Ignore borrow_deref_ref warnings in code from procedural macros.

tests/ui/borrow_deref_ref.fixed

@@ -1,7 +1,11 @@
 //@run-rustfix
+//@aux-build: proc_macros.rs
 
 #![allow(dead_code, unused_variables)]
 
+extern crate proc_macros;
+use proc_macros::with_span;
+
 fn main() {}
 
 mod should_lint {
@@ -47,6 +51,17 @@ mod should_not_lint2 {
     }
 }
 
+with_span!(
+    span
+
+    fn just_returning(x: &u32) -> &u32 {
+        x
+    }
+
+    fn dont_lint_proc_macro() {
+        let a = &mut &*just_returning(&12);
+    }
+);
 // this mod explains why we should not lint `& &* (&T)`
 mod false_negative {
     fn foo() {

tests/ui/borrow_deref_ref.rs

@@ -1,7 +1,11 @@
 //@run-rustfix
+//@aux-build: proc_macros.rs
 
 #![allow(dead_code, unused_variables)]
 
+extern crate proc_macros;
+use proc_macros::with_span;
+
 fn main() {}
 
 mod should_lint {
@@ -47,6 +51,17 @@ mod should_not_lint2 {
     }
 }
 
+with_span!(
+    span
+
+    fn just_returning(x: &u32) -> &u32 {
+        x
+    }
+
+    fn dont_lint_proc_macro() {
+        let a = &mut &*just_returning(&12);
+    }
+);
 // this mod explains why we should not lint `& &* (&T)`
 mod false_negative {
     fn foo() {

tests/ui/borrow_deref_ref.stderr

@@ -1,5 +1,5 @@
 error: deref on an immutable reference
-  --> $DIR/borrow_deref_ref.rs:10:17
+  --> $DIR/borrow_deref_ref.rs:14:17
    |
 LL |         let b = &*a;
    |                 ^^^ help: if you would like to reborrow, try removing `&*`: `a`
@@ -7,13 +7,13 @@ LL |         let b = &*a;
    = note: `-D clippy::borrow-deref-ref` implied by `-D warnings`
 
 error: deref on an immutable reference
-  --> $DIR/borrow_deref_ref.rs:12:22
+  --> $DIR/borrow_deref_ref.rs:16:22
    |
 LL |         let b = &mut &*bar(&12);
    |                      ^^^^^^^^^^ help: if you would like to reborrow, try removing `&*`: `bar(&12)`
 
 error: deref on an immutable reference
-  --> $DIR/borrow_deref_ref.rs:55:23
+  --> $DIR/borrow_deref_ref.rs:70:23
    |
 LL |         let addr_y = &&*x as *const _ as usize; // assert ok
    |                       ^^^ help: if you would like to reborrow, try removing `&*`: `x`