Auto merge of #99798 - JulianKnodt:ac1, r=BoxyUwU

Add `ConstKind::Expr`

Starting to implement `ty::ConstKind::Abstract`, most of the match cases are stubbed out, some I was unsure what to add, others I didn't want to add until a more complete implementation was ready.

r? `@lcnr`

Author: bors

compiler/rustc_const_eval/src/interpret/operand.rs

@@ -561,6 +561,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             ty::ConstKind::Param(_) | ty::ConstKind::Placeholder(..) => {
                 throw_inval!(TooGeneric)
             }
+            // FIXME(generic_const_exprs): `ConstKind::Expr` should be able to be evaluated
+            ty::ConstKind::Expr(_) => throw_inval!(TooGeneric),
             ty::ConstKind::Error(reported) => {
                 throw_inval!(AlreadyReported(reported))
             }

compiler/rustc_infer/src/infer/freshen.rs

@@ -248,6 +248,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
             ty::ConstKind::Param(_)
             | ty::ConstKind::Value(_)
             | ty::ConstKind::Unevaluated(..)
+            | ty::ConstKind::Expr(..)
             | ty::ConstKind::Error(_) => ct.super_fold_with(self),
         }
     }

compiler/rustc_infer/src/infer/mod.rs

@@ -23,7 +23,6 @@ use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKin
 use rustc_middle::mir::interpret::{ErrorHandled, EvalToValTreeResult};
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::traits::select;
-use rustc_middle::ty::abstract_const::{AbstractConst, FailureKind};
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::fold::BoundVarReplacerDelegate;
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
@@ -713,32 +712,6 @@ impl<'tcx> InferCtxt<'tcx> {
         TypeErrCtxt { infcx: self, typeck_results: None, fallback_has_occurred: false }
     }
 
-    /// calls `tcx.try_unify_abstract_consts` after
-    /// canonicalizing the consts.
-    #[instrument(skip(self), level = "debug")]
-    pub fn try_unify_abstract_consts(
-        &self,
-        a: ty::UnevaluatedConst<'tcx>,
-        b: ty::UnevaluatedConst<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
-    ) -> bool {
-        // Reject any attempt to unify two unevaluated constants that contain inference
-        // variables, since inference variables in queries lead to ICEs.
-        if a.substs.has_non_region_infer()
-            || b.substs.has_non_region_infer()
-            || param_env.has_non_region_infer()
-        {
-            debug!("a or b or param_env contain infer vars in its substs -> cannot unify");
-            return false;
-        }
-
-        let param_env_and = param_env.and((a, b));
-        let erased = self.tcx.erase_regions(param_env_and);
-        debug!("after erase_regions: {:?}", erased);
-
-        self.tcx.try_unify_abstract_consts(erased)
-    }
-
     pub fn is_in_snapshot(&self) -> bool {
         self.in_snapshot.get()
     }
@@ -1646,34 +1619,33 @@ impl<'tcx> InferCtxt<'tcx> {
 
         // Postpone the evaluation of constants whose substs depend on inference
         // variables
+        let tcx = self.tcx;
         if substs.has_non_region_infer() {
-            let ac = AbstractConst::new(self.tcx, unevaluated);
-            match ac {
-                Ok(None) => {
-                    substs = InternalSubsts::identity_for_item(self.tcx, unevaluated.def.did);
-                    param_env = self.tcx.param_env(unevaluated.def.did);
-                }
-                Ok(Some(ct)) => {
-                    if ct.unify_failure_kind(self.tcx) == FailureKind::Concrete {
-                        substs = replace_param_and_infer_substs_with_placeholder(self.tcx, substs);
-                    } else {
-                        return Err(ErrorHandled::TooGeneric);
-                    }
+            if let Some(ct) = tcx.bound_abstract_const(unevaluated.def)? {
+                let ct = tcx.expand_abstract_consts(ct.subst(tcx, substs));
+                if let Err(e) = ct.error_reported() {
+                    return Err(ErrorHandled::Reported(e));
+                } else if ct.has_non_region_infer() || ct.has_non_region_param() {
+                    return Err(ErrorHandled::TooGeneric);
+                } else {
+                    substs = replace_param_and_infer_substs_with_placeholder(tcx, substs);
                 }
-                Err(guar) => return Err(ErrorHandled::Reported(guar)),
+            } else {
+                substs = InternalSubsts::identity_for_item(tcx, unevaluated.def.did);
+                param_env = tcx.param_env(unevaluated.def.did);
             }
         }
 
-        let param_env_erased = self.tcx.erase_regions(param_env);
-        let substs_erased = self.tcx.erase_regions(substs);
+        let param_env_erased = tcx.erase_regions(param_env);
+        let substs_erased = tcx.erase_regions(substs);
         debug!(?param_env_erased);
         debug!(?substs_erased);
 
         let unevaluated = ty::UnevaluatedConst { def: unevaluated.def, substs: substs_erased };
 
