From cb00bc035be9fb3f8ce31f92de95a5eec5e2877c Mon Sep 17 00:00:00 2001
From: nils <48135649+Nilstrieb@users.noreply.github.com>
Date: Tue, 17 Jan 2023 14:06:12 +0100
Subject: [PATCH] Hide `_use_mk_alias_ty_instead` in `<AliasTy as Debug>::fmt`

---
 compiler/rustc_middle/src/ty/structural_impls.rs | 11 ++++++++++-
 compiler/rustc_middle/src/ty/sty.rs              |  2 +-
 tests/ui/chalkify/bugs/async.stderr              |  2 +-
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 8f64eb3e4baf6..1e43e8bf30d84 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -7,7 +7,7 @@ use crate::mir::{Field, ProjectionKind};
 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeSuperFoldable};
 use crate::ty::print::{with_no_trimmed_paths, FmtPrinter, Printer};
 use crate::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
-use crate::ty::{self, InferConst, Lift, Term, TermKind, Ty, TyCtxt};
+use crate::ty::{self, AliasTy, InferConst, Lift, Term, TermKind, Ty, TyCtxt};
 use rustc_data_structures::functor::IdFunctor;
 use rustc_hir::def::Namespace;
 use rustc_index::vec::{Idx, IndexVec};
@@ -180,6 +180,15 @@ impl<'tcx> fmt::Debug for ty::PredicateKind<'tcx> {
     }
 }
 
+impl<'tcx> fmt::Debug for AliasTy<'tcx> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("AliasTy")
+            .field("substs", &self.substs)
+            .field("def_id", &self.def_id)
+            .finish()
+    }
+}
+
 ///////////////////////////////////////////////////////////////////////////
 // Atomic structs
 //
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index e49e7e86da085..3f9e588358494 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -1226,7 +1226,7 @@ impl<'tcx> FallibleTypeFolder<'tcx> for SkipBindersAt<'tcx> {
 /// For a projection, this would be `<Ty as Trait<...>>::N`.
 ///
 /// For an opaque type, there is no explicit syntax.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct AliasTy<'tcx> {
     /// The parameters of the associated or opaque item.
diff --git a/tests/ui/chalkify/bugs/async.stderr b/tests/ui/chalkify/bugs/async.stderr
index d1508cb17001b..8043f1e5a0582 100644
--- a/tests/ui/chalkify/bugs/async.stderr
+++ b/tests/ui/chalkify/bugs/async.stderr
@@ -37,7 +37,7 @@ LL | async fn foo(x: u32) -> u32 {
    = help: the trait `Future` is not implemented for `[async fn body@$DIR/async.rs:23:29: 25:2]`
    = note: [async fn body@$DIR/async.rs:23:29: 25:2] must be a future or must implement `IntoFuture` to be awaited
 
-error: internal compiler error: projection clauses should be implied from elsewhere. obligation: `Obligation(predicate=Binder(ProjectionPredicate(AliasTy { substs: [[async fn body@$DIR/async.rs:23:29: 25:2]], def_id: ...), _use_mk_alias_ty_instead: () }, Term::Ty(u32)), []), depth=0)`
+error: internal compiler error: projection clauses should be implied from elsewhere. obligation: `Obligation(predicate=Binder(ProjectionPredicate(AliasTy { substs: [[async fn body@$DIR/async.rs:23:29: 25:2]], def_id: ...) }, Term::Ty(u32)), []), depth=0)`
   --> $DIR/async.rs:23:25
    |
 LL | async fn foo(x: u32) -> u32 {