sugg on expr 2

Author: ada4a

clippy_lints/src/mut_mut.rs

@@ -1,4 +1,4 @@
-use clippy_utils::diagnostics::{span_lint, span_lint_hir, span_lint_hir_and_then};
+use clippy_utils::diagnostics::{span_lint, span_lint_hir_and_then};
 use clippy_utils::higher;
 use clippy_utils::sugg::Sugg;
 use rustc_errors::Applicability;
@@ -72,12 +72,17 @@ impl<'tcx> intravisit::Visitor<'tcx> for MutVisitor<'_, 'tcx> {
             intravisit::walk_expr(self, body);
         } else if let hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Mut, e) = expr.kind {
             if let hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Mut, _) = e.kind {
-                span_lint_hir(
+                let mut applicability = Applicability::MaybeIncorrect;
+                let sugg = Sugg::hir_with_applicability(self.cx, e, "..", &mut applicability);
+                span_lint_hir_and_then(
                     self.cx,
                     MUT_MUT,
                     expr.hir_id,
                     expr.span,
-                    "generally you want to avoid `&mut &mut _` if possible",
+                    "an expression of form `&mut &mut _`",
+                    |diag| {
+                        diag.span_suggestion(expr.span, "remove the extra `&mut`", sugg, applicability);
+                    },
                 );
             } else if let ty::Ref(_, ty, hir::Mutability::Mut) = self.cx.typeck_results().expr_ty(e).kind()
                 && ty.peel_refs().is_sized(self.cx.tcx, self.cx.typing_env())

tests/ui/mut_mut.fixed

@@ -29,27 +29,27 @@ macro_rules! mut_ptr {
 #[allow(unused_mut, unused_variables)]
 #[inline_macros]
 fn main() {
-    let mut x = &mut &mut 1u32;
+    let mut x = &mut 1u32;
     //~^ mut_mut
     {
         let mut y = &mut *x;
         //~^ mut_mut
     }
 
     {
-        let y: &mut &mut u32 = &mut &mut 2;
+        let y: &mut &mut u32 = &mut 2;
         //~^ mut_mut
         //~| mut_mut
     }
 
     {
-        let y: &mut &mut &mut u32 = &mut &mut &mut 2;
+        let y: &mut &mut &mut u32 = &mut &mut 2;
         //~^ mut_mut
         //~| mut_mut
         //~| mut_mut
     }
 
-    let mut z = inline!(&mut $(&mut 3u32));
+    let mut z = inline!(&mut 3u32mut $(&mut 3u32));
     //~^ mut_mut
 }
 

tests/ui/mut_mut.stderr

@@ -7,17 +7,17 @@ LL | fn fun(x: &mut &mut u32) {
    = note: `-D clippy::mut-mut` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::mut_mut)]`
 
-error: generally you want to avoid `&mut &mut _` if possible
+error: an expression of form `&mut &mut _`
   --> tests/ui/mut_mut.rs:32:17
    |
 LL |     let mut x = &mut &mut 1u32;
-   |                 ^^^^^^^^^^^^^^
+   |                 ^^^^^^^^^^^^^^ help: remove the extra `&mut`: `&mut 1u32`
 
-error: generally you want to avoid `&mut &mut _` if possible
+error: an expression of form `&mut &mut _`
   --> tests/ui/mut_mut.rs:52:25
    |
 LL |     let mut z = inline!(&mut $(&mut 3u32));
-   |                         ^
+   |                         ^ help: remove the extra `&mut`: `&mut 3u32`
    |
    = note: this error originates in the macro `__inline_mac_fn_main` (in Nightly builds, run with -Z macro-backtrace for more info)
 
@@ -27,23 +27,23 @@ error: this expression mutably borrows a mutable reference
 LL |         let mut y = &mut x;
    |                     ^^^^^^ help: reborrow instead: `&mut *x`
 
-error: generally you want to avoid `&mut &mut _` if possible
+error: an expression of form `&mut &mut _`
   --> tests/ui/mut_mut.rs:40:32
    |
 LL |         let y: &mut &mut u32 = &mut &mut 2;
-   |                                ^^^^^^^^^^^
+   |                                ^^^^^^^^^^^ help: remove the extra `&mut`: `&mut 2`
 
 error: generally you want to avoid `&mut &mut _` if possible
   --> tests/ui/mut_mut.rs:40:16
    |
 LL |         let y: &mut &mut u32 = &mut &mut 2;
    |                ^^^^^^^^^^^^^
 
-error: generally you want to avoid `&mut &mut _` if possible
+error: an expression of form `&mut &mut _`
   --> tests/ui/mut_mut.rs:46:37
    |
 LL |         let y: &mut &mut &mut u32 = &mut &mut &mut 2;
-   |                                     ^^^^^^^^^^^^^^^^
+   |                                     ^^^^^^^^^^^^^^^^ help: remove the extra `&mut`: `&mut &mut 2`
 
 error: generally you want to avoid `&mut &mut _` if possible
   --> tests/ui/mut_mut.rs:46:16

tests/ui/mut_mut_unfixable.stderr

@@ -7,29 +7,29 @@ LL | fn fun(x: &mut &mut u32) -> bool {
    = note: `-D clippy::mut-mut` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::mut_mut)]`
 
-error: generally you want to avoid `&mut &mut _` if possible
+error: an expression of form `&mut &mut _`
   --> tests/ui/mut_mut_unfixable.rs:15:17
    |
 LL |     let mut x = &mut &mut 1u32;
-   |                 ^^^^^^^^^^^^^^
+   |                 ^^^^^^^^^^^^^^ help: remove the extra `&mut`: `&mut 1u32`
 
 error: this expression mutably borrows a mutable reference
   --> tests/ui/mut_mut_unfixable.rs:18:21
    |
 LL |         let mut y = &mut x;
    |                     ^^^^^^ help: reborrow instead: `&mut *x`
 
-error: generally you want to avoid `&mut &mut _` if possible
+error: an expression of form `&mut &mut _`
   --> tests/ui/mut_mut_unfixable.rs:24:17
    |
 LL |         let y = &mut &mut 2;
-   |                 ^^^^^^^^^^^
+   |                 ^^^^^^^^^^^ help: remove the extra `&mut`: `&mut 2`
 
-error: generally you want to avoid `&mut &mut _` if possible
+error: an expression of form `&mut &mut _`
   --> tests/ui/mut_mut_unfixable.rs:30:17
    |
 LL |         let y = &mut &mut &mut 2;
-   |                 ^^^^^^^^^^^^^^^^
+   |                 ^^^^^^^^^^^^^^^^ help: remove the extra `&mut`: `&mut &mut 2`
 
 error: aborting due to 5 previous errors