytes(Option<BadBytesAccess>),
 }
 pub type AllocResult<T = ()> = Result<T, AllocError>;
 
@@ -196,12 +196,14 @@ impl AllocError {
             ScalarSizeMismatch(s) => {
                 InterpError::UndefinedBehavior(UndefinedBehaviorInfo::ScalarSizeMismatch(s))
             }
-            ReadPointerAsBytes => InterpError::Unsupported(UnsupportedOpInfo::ReadPointerAsBytes),
-            PartialPointerOverwrite(offset) => InterpError::Unsupported(
-                UnsupportedOpInfo::PartialPointerOverwrite(Pointer::new(alloc_id, offset)),
+            ReadPointerAsInt(info) => InterpError::Unsupported(
+                UnsupportedOpInfo::ReadPointerAsInt(info.map(|b| (alloc_id, b))),
             ),
-            PartialPointerCopy(offset) => InterpError::Unsupported(
-                UnsupportedOpInfo::PartialPointerCopy(Pointer::new(alloc_id, offset)),
+            OverwritePartialPointer(offset) => InterpError::Unsupported(
+                UnsupportedOpInfo::OverwritePartialPointer(Pointer::new(alloc_id, offset)),
+            ),
+            ReadPartialPointer(offset) => InterpError::Unsupported(
+                UnsupportedOpInfo::ReadPartialPointer(Pointer::new(alloc_id, offset)),
             ),
             InvalidUninitBytes(info) => InterpError::UndefinedBehavior(
                 UndefinedBehaviorInfo::InvalidUninitBytes(info.map(|b| (alloc_id, b))),
@@ -433,14 +435,26 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
         range: AllocRange,
     ) -> AllocResult<&[u8]> {
         self.init_mask.is_range_initialized(range).map_err(|uninit_range| {
-            AllocError::InvalidUninitBytes(Some(UninitBytesAccess {
+            AllocError::InvalidUninitBytes(Some(BadBytesAccess {
                 access: range,
-                uninit: uninit_range,
+                bad: uninit_range,
             }))
         })?;
         if !Prov::OFFSET_IS_ADDR {
             if !self.provenance.range_empty(range, cx) {
-                return Err(AllocError::ReadPointerAsBytes);
+                // Find the provenance.
+                let (offset, _prov) = self
+                    .provenance
+                    .range_get_ptrs(range, cx)
+                    .first()
+                    .copied()
+                    .expect("there must be provenance somewhere here");
+                let start = offset.max(range.start); // the pointer might begin before `range`!
+                let end = (offset + cx.pointer_size()).min(range.end()); // the pointer might end after `range`!
+                return Err(AllocError::ReadPointerAsInt(Some(BadBytesAccess {
+                    access: range,
+                    bad: AllocRange::from(start..end),
+                })));
             }
         }
         Ok(self.get_bytes_unchecked(range))
@@ -536,23 +550,25 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
                 // Now use this provenance.
                 let ptr = Pointer::new(prov, Size::from_bytes(bits));
                 return Ok(Scalar::from_maybe_pointer(ptr, cx));
+            } else {
+                // Without OFFSET_IS_ADDR, the only remaining case we can handle is total absence of
+                // provenance.
+                if self.provenance.range_empty(range, cx) {
+                    return Ok(Scalar::from_uint(bits, range.size));
+                }
+                // Else we have mixed provenance, that doesn't work.
+                return Err(AllocError::ReadPartialPointer(range.start));
             }
         } else {
             // We are *not* reading a pointer.
-            // If we can just ignore provenance, do exactly that.
-            if Prov::OFFSET_IS_ADDR {
+            // If we can just ignore provenance or there is none, that's easy.
+            if Prov::OFFSET_IS_ADDR || self.provenance.range_empty(range, cx) {
                 // We just strip provenance.
                 return Ok(Scalar::from_uint(bits, range.size));
             }
+            // There is some provenance and we don't have OFFSET_IS_ADDR. This doesn't work.
+            return Err(AllocError::ReadPointerAsInt(None));
         }
-
-        // Fallback path for when we cannot treat provenance bytewise or ignore it.
-        assert!(!Prov::OFFSET_IS_ADDR);
-        if !self.provenance.range_empty(range, cx) {
-            return Err(AllocError::ReadPointerAsBytes);
-        }
-        // There is no provenance, we can just return the bits.
-        Ok(Scalar::from_uint(bits, range.size))
     }
 
