Rollup merge of #133218 - compiler-errors:const-opaque, r=fee1-dead

Implement `~const` item bounds in RPIT

an RPIT in a `const fn` is allowed to be conditionally const itself :)

r? fee1-dead or reroll

compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs

@@ -102,7 +102,7 @@ where
 
     /// Assemble additional assumptions for an alias that are not included
     /// in the item bounds of the alias. For now, this is limited to the
-    /// `implied_const_bounds` for an associated type.
+    /// `explicit_implied_const_bounds` for an associated type.
     fn consider_additional_alias_assumptions(
         ecx: &mut EvalCtxt<'_, D>,
         goal: Goal<I, Self>,

compiler/rustc_next_trait_solver/src/solve/effect_goals.rs

@@ -84,12 +84,9 @@ where
         let cx = ecx.cx();
         let mut candidates = vec![];
 
-        // FIXME(const_trait_impl): We elaborate here because the implied const bounds
-        // aren't necessarily elaborated. We probably should prefix this query
-        // with `explicit_`...
         for clause in elaborate::elaborate(
             cx,
-            cx.implied_const_bounds(alias_ty.def_id)
+            cx.explicit_implied_const_bounds(alias_ty.def_id)
                 .iter_instantiated(cx, alias_ty.args)
                 .map(|trait_ref| trait_ref.to_host_effect_clause(cx, goal.predicate.constness)),
         ) {