diff --git a/src/test/ui/rfc-2091-track-caller/error-odd-syntax.rs b/src/test/ui/rfc-2091-track-caller/error-odd-syntax.rs
index d6560231871c9..d400db8575e0a 100644
--- a/src/test/ui/rfc-2091-track-caller/error-odd-syntax.rs
+++ b/src/test/ui/rfc-2091-track-caller/error-odd-syntax.rs
@@ -1,4 +1,4 @@
-#![feature(track_caller)]
+#![feature(track_caller)] //~ WARN the feature `track_caller` is incomplete
 
 #[track_caller(1)]
 fn f() {}
diff --git a/src/test/ui/rfc-2091-track-caller/error-odd-syntax.stderr b/src/test/ui/rfc-2091-track-caller/error-odd-syntax.stderr
index 8906fa59506a7..a53a8ee2bedc6 100644
--- a/src/test/ui/rfc-2091-track-caller/error-odd-syntax.stderr
+++ b/src/test/ui/rfc-2091-track-caller/error-odd-syntax.stderr
@@ -4,5 +4,13 @@ error: malformed `track_caller` attribute input
 LL | #[track_caller(1)]
    | ^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[track_caller]`
 
+warning: the feature `track_caller` is incomplete and may cause the compiler to crash
+  --> $DIR/error-odd-syntax.rs:1:12
+   |
+LL | #![feature(track_caller)]
+   |            ^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
 error: aborting due to previous error
 
diff --git a/src/test/ui/rfc-2091-track-caller/error-with-invalid-abi.rs b/src/test/ui/rfc-2091-track-caller/error-with-invalid-abi.rs
index 5c42a1b3faa2d..2994f3c06212f 100644
--- a/src/test/ui/rfc-2091-track-caller/error-with-invalid-abi.rs
+++ b/src/test/ui/rfc-2091-track-caller/error-with-invalid-abi.rs
@@ -1,4 +1,4 @@
-#![feature(track_caller)]
+#![feature(track_caller)] //~ WARN the feature `track_caller` is incomplete
 
 #[track_caller]
 extern "C" fn f() {}
diff --git a/src/test/ui/rfc-2091-track-caller/error-with-invalid-abi.stderr b/src/test/ui/rfc-2091-track-caller/error-with-invalid-abi.stderr
index e39e4bee5cf9c..a34acf3fc6142 100644
--- a/src/test/ui/rfc-2091-track-caller/error-with-invalid-abi.stderr
+++ b/src/test/ui/rfc-2091-track-caller/error-with-invalid-abi.stderr
@@ -1,3 +1,11 @@
+warning: the feature `track_caller` is incomplete and may cause the compiler to crash
+  --> $DIR/error-with-invalid-abi.rs:1:12
+   |
+LL | #![feature(track_caller)]
+   |            ^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
 error[E0737]: rust ABI is required to use `#[track_caller]`
   --> $DIR/error-with-invalid-abi.rs:3:1
    |
diff --git a/src/test/ui/rfc-2091-track-caller/error-with-naked.rs b/src/test/ui/rfc-2091-track-caller/error-with-naked.rs
index dd9e5d0413585..bbbcec30e8d51 100644
--- a/src/test/ui/rfc-2091-track-caller/error-with-naked.rs
+++ b/src/test/ui/rfc-2091-track-caller/error-with-naked.rs
@@ -1,4 +1,4 @@
-#![feature(naked_functions, track_caller)]
+#![feature(naked_functions, track_caller)] //~ WARN the feature `track_caller` is incomplete
 