     /// Writes a *non-ZST* scalar.
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs b/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
index 318f93e12b5..0243fc4513a 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
@@ -66,7 +66,11 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
     /// Returns all ptr-sized provenance in the given range.
     /// If the range has length 0, returns provenance that crosses the edge between `start-1` and
     /// `start`.
-    fn range_get_ptrs(&self, range: AllocRange, cx: &impl HasDataLayout) -> &[(Size, Prov)] {
+    pub(super) fn range_get_ptrs(
+        &self,
+        range: AllocRange,
+        cx: &impl HasDataLayout,
+    ) -> &[(Size, Prov)] {
         // We have to go back `pointer_size - 1` bytes, as that one would still overlap with
         // the beginning of this range.
         let adjusted_start = Size::from_bytes(
@@ -158,7 +162,7 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
         if first < start {
             if !Prov::OFFSET_IS_ADDR {
                 // We can't split up the provenance into less than a pointer.
-                return Err(AllocError::PartialPointerOverwrite(first));
+                return Err(AllocError::OverwritePartialPointer(first));
             }
             // Insert the remaining part in the bytewise provenance.
             let prov = self.ptrs[&first];
@@ -171,7 +175,7 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
             let begin_of_last = last - cx.data_layout().pointer_size;
             if !Prov::OFFSET_IS_ADDR {
                 // We can't split up the provenance into less than a pointer.
-                return Err(AllocError::PartialPointerOverwrite(begin_of_last));
+                return Err(AllocError::OverwritePartialPointer(begin_of_last));
             }
             // Insert the remaining part in the bytewise provenance.
             let prov = self.ptrs[&begin_of_last];
@@ -246,10 +250,10 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
         if !Prov::OFFSET_IS_ADDR {
             // There can't be any bytewise provenance, and we cannot split up the begin/end overlap.
             if let Some(entry) = begin_overlap {
-                return Err(AllocError::PartialPointerCopy(entry.0));
+                return Err(AllocError::ReadPartialPointer(entry.0));
             }
             if let Some(entry) = end_overlap {
-                return Err(AllocError::PartialPointerCopy(entry.0));
+                return Err(AllocError::ReadPartialPointer(entry.0));
             }
             debug_assert!(self.bytes.is_none());
         } else {
diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs
index 65652b10afb..2e46bfc1a38 100644
--- a/compiler/rustc_middle/src/mir/interpret/error.rs
+++ b/compiler/rustc_middle/src/mir/interpret/error.rs
@@ -134,10 +134,6 @@ impl InterpErrorBacktrace {
 }
 
 impl<'tcx> InterpErrorInfo<'tcx> {
-    pub fn from_parts(kind: InterpError<'tcx>, backtrace: InterpErrorBacktrace) -> Self {
-        Self(Box::new(InterpErrorInfoInner { kind, backtrace }))
-    }
-
     pub fn into_parts(self) -> (InterpError<'tcx>, InterpErrorBacktrace) {
         let InterpErrorInfo(box InterpErrorInfoInner { kind, backtrace }) = self;
         (kind, backtrace)
@@ -226,13 +222,13 @@ impl IntoDiagnosticArg for InvalidMetaKind {
     }
 }
 
-/// Details of an access to uninitialized bytes where it is not allowed.
+/// Details of an access to uninitialized bytes / bad pointer bytes where it is not allowed.
 #[derive(Debug, Clone, Copy)]
-pub struct UninitBytesAccess {
+pub struct BadBytesAccess {
     /// Range of the original memory access.
     pub access: AllocRange,
-    /// Range of the uninit memory that was encountered. (Might not be maximal.)
-    pub uninit: AllocRange,
+    /// Range of the bad memory that was encountered. (Might not be maximal.)
+    pub bad: AllocRange,
 }
 
 /// Information about a size mismatch.
@@ -316,7 +312,7 @@ pub enum UndefinedBehaviorInfo<'a> {
     /// Using a string that is not valid UTF-8,
     InvalidStr(std::str::Utf8Error),
     /// Using uninitialized data where it is not allowed.
-    InvalidUninitBytes(Option<(AllocId, UninitBytesAccess)>),
+    InvalidUninitBytes(Option<(AllocId, BadBytesAccess)>),
     /// Working with a local that is not currently live.
     DeadLocal,
     /// Data size is not equal to target size.
@@ -326,7 +322,7 @@ pub enum UndefinedBehaviorInfo<'a> {
     /// An uninhabited enum variant is projected.
     UninhabitedEnumVariantRead(VariantIdx),
     /// Validation error.
-    Validation(ValidationErrorInfo<'a>),
+    ValidationError(ValidationErrorInfo<'a>),
     // FIXME(fee1-dead) these should all be actual variants of the enum instead of dynamically
     // dispatched
     /// A custom (free-form) error, created by `err_ub_custom!`.
@@ -368,6 +364,8 @@ pub enum ExpectedKind {
     Float,
     Int,
     FnPtr,
+    EnumTag,
+    Str,
 }
 
 impl From<PointerKind> for ExpectedKind {
@@ -381,10 +379,11 @@ impl From<PointerKind> for ExpectedKind {
 
