not lint on reborrow

Author: lengyijun

clippy_lints/src/needless_deref.rs

@@ -68,14 +68,21 @@ impl LateLintPass<'_> for NeedlessDeref {
                         return;
                     }
                     if matches!(deref_expr.kind, ExprKind::Path(..)) {
-                        let parent_node = map.find(parent_hir_id);
-                        if let Some(rustc_hir::Node::Expr(parent_expr)) = parent_node {
-                            if matches!(parent_expr.kind, ExprKind::AddrOf(_, Mutability::Mut, _)) {
-                                return;
+                        if let Some(parent_node) = map.find(parent_hir_id) {
+                            if let rustc_hir::Node::Local(..) = parent_node {
+                                let outer_ty = cx.typeck_results().node_type(parent_hir_id);
+                                if outer_ty == ref_ty {
+                                    return;
+                                }
                             }
-                            if matches!(parent_expr.kind, ExprKind::Unary(UnOp::Deref, ..)) &&
-                               !is_lint_allowed(cx, DEREF_ADDROF, parent_expr.hir_id) {
-                                return;
+                            if let rustc_hir::Node::Expr(parent_expr) = parent_node {
+                                if matches!(parent_expr.kind, ExprKind::AddrOf(_, Mutability::Mut, _)) {
+                                    return;
+                                }
+                                if matches!(parent_expr.kind, ExprKind::Unary(UnOp::Deref, ..)) &&
+                                   !is_lint_allowed(cx, DEREF_ADDROF, parent_expr.hir_id) {
+                                    return;
+                                }
                             }
                         }
                     }

tests/ui/needless_deref.rs

@@ -2,9 +2,6 @@ fn main() {}
 
 mod should_lint {
     fn foo() {
-        let a = &12;
-        let b = &*a;
-
         let s = &String::new();
         let a: &str = &*s;
 
@@ -17,8 +14,15 @@ mod should_lint {
     }
 }
 
-// this mod explains why we should not lint `&mut &* (&T)`
 mod should_not_lint1 {
+    fn not_lint_simple_reborrow() {
+        let a = &12;
+        let b = &*a;
+    }
+}
+
+// this mod explains why we should not lint `&mut &* (&T)`
+mod should_not_lint2 {
     fn foo(x: &mut &u32) {
         *x = &1;
     }

tests/ui/needless_deref.stderr

@@ -1,36 +1,28 @@
 error: deref on an immutable reference
-  --> $DIR/needless_deref.rs:6:17
-   |
-LL |         let b = &*a;
-   |                 ^^^
-   |
-   = note: `-D clippy::needless-deref` implied by `-D warnings`
-   = help: consider using `a` if you would like to reborrow
-
-error: deref on an immutable reference
-  --> $DIR/needless_deref.rs:9:23
+  --> $DIR/needless_deref.rs:6:23
    |
 LL |         let a: &str = &*s;
    |                       ^^^
    |
+   = note: `-D clippy::needless-deref` implied by `-D warnings`
    = help: consider using `&**s` if you would like to deref
    = help: consider using `s` if you would like to reborrow
 
 error: deref on an immutable reference
-  --> $DIR/needless_deref.rs:12:22
+  --> $DIR/needless_deref.rs:9:22
    |
 LL |         let b = &mut &*bar(a);
    |                      ^^^^^^^^
    |
    = help: consider using `bar(a)` if you would like to reborrow
 
 error: deref on an immutable reference
-  --> $DIR/needless_deref.rs:41:23
+  --> $DIR/needless_deref.rs:45:23
    |
 LL |         let addr_y = &&*x as *const _ as usize; // assert ok
    |                       ^^^
    |
    = help: consider using `x` if you would like to reborrow
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors