Rollup merge of #53364 - varkor:gat-warn-broken, r=pnkfelix

Warn if the user tries to use GATs

GATs are currently broken, but still accessible behind a feature gate. This leads to people attempting to use them and then immediately encountering ICEs (or other broken behaviour). Here, we emit a warning if the user tries to use any feature associated with GATs, hopefully making it obvious that ICEs and the like are expected. For the meantime, this seems better than continually getting reported errors (for example: [here](https://github.com/rust-lang/rust/issues?q=is%3Aissue+gat+is%3Aclosed) and [here](https://github.com/rust-lang/rust/issues?utf8=%E2%9C%93&q=is%3Aissue+generic_associated_types+is%3Aclosed)).

21 files changed, 152 insertions, 47 deletions

diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index f837bead6a0..395e5c98652 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -1922,6 +1922,11 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
         err.emit();
     }
 
+    // Some features are known to be incomplete and using them is likely to have
+    // unanticipated results, such as compiler crashes. We warn the user about these
+    // to alert them.
+    let incomplete_features = ["generic_associated_types"];
+
     let mut features = Features::new();
     let mut edition_enabled_features = FxHashMap();
 
@@ -1957,6 +1962,16 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
                 continue
             };
 
+            if incomplete_features.iter().any(|f| *f == name.as_str()) {
+                span_handler.struct_span_warn(
+                    mi.span,
+                    &format!(
+                        "the feature `{}` is incomplete and may cause the compiler to crash",
+                        name
+                    )
+                ).emit();
+            }
+
             if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
                 if *edition <= crate_edition {
                     continue
diff --git a/src/test/ui/rfc1598-generic-associated-types/collections.rs b/src/test/ui/rfc1598-generic-associated-types/collections.rs
index e71166ed65b..a6dbb03d379 100644
--- a/src/test/ui/rfc1598-generic-associated-types/collections.rs
+++ b/src/test/ui/rfc1598-generic-associated-types/collections.rs
@@ -9,10 +9,11 @@
 // except according to those terms.
 
 #![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
 #![feature(associated_type_defaults)]
 
-//FIXME(#44265): "lifetime parameters are not allowed on this type" errors will be addressed in a
-//follow-up PR
+// FIXME(#44265): "lifetime parameters are not allowed on this type" errors will be addressed in a
+// follow-up PR.
 
 // A Collection trait and collection families. Based on
 // http://smallcultfollowing.com/babysteps/blog/2016/11/03/
diff --git a/src/test/ui/rfc1598-generic-associated-types/collections.stderr b/src/test/ui/rfc1598-generic-associated-types/collections.stderr
index 8c31ab2ca88..0e7d6ace1bb 100644
--- a/src/test/ui/rfc1598-generic-associated-types/collections.stderr
+++ b/src/test/ui/rfc1598-generic-associated-types/collections.stderr
@@ -1,29 +1,35 @@
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/collections.rs:11:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0109]: type parameters are not allowed on this type
-  --> $DIR/collections.rs:65:90
+  --> $DIR/collections.rs:66:90
    |
 LL | fn floatify<C>(ints: &C) -> <<C as Collection<i32>>::Family as CollectionFamily>::Member<f32>
    |                                                                                          ^^^ type parameter not allowed
 
 error[E0109]: type parameters are not allowed on this type
-  --> $DIR/collections.rs:77:69
+  --> $DIR/collections.rs:78:69
    |
 LL | fn floatify_sibling<C>(ints: &C) -> <C as Collection<i32>>::Sibling<f32>
    |                                                                     ^^^ type parameter not allowed
 
 error[E0109]: type parameters are not allowed on this type
-  --> $DIR/collections.rs:26:71
+  --> $DIR/collections.rs:27:71
    |
 LL |         <<Self as Collection<T>>::Family as CollectionFamily>::Member<U>;
    |                                                                       ^ type parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/collections.rs:33:50
+  --> $DIR/collections.rs:34:50
    |
 LL |     fn iterate<'iter>(&'iter self) -> Self::Iter<'iter>;
    |                                                  ^^^^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/collections.rs:59:50
+  --> $DIR/collections.rs:60:50
    |
 LL |     fn iterate<'iter>(&'iter self) -> Self::Iter<'iter> {
    |                                                  ^^^^^ lifetime parameter not allowed
diff --git a/src/test/ui/rfc1598-generic-associated-types/construct_with_other_type.rs b/src/test/ui/rfc1598-generic-associated-types/construct_with_other_type.rs
index 04294100315..88a660b3a5a 100644
--- a/src/test/ui/rfc1598-generic-associated-types/construct_with_other_type.rs
+++ b/src/test/ui/rfc1598-generic-associated-types/construct_with_other_type.rs
@@ -9,11 +9,12 @@
 // except according to those terms.
 
