compile-time evaluation: emit a lint when a write through an immutable pointer occurs

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -9,8 +9,9 @@ use std::hash::Hash;
 use rustc_apfloat::{Float, FloatConvert};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_middle::mir;
+use rustc_middle::query::TyCtxtAt;
+use rustc_middle::ty;
 use rustc_middle::ty::layout::TyAndLayout;
-use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::def_id::DefId;
 use rustc_target::abi::{Align, Size};
 use rustc_target::spec::abi::Abi as CallAbi;
@@ -293,7 +294,7 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
     /// `def_id` is `Some` if this is the "lazy" allocation of a static.
     #[inline]
     fn before_access_global(
-        _tcx: TyCtxt<'tcx>,
+        _tcx: TyCtxtAt<'tcx>,
         _machine: &Self,
         _alloc_id: AllocId,
         _allocation: ConstAllocation<'tcx>,
@@ -388,7 +389,7 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
     /// need to mutate.
     #[inline(always)]
     fn before_memory_read(
-        _tcx: TyCtxt<'tcx>,
+        _tcx: TyCtxtAt<'tcx>,
         _machine: &Self,
         _alloc_extra: &Self::AllocExtra,
         _prov: (AllocId, Self::ProvenanceExtra),
@@ -400,7 +401,7 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
     /// Hook for performing extra checks on a memory write access.
     #[inline(always)]
     fn before_memory_write(
-        _tcx: TyCtxt<'tcx>,
+        _tcx: TyCtxtAt<'tcx>,
         _machine: &mut Self,
         _alloc_extra: &mut Self::AllocExtra,
         _prov: (AllocId, Self::ProvenanceExtra),
@@ -412,7 +413,7 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
     /// Hook for performing extra operations on a memory deallocation.
     #[inline(always)]
     fn before_memory_deallocation(
-        _tcx: TyCtxt<'tcx>,
+        _tcx: TyCtxtAt<'tcx>,
         _machine: &mut Self,
         _alloc_extra: &mut Self::AllocExtra,
         _prov: (AllocId, Self::ProvenanceExtra),
@@ -515,7 +516,7 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
 /// (CTFE and ConstProp) use the same instance. Here, we share that code.
 pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
     type Provenance = CtfeProvenance;
-    type ProvenanceExtra = (); // FIXME extract the "immutable" bool?
+    type ProvenanceExtra = bool; // the "immutable" flag
 
     type ExtraFnVal = !;
 
@@ -597,6 +598,6 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
     ) -> Option<(AllocId, Size, Self::ProvenanceExtra)> {
         // We know `offset` is relative to the allocation, so we can use `into_parts`.
         let (prov, offset) = ptr.into_parts();
-        Some((prov.alloc_id(), offset, ()))
+        Some((prov.alloc_id(), offset, prov.immutable()))
     }
 }

compiler/rustc_const_eval/src/interpret/memory.rs

@@ -339,7 +339,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // Let the machine take some extra action
         let size = alloc.size();
         M::before_memory_deallocation(
-            *self.tcx,
+            self.tcx,
             &mut self.machine,
             &mut alloc.extra,
             (alloc_id, prov),
@@ -561,7 +561,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 (val, Some(def_id))
             }
         };
-        M::before_access_global(*self.tcx, &self.machine, id, alloc, def_id, is_write)?;
+        M::before_access_global(self.tcx, &self.machine, id, alloc, def_id, is_write)?;
         // We got tcx memory. Let the machine initialize its "extra" stuff.
         M::adjust_allocation(
             self,
@@ -626,7 +626,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         )?;
         if let Some((alloc_id, offset, prov, alloc)) = ptr_and_alloc {
             let range = alloc_range(offset, size);
-            M::before_memory_read(*self.tcx, &self.machine, &alloc.extra, (alloc_id, prov), range)?;
+            M::before_memory_read(self.tcx, &self.machine, &alloc.extra, (alloc_id, prov), range)?;
             Ok(Some(AllocRef { alloc, range, tcx: *self.tcx, alloc_id }))
         } else {
             // Even in this branch we have to be sure that we actually access the allocation, in
@@ -687,13 +687,13 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     {
         let parts = self.get_ptr_access(ptr, size)?;
         if let Some((alloc_id, offset, prov)) = parts {
-            let tcx = *self.tcx;
+            let tcx = self.tcx;
             // FIXME: can we somehow avoid looking up the allocation twice here?
             // We cannot call `get_raw_mut` inside `check_and_deref_ptr` as that would duplicate `&mut self`.
             let (alloc, machine) = self.get_alloc_raw_mut(alloc_id)?;
             let range = alloc_range(offset, size);
             M::before_memory_write(tcx, machine, &mut alloc.extra, (alloc_id, prov), range)?;
-            Ok(Some(AllocRefMut { alloc, range, tcx, alloc_id }))
+            Ok(Some(AllocRefMut { alloc, range, tcx: *tcx, alloc_id }))
         } else {
             Ok(None)
         }
@@ -1133,7 +1133,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let src_alloc = self.get_alloc_raw(src_alloc_id)?;
         let src_range = alloc_range(src_offset, size);
         M::before_memory_read(
-            *tcx,
+            tcx,
             &self.machine,
             &src_alloc.extra,
             (src_alloc_id, src_prov),
@@ -1163,7 +1163,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let (dest_alloc, extra) = self.get_alloc_raw_mut(dest_alloc_id)?;
         let dest_range = alloc_range(dest_offset, size * num_copies);
         M::before_memory_write(
-            *tcx,
+            tcx,
             extra,
             &mut dest_alloc.extra,
             (dest_alloc_id, dest_prov),