Shorten output of E0391

[estebank]

Use the shorter def_span on the impl-Trait cyclic reference errors.

[rust-highfive]

r? @nikomatsakis

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[kennytm]

The output of issue-23305.rs is also affected.

 error[E0391]: unsupported cyclic reference between types/traits detected
--> $DIR/issue-23305.rs:15:12
|
15 | impl ToNbt<Self> {}
| ^^^^ cyclic reference
|
note: the cycle begins when processing `<impl at $DIR/issue-23305.rs:15:1: 15:20>`...
--> $DIR/issue-23305.rs:15:1
|
15 | impl ToNbt<Self> {}
- | ^^^^^^^^^^^^^^^^^^^+ | ^^^^^^^^^^^^^^^^
= note: ...which then again requires processing `<impl at $DIR/issue-23305.rs:15:1: 15:20>`, completing the cycle.
error: aborting due to previous error

[kennytm]

Actual output differs from expected output. Please update.

 error[E0391]: unsupported cyclic reference between types/traits detected
--> $DIR/auto-trait-leak.rs:52:1
|
-52 | fn cycle1() -> impl Clone {- | ^^^^^^^^^^^^^^^^^^^^^^^^^ cyclic reference+52 | fn cycle1() -> impl Clone {+ | _-^^^^^^^^^^^^^^^^^^^^^^^^+53 | | //~^ ERROR unsupported cyclic reference between types/traits detected+54 | | //~| cyclic reference+55 | | //~| NOTE the cycle begins when processing `cycle1`...+... |+60 | | Rc::new(Cell::new(5))+61 | | }+ | |_- cyclic reference

[estebank]

Missed the label. Done.

[arielb1]

@bors r+ rollup

[bors]

📌 Commit 487daab has been approved by arielb1