Rollup merge of #22364 - Manishearth:rfc-572-forbid-attr, r=nikomatsakis

 fixes #22203

r? @nikomatsakis

This breaks code that might be using attributes randomly, so it's technically a

[breaking-change]

1 files changed, 7 insertions, 0 deletions

diff --git a/src/doc/reference.md b/src/doc/reference.md
index 11b2afc1c88..00ed5d4562b 100644
--- a/src/doc/reference.md
+++ b/src/doc/reference.md
@@ -2398,6 +2398,10 @@ The currently implemented features of the reference compiler are:
                     ways insufficient for concatenating identifiers, and may be
                     removed entirely for something more wholesome.
 
+* `custom_attribute` - Allows the usage of attributes unknown to the compiler
+                       so that new attributes can be added in a bacwards compatible
+                       manner (RFC 572).
+
 * `intrinsics` - Allows use of the "rust-intrinsics" ABI. Compiler intrinsics
                  are inherently unstable and no promise about them is made.
 
@@ -2458,6 +2462,9 @@ The currently implemented features of the reference compiler are:
             implemented very poorly and will likely change significantly
             with a proper implementation.
 
+* `rustc_attrs` - Gates internal `#[rustc_*]` attributes which may be
+                  for internal use only or have meaning added to them in the future.
+
 * `rustc_diagnostic_macros`- A mysterious feature, used in the implementation
                              of rustc, not meant for mortals.