Readjust const qualification to detect statics again

Author: spastorino

src/librustc/mir/mod.rs

@@ -7,7 +7,7 @@
 use crate::hir::def::{CtorKind, Namespace};
 use crate::hir::def_id::DefId;
 use crate::hir;
-use crate::mir::interpret::{PanicInfo, Scalar};
+use crate::mir::interpret::{ConstValue, GlobalAlloc, PanicInfo, Scalar};
 use crate::mir::visit::MirVisitable;
 use crate::ty::adjustment::PointerCast;
 use crate::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
@@ -2341,6 +2341,24 @@ pub struct Constant<'tcx> {
     pub literal: &'tcx ty::Const<'tcx>,
 }
 
+impl Constant<'tcx> {
+    pub fn check_static_ptr(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
+        match self.literal.val {
+            ConstValue::Scalar(Scalar::Ptr(ptr)) => match tcx.alloc_map.lock().get(ptr.alloc_id) {
+                Some(GlobalAlloc::Static(def_id)) => Some(def_id),
+                Some(_) => None,
+                None => {
+                    tcx.sess.delay_span_bug(
+                        DUMMY_SP, "MIR cannot contain dangling const pointers",
+                    );
+                    None
+                },
+            },
+            _ => None,
+        }
+    }
+}
+
 /// A collection of projections into user types.
 ///
 /// They are projections because a binding can occur a part of a

src/librustc_mir/transform/check_consts/qualifs.rs

@@ -2,6 +2,7 @@
 
 use rustc::mir::*;
 use rustc::ty::{self, Ty};
+use rustc::hir::def_id::DefId;
 use syntax_pos::DUMMY_SP;
 
 use super::{ConstKind, Item as ConstCx};
@@ -32,7 +33,7 @@ pub trait Qualif {
     /// of the type.
     fn in_any_value_of_ty(_cx: &ConstCx<'_, 'tcx>, _ty: Ty<'tcx>) -> bool;
 
-    fn in_static(_cx: &ConstCx<'_, 'tcx>, _static: &Static<'tcx>) -> bool {
+    fn in_static(_cx: &ConstCx<'_, 'tcx>, _def_id: DefId) -> bool {
         // FIXME(eddyb) should we do anything here for value properties?
         false
     }
@@ -86,18 +87,9 @@ pub trait Qualif {
                 projection: [],
             } => per_local(*local),
             PlaceRef {
-                base: PlaceBase::Static(box Static {
-                    kind: StaticKind::Promoted(..),
-                    ..
-                }),
+                base: PlaceBase::Static(_),
                 projection: [],
             } => bug!("qualifying already promoted MIR"),
-            PlaceRef {
-                base: PlaceBase::Static(static_),
-                projection: [],
-            } => {
-                Self::in_static(cx, static_)
-            },
             PlaceRef {
                 base: _,
                 projection: [.., _],
@@ -115,7 +107,9 @@ pub trait Qualif {
             Operand::Move(ref place) => Self::in_place(cx, per_local, place.as_ref()),
 
             Operand::Constant(ref constant) => {
-                if let ty::ConstKind::Unevaluated(def_id, _) = constant.literal.val {
+                if let Some(static_) = constant.check_static_ptr(cx.tcx) {
+                    Self::in_static(cx, static_)
+                } else if let ty::ConstKind::Unevaluated(def_id, _) = constant.literal.val {
                     // Don't peek inside trait associated constants.
                     if cx.tcx.trait_of_item(def_id).is_some() {
                         Self::in_any_value_of_ty(cx, constant.literal.ty)

src/librustc_mir/transform/check_consts/validation.rs

@@ -408,12 +408,21 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
 
         match place_base {
             PlaceBase::Local(_) => {}
-            PlaceBase::Static(box Static{ kind: StaticKind::Promoted(_, _), .. }) => {
+            PlaceBase::Static(_) => {
                 bug!("Promotion must be run after const validation");
             }
+        }
+    }
 
-            PlaceBase::Static(box Static{ kind: StaticKind::Static, def_id, .. }) => {
-                let is_thread_local = self.tcx.has_attr(*def_id, sym::thread_local);
+    fn visit_operand(
+        &mut self,
+        op: &Operand<'tcx>,
+        location: Location,
+    ) {
+        self.super_operand(op, location);
+        if let Operand::Constant(c) = op {
+            if let Some(def_id) = c.check_static_ptr(self.tcx) {
+                let is_thread_local = self.tcx.has_attr(def_id, sym::thread_local);
                 if is_thread_local {
                     self.check_op(ops::ThreadLocalAccess);
                 } else if self.const_kind() != ConstKind::Static || !context.is_mutating_use() {

src/librustc_mir/transform/qualify_min_const_fn.rs

@@ -249,7 +249,10 @@ fn check_operand(
         Operand::Move(place) | Operand::Copy(place) => {
             check_place(tcx, place, span, def_id, body)
         }
-        Operand::Constant(_) => Ok(()),
+        Operand::Constant(c) => match c.check_static_ptr(tcx) {
+            Some(_) => Err((span, "cannot access `static` items in const fn".into())),
+            None => Ok(()),
+        },
     }
 }
 
@@ -285,13 +288,7 @@ fn check_place(
         }
     }
 
-    match place.base {
-        PlaceBase::Static(box Static { kind: StaticKind::Static, .. }) => {
-            Err((span, "cannot access `static` items in const fn".into()))
-        }
-        PlaceBase::Local(_)
-        | PlaceBase::Static(box Static { kind: StaticKind::Promoted(_, _), .. }) => Ok(()),
-    }
+    Ok(())
 }
 
 /// Returns whether `allow_internal_unstable(..., <feature_gate>, ...)` is present.

src/test/ui/consts/const-fn-not-safe-for-const.stderr

@@ -11,10 +11,10 @@ LL |     Y
    |     ^
 
 error[E0013]: constant functions cannot refer to statics, use a constant instead
-  --> $DIR/const-fn-not-safe-for-const.rs:25:5
+  --> $DIR/const-fn-not-safe-for-const.rs:25:6
    |
 LL |     &Y
-   |     ^^
+   |      ^
 
 error: aborting due to 3 previous errors
 

src/test/ui/consts/min_const_fn/min_const_fn.stderr

@@ -116,10 +116,10 @@ LL | const fn foo25() -> u32 { BAR }
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: cannot access `static` items in const fn
-  --> $DIR/min_const_fn.rs:91:36
+  --> $DIR/min_const_fn.rs:91:37
    |
 LL | const fn foo26() -> &'static u32 { &BAR }
-   |                                    ^^^^
+   |                                     ^^^
    |
    = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563
    = help: add `#![feature(const_fn)]` to the crate attributes to enable