try to evaluate in try_unify

compiler/rustc_infer/src/infer/mod.rs

@@ -691,11 +691,12 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         &self,
         a: ty::Unevaluated<'tcx, ()>,
         b: ty::Unevaluated<'tcx, ()>,
+        param_env: ty::ParamEnv<'tcx>,
     ) -> bool {
         let canonical = self.canonicalize_query((a, b), &mut OriginalQueryValues::default());
         debug!("canonical consts: {:?}", &canonical.value);
 
-        self.tcx.try_unify_abstract_consts(canonical.value)
+        self.tcx.try_unify_abstract_consts(param_env.and(canonical.value))
     }
 
     pub fn is_in_snapshot(&self) -> bool {

compiler/rustc_middle/src/query/mod.rs

@@ -329,12 +329,12 @@ rustc_queries! {
         }
     }
 
-    query try_unify_abstract_consts(key: (
+    query try_unify_abstract_consts(key:
-        ty::Unevaluated<'tcx, ()>, ty::Unevaluated<'tcx, ()>
+        ty::ParamEnvAnd<'tcx, (ty::Unevaluated<'tcx, ()>, ty::Unevaluated<'tcx, ()>
-    )) -> bool {
+    )>) -> bool {
         desc {
             |tcx| "trying to unify the generic constants {} and {}",
-            tcx.def_path_str(key.0.def.did), tcx.def_path_str(key.1.def.did)
+            tcx.def_path_str(key.value.0.def.did), tcx.def_path_str(key.value.1.def.did)
         }
     }
 

compiler/rustc_middle/src/ty/relate.rs

@@ -585,7 +585,7 @@ pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>(
         (ty::ConstKind::Unevaluated(au), ty::ConstKind::Unevaluated(bu))
             if tcx.features().generic_const_exprs =>
         {
-            tcx.try_unify_abstract_consts((au.shrink(), bu.shrink()))
+            tcx.try_unify_abstract_consts(relation.param_env().and((au.shrink(), bu.shrink())))
         }
 
         // While this is slightly incorrect, it shouldn't matter for `min_const_generics`

compiler/rustc_trait_selection/src/traits/const_evaluatable.rs

@@ -28,13 +28,13 @@ use std::iter;
 use std::ops::ControlFlow;
 
 /// Check if a given constant can be evaluated.
+#[instrument(skip(infcx), level = "debug")]
 pub fn is_const_evaluatable<'cx, 'tcx>(
     infcx: &InferCtxt<'cx, 'tcx>,
     uv: ty::Unevaluated<'tcx, ()>,
     param_env: ty::ParamEnv<'tcx>,
     span: Span,
 ) -> Result<(), NotConstEvaluatable> {
-    debug!("is_const_evaluatable({:?})", uv);
     let tcx = infcx.tcx;
 
     if tcx.features().generic_const_exprs {
@@ -185,6 +185,7 @@ pub fn is_const_evaluatable<'cx, 'tcx>(
     }
 }
 
+#[instrument(skip(tcx), level = "debug")]
 fn satisfied_from_param_env<'tcx>(
     tcx: TyCtxt<'tcx>,
     ct: AbstractConst<'tcx>,
@@ -197,10 +198,11 @@ fn satisfied_from_param_env<'tcx>(
                     // Try to unify with each subtree in the AbstractConst to allow for
                     // `N + 1` being const evaluatable even if theres only a `ConstEvaluatable`
                     // predicate for `(N + 1) * 2`
-                    let result =
+                    let result = walk_abstract_const(tcx, b_ct, |b_ct| {
-                        walk_abstract_const(tcx, b_ct, |b_ct| match try_unify(tcx, ct, b_ct) {
+                        match try_unify(tcx, ct, b_ct, param_env) {
                             true => ControlFlow::BREAK,
                             false => ControlFlow::CONTINUE,
+                        }
                     });
 
                     if let ControlFlow::Break(()) = result {
@@ -570,11 +572,12 @@ pub(super) fn thir_abstract_const<'tcx>(
 pub(super) fn try_unify_abstract_consts<'tcx>(
     tcx: TyCtxt<'tcx>,
     (a, b): (ty::Unevaluated<'tcx, ()>, ty::Unevaluated<'tcx, ()>),
+    param_env: ty::ParamEnv<'tcx>,
 ) -> bool {
     (|| {
         if let Some(a) = AbstractConst::new(tcx, a)? {
             if let Some(b) = AbstractConst::new(tcx, b)? {
-                return Ok(try_unify(tcx, a, b));
+                return Ok(try_unify(tcx, a, b, param_env));
             }
         }
 
