tests/ui/extern: add annotations for reference rules

tests/ui/extern/extern-crate-rename.rs

@@ -1,5 +1,6 @@
 //@ aux-build:m1.rs
 //@ aux-build:m2.rs
+//@ reference: items.extern-crate.as
 
 
 extern crate m1;

tests/ui/extern/extern-crate-rename.stderr

@@ -1,5 +1,5 @@
 error[E0259]: the name `m1` is defined multiple times
-  --> $DIR/extern-crate-rename.rs:6:1
+  --> $DIR/extern-crate-rename.rs:7:1
    |
 LL | extern crate m1;
    | ---------------- previous import of the extern crate `m1` here

tests/ui/extern/extern-ffi-fn-with-body.rs

@@ -1,3 +1,6 @@
+//@ reference: items.extern.fn.body
+//@ reference: items.fn.extern.intro
+
 extern "C" {
     fn foo() -> i32 { //~ ERROR incorrect function inside `extern` block
         return 0;

tests/ui/extern/extern-ffi-fn-with-body.stderr

@@ -1,5 +1,5 @@
 error: incorrect function inside `extern` block
-  --> $DIR/extern-ffi-fn-with-body.rs:2:8
+  --> $DIR/extern-ffi-fn-with-body.rs:5:8
    |
 LL |   extern "C" {
    |   ---------- `extern` blocks define existing foreign functions and functions inside of them cannot have a body

tests/ui/extern/extern-thiscall.rs

@@ -1,5 +1,6 @@
 //@ run-pass
 //@ only-x86
+//@ reference: items.extern.abi.thiscall
 
 trait A {
     extern "thiscall" fn test1(i: i32);

tests/ui/extern/function-definition-in-extern-block-75283.rs

@@ -1,3 +1,4 @@
+//@ reference: items.extern.fn.body
 // https://github.com/rust-lang/rust/issues/75283
 extern "C" {
     fn lol() { //~ ERROR incorrect function inside `extern` block

tests/ui/extern/function-definition-in-extern-block-75283.stderr

@@ -1,5 +1,5 @@
 error: incorrect function inside `extern` block
-  --> $DIR/function-definition-in-extern-block-75283.rs:3:8
+  --> $DIR/function-definition-in-extern-block-75283.rs:4:8
    |
 LL |   extern "C" {
    |   ---------- `extern` blocks define existing foreign functions and functions inside of them cannot have a body

tests/ui/extern/issue-28324.rs

@@ -1,3 +1,5 @@
+//@ reference: const-eval.const-expr.path-static
+//@ reference: items.extern.static.safety
 extern "C" {
     static error_message_count: u32;
 }

tests/ui/extern/issue-28324.stderr

@@ -1,11 +1,11 @@
 error[E0080]: cannot access extern static `error_message_count`
-  --> $DIR/issue-28324.rs:5:23
+  --> $DIR/issue-28324.rs:7:23
    |
 LL | pub static BAZ: u32 = *&error_message_count;
    |                       ^^^^^^^^^^^^^^^^^^^^^ evaluation of `BAZ` failed here
 
 error[E0133]: use of extern static is unsafe and requires unsafe function or block
-  --> $DIR/issue-28324.rs:5:25
+  --> $DIR/issue-28324.rs:7:25
    |
 LL | pub static BAZ: u32 = *&error_message_count;
    |                         ^^^^^^^^^^^^^^^^^^^ use of extern static

tests/ui/extern/issue-47725.rs

@@ -1,3 +1,4 @@
+//@ reference: items.extern.attributes.link_name.allowed-positions
 #![warn(unused_attributes)] //~ NOTE lint level is defined here
 
 #[link_name = "foo"]

tests/ui/extern/issue-47725.stderr

@@ -1,5 +1,5 @@
 error[E0539]: malformed `link_name` attribute input
-  --> $DIR/issue-47725.rs:19:1
+  --> $DIR/issue-47725.rs:20:1
    |
 LL | #[link_name]
    | ^^^^^^^^^^^^
@@ -11,21 +11,21 @@ LL | #[link_name = "name"]
    |             ++++++++
 
 warning: `#[link_name]` attribute cannot be used on structs
-  --> $DIR/issue-47725.rs:3:1
+  --> $DIR/issue-47725.rs:4:1
    |
 LL | #[link_name = "foo"]
    | ^^^^^^^^^^^^^^^^^^^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = help: `#[link_name]` can be applied to foreign functions and foreign statics
 note: the lint level is defined here
-  --> $DIR/issue-47725.rs:1:9
+  --> $DIR/issue-47725.rs:2:9
    |
 LL | #![warn(unused_attributes)]
    |         ^^^^^^^^^^^^^^^^^
 
 warning: `#[link_name]` attribute cannot be used on foreign modules
-  --> $DIR/issue-47725.rs:10:1
+  --> $DIR/issue-47725.rs:11:1
    |
 LL | #[link_name = "foobar"]
    | ^^^^^^^^^^^^^^^^^^^^^^^
@@ -34,7 +34,7 @@ LL | #[link_name = "foobar"]
    = help: `#[link_name]` can be applied to foreign functions and foreign statics
 
 warning: `#[link_name]` attribute cannot be used on foreign modules
-  --> $DIR/issue-47725.rs:19:1
+  --> $DIR/issue-47725.rs:20:1
    |
 LL | #[link_name]
    | ^^^^^^^^^^^^

tests/ui/extern/issue-95829.rs

@@ -1,4 +1,5 @@
 //@ edition:2018
+//@ reference: items.extern.fn.qualifiers
 
 extern "C" {
     async fn L() { //~ ERROR: incorrect function inside `extern` block

tests/ui/extern/issue-95829.stderr

@@ -1,5 +1,5 @@
 error: incorrect function inside `extern` block
-  --> $DIR/issue-95829.rs:4:14
+  --> $DIR/issue-95829.rs:5:14
    |
 LL |   extern "C" {
    |   ---------- `extern` blocks define existing foreign functions and functions inside of them cannot have a body
@@ -16,7 +16,7 @@ LL | |     }
    = note: for more information, visit https://doc.rust-lang.org/std/keyword.extern.html
 
 error: functions in `extern` blocks cannot have `async` qualifier
-  --> $DIR/issue-95829.rs:4:5
+  --> $DIR/issue-95829.rs:5:5
    |
 LL | extern "C" {
    | ---------- in this `extern` block