 #![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
 
 use std::ops::Deref;
 
-//FIXME(#44265): "lifetime parameters are not allowed on this type" errors will be addressed in a
-//follow-up PR
+// FIXME(#44265): "lifetime parameters are not allowed on this type" errors will be addressed in a
+// follow-up PR.
 
 trait Foo {
     type Bar<'a, 'b>;
diff --git a/src/test/ui/rfc1598-generic-associated-types/construct_with_other_type.stderr b/src/test/ui/rfc1598-generic-associated-types/construct_with_other_type.stderr
index 1746122eb49..5c85698fa55 100644
--- a/src/test/ui/rfc1598-generic-associated-types/construct_with_other_type.stderr
+++ b/src/test/ui/rfc1598-generic-associated-types/construct_with_other_type.stderr
@@ -1,17 +1,23 @@
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/construct_with_other_type.rs:11:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/construct_with_other_type.rs:26:46
+  --> $DIR/construct_with_other_type.rs:27:46
    |
 LL |     type Baa<'a>: Deref<Target = <Self::Quux<'a> as Foo>::Bar<'a, 'static>>;
    |                                              ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/construct_with_other_type.rs:26:63
+  --> $DIR/construct_with_other_type.rs:27:63
    |
 LL |     type Baa<'a>: Deref<Target = <Self::Quux<'a> as Foo>::Bar<'a, 'static>>;
    |                                                               ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/construct_with_other_type.rs:34:40
+  --> $DIR/construct_with_other_type.rs:35:40
    |
 LL |     type Baa<'a> = &'a <T as Foo>::Bar<'a, 'static>;
    |                                        ^^ lifetime parameter not allowed
diff --git a/src/test/ui/rfc1598-generic-associated-types/empty_generics.rs b/src/test/ui/rfc1598-generic-associated-types/empty_generics.rs
index b12c075d132..d8a2a1b73f7 100644
--- a/src/test/ui/rfc1598-generic-associated-types/empty_generics.rs
+++ b/src/test/ui/rfc1598-generic-associated-types/empty_generics.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 #![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
 
 trait Foo {
     type Bar<,>;
diff --git a/src/test/ui/rfc1598-generic-associated-types/empty_generics.stderr b/src/test/ui/rfc1598-generic-associated-types/empty_generics.stderr
index aff3044e9a1..2670c3aa142 100644
--- a/src/test/ui/rfc1598-generic-associated-types/empty_generics.stderr
+++ b/src/test/ui/rfc1598-generic-associated-types/empty_generics.stderr
@@ -1,8 +1,14 @@
 error: expected one of `>`, identifier, or lifetime, found `,`
-  --> $DIR/empty_generics.rs:14:14
+  --> $DIR/empty_generics.rs:15:14
    |
 LL |     type Bar<,>;
    |              ^ expected one of `>`, identifier, or lifetime here
 
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/empty_generics.rs:11:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error: aborting due to previous error
 
diff --git a/src/test/ui/rfc1598-generic-associated-types/gat-incomplete-warning.rs b/src/test/ui/rfc1598-generic-associated-types/gat-incomplete-warning.rs
new file mode 100644
index 00000000000..7f48408b369
--- /dev/null
+++ b/src/test/ui/rfc1598-generic-associated-types/gat-incomplete-warning.rs
@@ -0,0 +1,16 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-pass
+
+#![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
+
+fn main() {}
diff --git a/src/test/ui/rfc1598-generic-associated-types/gat-incomplete-warning.stderr b/src/test/ui/rfc1598-generic-associated-types/gat-incomplete-warning.stderr
new file mode 100644
index 00000000000..67682dcb8fb
--- /dev/null
+++ b/src/test/ui/rfc1598-generic-associated-types/gat-incomplete-warning.stderr
@@ -0,0 +1,6 @@
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/gat-incomplete-warning.rs:13:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
diff --git a/src/test/ui/rfc1598-generic-associated-types/generic-associated-types-where.stderr b/src/test/ui/rfc1598-generic-associated-types/generic-associated-types-where.stderr
new file mode 100644
index 00000000000..97d5482735f
--- /dev/null
+++ b/src/test/ui/rfc1598-generic-associated-types/generic-associated-types-where.stderr
@@ -0,0 +1,6 @@
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/generic-associated-types-where.rs:11:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
diff --git a/src/test/ui/rfc1598-generic-associated-types/generic_associated_type_undeclared_lifetimes.rs b/src/test/ui/rfc1598-generic-associated-types/generic_associated_type_undeclared_lifetimes.rs
index 263b3cb42eb..267272ded8c 100644
--- a/src/test/ui/rfc1598-generic-associated-types/generic_associated_type_undeclared_lifetimes.rs
+++ b/src/test/ui/rfc1598-generic-associated-types/generic_associated_type_undeclared_lifetimes.rs
@@ -9,11 +9,12 @@
 // except according to those terms.
 
