Auto merge of rust-lang#8268 - Jarcho:deref_addrof_8247, r=flip1995

Fix `deref_addrof`

fixes rust-lang#8247

This would supersede rust-lang#8259

changelog: Don't lint `deref_addrof` when the dereference and the borrow occur in different contexts

clippy_lints/src/reference.rs

@@ -50,6 +50,7 @@ impl EarlyLintPass for DerefAddrOf {
         if_chain! {
             if let ExprKind::Unary(UnOp::Deref, ref deref_target) = e.kind;
             if let ExprKind::AddrOf(_, ref mutability, ref addrof_target) = without_parens(deref_target).kind;
+            if deref_target.span.ctxt() == e.span.ctxt();
             if !addrof_target.span.from_expansion();
             then {
                 let mut applicability = Applicability::MachineApplicable;

tests/ui/deref_addrof.fixed

@@ -37,6 +37,8 @@ fn main() {
     let b = &a;
 
     let b = *aref;
+
+    let _ = unsafe { *core::ptr::addr_of!(a) };
 }
 
 #[rustfmt::skip]

tests/ui/deref_addrof.rs

@@ -37,6 +37,8 @@ fn main() {
     let b = *&&a;
 
     let b = **&aref;
+
+    let _ = unsafe { *core::ptr::addr_of!(a) };
 }
 
 #[rustfmt::skip]

tests/ui/deref_addrof.stderr

@@ -49,7 +49,7 @@ LL |     let b = **&aref;
    |              ^^^^^^ help: try this: `aref`
 
 error: immediately dereferencing a reference
-  --> $DIR/deref_addrof.rs:45:9
+  --> $DIR/deref_addrof.rs:47:9
    |
 LL |         *& $visitor
    |         ^^^^^^^^^^^ help: try this: `$visitor`
@@ -60,7 +60,7 @@ LL |         m!(self)
    = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: immediately dereferencing a reference
-  --> $DIR/deref_addrof.rs:52:9
+  --> $DIR/deref_addrof.rs:54:9
    |
 LL |         *& mut $visitor
    |         ^^^^^^^^^^^^^^^ help: try this: `$visitor`