error[E0308]: mismatched types
 --> tests/compile-fail/rust_action_type_error.rs:7:27
  |
7 |     rule foo() -> X = "a" { Y } //~ ERROR
  |                           ^^^^^
  |                           |
  |                           expected struct `X`, found struct `Y`
  |                           arguments to this enum variant are incorrect
  |
help: the type constructed contains `Y` due to the type of the argument passed
  --> tests/compile-fail/rust_action_type_error.rs:7:27
   |
7  |     rule foo() -> X = "a" { Y } //~ ERROR
   |                           ^^^^^ this argument influences the type of `{{root}}`
note: tuple variant defined here
  --> peg-runtime/lib.rs
   |
   |     Matched(usize, T),
   |     ^^^^^^^
   = note: this error originates in the macro `peg::parser` (in Nightly builds, run with -Z macro-backtrace for more info)