consider mutability on useless_vec suggestions

https://github.com/rust-lang/rust-clippy/issues/7035

clippy_lints/src/vec.rs

@@ -6,7 +6,7 @@ use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::ty::is_copy;
 use if_chain::if_chain;
 use rustc_errors::Applicability;
-use rustc_hir::{BorrowKind, Expr, ExprKind};
+use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::{self, Ty};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
@@ -49,10 +49,10 @@ impl<'tcx> LateLintPass<'tcx> for UselessVec {
         if_chain! {
             if let ty::Ref(_, ty, _) = cx.typeck_results().expr_ty_adjusted(expr).kind();
             if let ty::Slice(..) = ty.kind();
-            if let ExprKind::AddrOf(BorrowKind::Ref, _, ref addressee) = expr.kind;
+            if let ExprKind::AddrOf(BorrowKind::Ref, mutability, ref addressee) = expr.kind;
             if let Some(vec_args) = higher::vec_macro(cx, addressee);
             then {
-                self.check_vec_macro(cx, &vec_args, expr.span);
+                self.check_vec_macro(cx, &vec_args, mutability, expr.span);
             }
         }
 
@@ -70,14 +70,20 @@ impl<'tcx> LateLintPass<'tcx> for UselessVec {
                     .ctxt()
                     .outer_expn_data()
                     .call_site;
-                self.check_vec_macro(cx, &vec_args, span);
+                self.check_vec_macro(cx, &vec_args, Mutability::Not, span);
             }
         }
     }
 }
 
 impl UselessVec {
-    fn check_vec_macro<'tcx>(self, cx: &LateContext<'tcx>, vec_args: &higher::VecArgs<'tcx>, span: Span) {
+    fn check_vec_macro<'tcx>(
+        self,
+        cx: &LateContext<'tcx>,
+        vec_args: &higher::VecArgs<'tcx>,
+        mutability: Mutability,
+        span: Span,
+    ) {
         let mut applicability = Applicability::MachineApplicable;
         let snippet = match *vec_args {
             higher::VecArgs::Repeat(elem, len) => {
@@ -87,11 +93,22 @@ impl UselessVec {
                         return;
                     }
 
-                    format!(
+                    match mutability {
-                        "&[{}; {}]",
+                        Mutability::Mut => {
-                        snippet_with_applicability(cx, elem.span, "elem", &mut applicability),
+                            format!(
-                        snippet_with_applicability(cx, len.span, "len", &mut applicability)
+                                "&mut [{}; {}]",
-                    )
+                                snippet_with_applicability(cx, elem.span, "elem", &mut applicability),
+                                snippet_with_applicability(cx, len.span, "len", &mut applicability)
+                            )
+                        },
+                        Mutability::Not => {
+                            format!(
+                                "&[{}; {}]",
+                                snippet_with_applicability(cx, elem.span, "elem", &mut applicability),
+                                snippet_with_applicability(cx, len.span, "len", &mut applicability)
+                            )
+                        },
+                    }
                 } else {
                     return;
                 }
@@ -104,9 +121,22 @@ impl UselessVec {
                     }
                     let span = args[0].span.to(last.span);
 
-                    format!("&[{}]", snippet_with_applicability(cx, span, "..", &mut applicability))
+                    match mutability {
+                        Mutability::Mut => {
+                            format!(
+                                "&mut [{}]",
+                                snippet_with_applicability(cx, span, "..", &mut applicability)
+                            )
+                        },
+                        Mutability::Not => {
+                            format!("&[{}]", snippet_with_applicability(cx, span, "..", &mut applicability))
+                        },
+                    }
                 } else {
-                    "&[]".into()
+                    match mutability {
+                        Mutability::Mut => "&mut []".into(),
+                        Mutability::Not => "&[]".into(),
+                    }
                 }
             },
         };

tests/ui/vec.fixed

@@ -6,9 +6,14 @@
 struct NonCopy;
 
 fn on_slice(_: &[u8]) {}
+
+fn on_mut_slice(_: &mut [u8]) {}
+
 #[allow(clippy::ptr_arg)]
 fn on_vec(_: &Vec<u8>) {}
 
+fn on_mut_vec(_: &mut Vec<u8>) {}
+
 struct Line {
     length: usize,
 }
@@ -22,28 +27,38 @@ impl Line {
 fn main() {
     on_slice(&[]);
     on_slice(&[]);
+    on_mut_slice(&mut []);
 
     on_slice(&[1, 2]);
     on_slice(&[1, 2]);
+    on_mut_slice(&mut [1, 2]);
 
     on_slice(&[1, 2]);
     on_slice(&[1, 2]);
+    on_mut_slice(&mut [1, 2]);
     #[rustfmt::skip]
     on_slice(&[1, 2]);
     on_slice(&[1, 2]);
+    on_mut_slice(&mut [1, 2]);
 
     on_slice(&[1; 2]);
     on_slice(&[1; 2]);
+    on_mut_slice(&mut [1; 2]);
 
     on_vec(&vec![]);
     on_vec(&vec![1, 2]);
     on_vec(&vec![1; 2]);
+    on_mut_vec(&mut vec![]);
+    on_mut_vec(&mut vec![1, 2]);
+    on_mut_vec(&mut vec![1; 2]);
 
