error: expected identifier, found reserved identifier `_`
  --> $DIR/issue-91461.rs:2:7
   |
LL |     a(_:b:,)
   |       ^ expected identifier, found reserved identifier

error: expected type, found `,`
  --> $DIR/issue-91461.rs:2:11
   |
LL |     a(_:b:,)
   |     -    -^ expected type
   |     |    |
   |     |    tried to parse a type due to this type ascription
   |     while parsing this struct
   |
   = note: `#![feature(type_ascription)]` lets you annotate an expression with a type: `<expr>: <type>`
   = note: see issue #23416 <https://github.com/rust-lang/rust/issues/23416> for more information

error: expected type, found `,`
  --> $DIR/issue-91461.rs:2:11
   |
LL |     a(_:b:,)
   |          -^ expected type
   |          |
   |          tried to parse a type due to this type ascription
   |
   = note: `#![feature(type_ascription)]` lets you annotate an expression with a type: `<expr>: <type>`
   = note: see issue #23416 <https://github.com/rust-lang/rust/issues/23416> for more information

error: aborting due to 3 previous errors

