bors ba196bdcb1 Auto merge of #51444 - estebank:impl-static, r=nikomatsakis
Suggestion for 'static impl Trait return

When encountering a named or anonymous sup requirement (for example,
`&'a self`) and a `'static` impl Trait return type, suggest adding the
`'_` lifetime constraing to the return type.

Fix #43719, #51282.

```
error: cannot infer an appropriate lifetime
  --> $DIR/static-return-lifetime-infered.rs:17:16
   |
LL |     fn iter_values_anon(&self) -> impl Iterator<Item=u32> {
   |                                   ----------------------- this return type evaluates to the `'static` lifetime...
LL |         self.x.iter().map(|a| a.0)
   |         ------ ^^^^
   |         |
   |         ...but this borrow...
   |
note: ...can't outlive the anonymous lifetime #1 defined on the method body at 16:5
  --> $DIR/static-return-lifetime-infered.rs:16:5
   |
LL | /     fn iter_values_anon(&self) -> impl Iterator<Item=u32> {
LL | |         self.x.iter().map(|a| a.0)
LL | |     }
   | |_____^
help: you can add a constraint to the return type to make it last less than `'static` and match the anonymous lifetime #1 defined on the method body at 16:5
   |
LL |     fn iter_values_anon(&self) -> impl Iterator<Item=u32> + '_ {
   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
2018-06-28 03:57:28 +00:00
..
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2018-06-27 16:30:38 -04:00

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