     // Now with non-constant expressions
     let line = Line { length: 2 };
 
     on_slice(&vec![2; line.length]);
     on_slice(&vec![2; line.length()]);
+    on_mut_slice(&mut vec![2; line.length]);
+    on_mut_slice(&mut vec![2; line.length()]);
 
     for a in &[1, 2, 3] {
         println!("{:?}", a);
@@ -54,6 +69,7 @@ fn main() {
     }
 
     on_vec(&vec![1; 201]); // Ok, size of `vec` higher than `too_large_for_stack`
+    on_mut_vec(&mut vec![1; 201]); // Ok, size of `vec` higher than `too_large_for_stack`
 
     // Ok
     for a in vec![1; 201] {

tests/ui/vec.rs

@@ -6,9 +6,14 @@
 struct NonCopy;
 
 fn on_slice(_: &[u8]) {}
+
+fn on_mut_slice(_: &mut [u8]) {}
+
 #[allow(clippy::ptr_arg)]
 fn on_vec(_: &Vec<u8>) {}
 
+fn on_mut_vec(_: &mut Vec<u8>) {}
+
 struct Line {
     length: usize,
 }
@@ -22,28 +27,38 @@ impl Line {
 fn main() {
     on_slice(&vec![]);
     on_slice(&[]);
+    on_mut_slice(&mut vec![]);
 
     on_slice(&vec![1, 2]);
     on_slice(&[1, 2]);
+    on_mut_slice(&mut vec![1, 2]);
 
     on_slice(&vec![1, 2]);
     on_slice(&[1, 2]);
+    on_mut_slice(&mut vec![1, 2]);
     #[rustfmt::skip]
     on_slice(&vec!(1, 2));
     on_slice(&[1, 2]);
+    on_mut_slice(&mut vec![1, 2]);
 
     on_slice(&vec![1; 2]);
     on_slice(&[1; 2]);
+    on_mut_slice(&mut vec![1; 2]);
 
     on_vec(&vec![]);
     on_vec(&vec![1, 2]);
     on_vec(&vec![1; 2]);
+    on_mut_vec(&mut vec![]);
+    on_mut_vec(&mut vec![1, 2]);
+    on_mut_vec(&mut vec![1; 2]);
 
     // Now with non-constant expressions
     let line = Line { length: 2 };
 
     on_slice(&vec![2; line.length]);
     on_slice(&vec![2; line.length()]);
+    on_mut_slice(&mut vec![2; line.length]);
+    on_mut_slice(&mut vec![2; line.length()]);
 
     for a in vec![1, 2, 3] {
         println!("{:?}", a);
@@ -54,6 +69,7 @@ fn main() {
     }
 
     on_vec(&vec![1; 201]); // Ok, size of `vec` higher than `too_large_for_stack`
+    on_mut_vec(&mut vec![1; 201]); // Ok, size of `vec` higher than `too_large_for_stack`
 
     // Ok
     for a in vec![1; 201] {

tests/ui/vec.stderr

@@ -1,5 +1,5 @@
 error: useless use of `vec!`
-  --> $DIR/vec.rs:23:14
+  --> $DIR/vec.rs:28:14
    |
 LL |     on_slice(&vec![]);
    |              ^^^^^^^ help: you can use a slice directly: `&[]`
@@ -7,34 +7,64 @@ LL |     on_slice(&vec![]);
    = note: `-D clippy::useless-vec` implied by `-D warnings`
 
 error: useless use of `vec!`
-  --> $DIR/vec.rs:26:14
+  --> $DIR/vec.rs:30:18
    |
-LL |     on_slice(&vec![1, 2]);
+LL |     on_mut_slice(&mut vec![]);
-   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`
+   |                  ^^^^^^^^^^^ help: you can use a slice directly: `&mut []`
-
-error: useless use of `vec!`
-  --> $DIR/vec.rs:29:14
-   |
-LL |     on_slice(&vec![1, 2]);
-   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`
 
 error: useless use of `vec!`
   --> $DIR/vec.rs:32:14
    |
+LL |     on_slice(&vec![1, 2]);
+   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`
+
+error: useless use of `vec!`
+  --> $DIR/vec.rs:34:18
+   |
+LL |     on_mut_slice(&mut vec![1, 2]);
+   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`
+
+error: useless use of `vec!`
+  --> $DIR/vec.rs:36:14
+   |
+LL |     on_slice(&vec![1, 2]);
+   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`
+
+error: useless use of `vec!`
+  --> $DIR/vec.rs:38:18
+   |
+LL |     on_mut_slice(&mut vec![1, 2]);
+   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`
+
+error: useless use of `vec!`
+  --> $DIR/vec.rs:40:14
+   |
 LL |     on_slice(&vec!(1, 2));
    |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`
 
 error: useless use of `vec!`
-  --> $DIR/vec.rs:35:14
+  --> $DIR/vec.rs:42:18
+   |
+LL |     on_mut_slice(&mut vec![1, 2]);
+   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`
+
+error: useless use of `vec!`
+  --> $DIR/vec.rs:44:14
    |
 LL |     on_slice(&vec![1; 2]);
    |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1; 2]`
 
 error: useless use of `vec!`
-  --> $DIR/vec.rs:48:14
+  --> $DIR/vec.rs:46:18
+   |
+LL |     on_mut_slice(&mut vec![1; 2]);
+   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1; 2]`
+
+error: useless use of `vec!`
+  --> $DIR/vec.rs:63:14
    |
 LL |     for a in vec![1, 2, 3] {
    |              ^^^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2, 3]`
 
-error: aborting due to 6 previous errors
+error: aborting due to 11 previous errors