 #[derive(Debug)]
 pub enum ValidationErrorKind<'tcx> {
+    PointerAsInt { expected: ExpectedKind },
+    PartialPointer,
     PtrToUninhabited { ptr_kind: PointerKind, ty: Ty<'tcx> },
     PtrToStatic { ptr_kind: PointerKind },
     PtrToMut { ptr_kind: PointerKind },
-    ExpectedNonPtr { value: String },
     MutableRefInConst,
     NullFnPtr,
     NeverVal,
@@ -394,11 +393,8 @@ pub enum ValidationErrorKind<'tcx> {
     UnsafeCell,
     UninhabitedVal { ty: Ty<'tcx> },
     InvalidEnumTag { value: String },
-    UninhabitedEnumTag,
-    UninitEnumTag,
-    UninitStr,
+    UninhabitedEnumVariant,
     Uninit { expected: ExpectedKind },
-    UninitVal,
     InvalidVTablePtr { value: String },
     InvalidMetaSliceTooLarge { ptr_kind: PointerKind },
     InvalidMetaTooLarge { ptr_kind: PointerKind },
@@ -426,12 +422,12 @@ pub enum UnsupportedOpInfo {
     //
     /// Overwriting parts of a pointer; without knowing absolute addresses, the resulting state
     /// cannot be represented by the CTFE interpreter.
-    PartialPointerOverwrite(Pointer<AllocId>),
-    /// Attempting to `copy` parts of a pointer to somewhere else; without knowing absolute
+    OverwritePartialPointer(Pointer<AllocId>),
+    /// Attempting to read or copy parts of a pointer to somewhere else; without knowing absolute
     /// addresses, the resulting state cannot be represented by the CTFE interpreter.
-    PartialPointerCopy(Pointer<AllocId>),
-    /// Encountered a pointer where we needed raw bytes.
-    ReadPointerAsBytes,
+    ReadPartialPointer(Pointer<AllocId>),
+    /// Encountered a pointer where we needed an integer.
+    ReadPointerAsInt(Option<(AllocId, BadBytesAccess)>),
     /// Accessing thread local statics
     ThreadLocalStatic(DefId),
     /// Accessing an unsupported extern static.
@@ -497,7 +493,7 @@ impl InterpError<'_> {
         matches!(
             self,
             InterpError::Unsupported(UnsupportedOpInfo::Unsupported(_))
-                | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::Validation { .. })
+                | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::ValidationError { .. })
                 | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::Ub(_))
         )
     }
diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs
index b35ba9503db..3543158bf82 100644
--- a/compiler/rustc_middle/src/mir/interpret/mod.rs
+++ b/compiler/rustc_middle/src/mir/interpret/mod.rs
@@ -142,11 +142,11 @@ use crate::ty::GenericArgKind;
 use crate::ty::{self, Instance, Ty, TyCtxt};
 
 pub use self::error::{
-    struct_error, CheckInAllocMsg, ErrorHandled, EvalToAllocationRawResult, EvalToConstValueResult,
-    EvalToValTreeResult, ExpectedKind, InterpError, InterpErrorInfo, InterpResult, InvalidMetaKind,
-    InvalidProgramInfo, MachineStopType, PointerKind, ReportedErrorInfo, ResourceExhaustionInfo,
-    ScalarSizeMismatch, UndefinedBehaviorInfo, UninitBytesAccess, UnsupportedOpInfo,
-    ValidationErrorInfo, ValidationErrorKind,
+    struct_error, BadBytesAccess, CheckInAllocMsg, ErrorHandled, EvalToAllocationRawResult,
+    EvalToConstValueResult, EvalToValTreeResult, ExpectedKind, InterpError, InterpErrorInfo,
+    InterpResult, InvalidMetaKind, InvalidProgramInfo, MachineStopType, PointerKind,
+    ReportedErrorInfo, ResourceExhaustionInfo, ScalarSizeMismatch, UndefinedBehaviorInfo,
+    UnsupportedOpInfo, ValidationErrorInfo, ValidationErrorKind,
 };
 
 pub use self::value::{get_slice_bytes, ConstAlloc, ConstValue, Scalar};
diff --git a/compiler/rustc_middle/src/mir/interpret/value.rs b/compiler/rustc_middle/src/mir/interpret/value.rs
index 20861d5ffa4..5345a658803 100644
--- a/compiler/rustc_middle/src/mir/interpret/value.rs
+++ b/compiler/rustc_middle/src/mir/interpret/value.rs
@@ -378,15 +378,16 @@ impl<'tcx, Prov: Provenance> Scalar<Prov> {
     #[inline]
     pub fn to_bits(self, target_size: Size) -> InterpResult<'tcx, u128> {
         assert_ne!(target_size.bytes(), 0, "you should never look at the bits of a ZST");
-        self.try_to_int().map_err(|_| err_unsup!(ReadPointerAsBytes))?.to_bits(target_size).map_err(
-            |size| {
+        self.try_to_int()
+            .map_err(|_| err_unsup!(ReadPointerAsInt(None)))?
+            .to_bits(target_size)
+            .map_err(|size| {
                 err_ub!(ScalarSizeMismatch(ScalarSizeMismatch {
                     target_size: target_size.bytes(),
                     data_size: size.bytes(),
                 }))
                 .into()
-            },
-        )
+            })
     }
 
     #[inline(always)]