fix(rc_buffer): don't touch the path to Rc/Arc in the suggestion (#15803)

Fixes https://github.com/rust-lang/rust-clippy/issues/15802

changelog: [`rc_buffer`]: don't touch the path to `Rc`/`Arc` in the
suggestion

clippy_lints/src/types/rc_buffer.rs

@@ -1,115 +1,74 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::qpath_generic_tys;
-use clippy_utils::res::{MaybeDef, MaybeResPath};
+use clippy_utils::res::MaybeResPath;
 use clippy_utils::source::snippet_with_applicability;
 use rustc_errors::Applicability;
 use rustc_hir::def_id::DefId;
-use rustc_hir::{self as hir, QPath, TyKind};
+use rustc_hir::{QPath, Ty, TyKind};
 use rustc_lint::LateContext;
 use rustc_span::symbol::sym;
+use std::borrow::Cow;
+use std::fmt;
 
 use super::RC_BUFFER;
 
-pub(super) fn check(cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, qpath: &QPath<'_>, def_id: DefId) -> bool {
-    let app = Applicability::Unspecified;
-    let name = cx.tcx.get_diagnostic_name(def_id);
-    if name == Some(sym::Rc) {
-        if let Some(alternate) = match_buffer_type(cx, qpath) {
-            #[expect(clippy::collapsible_span_lint_calls, reason = "rust-clippy#7797")]
-            span_lint_and_then(
-                cx,
-                RC_BUFFER,
-                hir_ty.span,
-                "usage of `Rc<T>` when T is a buffer type",
-                |diag| {
-                    diag.span_suggestion(hir_ty.span, "try", format!("Rc<{alternate}>"), app);
-                },
-            );
-        } else {
-            let Some(ty) = qpath_generic_tys(qpath).next() else {
-                return false;
-            };
-            if !ty.basic_res().is_diag_item(cx, sym::Vec) {
-                return false;
-            }
-            let TyKind::Path(qpath) = &ty.kind else { return false };
-            let inner_span = match qpath_generic_tys(qpath).next() {
-                Some(ty) => ty.span,
-                None => return false,
-            };
-            span_lint_and_then(
-                cx,
-                RC_BUFFER,
-                hir_ty.span,
-                "usage of `Rc<T>` when T is a buffer type",
-                |diag| {
-                    let mut applicability = app;
-                    diag.span_suggestion(
-                        hir_ty.span,
-                        "try",
-                        format!(
-                            "Rc<[{}]>",
-                            snippet_with_applicability(cx, inner_span, "..", &mut applicability)
-                        ),
-                        app,
-                    );
-                },
-            );
-            return true;
-        }
-    } else if name == Some(sym::Arc) {
-        if let Some(alternate) = match_buffer_type(cx, qpath) {
-            #[expect(clippy::collapsible_span_lint_calls, reason = "rust-clippy#7797")]
-            span_lint_and_then(
-                cx,
-                RC_BUFFER,
-                hir_ty.span,
-                "usage of `Arc<T>` when T is a buffer type",
-                |diag| {
-                    diag.span_suggestion(hir_ty.span, "try", format!("Arc<{alternate}>"), app);
-                },
-            );
-        } else if let Some(ty) = qpath_generic_tys(qpath).next() {
-            if !ty.basic_res().is_diag_item(cx, sym::Vec) {
-                return false;
-            }
-            let TyKind::Path(qpath) = &ty.kind else { return false };
-            let inner_span = match qpath_generic_tys(qpath).next() {
-                Some(ty) => ty.span,
-                None => return false,
-            };
-            span_lint_and_then(
-                cx,
-                RC_BUFFER,
-                hir_ty.span,
-                "usage of `Arc<T>` when T is a buffer type",
-                |diag| {
-                    let mut applicability = app;
-                    diag.span_suggestion(
-                        hir_ty.span,
-                        "try",
-                        format!(
-                            "Arc<[{}]>",
-                            snippet_with_applicability(cx, inner_span, "..", &mut applicability)
-                        ),
-                        app,
-                    );
-                },
-            );
-            return true;
-        }
+pub(super) fn check(cx: &LateContext<'_>, hir_ty: &Ty<'_>, qpath: &QPath<'_>, def_id: DefId) -> bool {
+    let mut app = Applicability::Unspecified;
+    let kind = match cx.tcx.get_diagnostic_name(def_id) {
+        Some(sym::Rc) => RcKind::Rc,
+        Some(sym::Arc) => RcKind::Arc,
+        _ => return false,
+    };
+    if let Some(ty) = qpath_generic_tys(qpath).next()
+        && let Some(alternate) = match_buffer_type(cx, ty, &mut app)
+    {
+        span_lint_and_then(
+            cx,
+            RC_BUFFER,
+            hir_ty.span,
+            format!("usage of `{kind}<T>` when `T` is a buffer type"),
+            |diag| {
+                diag.span_suggestion_verbose(ty.span, "try", alternate, app);
+            },
+        );
+        true
+    } else {
+        false
     }
-
-    false
 }
 
