Add enum for can_access_statics boolean

`/*can_access_statics:*/ false` is one of the ways to do this, but not
the one I like.

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -14,7 +14,7 @@ use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::source_map::Span;
 use rustc_target::abi::{self, Abi};
 
-use super::{CompileTimeEvalContext, CompileTimeInterpreter};
+use super::{CanAccessStatics, CompileTimeEvalContext, CompileTimeInterpreter};
 use crate::errors;
 use crate::interpret::eval_nullary_intrinsic;
 use crate::interpret::{
@@ -93,7 +93,7 @@ pub(super) fn mk_eval_cx<'mir, 'tcx>(
     tcx: TyCtxt<'tcx>,
     root_span: Span,
     param_env: ty::ParamEnv<'tcx>,
-    can_access_statics: bool,
+    can_access_statics: CanAccessStatics,
 ) -> CompileTimeEvalContext<'mir, 'tcx> {
     debug!("mk_eval_cx: {:?}", param_env);
     InterpCx::new(
@@ -207,7 +207,7 @@ pub(crate) fn turn_into_const_value<'tcx>(
         tcx,
         tcx.def_span(key.value.instance.def_id()),
         key.param_env,
-        /*can_access_statics:*/ is_static,
+        CanAccessStatics::from(is_static),
     );
 
     let mplace = ecx.raw_const_to_mplace(constant).expect(
@@ -309,7 +309,7 @@ pub fn eval_to_allocation_raw_provider<'tcx>(
         // Statics (and promoteds inside statics) may access other statics, because unlike consts
         // they do not have to behave "as if" they were evaluated at runtime.
         CompileTimeInterpreter::new(
-            /*can_access_statics:*/ is_static,
+            CanAccessStatics::from(is_static),
             if tcx.sess.opts.unstable_opts.extra_const_ub_checks {
                 CheckAlignment::Error
             } else {

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -57,7 +57,7 @@ pub struct CompileTimeInterpreter<'mir, 'tcx> {
     /// * Interning makes everything outside of statics immutable.
     /// * Pointers to allocations inside of statics can never leak outside, to a non-static global.
     /// This boolean here controls the second part.
-    pub(super) can_access_statics: bool,
+    pub(super) can_access_statics: CanAccessStatics,
 
     /// Whether to check alignment during evaluation.
     pub(super) check_alignment: CheckAlignment,
@@ -83,8 +83,23 @@ impl CheckAlignment {
     }
 }
 
+#[derive(Copy, Clone, PartialEq)]
+pub(crate) enum CanAccessStatics {
+    No,
+    Yes,
+}
+
+impl From<bool> for CanAccessStatics {
+    fn from(value: bool) -> Self {
+        if value { Self::Yes } else { Self::No }
+    }
+}
+
 impl<'mir, 'tcx> CompileTimeInterpreter<'mir, 'tcx> {
-    pub(crate) fn new(can_access_statics: bool, check_alignment: CheckAlignment) -> Self {
+    pub(crate) fn new(
+        can_access_statics: CanAccessStatics,
+        check_alignment: CheckAlignment,
+    ) -> Self {
         CompileTimeInterpreter {
             num_evaluated_steps: 0,
             stack: Vec::new(),
@@ -699,7 +714,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
             }
         } else {
             // Read access. These are usually allowed, with some exceptions.
-            if machine.can_access_statics {
+            if machine.can_access_statics == CanAccessStatics::Yes {
                 // Machine configuration allows us read from anything (e.g., `static` initializer).
                 Ok(())
             } else if static_def_id.is_some() {

compiler/rustc_const_eval/src/const_eval/mod.rs

@@ -26,7 +26,7 @@ pub(crate) fn const_caller_location(
     (file, line, col): (Symbol, u32, u32),
 ) -> ConstValue<'_> {
     trace!("const_caller_location: {}:{}:{}", file, line, col);
-    let mut ecx = mk_eval_cx(tcx, DUMMY_SP, ty::ParamEnv::reveal_all(), false);
+    let mut ecx = mk_eval_cx(tcx, DUMMY_SP, ty::ParamEnv::reveal_all(), CanAccessStatics::No);
 
     let loc_place = ecx.alloc_caller_location(file, line, col);
     if intern_const_alloc_recursive(&mut ecx, InternKind::Constant, &loc_place).is_err() {
@@ -55,10 +55,12 @@ pub(crate) fn eval_to_valtree<'tcx>(
 
