*error*.txt

error[E0495]: this data would have to have static lifetime
  --> dyn-trait-underscore.rs:18:20
   |
16 |   fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T>> {
   |                  ---- SourceArgument
18 |       Box::new(items.iter())
   |       ^^^^^^^^^^^^^^^^^^^^^^ InterestingSpot(Cast)
19 |  }

error[E0495]: this data would have to have static lifetime
  --> dyn-trait-underscore.rs:18:20
   |
16 |   fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T>> {
   |                  ---- SourceArgument
18 |       Box::new(items.iter())
   |       ^^^^^^^^^^^^^^^^^^^^^^ InterestingSpot(Cast)
   |       |
   |       call to box
19 |  }

1. write some function that takes a Location + MIR => ConstraintCategory
2. write some semi-arbitrary ordering on ConstraintCategories to pick the "master" one
3. make the labels and emit the error

then as followup:

4. write code to find the argument (if any) that contains the universal region
  - maybe we want to reuse `find_arg_with_region` from `nice_region_error`
  - would have to convert from RegionVid to error-region using `RegionInferenceContext::to_error_region`
  
---

error[E0495]: this data would have to have static lifetime
  --> dyn-trait-underscore.rs:18:20
   |
16 |   fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T>> {
   |                  ---- source value starts here
18 |       Box::new(items.iter())
   |       ^^^^^^^^^^^^^^^^^^^^^^ casting this value to `dyn Iterator<Item=&T> + 'static` requires data to have `'static` lifetime
19 |  }

- we filter the edges to interesting ones
  - for a given MIR statement, "categorize" why it's interesting
    - assignments, call arguments, casts
- we pick some edge to be the "primary point"
  - this will just be a heurstic
- for each of those places, we put a label and describe
  - "data flows here..."
- the universal region `'1` -- find the argument(s) in which it appears and underline those,
  saying "data has to have static lifetime" ("source value starts here")

----

error[E0495]: this data would have to have static lifetime
  --> dyn-trait-underscore.rs:18:20
   |
16 |   fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T>> {
   |                  ---- fully elaborated type is `&'1 [T]`
18 |       Box::new(items.iter())
   |       ^^^^^^^^^^^^^^^^^^^^^^ casting this value to a `dyn Iterator` requires `'1` to outlive `'static` 
19 |  }

----

error[E0495]: cannot infer an appropriate lifetime for autoref due to conflicting requirements
  --> dyn-trait-underscore.rs:18:20
   |
18 |     Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime
   |                    ^^^^
   |
note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the function body at 16:1...
  --> dyn-trait-underscore.rs:16:1
   |
16 | / fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T>> {
17 | |     //                      ^^^^^^^^^^^^^^^^^^^^^ bound *here* defaults to `'static`
18 | |     Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime
19 | | }
   | |_^
note: ...so that reference does not outlive borrowed content
  --> dyn-trait-underscore.rs:18:14
   |
18 |     Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime
   |              ^^^^^
   = note: but, the lifetime must be valid for the static lifetime...
   = note: ...so that the expression is assignable:
           expected std::boxed::Box<std::iter::Iterator<Item=&T> + 'static>
              found std::boxed::Box<std::iter::Iterator<Item=&T>>