Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/compiler/rustc_error_codes/src/error_codes/E0554.md b/compiler/rustc_error_codes/src/error_codes/E0554.md
new file mode 100644
index 000000000..3178bf219
--- /dev/null
+++ b/compiler/rustc_error_codes/src/error_codes/E0554.md
@@ -0,0 +1,12 @@
+Feature attributes are only allowed on the nightly release channel. Stable or
+beta compilers will not comply.
+
+Erroneous code example:
+
+```ignore (depends on release channel)
+#![feature(lang_items)] // error: `#![feature]` may not be used on the
+                        //        stable release channel
+```
+
+If you need the feature, make sure to use a nightly release of the compiler
+(but be warned that the feature may be removed or altered in the future).