Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`

```
error[E0310]: the parameter type `R` may not live long enough
  --> $DIR/implicit-static-lifetime-in-dyn-trait-return-type.rs:10:5
   |
LL | fn bb<R>(r: R) -> Box<dyn Foo> {
   |                       ------- this `dyn Trait` has an implicit `'static` lifetime bound
LL |     Box::new(Bar(r))
   |     ^^^^^^^^^^^^^^^^
   |     |
   |     the parameter type `R` must be valid for the static lifetime...
   |     ...so that the type `R` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | fn bb<R: 'static>(r: R) -> Box<dyn Foo> {
   |        +++++++++
```

Partly address rust-lang#41966 and rust-lang#54753. rust-lang#103849, which shows a case where there's an intermediary binding, is not addressed at all, as aren't cases *other* than `Box<dyn Trait>` return type.

Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`

```
error[E0310]: the parameter type `R` may not live long enough
  --> $DIR/implicit-static-lifetime-in-dyn-trait-return-type.rs:10:5
   |
LL | fn bb<R>(r: R) -> Box<dyn Foo> {
   |                       ------- this `dyn Trait` has an implicit `'static` lifetime bound
LL |     Box::new(Bar(r))
   |     ^^^^^^^^^^^^^^^^
   |     |
   |     the parameter type `R` must be valid for the static lifetime...
   |     ...so that the type `R` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | fn bb<R: 'static>(r: R) -> Box<dyn Foo> {
   |        +++++++++
```

Partly address rust-lang#41966 and rust-lang#54753. rust-lang#103849, which shows a case where there's an intermediary binding, is not addressed at all, as aren't cases *other* than `Box<dyn Trait>` return type.

Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`

```
error[E0310]: the parameter type `R` may not live long enough
  --> $DIR/implicit-static-lifetime-in-dyn-trait-return-type.rs:10:5
   |
LL | fn bb<R>(r: R) -> Box<dyn Foo> {
   |                       ------- this `dyn Trait` has an implicit `'static` lifetime bound
LL |     Box::new(Bar(r))
   |     ^^^^^^^^^^^^^^^^
   |     |
   |     the parameter type `R` must be valid for the static lifetime...
   |     ...so that the type `R` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | fn bb<R: 'static>(r: R) -> Box<dyn Foo> {
   |        +++++++++
```

Partly address rust-lang#41966 and rust-lang#54753. rust-lang#103849, which shows a case where there's an intermediary binding, is not addressed at all, as aren't cases *other* than `Box<dyn Trait>` return type.

Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`

```
error[E0310]: the parameter type `R` may not live long enough
  --> $DIR/implicit-static-lifetime-in-dyn-trait-return-type.rs:10:5
   |
LL | fn bb<R>(r: R) -> Box<dyn Foo> {
   |                       ------- this `dyn Trait` has an implicit `'static` lifetime bound
LL |     Box::new(Bar(r))
   |     ^^^^^^^^^^^^^^^^
   |     |
   |     the parameter type `R` must be valid for the static lifetime...
   |     ...so that the type `R` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | fn bb<R: 'static>(r: R) -> Box<dyn Foo> {
   |        +++++++++
```

Partly address rust-lang#41966 and rust-lang#54753. rust-lang#103849, which shows a case where there's an intermediary binding, is not addressed at all, as aren't cases *other* than `Box<dyn Trait>` return type.