 #![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
 
 use std::ops::Deref;
 
-//FIXME(#44265): "lifetime parameters are not allowed on this type" errors will be addressed in a
-//follow-up PR
+// FIXME(#44265): "lifetime parameters are not allowed on this type" errors will be addressed in a
+// follow-up PR.
 
 trait Iterable {
     type Item<'a>;
diff --git a/src/test/ui/rfc1598-generic-associated-types/generic_associated_type_undeclared_lifetimes.stderr b/src/test/ui/rfc1598-generic-associated-types/generic_associated_type_undeclared_lifetimes.stderr
index d48c21477b3..79b29902ccd 100644
--- a/src/test/ui/rfc1598-generic-associated-types/generic_associated_type_undeclared_lifetimes.stderr
+++ b/src/test/ui/rfc1598-generic-associated-types/generic_associated_type_undeclared_lifetimes.stderr
@@ -1,29 +1,35 @@
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:11:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0261]: use of undeclared lifetime name `'b`
-  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:22:37
+  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:23:37
    |
 LL |         + Deref<Target = Self::Item<'b>>;
    |                                     ^^ undeclared lifetime
 
 error[E0261]: use of undeclared lifetime name `'undeclared`
-  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:26:41
+  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:27:41
    |
 LL |     fn iter<'a>(&'a self) -> Self::Iter<'undeclared>;
    |                                         ^^^^^^^^^^^ undeclared lifetime
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:20:47
+  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:21:47
    |
 LL |     type Iter<'a>: Iterator<Item = Self::Item<'a>>
    |                                               ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:22:37
+  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:23:37
    |
 LL |         + Deref<Target = Self::Item<'b>>;
    |                                     ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:26:41
+  --> $DIR/generic_associated_type_undeclared_lifetimes.rs:27:41
    |
 LL |     fn iter<'a>(&'a self) -> Self::Iter<'undeclared>;
    |                                         ^^^^^^^^^^^ lifetime parameter not allowed
diff --git a/src/test/ui/rfc1598-generic-associated-types/iterable.rs b/src/test/ui/rfc1598-generic-associated-types/iterable.rs
index 38967dbbe45..b52b6e02421 100644
--- a/src/test/ui/rfc1598-generic-associated-types/iterable.rs
+++ b/src/test/ui/rfc1598-generic-associated-types/iterable.rs
@@ -9,11 +9,12 @@
 // except according to those terms.
 
 #![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
 
 use std::ops::Deref;
 
-//FIXME(#44265): "lifetime parameters are not allowed on this type" errors will be addressed in a
-//follow-up PR
+// FIXME(#44265): "lifetime parameters are not allowed on this type" errors will be addressed in a
+// follow-up PR.
 
 trait Iterable {
     type Item<'a>;
diff --git a/src/test/ui/rfc1598-generic-associated-types/iterable.stderr b/src/test/ui/rfc1598-generic-associated-types/iterable.stderr
index 737a29ec2c8..de3563c14eb 100644
--- a/src/test/ui/rfc1598-generic-associated-types/iterable.stderr
+++ b/src/test/ui/rfc1598-generic-associated-types/iterable.stderr
@@ -1,35 +1,41 @@
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/iterable.rs:11:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/iterable.rs:20:47
+  --> $DIR/iterable.rs:21:47
    |
 LL |     type Iter<'a>: Iterator<Item = Self::Item<'a>>;
    |                                               ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/iterable.rs:49:53
+  --> $DIR/iterable.rs:50:53
    |
 LL | fn make_iter<'a, I: Iterable>(it: &'a I) -> I::Iter<'a> {
    |                                                     ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/iterable.rs:54:60
+  --> $DIR/iterable.rs:55:60
    |
 LL | fn get_first<'a, I: Iterable>(it: &'a I) -> Option<I::Item<'a>> {
    |                                                            ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/iterable.rs:23:41
+  --> $DIR/iterable.rs:24:41
    |
 LL |     fn iter<'a>(&'a self) -> Self::Iter<'a>;
    |                                         ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/iterable.rs:32:41
+  --> $DIR/iterable.rs:33:41
    |
 LL |     fn iter<'a>(&'a self) -> Self::Iter<'a> {
    |                                         ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/iterable.rs:43:41
+  --> $DIR/iterable.rs:44:41
    |
 LL |     fn iter<'a>(&'a self) -> Self::Iter<'a> {
    |                                         ^^ lifetime parameter not allowed
diff --git a/src/test/ui/rfc1598-generic-associated-types/parameter_number_and_kind.rs b/src/test/ui/rfc1598-generic-associated-types/parameter_number_and_kind.rs
index 51527d4117c..82e82e6dbcc 100644
--- a/src/test/ui/rfc1598-generic-associated-types/parameter_number_and_kind.rs
+++ b/src/test/ui/rfc1598-generic-associated-types/parameter_number_and_kind.rs
@@ -9,12 +9,13 @@
 // except according to those terms.
 
 #![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
 #![feature(associated_type_defaults)]
 
-//FIXME(#44265): "lifetime parameters are not allowed on this type" errors will be addressed in a
-//follow-up PR
+// FIXME(#44265): "lifetime parameters are not allowed on this type" errors will be addressed in a
+// follow-up PR.
 
-//FIXME(#44265): Update expected errors once E110 is resolved, now does not get past `trait Foo`
+// FIXME(#44265): Update expected errors once E110 is resolved, now does not get past `trait Foo`.
 
 trait Foo {
     type A<'a>;
diff --git a/src/test/ui/rfc1598-generic-associated-types/parameter_number_and_kind.stderr b/src/test/ui/rfc1598-generic-associated-types/parameter_number_and_kind.stderr
index c8d37a51fa9..e47daf2ae1b 100644
--- a/src/test/ui/rfc1598-generic-associated-types/parameter_number_and_kind.stderr
+++ b/src/test/ui/rfc1598-generic-associated-types/parameter_number_and_kind.stderr
@@ -1,29 +1,35 @@
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/parameter_number_and_kind.rs:11:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/parameter_number_and_kind.rs:26:27
+  --> $DIR/parameter_number_and_kind.rs:27:27
    |
 LL |     type FOk<T> = Self::E<'static, T>;
    |                           ^^^^^^^ lifetime parameter not allowed
 
 error[E0109]: type parameters are not allowed on this type
-  --> $DIR/parameter_number_and_kind.rs:26:36
+  --> $DIR/parameter_number_and_kind.rs:27:36
    |
 LL |     type FOk<T> = Self::E<'static, T>;
    |                                    ^ type parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/parameter_number_and_kind.rs:29:26
+  --> $DIR/parameter_number_and_kind.rs:30:26
    |
 LL |     type FErr1 = Self::E<'static, 'static>; // Error
    |                          ^^^^^^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/parameter_number_and_kind.rs:31:29
+  --> $DIR/parameter_number_and_kind.rs:32:29
    |
 LL |     type FErr2<T> = Self::E<'static, T, u32>; // Error
    |                             ^^^^^^^ lifetime parameter not allowed
 
 error[E0109]: type parameters are not allowed on this type
-  --> $DIR/parameter_number_and_kind.rs:31:38
+  --> $DIR/parameter_number_and_kind.rs:32:38
    |
 LL |     type FErr2<T> = Self::E<'static, T, u32>; // Error
    |                                      ^ type parameter not allowed
diff --git a/src/test/ui/rfc1598-generic-associated-types/pointer_family.rs b/src/test/ui/rfc1598-generic-associated-types/pointer_family.rs
index cbeeb1d6ca7..0300ad06194 100644
--- a/src/test/ui/rfc1598-generic-associated-types/pointer_family.rs
+++ b/src/test/ui/rfc1598-generic-associated-types/pointer_family.rs
@@ -9,8 +9,9 @@
 // except according to those terms.
 
 #![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
 
-//FIXME(#44265): "type parameter not allowed" errors will be addressed in a follow-up PR
+// FIXME(#44265): "type parameter not allowed" errors will be addressed in a follow-up PR.
 
 use std::rc::Rc;
 use std::sync::Arc;
diff --git a/src/test/ui/rfc1598-generic-associated-types/pointer_family.stderr b/src/test/ui/rfc1598-generic-associated-types/pointer_family.stderr
index 3e772eee4f4..3be0481dc67 100644
--- a/src/test/ui/rfc1598-generic-associated-types/pointer_family.stderr
+++ b/src/test/ui/rfc1598-generic-associated-types/pointer_family.stderr
@@ -1,23 +1,29 @@
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/pointer_family.rs:11:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0109]: type parameters are not allowed on this type
-  --> $DIR/pointer_family.rs:46:21
+  --> $DIR/pointer_family.rs:47:21
    |
 LL |     bar: P::Pointer<String>,
    |                     ^^^^^^ type parameter not allowed
 
 error[E0109]: type parameters are not allowed on this type
-  --> $DIR/pointer_family.rs:21:42
+  --> $DIR/pointer_family.rs:22:42
    |
 LL |     fn new<T>(value: T) -> Self::Pointer<T>;
    |                                          ^ type parameter not allowed
 
 error[E0109]: type parameters are not allowed on this type
-  --> $DIR/pointer_family.rs:29:42
+  --> $DIR/pointer_family.rs:30:42
    |
 LL |     fn new<T>(value: T) -> Self::Pointer<T> {
    |                                          ^ type parameter not allowed
 
 error[E0109]: type parameters are not allowed on this type
-  --> $DIR/pointer_family.rs:39:42
+  --> $DIR/pointer_family.rs:40:42
    |
 LL |     fn new<T>(value: T) -> Self::Pointer<T> {
    |                                          ^ type parameter not allowed
diff --git a/src/test/ui/rfc1598-generic-associated-types/shadowing.stderr b/src/test/ui/rfc1598-generic-associated-types/shadowing.stderr
new file mode 100644
index 00000000000..f2d626f921c
--- /dev/null
+++ b/src/test/ui/rfc1598-generic-associated-types/shadowing.stderr
@@ -0,0 +1,6 @@
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/shadowing.rs:11:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
diff --git a/src/test/ui/rfc1598-generic-associated-types/streaming_iterator.rs b/src/test/ui/rfc1598-generic-associated-types/streaming_iterator.rs
index 522ddb5dc13..aa90886fdfd 100644
--- a/src/test/ui/rfc1598-generic-associated-types/streaming_iterator.rs
+++ b/src/test/ui/rfc1598-generic-associated-types/streaming_iterator.rs
@@ -9,8 +9,9 @@
 // except according to those terms.
 
 #![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
 
-//FIXME(#44265): "lifetime parameter not allowed on this type" errors will be addressed in a
+// FIXME(#44265): "lifetime parameter not allowed on this type" errors will be addressed in a
 // follow-up PR
 
 use std::fmt::Display;
diff --git a/src/test/ui/rfc1598-generic-associated-types/streaming_iterator.stderr b/src/test/ui/rfc1598-generic-associated-types/streaming_iterator.stderr
index 12e206cbd47..4aca8d47687 100644
--- a/src/test/ui/rfc1598-generic-associated-types/streaming_iterator.stderr
+++ b/src/test/ui/rfc1598-generic-associated-types/streaming_iterator.stderr
@@ -1,29 +1,35 @@
+warning: the feature `generic_associated_types` is incomplete and may cause the compiler to crash
+  --> $DIR/streaming_iterator.rs:11:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/streaming_iterator.rs:27:41
+  --> $DIR/streaming_iterator.rs:28:41
    |
 LL |     bar: <T as StreamingIterator>::Item<'static>,
    |                                         ^^^^^^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/streaming_iterator.rs:35:64
+  --> $DIR/streaming_iterator.rs:36:64
    |
 LL | fn foo<T>(iter: T) where T: StreamingIterator, for<'a> T::Item<'a>: Display { /* ... */ }
    |                                                                ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/streaming_iterator.rs:21:48
+  --> $DIR/streaming_iterator.rs:22:48
    |
 LL |     fn next<'a>(&'a self) -> Option<Self::Item<'a>>;
    |                                                ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/streaming_iterator.rs:47:37
+  --> $DIR/streaming_iterator.rs:48:37
    |
 LL |     type Item<'a> = (usize, I::Item<'a>);
    |                                     ^^ lifetime parameter not allowed
 
 error[E0110]: lifetime parameters are not allowed on this type
-  --> $DIR/streaming_iterator.rs:49:48
+  --> $DIR/streaming_iterator.rs:50:48
    |
 LL |     fn next<'a>(&'a self) -> Option<Self::Item<'a>> {
    |                                                ^^ lifetime parameter not allowed