@@ -619,32 +622,59 @@ where
     recurse(tcx, ct, &mut f)
 }
 
-/// Tries to unify two abstract constants using structural equality.
+// Substitutes generics repeatedly to allow AbstractConsts to unify where a
-pub(super) fn try_unify<'tcx>(
+// ConstKind::Unevalated could be turned into an AbstractConst that would unify e.g.
+// Param(N) should unify with Param(T), substs: [Unevaluated("T2", [Unevaluated("T3", [Param(N)])])]
+#[inline]
+#[instrument(skip(tcx), level = "debug")]
+fn try_replace_substs_in_root<'tcx>(
     tcx: TyCtxt<'tcx>,
-    mut a: AbstractConst<'tcx>,
+    mut abstr_const: AbstractConst<'tcx>,
-    mut b: AbstractConst<'tcx>,
+) -> Option<AbstractConst<'tcx>> {
-) -> bool {
+    while let Node::Leaf(ct) = abstr_const.root(tcx) {
-    // We substitute generics repeatedly to allow AbstractConsts to unify where a
+        match AbstractConst::from_const(tcx, ct) {
-    // ConstKind::Unevalated could be turned into an AbstractConst that would unify e.g.
+            Ok(Some(act)) => abstr_const = act,
-    // Param(N) should unify with Param(T), substs: [Unevaluated("T2", [Unevaluated("T3", [Param(N)])])]
-    while let Node::Leaf(a_ct) = a.root(tcx) {
-        match AbstractConst::from_const(tcx, a_ct) {
-            Ok(Some(a_act)) => a = a_act,
             Ok(None) => break,
-            Err(_) => return true,
+            Err(_) => return None,
-        }
-    }
-    while let Node::Leaf(b_ct) = b.root(tcx) {
-        match AbstractConst::from_const(tcx, b_ct) {
-            Ok(Some(b_act)) => b = b_act,
-            Ok(None) => break,
-            Err(_) => return true,
         }
     }
 
-    match (a.root(tcx), b.root(tcx)) {
+    Some(abstr_const)
+}
+
+/// Tries to unify two abstract constants using structural equality.
+#[instrument(skip(tcx), level = "debug")]
+pub(super) fn try_unify<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    a: AbstractConst<'tcx>,
+    b: AbstractConst<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+) -> bool {
+    let a = match try_replace_substs_in_root(tcx, a) {
+        Some(a) => a,
+        None => {
+            return true;
+        }
+    };
+
+    let b = match try_replace_substs_in_root(tcx, b) {
+        Some(b) => b,
+        None => {
+            return true;
+        }
+    };
+
+    let a_root = a.root(tcx);
+    let b_root = b.root(tcx);
+    debug!(?a_root, ?b_root);
+
+    match (a_root, b_root) {
         (Node::Leaf(a_ct), Node::Leaf(b_ct)) => {
+            let a_ct = a_ct.eval(tcx, param_env);
+            debug!("a_ct evaluated: {:?}", a_ct);
+            let b_ct = b_ct.eval(tcx, param_env);
+            debug!("b_ct evaluated: {:?}", b_ct);
+
             if a_ct.ty() != b_ct.ty() {
                 return false;
             }
@@ -678,23 +708,23 @@ pub(super) fn try_unify<'tcx>(
             }
         }
         (Node::Binop(a_op, al, ar), Node::Binop(b_op, bl, br)) if a_op == b_op => {
-            try_unify(tcx, a.subtree(al), b.subtree(bl))
+            try_unify(tcx, a.subtree(al), b.subtree(bl), param_env)
-                && try_unify(tcx, a.subtree(ar), b.subtree(br))
+                && try_unify(tcx, a.subtree(ar), b.subtree(br), param_env)
         }
         (Node::UnaryOp(a_op, av), Node::UnaryOp(b_op, bv)) if a_op == b_op => {
-            try_unify(tcx, a.subtree(av), b.subtree(bv))
+            try_unify(tcx, a.subtree(av), b.subtree(bv), param_env)
         }
         (Node::FunctionCall(a_f, a_args), Node::FunctionCall(b_f, b_args))
             if a_args.len() == b_args.len() =>
         {
-            try_unify(tcx, a.subtree(a_f), b.subtree(b_f))
+            try_unify(tcx, a.subtree(a_f), b.subtree(b_f), param_env)
                 && iter::zip(a_args, b_args)
-                    .all(|(&an, &bn)| try_unify(tcx, a.subtree(an), b.subtree(bn)))
+                    .all(|(&an, &bn)| try_unify(tcx, a.subtree(an), b.subtree(bn), param_env))
         }
         (Node::Cast(a_kind, a_operand, a_ty), Node::Cast(b_kind, b_operand, b_ty))
             if (a_ty == b_ty) && (a_kind == b_kind) =>
         {
-            try_unify(tcx, a.subtree(a_operand), b.subtree(b_operand))
+            try_unify(tcx, a.subtree(a_operand), b.subtree(b_operand), param_env)
         }
         // use this over `_ => false` to make adding variants to `Node` less error prone
         (Node::Cast(..), _)