Allow unsafe through inline const

compiler/rustc_mir_build/src/build/custom/mod.rs

@@ -20,6 +20,7 @@
 use rustc_ast::Attribute;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::DefId;
+use rustc_hir::HirId;
 use rustc_index::vec::IndexVec;
 use rustc_middle::{
     mir::*,
@@ -33,6 +34,7 @@ mod parse;
 pub(super) fn build_custom_mir<'tcx>(
     tcx: TyCtxt<'tcx>,
     did: DefId,
+    hir_id: HirId,
     thir: &Thir<'tcx>,
     expr: ExprId,
     params: &IndexVec<ParamId, Param<'tcx>>,
@@ -67,7 +69,10 @@ pub(super) fn build_custom_mir<'tcx>(
         parent_scope: None,
         inlined: None,
         inlined_parent_scope: None,
-        local_data: ClearCrossCrate::Clear,
+        local_data: ClearCrossCrate::Set(SourceScopeLocalData {
+            lint_root: hir_id,
+            safety: Safety::Safe,
+        }),
     });
     body.injection_phase = Some(parse_attribute(attr));
 

compiler/rustc_mir_build/src/build/mod.rs

@@ -487,6 +487,7 @@ fn construct_fn<'tcx>(
         return custom::build_custom_mir(
             tcx,
             fn_def.did.to_def_id(),
+            fn_id,
             thir,
             expr,
             arguments,

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -132,6 +132,18 @@ impl<'tcx> UnsafetyVisitor<'_, 'tcx> {
     fn unsafe_op_in_unsafe_fn_allowed(&self) -> bool {
         self.tcx.lint_level_at_node(UNSAFE_OP_IN_UNSAFE_FN, self.hir_context).0 == Level::Allow
     }
+
+    /// Handle closures/generators/inline-consts, which is unsafecked with their parent body.
+    fn visit_inner_body(&mut self, def: ty::WithOptConstParam<LocalDefId>) {
+        if let Ok((inner_thir, expr)) = self.tcx.thir_body(def) {
+            let inner_thir = &inner_thir.borrow();
+            let hir_context = self.tcx.hir().local_def_id_to_hir_id(def.did);
+            let mut inner_visitor = UnsafetyVisitor { thir: inner_thir, hir_context, ..*self };
+            inner_visitor.visit_expr(&inner_thir[expr]);
+            // Unsafe blocks can be used in the inner body, make sure to take it into account
+            self.safety_context = inner_visitor.safety_context;
+        }
+    }
 }
 
 // Searches for accesses to layout constrained fields.
@@ -408,16 +420,11 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                 } else {
                     ty::WithOptConstParam::unknown(closure_id)
                 };
-                let (closure_thir, expr) = self.tcx.thir_body(closure_def).unwrap_or_else(|_| {
-                    (self.tcx.alloc_steal_thir(Thir::new()), ExprId::from_u32(0))
-                });
-                let closure_thir = &closure_thir.borrow();
-                let hir_context = self.tcx.hir().local_def_id_to_hir_id(closure_id);
-                let mut closure_visitor =
-                    UnsafetyVisitor { thir: closure_thir, hir_context, ..*self };
-                closure_visitor.visit_expr(&closure_thir[expr]);
-                // Unsafe blocks can be used in closures, make sure to take it into account
-                self.safety_context = closure_visitor.safety_context;
+                self.visit_inner_body(closure_def);
+            }
+            ExprKind::ConstBlock { did, substs: _ } => {
+                let def_id = did.expect_local();
+                self.visit_inner_body(ty::WithOptConstParam::unknown(def_id));
             }
             ExprKind::Field { lhs, .. } => {
                 let lhs = &self.thir[lhs];
@@ -612,11 +619,8 @@ pub fn check_unsafety<'tcx>(tcx: TyCtxt<'tcx>, def: ty::WithOptConstParam<LocalD
         return;
     }
 
-    // Closures are handled by their owner, if it has a body
-    if tcx.is_closure(def.did.to_def_id()) {
-        let hir = tcx.hir();
-        let owner = hir.enclosing_body_owner(hir.local_def_id_to_hir_id(def.did));
-        tcx.ensure().thir_check_unsafety(owner);
+    // Closures and inline consts are handled by their owner, if it has a body
+    if tcx.is_typeck_child(def.did.to_def_id()) {
         return;
     }
 

compiler/rustc_mir_transform/src/check_unsafety.rs

@@ -1,6 +1,7 @@
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
+use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::hir_id::HirId;
 use rustc_hir::intravisit;
@@ -134,6 +135,28 @@ impl<'tcx> Visitor<'tcx> for UnsafetyChecker<'_, 'tcx> {
         self.super_rvalue(rvalue, location);
     }
 
+    fn visit_operand(&mut self, op: &Operand<'tcx>, location: Location) {
+        if let Operand::Constant(constant) = op {
+            let maybe_uneval = match constant.literal {
+                ConstantKind::Val(..) | ConstantKind::Ty(_) => None,
+                ConstantKind::Unevaluated(uv, _) => Some(uv),
+            };
+
+            if let Some(uv) = maybe_uneval {
+                if uv.promoted.is_none() {
+                    let def_id = uv.def.def_id_for_type_of();
+                    if self.tcx.def_kind(def_id) == DefKind::InlineConst {
+                        let local_def_id = def_id.expect_local();
+                        let UnsafetyCheckResult { violations, used_unsafe_blocks, .. } =
+                            self.tcx.unsafety_check_result(local_def_id);
+                        self.register_violations(violations, used_unsafe_blocks.iter().copied());
+                    }
+                }
+            }
+        }
+        self.super_operand(op, location);
+    }
+
     fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
         // On types with `scalar_valid_range`, prevent
         // * `&mut x.field`
@@ -410,6 +433,12 @@ impl<'tcx> intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'_, 'tcx> {
         intravisit::walk_block(self, block);
     }
 