Rollup of 16 pull requests

Successful merges:

 - #141470 (Add new `function_casts_as_integer` lint)
 - #143619 (`c_variadic`: Add future-incompatibility warning for `...` arguments without a pattern outside of `extern` blocks)
 - #146495 (rustdoc: Erase `#![doc(document_private_items)]`)
 - #147771 (Rename `*exact_{div,shr,shl}` to `*{div,shr,shl}_exact`)
 - #147833 (rustdoc-json: move `target` to `json::conversions`)
 - #147952 (Add a timeout to the `remote-test-client` connection)
 - #147955 (compiletest: Migrate `TestProps` directive handling to a system of named handlers)
 - #148480 (Add `Steal::risky_hack_borrow_mut`)
 - #148506 (Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`)
 - #148508 (Provide more context when mutably borrowing an imutably borrowed value)
 - #148530 (update the bootstrap readme)
 - #148608 (Add test for --test-builder success path)
 - #148636 (bootstrap: respect `build.python` on macOS)
 - #148639 (test(rustdoc): move tests into jump-to-def)
 - #148647 (Check unsafety for non-macro attributes in `validate_attr`)
 - #148667 (a few small clippy fixes)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup of 16 pull requests

Successful merges:

 - #141470 (Add new `function_casts_as_integer` lint)
 - #143619 (`c_variadic`: Add future-incompatibility warning for `...` arguments without a pattern outside of `extern` blocks)
 - #146495 (rustdoc: Erase `#![doc(document_private_items)]`)
 - #147771 (Rename `*exact_{div,shr,shl}` to `*{div,shr,shl}_exact`)
 - #147833 (rustdoc-json: move `target` to `json::conversions`)
 - #147952 (Add a timeout to the `remote-test-client` connection)
 - #147955 (compiletest: Migrate `TestProps` directive handling to a system of named handlers)
 - #148480 (Add `Steal::risky_hack_borrow_mut`)
 - #148506 (Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`)
 - #148508 (Provide more context when mutably borrowing an imutably borrowed value)
 - #148530 (update the bootstrap readme)
 - #148608 (Add test for --test-builder success path)
 - #148636 (bootstrap: respect `build.python` on macOS)
 - #148639 (test(rustdoc): move tests into jump-to-def)
 - #148647 (Check unsafety for non-macro attributes in `validate_attr`)
 - #148667 (a few small clippy fixes)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup of 15 pull requests

Successful merges:

 - #141470 (Add new `function_casts_as_integer` lint)
 - #143619 (`c_variadic`: Add future-incompatibility warning for `...` arguments without a pattern outside of `extern` blocks)
 - #146495 (rustdoc: Erase `#![doc(document_private_items)]`)
 - #147771 (Rename `*exact_{div,shr,shl}` to `*{div,shr,shl}_exact`)
 - #147833 (rustdoc-json: move `target` to `json::conversions`)
 - #147955 (compiletest: Migrate `TestProps` directive handling to a system of named handlers)
 - #148480 (Add `Steal::risky_hack_borrow_mut`)
 - #148506 (Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`)
 - #148508 (Provide more context when mutably borrowing an imutably borrowed value)
 - #148530 (update the bootstrap readme)
 - #148608 (Add test for --test-builder success path)
 - #148636 (bootstrap: respect `build.python` on macOS)
 - #148639 (test(rustdoc): move tests into jump-to-def)
 - #148647 (Check unsafety for non-macro attributes in `validate_attr`)
 - #148667 (a few small clippy fixes)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup merge of #148506 - estebank:issue-41966, r=davidtwco

Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`

```
error[E0310]: the parameter type `R` may not live long enough
  --> $DIR/implicit-static-lifetime-in-dyn-trait-return-type.rs:10:5
   |
LL | fn bb<R>(r: R) -> Box<dyn Foo> {
   |                       ------- this `dyn Trait` has an implicit `'static` lifetime bound
LL |     Box::new(Bar(r))
   |     ^^^^^^^^^^^^^^^^
   |     |
   |     the parameter type `R` must be valid for the static lifetime...
   |     ...so that the type `R` will meet its required lifetime bounds
   |
help: consider adding an explicit lifetime bound
   |
LL | fn bb<R: 'static>(r: R) -> Box<dyn Foo> {
   |        +++++++++
```

Partly address #41966 and #54753. #103849, which shows a case where there's an intermediary binding, is not addressed at all, as aren't cases *other* than `Box<dyn Trait>` return type.