Add Constness::Comptime

Author: oli-obk

compiler/rustc_hir/src/hir.rs

@@ -4238,11 +4238,13 @@ pub enum Constness {
     #[default]
     Const,
     NotConst,
+    Comptime,
 }
 
 impl fmt::Display for Constness {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str(match *self {
+            Self::Comptime => "comptime",
             Self::Const => "const",
             Self::NotConst => "non-const",
         })

compiler/rustc_hir_pretty/src/lib.rs

@@ -2571,6 +2571,7 @@ impl<'a> State<'a> {
         match s {
             hir::Constness::NotConst => {}
             hir::Constness::Const => self.word_nbsp("const"),
+            hir::Constness::Comptime => { /* printed as an attribute */ }
         }
     }
 

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1524,7 +1524,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             }
             if should_encode_constness(def_kind) {
                 let constness = self.tcx.constness(def_id);
-                self.tables.constness.set(def_id.index, constness);
+                self.tables.constness.set(def_id.index, constness)
             }
             if let DefKind::Fn | DefKind::AssocFn = def_kind {
                 let asyncness = tcx.asyncness(def_id);

compiler/rustc_metadata/src/rmeta/table.rs

@@ -234,6 +234,7 @@ defaulted_enum! {
     hir::Constness {
         ( Const    )
         ( NotConst )
+        ( Comptime )
     }
 }
 

compiler/rustc_middle/src/ty/adt.rs

@@ -247,6 +247,7 @@ impl<'tcx> rustc_type_ir::inherent::AdtDef<TyCtxt<'tcx>> for AdtDef<'tcx> {
 
     fn destructor(self, tcx: TyCtxt<'tcx>) -> Option<AdtDestructorKind> {
         Some(match tcx.constness(self.destructor(tcx)?.did) {
+            hir::Constness::Comptime => todo!("FIXME(comptime)"),
             hir::Constness::Const => AdtDestructorKind::Const,
             hir::Constness::NotConst => AdtDestructorKind::NotConst,
         })

compiler/rustc_passes/src/check_attr.rs

@@ -535,7 +535,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         if matches!(target, Target::Impl { of_trait: true }) {
             match item.unwrap() {
                 ItemLike::Item(it) => match it.expect_impl().constness {
-                    Constness::Const => {}
+                    Constness::Const | Constness::Comptime => {}
                     Constness::NotConst => return,
                 },
                 ItemLike::ForeignItem => {}

compiler/rustc_trait_selection/src/traits/effects.rs

@@ -435,6 +435,7 @@ fn evaluate_host_effect_for_destruct_goal<'tcx>(
                 .map(|field| ty::TraitRef::new(tcx, destruct_def_id, [field.ty(tcx, args)]))
                 .collect();
             match adt_def.destructor(tcx).map(|dtor| tcx.constness(dtor.did)) {
+                Some(hir::Constness::Comptime) => todo!("FIXME(comptime)"),
                 // `Drop` impl exists, but it's not const. Type cannot be `[const] Destruct`.
                 Some(hir::Constness::NotConst) => return Err(EvaluationFailure::NoSolution),
                 // `Drop` impl exists, and it's const. Require `Ty: [const] Drop` to hold.
@@ -530,6 +531,8 @@ fn evaluate_host_effect_for_fn_goal<'tcx>(
     };
 
     match tcx.constness(def) {
+        // FIXME(comptime)
+        hir::Constness::Comptime => Err(EvaluationFailure::NoSolution),
         hir::Constness::Const => Ok(tcx
             .const_conditions(def)
             .instantiate(tcx, args)

src/librustdoc/html/format.rs

@@ -1479,14 +1479,18 @@ pub(crate) fn print_constness_with_space(
     const_stab: Option<ConstStability>,
 ) -> &'static str {
     match c {
-        hir::Constness::Const => match (overall_stab, const_stab) {
+        hir::Constness::Comptime | hir::Constness::Const => match (overall_stab, const_stab) {
             // const stable...
             (_, Some(ConstStability { level: StabilityLevel::Stable { .. }, .. }))
             // ...or when feature(staged_api) is not set...
             | (_, None)
             // ...or when const unstable, but overall unstable too
             | (None, Some(ConstStability { level: StabilityLevel::Unstable { .. }, .. })) => {
-                "const "
+                match c {
+                    hir::Constness::Comptime => "",
+                    hir::Constness::Const => "const ",
+                    _ => unreachable!(),
+                }
             }
             // const unstable (and overall stable)
             (Some(_), Some(ConstStability { level: StabilityLevel::Unstable { .. }, .. })) => "",