run rust-fix in amputate-span.rs. (Thanks to ekuber for pushing me to do this.)

src/test/ui/proc-macro/amputate-span.fixed

@@ -0,0 +1,69 @@
+// aux-build:amputate-span.rs
+// run-rustfix
+// edition:2018
+// compile-flags: --extern amputate_span
+
+// This test has been crafted to ensure the following things:
+//
+// 1. There's a resolution error that prompts the compiler to suggest
+//    adding a `use` item.
+//
+// 2. There are no `use` or `extern crate` items in the source
+//    code. In fact, there is only one item, the `fn main`
+//    declaration.
+//
+// 3. The single `fn main` declaration has an attribute attached to it
+//    that just deletes the first token from the given item.
+//
+// You need all of these conditions to hold in order to replicate the
+// scenario that yielded issue 87613, where the compiler's suggestion
+// looks like:
+//
+// ```
+// help: consider importing this struct
+//    |
+// 47 | hey */ async use std::process::Command;
+//    |              ++++++++++++++++++++++++++
+// ```
+//
+// The first condition is necessary to force the compiler issue a
+// suggestion. The second condition is necessary to force the
+// suggestion to be issued at a span associated with the sole
+// `fn`-item of this crate. The third condition is necessary in order
+// to yield the weird state where the associated span of the `fn`-item
+// does not actually cover all of the original source code of the
+// `fn`-item (which is why we are calling it an "amputated" span
+// here).
+//
+// Note that satisfying conditions 2 and 3 requires the use of the
+// `--extern` compile flag.
+//
+// You might ask yourself: What code would do such a thing?  The
+// answer is: the #[tokio::main] attribute does *exactly* this (as
+// well as injecting some other code into the `fn main` that it
+// constructs).
+
+use std::process::Command;
+
+#[amputate_span::drop_first_token]
+/* what the
+hey */ async fn main() {
+    Command::new("git"); //~ ERROR [E0433]
+}
+
+// (The /* ... */ comment in the above is not part of the original
+// bug. It is just meant to illustrate one particular facet of the
+// original non-ideal behavior, where we were transcribing the
+// trailing comment as part of the emitted suggestion, for better or
+// for worse.)
+
+#[allow(dead_code)]
+mod inner {
+    use std::process::Command;
+
+#[amputate_span::drop_first_token]
+        /* another interesting
+    case */ async fn foo() {
+        Command::new("git"); //~ ERROR [E0433]
+    }
+}

src/test/ui/proc-macro/amputate-span.rs

@@ -1,4 +1,5 @@
 // aux-build:amputate-span.rs
+// run-rustfix
 // edition:2018
 // compile-flags: --extern amputate_span
 
@@ -54,6 +55,7 @@ hey */ async fn main() {
 // trailing comment as part of the emitted suggestion, for better or
 // for worse.)
 
+#[allow(dead_code)]
 mod inner {
     #[amputate_span::drop_first_token]
         /* another interesting

src/test/ui/proc-macro/amputate-span.stderr

@@ -1,5 +1,5 @@
 error[E0433]: failed to resolve: use of undeclared type `Command`
-  --> $DIR/amputate-span.rs:48:5
+  --> $DIR/amputate-span.rs:49:5
    |
 LL |     Command::new("git");
    |     ^^^^^^^ not found in this scope
@@ -10,7 +10,7 @@ LL | use std::process::Command;
    |
 
 error[E0433]: failed to resolve: use of undeclared type `Command`
-  --> $DIR/amputate-span.rs:61:9
+  --> $DIR/amputate-span.rs:63:9
    |
 LL |         Command::new("git");
    |         ^^^^^^^ not found in this scope