Rollup merge of #82707 - BoxyUwU:errooaaar, r=oli-obk

const_evaluatable_checked: Stop eagerly erroring in `is_const_evaluatable`

Fixes #82279

We don't want to be emitting errors inside of is_const_evaluatable because we may call this during selection where it should be able to fail silently

There were two errors being emitted in `is_const_evaluatable`. The one causing the compile error in #82279 was inside the match arm for `FailureKind::MentionsParam` but I moved the other error being emitted too since it made things cleaner imo

The `NotConstEvaluatable` enum \*should\* have a fourth variant for when we fail to evaluate a concrete const, e.g. `0 - 1` but that cant happen until #81339

cc `@oli-obk` `@lcnr`
r? `@nikomatsakis`

compiler/rustc_middle/src/mir/abstract_const.rs

@@ -18,3 +18,20 @@ pub enum Node<'tcx> {
     UnaryOp(mir::UnOp, NodeId),
     FunctionCall(NodeId, &'tcx [NodeId]),
 }
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
+pub enum NotConstEvaluatable {
+    Error(rustc_errors::ErrorReported),
+    MentionsInfer,
+    MentionsParam,
+}
+
+impl From<rustc_errors::ErrorReported> for NotConstEvaluatable {
+    fn from(e: rustc_errors::ErrorReported) -> NotConstEvaluatable {
+        NotConstEvaluatable::Error(e)
+    }
+}
+
+TrivialTypeFoldableAndLiftImpls! {
+    NotConstEvaluatable,
+}

compiler/rustc_middle/src/traits/mod.rs

@@ -9,7 +9,7 @@ pub mod specialization_graph;
 mod structural_impls;
 
 use crate::infer::canonical::Canonical;
-use crate::mir::interpret::ErrorHandled;
+use crate::mir::abstract_const::NotConstEvaluatable;
 use crate::ty::subst::SubstsRef;
 use crate::ty::{self, AdtKind, Ty, TyCtxt};
 
@@ -398,7 +398,7 @@ pub enum SelectionError<'tcx> {
         ty::error::TypeError<'tcx>,
     ),
     TraitNotObjectSafe(DefId),
-    ConstEvalFailure(ErrorHandled),
+    NotConstEvaluatable(NotConstEvaluatable),
     Overflow,
 }