warning: `#[derive]` does nothing on macro invocations
  --> $DIR/issue-49934.rs:30:5
   |
LL |     #[derive(Debug)]
   |     ^^^^^^^^^^^^^^^^
   |
   = note: this may become a hard error in a future release

warning: unused attribute
  --> $DIR/issue-49934.rs:16:8
   |
LL | fn foo<#[derive(Debug)] T>() { //~ WARN unused attribute
   |        ^^^^^^^^^^^^^^^^
   |
note: lint level defined here
  --> $DIR/issue-49934.rs:14:9
   |
LL | #![warn(unused_attributes)] //~ NOTE lint level defined here
   |         ^^^^^^^^^^^^^^^^^

warning: unused attribute
  --> $DIR/issue-49934.rs:18:9
   |
LL |         #[derive(Debug)] //~ WARN unused attribute
   |         ^^^^^^^^^^^^^^^^

warning: unused attribute
  --> $DIR/issue-49934.rs:36:5
   |
LL |     #[derive(Debug)] //~ WARN unused attribute
   |     ^^^^^^^^^^^^^^^^

warning: unused attribute
  --> $DIR/issue-49934.rs:40:5
   |
LL |     #[derive(Debug)] //~ WARN unused attribute
   |     ^^^^^^^^^^^^^^^^

warning: unused attribute
  --> $DIR/issue-49934.rs:44:13
   |
LL |     let _ = #[derive(Debug)] "Hello, world!";
   |             ^^^^^^^^^^^^^^^^

warning: unused attribute
  --> $DIR/issue-49934.rs:49:9
   |
LL |         #[derive(Debug)] //~ WARN unused attribute
   |         ^^^^^^^^^^^^^^^^