new test

Author: lengyijun

clippy_lints/src/needless_deref.rs

@@ -1,8 +1,7 @@
 use clippy_utils::diagnostics::span_lint_and_help;
 use clippy_utils::in_macro;
 use clippy_utils::source::snippet_opt;
-use rustc_hir::ExprKind;
-use rustc_hir::UnOp;
+use rustc_hir::{ExprKind, UnOp};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::mir::Mutability;
 use rustc_middle::ty;
@@ -51,13 +50,13 @@ impl LateLintPass<'_> for NeedlessDeref {
             if let ty::Ref(_, _, Mutability::Not) = inner_ty.kind();
             then{
 
-                let map=cx.tcx.hir();
+                let map = cx.tcx.hir();
                 if let Some(parent_hir_id) = map.find_parent_node(e.hir_id){
                     let span=map.span(parent_hir_id);
                     if span.from_expansion() || in_macro(span) {
                         return;
                     }
-                    let parent_node=map.find(parent_hir_id);
+                    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::Unary(UnOp::Deref, ..)) ||
                             matches!(parent_expr.kind, ExprKind::AddrOf(..) ){
@@ -66,7 +65,6 @@ impl LateLintPass<'_> for NeedlessDeref {
                     }
                 }
 
-
                 span_lint_and_help(
                     cx,
                     NEEDLESS_DEREF,
@@ -75,7 +73,7 @@ impl LateLintPass<'_> for NeedlessDeref {
                     None,
                     &format!(
                         "consider using `{}` if you would like to deref\nconsider using `{}` if you would like to reborrow",
-                        "&**".to_owned()+&snippet_opt(cx, deref_target.span).unwrap(),
+                        "&**".to_owned() + &snippet_opt(cx, deref_target.span).unwrap(),
                         &snippet_opt(cx, deref_target.span).unwrap(),
                      )
                 );

tests/ui/needless_deref.rs

@@ -4,6 +4,9 @@ mod should_lint {
     fn foo() {
         let a = &12;
         let _b = &*a;
+
+        let s = &String::new();
+        let a: &str = &*s;
     }
 }
 

tests/ui/needless_deref.stderr

@@ -8,5 +8,14 @@ LL |         let _b = &*a;
    = help: consider using `&**a` if you would like to deref
            consider using `a` if you would like to reborrow
 
-error: aborting due to previous error
+error: reference on a de-referenced
+  --> $DIR/needless_deref.rs:9:23
+   |
+LL |         let a: &str = &*s;
+   |                       ^^^
+   |
+   = help: consider using `&**s` if you would like to deref
+           consider using `s` if you would like to reborrow
+
+error: aborting due to 2 previous errors