Preserve explicit lifetime information when removing mut

clippy_lints/src/needless_pass_by_ref_mut.rs

@@ -1,7 +1,7 @@
 use super::needless_pass_by_value::requires_exact_signature;
 use clippy_config::Conf;
 use clippy_utils::diagnostics::span_lint_hir_and_then;
-use clippy_utils::source::snippet;
+use clippy_utils::source::HasSession as _;
 use clippy_utils::visitors::for_each_expr;
 use clippy_utils::{inherits_cfg, is_from_proc_macro, is_self};
 use core::ops::ControlFlow;
@@ -18,9 +18,9 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::mir::FakeReadCause;
 use rustc_middle::ty::{self, Ty, TyCtxt, UpvarId, UpvarPath};
 use rustc_session::impl_lint_pass;
-use rustc_span::Span;
 use rustc_span::def_id::LocalDefId;
 use rustc_span::symbol::kw;
+use rustc_span::{BytePos, Span};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -269,18 +269,27 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByRefMut<'tcx> {
                 // If the argument is never used mutably, we emit the warning.
                 let sp = input.span;
                 if let rustc_hir::TyKind::Ref(_, inner_ty) = input.kind {
+                    let Some(after_mut_span) = cx.sess().source_map().span_extend_to_prev_str(
+                        inner_ty.ty.span.shrink_to_lo(),
+                        "mut",
+                        true,
+                        true,
+                    ) else {
+                        return;
+                    };
+                    let mut_span = after_mut_span.with_lo(after_mut_span.lo() - BytePos(3));
                     let is_cfged = is_cfged.get_or_insert_with(|| inherits_cfg(cx.tcx, *fn_def_id));
                     span_lint_hir_and_then(
                         cx,
                         NEEDLESS_PASS_BY_REF_MUT,
                         cx.tcx.local_def_id_to_hir_id(*fn_def_id),
                         sp,
-                        "this argument is a mutable reference, but not used mutably",
+                        "this parameter is a mutable reference but is not used mutably",
                         |diag| {
                             diag.span_suggestion(
-                                sp,
-                                "consider changing to".to_string(),
-                                format!("&{}", snippet(cx, cx.tcx.hir_span(inner_ty.ty.hir_id), "_"),),
+                                mut_span,
+                                "consider removing this `mut`",
+                                "",
                                 Applicability::Unspecified,
                             );
                             if cx.effective_visibilities.is_exported(*fn_def_id) {

tests/ui-toml/needless_pass_by_ref_mut/needless_pass_by_ref_mut.fixed

@@ -3,7 +3,7 @@
 
 // Should warn
 pub fn pub_foo(s: &Vec<u32>, b: &u32, x: &mut u32) {
-    //~^ ERROR: this argument is a mutable reference, but not used mutably
+    //~^ needless_pass_by_ref_mut
     *x += *b + s.len() as u32;
 }
 

tests/ui-toml/needless_pass_by_ref_mut/needless_pass_by_ref_mut.rs

@@ -3,7 +3,7 @@
 
 // Should warn
 pub fn pub_foo(s: &mut Vec<u32>, b: &u32, x: &mut u32) {
-    //~^ ERROR: this argument is a mutable reference, but not used mutably
+    //~^ needless_pass_by_ref_mut
     *x += *b + s.len() as u32;
 }
 

tests/ui-toml/needless_pass_by_ref_mut/needless_pass_by_ref_mut.stderr

@@ -1,8 +1,10 @@
-error: this argument is a mutable reference, but not used mutably
+error: this parameter is a mutable reference but is not used mutably
   --> tests/ui-toml/needless_pass_by_ref_mut/needless_pass_by_ref_mut.rs:5:19
    |
 LL | pub fn pub_foo(s: &mut Vec<u32>, b: &u32, x: &mut u32) {
-   |                   ^^^^^^^^^^^^^ help: consider changing to: `&Vec<u32>`
+   |                   ^----^^^^^^^^
+   |                    |
+   |                    help: consider removing this `mut`
    |
    = warning: changing this function will impact semver compatibility
    = note: `-D clippy::needless-pass-by-ref-mut` implied by `-D warnings`