Use trait definition cycle detection for trait alias definitions, too

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

@@ -653,7 +653,7 @@ pub(super) fn implied_predicates_with_filter<'tcx>(
                 }
             }
         }
-        PredicateFilter::SelfAndAssociatedTypeBounds => {
+        PredicateFilter::All | PredicateFilter::SelfAndAssociatedTypeBounds => {
             for &(pred, span) in implied_bounds {
                 debug!("superbound: {:?}", pred);
                 if let ty::ClauseKind::Trait(bound) = pred.kind().skip_binder()

compiler/rustc_middle/src/ty/sty.rs

@@ -401,7 +401,7 @@ impl<'tcx> Ty<'tcx> {
     /// The more specific methods will often optimize their creation.
     #[allow(rustc::usage_of_ty_tykind)]
     #[inline]
-    pub fn new(tcx: TyCtxt<'tcx>, st: TyKind<'tcx>) -> Ty<'tcx> {
+    fn new(tcx: TyCtxt<'tcx>, st: TyKind<'tcx>) -> Ty<'tcx> {
         tcx.mk_ty_from_kind(st)
     }
 
@@ -613,6 +613,41 @@ impl<'tcx> Ty<'tcx> {
     #[inline]
     pub fn new_adt(tcx: TyCtxt<'tcx>, def: AdtDef<'tcx>, args: GenericArgsRef<'tcx>) -> Ty<'tcx> {
         tcx.debug_assert_args_compatible(def.did(), args);
+        if cfg!(debug_assertions) {
+            match tcx.def_kind(def.did()) {
+                DefKind::Struct | DefKind::Union | DefKind::Enum => {}
+                DefKind::Mod
+                | DefKind::Variant
+                | DefKind::Trait
+                | DefKind::TyAlias
+                | DefKind::ForeignTy
+                | DefKind::TraitAlias
+                | DefKind::AssocTy
+                | DefKind::TyParam
+                | DefKind::Fn
+                | DefKind::Const
+                | DefKind::ConstParam
+                | DefKind::Static { .. }
+                | DefKind::Ctor(..)
+                | DefKind::AssocFn
+                | DefKind::AssocConst
+                | DefKind::Macro(..)
+                | DefKind::ExternCrate
+                | DefKind::Use
+                | DefKind::ForeignMod
+                | DefKind::AnonConst
+                | DefKind::InlineConst
+                | DefKind::OpaqueTy
+                | DefKind::Field
+                | DefKind::LifetimeParam
+                | DefKind::GlobalAsm
+                | DefKind::Impl { .. }
+                | DefKind::Closure
+                | DefKind::SyntheticCoroutineBody => {
+                    bug!("not an adt: {def:?} ({:?})", tcx.def_kind(def.did()))
+                }
+            }
+        }
         Ty::new(tcx, Adt(def, args))
     }
 
@@ -772,7 +807,7 @@ impl<'tcx> Ty<'tcx> {
                 }
             }
         });
-        Ty::new(tcx, Adt(adt_def, args))
+        Ty::new_adt(tcx, adt_def, args)
     }
 
     #[inline]

tests/ui/infinite/infinite-trait-alias-recursion.rs

@@ -1,7 +1,7 @@
 #![feature(trait_alias)]
 
 trait T1 = T2;
-//~^ ERROR cycle detected when computing the super predicates of `T1`
+//~^ ERROR cycle detected when computing the implied predicates of `T1`
 
 trait T2 = T3;
 

tests/ui/infinite/infinite-trait-alias-recursion.stderr

@@ -1,20 +1,20 @@
-error[E0391]: cycle detected when computing the super predicates of `T1`
+error[E0391]: cycle detected when computing the implied predicates of `T1`
   --> $DIR/infinite-trait-alias-recursion.rs:3:12
    |
 LL | trait T1 = T2;
    |            ^^
    |
-note: ...which requires computing the super predicates of `T2`...
+note: ...which requires computing the implied predicates of `T2`...
   --> $DIR/infinite-trait-alias-recursion.rs:6:12
    |
 LL | trait T2 = T3;
    |            ^^
-note: ...which requires computing the super predicates of `T3`...
+note: ...which requires computing the implied predicates of `T3`...
   --> $DIR/infinite-trait-alias-recursion.rs:8:12
    |
 LL | trait T3 = T1 + T3;
    |            ^^
-   = note: ...which again requires computing the super predicates of `T1`, completing the cycle
+   = note: ...which again requires computing the implied predicates of `T1`, completing the cycle
    = note: trait aliases cannot be recursive
 note: cycle used when checking that `T1` is well-formed
   --> $DIR/infinite-trait-alias-recursion.rs:3:1

tests/ui/traits/alias/infinite_normalization.rs

@@ -0,0 +1,11 @@
+//! This test used to get stuck in an infinite
+//! recursion during normalization.
+//!
+//! issue: https://github.com/rust-lang/rust/issues/133901
+
+#![feature(trait_alias)]
+fn foo<T: Baz<i32>>() {}
+trait Baz<A> = Baz<Option<A>>;
+//~^ ERROR: cycle detected when computing the implied predicates of `Baz`
+
+fn main() {}

tests/ui/traits/alias/infinite_normalization.stderr

@@ -0,0 +1,18 @@
+error[E0391]: cycle detected when computing the implied predicates of `Baz`
+  --> $DIR/infinite_normalization.rs:8:16
+   |
+LL | trait Baz<A> = Baz<Option<A>>;
+   |                ^^^^^^^^^^^^^^
+   |
+   = note: ...which immediately requires computing the implied predicates of `Baz` again
+   = note: trait aliases cannot be recursive
+note: cycle used when computing normalized predicates of `foo`
+  --> $DIR/infinite_normalization.rs:7:1
+   |
+LL | fn foo<T: Baz<i32>>() {}
+   | ^^^^^^^^^^^^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0391`.