error[E0309]: the parameter type `T` may not live long enough
  --> $DIR/unactionable_diagnostic.rs:21:5
   |
LL | pub fn bar<'t, T>(
   |            -- the parameter type `T` must be valid for the lifetime `'t` as defined here...
...
LL |     foo(post, x)
   |     ^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | pub fn bar<'t, T: 't>(
   |                 ++++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0309`.