Not sure who to assign this to, starting with Rust maintainer...

The Rust 1.33.0 update
https://build.opensuse.org/request/show/688611

breaks builds of Firefox and Thunderbird

https://build.opensuse.org/package/live_build_log/openSUSE:Leap:15.1:Staging:C/MozillaFirefox/standard/x86_64
https://build.opensuse.org/package/live_build_log/openSUSE:Leap:15.1:Staging:C/MozillaThunderbird/standard/x86_64

[ 2335s] 37:18.09 error: missing documentation for macro
[ 2335s] 37:18.09    --> servo/components/style_traits/values.rs:139:1
[ 2335s] 37:18.09     |
[ 2335s] 37:18.09 139 | macro_rules! serialize_function {
[ 2335s] 37:18.09     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[ 2335s] 37:18.09     |
[ 2335s] 37:18.10 note: lint level defined here
[ 2335s] 37:18.10    --> servo/components/style_traits/lib.rs:12:22
[ 2335s] 37:18.10     |
[ 2335s] 37:18.10 12  | #![deny(unsafe_code, missing_docs)]
[ 2335s] 37:18.10     |                      ^^^^^^^^^^^^
[ 2335s] 37:18.10 
[ 2335s] 37:18.10 error: missing documentation for macro
[ 2335s] 37:18.10    --> servo/components/style_traits/values.rs:408:1
[ 2335s] 37:18.10     |
[ 2335s] 37:18.10 408 | macro_rules! define_css_keyword_enum {
[ 2335s] 37:18.10     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[ 2335s] 37:18.10 
[ 2335s] 37:18.12 error: aborting due to 2 previous errors
[ 2335s] 37:18.12 
[ 2335s] 37:18.14 error: Could not compile `style_traits`.