+    fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
+        if matches!(self.tcx.def_kind(c.def_id), DefKind::InlineConst) {
+            self.visit_body(self.tcx.hir().body(c.body))
+        }
+    }
+
     fn visit_fn(
         &mut self,
         fk: intravisit::FnKind<'tcx>,
@@ -484,7 +513,7 @@ fn unsafety_check_result<'tcx>(
     let mut checker = UnsafetyChecker::new(body, def.did, tcx, param_env);
     checker.visit_body(&body);
 
-    let unused_unsafes = (!tcx.is_closure(def.did.to_def_id()))
+    let unused_unsafes = (!tcx.is_typeck_child(def.did.to_def_id()))
         .then(|| check_unused_unsafe(tcx, def.did, &checker.used_unsafe_blocks));
 
     tcx.arena.alloc(UnsafetyCheckResult {
@@ -516,8 +545,8 @@ fn report_unused_unsafe(tcx: TyCtxt<'_>, kind: UnusedUnsafe, id: HirId) {
 pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     debug!("check_unsafety({:?})", def_id);
 
-    // closures are handled by their parent fn.
-    if tcx.is_closure(def_id.to_def_id()) {
+    // closures and inline consts are handled by their parent fn.
+    if tcx.is_typeck_child(def_id.to_def_id()) {
         return;
     }
 

src/test/ui/inline-const/expr-unsafe-err.mir.stderr

@@ -0,0 +1,11 @@
+error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
+  --> $DIR/expr-unsafe-err.rs:8:9
+   |
+LL |         require_unsafe();
+   |         ^^^^^^^^^^^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0133`.

src/test/ui/inline-const/expr-unsafe-err.rs

@@ -0,0 +1,11 @@
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+#![feature(inline_const)]
+const unsafe fn require_unsafe() -> usize { 1 }
+
+fn main() {
+    const {
+        require_unsafe();
+        //~^ ERROR [E0133]
+    }
+}

src/test/ui/inline-const/expr-unsafe-err.thir.stderr

@@ -0,0 +1,11 @@
+error[E0133]: call to unsafe function `require_unsafe` is unsafe and requires unsafe function or block
+  --> $DIR/expr-unsafe-err.rs:8:9
+   |
+LL |         require_unsafe();
+   |         ^^^^^^^^^^^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0133`.

src/test/ui/inline-const/expr-unsafe.mir.stderr

@@ -0,0 +1,14 @@
+warning: unnecessary `unsafe` block
+  --> $DIR/expr-unsafe.rs:12:13
+   |
+LL |             unsafe {}
+   |             ^^^^^^ unnecessary `unsafe` block
+   |
+note: the lint level is defined here
+  --> $DIR/expr-unsafe.rs:4:9
+   |
+LL | #![warn(unused_unsafe)]
+   |         ^^^^^^^^^^^^^
+
+warning: 1 warning emitted
+

src/test/ui/inline-const/expr-unsafe.rs

@@ -0,0 +1,16 @@
+// check-pass
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+#![warn(unused_unsafe)]
+#![feature(inline_const)]
+const unsafe fn require_unsafe() -> usize { 1 }
+
+fn main() {
+    unsafe {
+        const {
+            require_unsafe();
+            unsafe {}
+            //~^ WARNING unnecessary `unsafe` block
+        }
+    }
+}

src/test/ui/inline-const/expr-unsafe.thir.stderr

@@ -0,0 +1,17 @@
+warning: unnecessary `unsafe` block
+  --> $DIR/expr-unsafe.rs:12:13
+   |
+LL |     unsafe {
+   |     ------ because it's nested under this `unsafe` block
+...
+LL |             unsafe {}
+   |             ^^^^^^ unnecessary `unsafe` block
+   |
+note: the lint level is defined here
+  --> $DIR/expr-unsafe.rs:4:9
+   |
+LL | #![warn(unused_unsafe)]
+   |         ^^^^^^^^^^^^^
+
+warning: 1 warning emitted
+

src/test/ui/inline-const/pat-unsafe-err.rs

@@ -0,0 +1,17 @@
+// ignore-test This is currently broken
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+
+#![allow(incomplete_features)]
+#![feature(inline_const_pat)]
+
+const unsafe fn require_unsafe() -> usize { 1 }
+
+fn main() {
+    match () {
+        const {
+            require_unsafe();
+            //~^ ERROR [E0133]
+        } => (),
+    }
+}

src/test/ui/inline-const/pat-unsafe.rs

@@ -0,0 +1,22 @@
+// ignore-test This is currently broken
+// check-pass
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+
+#![allow(incomplete_features)]
+#![warn(unused_unsafe)]
+#![feature(inline_const_pat)]
+
+const unsafe fn require_unsafe() -> usize { 1 }
+
+fn main() {
+    unsafe {
+        match () {
+            const {
+                require_unsafe();
+                unsafe {}
+                //~^ WARNING unnecessary `unsafe` block
+            } => (),
+        }
+    }
+}