Auto merge of #95826 - carbotaniuman:miri-permissive-provenance, r=RalfJung

Initial work on Miri permissive-exposed-provenance

Rustc portion of the changes for portions of a permissive ptr-to-int model for Miri. The main changes here are changing `ptr_get_alloc` and `get_alloc_id` to return an Option, and also making ptr-to-int casts have an expose side effect.

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -18,7 +18,7 @@ use rustc_target::spec::abi::Abi;
 
 use crate::interpret::{
     self, compile_time_machine, AllocId, ConstAllocation, Frame, ImmTy, InterpCx, InterpResult,
-    OpTy, PlaceTy, Scalar, StackPopUnwind,
+    OpTy, PlaceTy, Pointer, Scalar, StackPopUnwind,
 };
 
 use super::error::*;
@@ -443,6 +443,14 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
         Ok(())
     }
 
+    #[inline(always)]
+    fn expose_ptr(
+        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
+        _ptr: Pointer<AllocId>,
+    ) -> InterpResult<'tcx> {
+        Err(ConstEvalErrKind::NeedsRfc("exposing pointers".to_string()).into())
+    }
+
     #[inline(always)]
     fn init_frame_extra(
         ecx: &mut InterpCx<'mir, 'tcx, Self>,