Do not panic in return_type_impl_trait

compiler/rustc_middle/src/ty/context.rs

@@ -43,7 +43,8 @@ use rustc_hir::definitions::Definitions;
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{
-    Constness, HirId, ItemKind, ItemLocalId, ItemLocalMap, ItemLocalSet, Node, TraitCandidate,
+    Constness, ExprKind, HirId, ImplItemKind, ItemKind, ItemLocalId, ItemLocalMap, ItemLocalSet,
+    Node, TraitCandidate, TraitItemKind,
 };
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_macros::HashStable;
@@ -1498,18 +1499,14 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     pub fn return_type_impl_trait(self, scope_def_id: LocalDefId) -> Option<(Ty<'tcx>, Span)> {
-        // HACK: `type_of_def_id()` will fail on these (#55796), so return `None`.
+        // `type_of()` will fail on these (#55796, #86483), so only allow `fn`s or closures.
         let hir_id = self.hir().local_def_id_to_hir_id(scope_def_id);
         match self.hir().get(hir_id) {
-            Node::Item(item) => {
-                match item.kind {
-                    ItemKind::Fn(..) => { /* `type_of_def_id()` will work */ }
-                    _ => {
-                        return None;
-                    }
-                }
-            }
-            _ => { /* `type_of_def_id()` will work or panic */ }
+            Node::Item(&hir::Item { kind: ItemKind::Fn(..), .. }) => {}
+            Node::TraitItem(&hir::TraitItem { kind: TraitItemKind::Fn(..), .. }) => {}
+            Node::ImplItem(&hir::ImplItem { kind: ImplItemKind::Fn(..), .. }) => {}
+            Node::Expr(&hir::Expr { kind: ExprKind::Closure(..), .. }) => {}
+            _ => return None,
         }
 
         let ret_ty = self.type_of(scope_def_id);

compiler/rustc_typeck/src/collect/type_of.rs

@@ -492,7 +492,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
 
                 x => tcx.ty_error_with_message(
                     DUMMY_SP,
-                    &format!("unexpected const parent in type_of_def_id(): {:?}", x),
+                    &format!("unexpected const parent in type_of(): {:?}", x),
                 ),
             }
         }
@@ -504,7 +504,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
         },
 
         x => {
-            bug!("unexpected sort of node in type_of_def_id(): {:?}", x);
+            bug!("unexpected sort of node in type_of(): {:?}", x);
         }
     }
 }

src/test/ui/generic-associated-types/issue-86483.rs

@@ -0,0 +1,15 @@
+// Regression test of #86483.
+
+#![feature(generic_associated_types)]
+#![allow(incomplete_features)]
+
+pub trait IceIce<T> //~ ERROR: the parameter type `T` may not live long enough
+where
+    for<'a> T: 'a,
+{
+    type Ice<'v>: IntoIterator<Item = &'v T>;
+    //~^ ERROR: the parameter type `T` may not live long enough
+    //~| ERROR: the parameter type `T` may not live long enough
+}
+
+fn main() {}

src/test/ui/generic-associated-types/issue-86483.stderr

@@ -0,0 +1,36 @@
+error[E0311]: the parameter type `T` may not live long enough
+  --> $DIR/issue-86483.rs:6:1
+   |
+LL |   pub trait IceIce<T>
+   |   ^                - help: consider adding an explicit lifetime bound...: `T: 'a`
+   |  _|
+   | |
+LL | | where
+LL | |     for<'a> T: 'a,
+LL | | {
+...  |
+LL | |
+LL | | }
+   | |_^ ...so that the type `T` will meet its required lifetime bounds
+
+error[E0311]: the parameter type `T` may not live long enough
+  --> $DIR/issue-86483.rs:10:5
+   |
+LL | pub trait IceIce<T>
+   |                  - help: consider adding an explicit lifetime bound...: `T: 'a`
+...
+LL |     type Ice<'v>: IntoIterator<Item = &'v T>;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
+
+error[E0309]: the parameter type `T` may not live long enough
+  --> $DIR/issue-86483.rs:10:32
+   |
+LL | pub trait IceIce<T>
+   |                  - help: consider adding an explicit lifetime bound...: `T: 'v`
+...
+LL |     type Ice<'v>: IntoIterator<Item = &'v T>;
+   |                                ^^^^^^^^^^^^ ...so that the reference type `&'v T` does not outlive the data it points at
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0309`.