Remove std lib Span from expected boxed future test

src/test/ui/suggestions/expected-boxed-future-isnt-pinned.fixed

@@ -7,10 +7,9 @@ use std::pin::Pin;
 type BoxFuture<'a, T> = Pin<Box<dyn Future<Output = T> + Send + 'a>>;
 //   ^^^^^^^^^ This would come from the `futures` crate in real code.
 
-fn foo() -> BoxFuture<'static, i32> {
-    Box::pin(async { //~ ERROR mismatched types
-        42
-    })
+fn foo<F: Future<Output=i32> + Send + 'static>(x: F) -> BoxFuture<'static, i32> {
+    // We could instead use an `async` block, but this way we have no std spans.
+    Box::pin(x) //~ ERROR mismatched types
 }
 
 fn main() {}

src/test/ui/suggestions/expected-boxed-future-isnt-pinned.rs

@@ -7,10 +7,9 @@ use std::pin::Pin;
 type BoxFuture<'a, T> = Pin<Box<dyn Future<Output = T> + Send + 'a>>;
 //   ^^^^^^^^^ This would come from the `futures` crate in real code.
 
-fn foo() -> BoxFuture<'static, i32> {
-    async { //~ ERROR mismatched types
-        42
-    }
+fn foo<F: Future<Output=i32> + Send + 'static>(x: F) -> BoxFuture<'static, i32> {
+    // We could instead use an `async` block, but this way we have no std spans.
+    x //~ ERROR mismatched types
 }
 
 fn main() {}

src/test/ui/suggestions/expected-boxed-future-isnt-pinned.stderr

@@ -1,26 +1,19 @@
 error[E0308]: mismatched types
-  --> $DIR/expected-boxed-future-isnt-pinned.rs:11:5
+  --> $DIR/expected-boxed-future-isnt-pinned.rs:12:5
    |
-LL |   fn foo() -> BoxFuture<'static, i32> {
-   |               ----------------------- expected `std::pin::Pin<std::boxed::Box<(dyn std::future::Future<Output = i32> + std::marker::Send + 'static)>>` because of return type
-LL | /     async {
-LL | |         42
-LL | |     }
-   | |_____^ expected struct `std::pin::Pin`, found opaque type
-   | 
-  ::: $SRC_DIR/libstd/future.rs:LL:COL
-   |
-LL |   pub fn from_generator<T: Generator<Yield = ()>>(x: T) -> impl Future<Output = T::Return> {
-   |                                                            ------------------------------- the found opaque type
-   |
-   = note:   expected struct `std::pin::Pin<std::boxed::Box<(dyn std::future::Future<Output = i32> + std::marker::Send + 'static)>>`
-           found opaque type `impl std::future::Future`
-help: you need to pin and box this expression
-   |
-LL |     Box::pin(async {
-LL |         42
-LL |     })
+LL | fn foo<F: Future<Output=i32> + Send + 'static>(x: F) -> BoxFuture<'static, i32> {
+   |        - this type parameter                            ----------------------- expected `std::pin::Pin<std::boxed::Box<(dyn std::future::Future<Output = i32> + std::marker::Send + 'static)>>` because of return type
+LL |     // We could instead use an `async` block, but this way we have no std spans.
+LL |     x
+   |     ^
+   |     |
+   |     expected struct `std::pin::Pin`, found type parameter `F`
+   |     help: you need to pin and box this expression: `Box::pin(x)`
    |
+   = note:      expected struct `std::pin::Pin<std::boxed::Box<(dyn std::future::Future<Output = i32> + std::marker::Send + 'static)>>`
+           found type parameter `F`
+   = help: type parameters must be constrained to match other types
+   = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
 
 error: aborting due to previous error