Auto merge of rust-lang#10761 - lochetti:fix_9871, r=Manishearth

Ignore `borrow_deref_ref` warnings in code from procedural macros.

Don't linting `borrow_deref_ref` if code was generated by procedural macro.

This PR fixes rust-lang/rust-clippy#8971

changelog: [`borrow_deref_ref`] avoiding warnings in macro-generated code

clippy_lints/src/borrow_deref_ref.rs

@@ -1,5 +1,6 @@
 use crate::reference::DEREF_ADDROF;
 use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::is_from_proc_macro;
 use clippy_utils::source::snippet_opt;
 use clippy_utils::ty::implements_trait;
 use clippy_utils::{get_parent_expr, is_lint_allowed};
@@ -47,8 +48,8 @@ declare_clippy_lint! {
 
 declare_lint_pass!(BorrowDerefRef => [BORROW_DEREF_REF]);
 
-impl LateLintPass<'_> for BorrowDerefRef {
-    fn check_expr(&mut self, cx: &LateContext<'_>, e: &rustc_hir::Expr<'_>) {
+impl<'tcx> LateLintPass<'tcx> for BorrowDerefRef {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &rustc_hir::Expr<'tcx>) {
         if_chain! {
             if !e.span.from_expansion();
             if let ExprKind::AddrOf(_, Mutability::Not, addrof_target) = e.kind;
@@ -58,6 +59,7 @@ impl LateLintPass<'_> for BorrowDerefRef {
             if !matches!(deref_target.kind, ExprKind::Unary(UnOp::Deref, ..) );
             let ref_ty = cx.typeck_results().expr_ty(deref_target);
             if let ty::Ref(_, inner_ty, Mutability::Not) = ref_ty.kind();
+            if !is_from_proc_macro(cx, e);
             then{
 
                 if let Some(parent_expr) = get_parent_expr(cx, e){

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

@@ -1,19 +1,19 @@
 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`
    |
    = 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`