Use `$message_type` as the tag

`type` turned out to be controversial.

1 files changed, 3 insertions, 3 deletions

diff --git a/tests/ui/diagnostic-width/flag-json.stderr b/tests/ui/diagnostic-width/flag-json.stderr
index 33d05003aae..16c17526809 100644
--- a/tests/ui/diagnostic-width/flag-json.stderr
+++ b/tests/ui/diagnostic-width/flag-json.stderr
@@ -1,4 +1,4 @@
-{"type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
+{"$message_type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
 
 Erroneous code examples:
 
@@ -33,8 +33,8 @@ LL | ..._: () = 42;
    |       expected due to this
 
 "}
-{"type":"diagnostic","message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error
+{"$message_type":"diagnostic","message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error
 
 "}
-{"type":"diagnostic","message":"For more information about this error, try `rustc --explain E0308`.","code":null,"level":"failure-note","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0308`.
+{"$message_type":"diagnostic","message":"For more information about this error, try `rustc --explain E0308`.","code":null,"level":"failure-note","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0308`.
 "}