         // The return value is the evaluated value which doesn't contain any reference to inference
         // variables, thus we don't need to substitute back the original values.
-        self.tcx.const_eval_resolve_for_typeck(param_env_erased, unevaluated, span)
+        tcx.const_eval_resolve_for_typeck(param_env_erased, unevaluated, span)
     }
 
     /// `ty_or_const_infer_var_changed` is equivalent to one of these two:

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -644,12 +644,6 @@ impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for Symbol {
     }
 }
 
-impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for &'tcx [ty::abstract_const::Node<'tcx>] {
-    fn decode(d: &mut DecodeContext<'a, 'tcx>) -> Self {
-        ty::codec::RefDecodable::decode(d)
-    }
-}
-
 impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for &'tcx [(ty::Predicate<'tcx>, Span)] {
     fn decode(d: &mut DecodeContext<'a, 'tcx>) -> Self {
         ty::codec::RefDecodable::decode(d)

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -366,7 +366,7 @@ define_tables! {
     mir_for_ctfe: Table<DefIndex, LazyValue<mir::Body<'static>>>,
     promoted_mir: Table<DefIndex, LazyValue<IndexVec<mir::Promoted, mir::Body<'static>>>>,
     // FIXME(compiler-errors): Why isn't this a LazyArray?
-    thir_abstract_const: Table<DefIndex, LazyValue<&'static [ty::abstract_const::Node<'static>]>>,
+    thir_abstract_const: Table<DefIndex, LazyValue<ty::Const<'static>>>,
     impl_parent: Table<DefIndex, RawDefId>,
     impl_polarity: Table<DefIndex, ty::ImplPolarity>,
     constness: Table<DefIndex, hir::Constness>,

compiler/rustc_middle/src/mir/pretty.rs

@@ -476,6 +476,7 @@ impl<'tcx> Visitor<'tcx> for ExtraComments<'tcx> {
                     // These variants shouldn't exist in the MIR.
                     ty::ConstKind::Placeholder(_)
                     | ty::ConstKind::Infer(_)
+                    | ty::ConstKind::Expr(_)
                     | ty::ConstKind::Bound(..) => bug!("unexpected MIR constant: {:?}", literal),
                 },
                 ConstantKind::Unevaluated(uv, _) => {

compiler/rustc_middle/src/mir/syntax.rs

@@ -1185,15 +1185,17 @@ pub enum NullOp {
     AlignOf,
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[derive(HashStable, TyEncodable, TyDecodable, TypeFoldable, TypeVisitable)]
 pub enum UnOp {
     /// The `!` operator for logical inversion
     Not,
     /// The `-` operator for negation
     Neg,
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
+#[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Ord, Eq, Hash)]
+#[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub enum BinOp {
     /// The `+` operator (addition)
     Add,

compiler/rustc_middle/src/mir/type_foldable.rs

@@ -16,9 +16,7 @@ TrivialTypeTraversalAndLiftImpls! {
     UserTypeAnnotationIndex,
     BorrowKind,
     CastKind,
-    BinOp,
     NullOp,
-    UnOp,
     hir::Movability,
     BasicBlock,
     SwitchTargets,

compiler/rustc_middle/src/query/mod.rs

@@ -400,7 +400,7 @@ rustc_queries! {
     /// Try to build an abstract representation of the given constant.
     query thir_abstract_const(
         key: DefId
-    ) -> Result<Option<&'tcx [ty::abstract_const::Node<'tcx>]>, ErrorGuaranteed> {
+    ) -> Result<Option<ty::Const<'tcx>>, ErrorGuaranteed> {
         desc {
             |tcx| "building an abstract representation for `{}`", tcx.def_path_str(key),
         }
@@ -409,23 +409,14 @@ rustc_queries! {
     /// Try to build an abstract representation of the given constant.
     query thir_abstract_const_of_const_arg(
         key: (LocalDefId, DefId)
-    ) -> Result<Option<&'tcx [ty::abstract_const::Node<'tcx>]>, ErrorGuaranteed> {
+    ) -> Result<Option<ty::Const<'tcx>>, ErrorGuaranteed> {
         desc {
             |tcx|
             "building an abstract representation for the const argument `{}`",
             tcx.def_path_str(key.0.to_def_id()),
         }
     }
 
-    query try_unify_abstract_consts(key:
-        ty::ParamEnvAnd<'tcx, (ty::UnevaluatedConst<'tcx>, ty::UnevaluatedConst<'tcx>
-    )>) -> bool {
-        desc {
-            |tcx| "trying to unify the generic constants `{}` and `{}`",
-            tcx.def_path_str(key.value.0.def.did), tcx.def_path_str(key.value.1.def.did)
-        }
-    }
-
     query mir_drops_elaborated_and_const_checked(
         key: ty::WithOptConstParam<LocalDefId>
     ) -> &'tcx Steal<mir::Body<'tcx>> {