-fn match_buffer_type(cx: &LateContext<'_>, qpath: &QPath<'_>) -> Option<&'static str> {
-    let ty = qpath_generic_tys(qpath).next()?;
+enum RcKind {
+    Rc,
+    Arc,
+}
+
+impl fmt::Display for RcKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Rc => f.write_str("Rc"),
+            Self::Arc => f.write_str("Arc"),
+        }
+    }
+}
+
+fn match_buffer_type(
+    cx: &LateContext<'_>,
+    ty: &Ty<'_>,
+    applicability: &mut Applicability,
+) -> Option<Cow<'static, str>> {
     let id = ty.basic_res().opt_def_id()?;
     let path = match cx.tcx.get_diagnostic_name(id) {
-        Some(sym::OsString) => "std::ffi::OsStr",
-        Some(sym::PathBuf) => "std::path::Path",
-        _ if Some(id) == cx.tcx.lang_items().string() => "str",
+        Some(sym::OsString) => "std::ffi::OsStr".into(),
+        Some(sym::PathBuf) => "std::path::Path".into(),
+        Some(sym::Vec) => {
+            let TyKind::Path(vec_qpath) = &ty.kind else {
+                return None;
+            };
+            let vec_generic_ty = qpath_generic_tys(vec_qpath).next()?;
+            let snippet = snippet_with_applicability(cx, vec_generic_ty.span, "_", applicability);
+            format!("[{snippet}]").into()
+        },
+        _ if Some(id) == cx.tcx.lang_items().string() => "str".into(),
         _ => return None,
     };
     Some(path)

tests/ui/rc_buffer.fixed

@@ -1,5 +1,4 @@
 #![warn(clippy::rc_buffer)]
-#![allow(dead_code, unused_imports)]
 
 use std::cell::RefCell;
 use std::ffi::OsString;
@@ -32,4 +31,9 @@ fn func_bad4(_: Rc<std::ffi::OsStr>) {}
 // does not trigger lint
 fn func_good1(_: Rc<RefCell<String>>) {}
 
+mod issue_15802 {
+    fn foo(_: std::rc::Rc<[u8]>) {}
+    //~^ rc_buffer
+}
+
 fn main() {}

tests/ui/rc_buffer.rs

@@ -1,5 +1,4 @@
 #![warn(clippy::rc_buffer)]
-#![allow(dead_code, unused_imports)]
 
 use std::cell::RefCell;
 use std::ffi::OsString;
@@ -32,4 +31,9 @@ fn func_bad4(_: Rc<OsString>) {}
 // does not trigger lint
 fn func_good1(_: Rc<RefCell<String>>) {}
 
+mod issue_15802 {
+    fn foo(_: std::rc::Rc<Vec<u8>>) {}
+    //~^ rc_buffer
+}
+
 fn main() {}

tests/ui/rc_buffer.stderr

@@ -1,53 +1,112 @@
-error: usage of `Rc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer.rs:11:11
+error: usage of `Rc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer.rs:10:11
    |
 LL |     bad1: Rc<String>,
-   |           ^^^^^^^^^^ help: try: `Rc<str>`
+   |           ^^^^^^^^^^
    |
    = note: `-D clippy::rc-buffer` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::rc_buffer)]`
+help: try
+   |
+LL -     bad1: Rc<String>,
+LL +     bad1: Rc<str>,
+   |
 