 #[track_caller]
 #[naked]
diff --git a/src/test/ui/rfc-2091-track-caller/error-with-naked.stderr b/src/test/ui/rfc-2091-track-caller/error-with-naked.stderr
index 2f5003cfdb7a5..93e6f7a4cd32c 100644
--- a/src/test/ui/rfc-2091-track-caller/error-with-naked.stderr
+++ b/src/test/ui/rfc-2091-track-caller/error-with-naked.stderr
@@ -1,3 +1,11 @@
+warning: the feature `track_caller` is incomplete and may cause the compiler to crash
+  --> $DIR/error-with-naked.rs:1:29
+   |
+LL | #![feature(naked_functions, track_caller)]
+   |                             ^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
 error[E0736]: cannot use `#[track_caller]` with `#[naked]`
   --> $DIR/error-with-naked.rs:3:1
    |
diff --git a/src/test/ui/rfc-2091-track-caller/error-with-trait-fns.rs b/src/test/ui/rfc-2091-track-caller/error-with-trait-fns.rs
index c00cf7367ce54..e42568076b9dc 100644
--- a/src/test/ui/rfc-2091-track-caller/error-with-trait-fns.rs
+++ b/src/test/ui/rfc-2091-track-caller/error-with-trait-fns.rs
@@ -1,4 +1,4 @@
-#![feature(track_caller)]
+#![feature(track_caller)] //~ WARN the feature `track_caller` is incomplete
 
 trait Trait {
     #[track_caller]
diff --git a/src/test/ui/rfc-2091-track-caller/error-with-trait-fns.stderr b/src/test/ui/rfc-2091-track-caller/error-with-trait-fns.stderr
index e3f3135cd7366..c5c2f136a3a81 100644
--- a/src/test/ui/rfc-2091-track-caller/error-with-trait-fns.stderr
+++ b/src/test/ui/rfc-2091-track-caller/error-with-trait-fns.stderr
@@ -1,3 +1,11 @@
+warning: the feature `track_caller` is incomplete and may cause the compiler to crash
+  --> $DIR/error-with-trait-fns.rs:1:12
+   |
+LL | #![feature(track_caller)]
+   |            ^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
 error[E0738]: `#[track_caller]` is not supported for trait items yet.
   --> $DIR/error-with-trait-fns.rs:4:5
    |
diff --git a/src/test/ui/rfc-2091-track-caller/only-for-fns.rs b/src/test/ui/rfc-2091-track-caller/only-for-fns.rs
index 0fd59b4bf4918..01ebf13b521b2 100644
--- a/src/test/ui/rfc-2091-track-caller/only-for-fns.rs
+++ b/src/test/ui/rfc-2091-track-caller/only-for-fns.rs
@@ -1,4 +1,4 @@
-#![feature(track_caller)]
+#![feature(track_caller)] //~ WARN the feature `track_caller` is incomplete
 
 #[track_caller]
 struct S;
diff --git a/src/test/ui/rfc-2091-track-caller/only-for-fns.stderr b/src/test/ui/rfc-2091-track-caller/only-for-fns.stderr
index ac5ba0bfbaac6..e2d3d57f0adf4 100644
--- a/src/test/ui/rfc-2091-track-caller/only-for-fns.stderr
+++ b/src/test/ui/rfc-2091-track-caller/only-for-fns.stderr
@@ -1,3 +1,11 @@
+warning: the feature `track_caller` is incomplete and may cause the compiler to crash
+  --> $DIR/only-for-fns.rs:1:12
+   |
+LL | #![feature(track_caller)]
+   |            ^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
 error[E0735]: attribute should be applied to function
   --> $DIR/only-for-fns.rs:3:1
    |
@@ -8,4 +16,3 @@ LL | struct S;
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0735`.
diff --git a/src/test/ui/rfc-2091-track-caller/pass.rs b/src/test/ui/rfc-2091-track-caller/pass.rs
index eef83b3d68f97..f2c3f0dc59e01 100644
--- a/src/test/ui/rfc-2091-track-caller/pass.rs
+++ b/src/test/ui/rfc-2091-track-caller/pass.rs
@@ -1,5 +1,5 @@
 // run-pass
-#![feature(track_caller)]
+#![feature(track_caller)] //~ WARN the feature `track_caller` is incomplete
 
 #[track_caller]
 fn f() {}
diff --git a/src/test/ui/rfc-2091-track-caller/pass.stderr b/src/test/ui/rfc-2091-track-caller/pass.stderr
new file mode 100644
index 0000000000000..b1fd23a6a9ddb
--- /dev/null
+++ b/src/test/ui/rfc-2091-track-caller/pass.stderr
@@ -0,0 +1,8 @@
+warning: the feature `track_caller` is incomplete and may cause the compiler to crash
+  --> $DIR/pass.rs:2:12
+   |
+LL | #![feature(track_caller)]
+   |            ^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+