     // FIXME Need to provide a span to `eval_to_valtree`
     let ecx = mk_eval_cx(
-        tcx, DUMMY_SP, param_env,
+        tcx,
+        DUMMY_SP,
+        param_env,
         // It is absolutely crucial for soundness that
         // we do not read from static items or other mutable memory.
-        false,
+        CanAccessStatics::No,
     );
     let place = ecx.raw_const_to_mplace(const_alloc).unwrap();
     debug!(?place);
@@ -91,7 +93,7 @@ pub(crate) fn try_destructure_mir_constant<'tcx>(
     val: mir::ConstantKind<'tcx>,
 ) -> InterpResult<'tcx, mir::DestructuredConstant<'tcx>> {
     trace!("destructure_mir_constant: {:?}", val);
-    let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, false);
+    let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, CanAccessStatics::No);
     let op = ecx.eval_mir_constant(&val, None, None)?;
 
     // We go to `usize` as we cannot allocate anything bigger anyway.

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -1,6 +1,7 @@
 use super::eval_queries::{mk_eval_cx, op_to_const};
 use super::machine::CompileTimeEvalContext;
 use super::{ValTreeCreationError, ValTreeCreationResult, VALTREE_MAX_NODES};
+use crate::const_eval::CanAccessStatics;
 use crate::interpret::{
     intern_const_alloc_recursive, ConstValue, ImmTy, Immediate, InternKind, MemPlaceMeta,
     MemoryKind, PlaceTy, Scalar,
@@ -263,7 +264,11 @@ pub fn valtree_to_const_value<'tcx>(
     // FIXME Does this need an example?
 
     let (param_env, ty) = param_env_ty.into_parts();
-    let mut ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, false);
+    let mut ecx: crate::interpret::InterpCx<
+        '_,
+        '_,
+        crate::const_eval::CompileTimeInterpreter<'_, '_>,
+    > = mk_eval_cx(tcx, DUMMY_SP, param_env, CanAccessStatics::No);
 
     match ty.kind() {
         ty::FnDef(..) => {

compiler/rustc_const_eval/src/util/check_validity_requirement.rs

@@ -2,7 +2,7 @@ use rustc_middle::ty::layout::{LayoutCx, LayoutError, LayoutOf, TyAndLayout, Val
 use rustc_middle::ty::{ParamEnv, ParamEnvAnd, Ty, TyCtxt};
 use rustc_target::abi::{Abi, FieldsShape, Scalar, Variants};
 
-use crate::const_eval::{CheckAlignment, CompileTimeInterpreter};
+use crate::const_eval::{CanAccessStatics, CheckAlignment, CompileTimeInterpreter};
 use crate::interpret::{InterpCx, MemoryKind, OpTy};
 
 /// Determines if this type permits "raw" initialization by just transmuting some memory into an
@@ -44,8 +44,7 @@ fn might_permit_raw_init_strict<'tcx>(
     tcx: TyCtxt<'tcx>,
     kind: ValidityRequirement,
 ) -> Result<bool, LayoutError<'tcx>> {
-    let machine =
-        CompileTimeInterpreter::new(/*can_access_statics:*/ false, CheckAlignment::Error);
+    let machine = CompileTimeInterpreter::new(CanAccessStatics::No, CheckAlignment::Error);
 
     let mut cx = InterpCx::new(tcx, rustc_span::DUMMY_SP, ParamEnv::reveal_all(), machine);