-error: usage of `Rc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer.rs:13:11
+error: usage of `Rc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer.rs:12:11
    |
 LL |     bad2: Rc<PathBuf>,
-   |           ^^^^^^^^^^^ help: try: `Rc<std::path::Path>`
+   |           ^^^^^^^^^^^
+   |
+help: try
+   |
+LL -     bad2: Rc<PathBuf>,
+LL +     bad2: Rc<std::path::Path>,
+   |
 
-error: usage of `Rc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer.rs:15:11
+error: usage of `Rc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer.rs:14:11
    |
 LL |     bad3: Rc<Vec<u8>>,
-   |           ^^^^^^^^^^^ help: try: `Rc<[u8]>`
+   |           ^^^^^^^^^^^
+   |
+help: try
+   |
+LL -     bad3: Rc<Vec<u8>>,
+LL +     bad3: Rc<[u8]>,
+   |
 
-error: usage of `Rc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer.rs:17:11
+error: usage of `Rc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer.rs:16:11
    |
 LL |     bad4: Rc<OsString>,
-   |           ^^^^^^^^^^^^ help: try: `Rc<std::ffi::OsStr>`
+   |           ^^^^^^^^^^^^
+   |
+help: try
+   |
+LL -     bad4: Rc<OsString>,
+LL +     bad4: Rc<std::ffi::OsStr>,
+   |
 
-error: usage of `Rc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer.rs:24:17
+error: usage of `Rc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer.rs:23:17
    |
 LL | fn func_bad1(_: Rc<String>) {}
-   |                 ^^^^^^^^^^ help: try: `Rc<str>`
+   |                 ^^^^^^^^^^
+   |
+help: try
+   |
+LL - fn func_bad1(_: Rc<String>) {}
+LL + fn func_bad1(_: Rc<str>) {}
+   |
 
-error: usage of `Rc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer.rs:26:17
+error: usage of `Rc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer.rs:25:17
    |
 LL | fn func_bad2(_: Rc<PathBuf>) {}
-   |                 ^^^^^^^^^^^ help: try: `Rc<std::path::Path>`
+   |                 ^^^^^^^^^^^
+   |
+help: try
+   |
+LL - fn func_bad2(_: Rc<PathBuf>) {}
+LL + fn func_bad2(_: Rc<std::path::Path>) {}
+   |
 
-error: usage of `Rc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer.rs:28:17
+error: usage of `Rc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer.rs:27:17
    |
 LL | fn func_bad3(_: Rc<Vec<u8>>) {}
-   |                 ^^^^^^^^^^^ help: try: `Rc<[u8]>`
+   |                 ^^^^^^^^^^^
+   |
+help: try
+   |
+LL - fn func_bad3(_: Rc<Vec<u8>>) {}
+LL + fn func_bad3(_: Rc<[u8]>) {}
+   |
 
-error: usage of `Rc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer.rs:30:17
+error: usage of `Rc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer.rs:29:17
    |
 LL | fn func_bad4(_: Rc<OsString>) {}
-   |                 ^^^^^^^^^^^^ help: try: `Rc<std::ffi::OsStr>`
+   |                 ^^^^^^^^^^^^
+   |
+help: try
+   |
+LL - fn func_bad4(_: Rc<OsString>) {}
+LL + fn func_bad4(_: Rc<std::ffi::OsStr>) {}
+   |
 
-error: aborting due to 8 previous errors
+error: usage of `Rc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer.rs:35:15
+   |
+LL |     fn foo(_: std::rc::Rc<Vec<u8>>) {}
+   |               ^^^^^^^^^^^^^^^^^^^^
+   |
+help: try
+   |
+LL -     fn foo(_: std::rc::Rc<Vec<u8>>) {}
+LL +     fn foo(_: std::rc::Rc<[u8]>) {}
+   |
+
+error: aborting due to 9 previous errors
 

tests/ui/rc_buffer_arc.fixed

@@ -1,5 +1,4 @@
 #![warn(clippy::rc_buffer)]
-#![allow(dead_code, unused_imports)]
 
 use std::ffi::OsString;
 use std::path::PathBuf;
@@ -31,4 +30,9 @@ fn func_bad4(_: Arc<std::ffi::OsStr>) {}
 // does not trigger lint
 fn func_good1(_: Arc<Mutex<String>>) {}
 
