error: expected one of `>`, a const expression, lifetime, or type, found `:`
  --> $DIR/trait-path-missing-gen_arg.rs:6:30
   |
LL |   fn f1<'a>(arg : Box<dyn X< : 32 >>) {}
   |                              ^ expected one of `>`, a const expression, lifetime, or type

error: expected one of `>`, a const expression, lifetime, or type, found `=`
  --> $DIR/trait-path-missing-gen_arg.rs:11:30
   |
LL |   fn f1<'a>(arg : Box<dyn X< = 32 >>) {}
   |                            - ^ expected one of `>`, a const expression, lifetime, or type
   |                            |
   |                            maybe try to close unmatched angle bracket

error: aborting due to 2 previous errors