+mod issue_15802 {
+    fn foo(_: std::sync::Arc<[u8]>) {}
+    //~^ rc_buffer
+}
+
 fn main() {}

tests/ui/rc_buffer_arc.rs

@@ -1,5 +1,4 @@
 #![warn(clippy::rc_buffer)]
-#![allow(dead_code, unused_imports)]
 
 use std::ffi::OsString;
 use std::path::PathBuf;
@@ -31,4 +30,9 @@ fn func_bad4(_: Arc<OsString>) {}
 // does not trigger lint
 fn func_good1(_: Arc<Mutex<String>>) {}
 
+mod issue_15802 {
+    fn foo(_: std::sync::Arc<Vec<u8>>) {}
+    //~^ rc_buffer
+}
+
 fn main() {}

tests/ui/rc_buffer_arc.stderr

@@ -1,53 +1,112 @@
-error: usage of `Arc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer_arc.rs:10:11
+error: usage of `Arc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer_arc.rs:9:11
    |
 LL |     bad1: Arc<String>,
-   |           ^^^^^^^^^^^ help: try: `Arc<str>`
+   |           ^^^^^^^^^^^
    |
    = note: `-D clippy::rc-buffer` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::rc_buffer)]`
+help: try
+   |
+LL -     bad1: Arc<String>,
+LL +     bad1: Arc<str>,
+   |
 
-error: usage of `Arc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer_arc.rs:12:11
+error: usage of `Arc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer_arc.rs:11:11
    |
 LL |     bad2: Arc<PathBuf>,
-   |           ^^^^^^^^^^^^ help: try: `Arc<std::path::Path>`
+   |           ^^^^^^^^^^^^
+   |
+help: try
+   |
+LL -     bad2: Arc<PathBuf>,
+LL +     bad2: Arc<std::path::Path>,
+   |
 
-error: usage of `Arc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer_arc.rs:14:11
+error: usage of `Arc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer_arc.rs:13:11
    |
 LL |     bad3: Arc<Vec<u8>>,
-   |           ^^^^^^^^^^^^ help: try: `Arc<[u8]>`
+   |           ^^^^^^^^^^^^
+   |
+help: try
+   |
+LL -     bad3: Arc<Vec<u8>>,
+LL +     bad3: Arc<[u8]>,
+   |
 
-error: usage of `Arc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer_arc.rs:16:11
+error: usage of `Arc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer_arc.rs:15:11
    |
 LL |     bad4: Arc<OsString>,
-   |           ^^^^^^^^^^^^^ help: try: `Arc<std::ffi::OsStr>`
+   |           ^^^^^^^^^^^^^
+   |
+help: try
+   |
+LL -     bad4: Arc<OsString>,
+LL +     bad4: Arc<std::ffi::OsStr>,
+   |
 
-error: usage of `Arc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer_arc.rs:23:17
+error: usage of `Arc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer_arc.rs:22:17
    |
 LL | fn func_bad1(_: Arc<String>) {}
-   |                 ^^^^^^^^^^^ help: try: `Arc<str>`
+   |                 ^^^^^^^^^^^
+   |
+help: try
+   |
+LL - fn func_bad1(_: Arc<String>) {}
+LL + fn func_bad1(_: Arc<str>) {}
+   |
 
-error: usage of `Arc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer_arc.rs:25:17
+error: usage of `Arc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer_arc.rs:24:17
    |
 LL | fn func_bad2(_: Arc<PathBuf>) {}
-   |                 ^^^^^^^^^^^^ help: try: `Arc<std::path::Path>`
+   |                 ^^^^^^^^^^^^
+   |
+help: try
+   |
+LL - fn func_bad2(_: Arc<PathBuf>) {}
+LL + fn func_bad2(_: Arc<std::path::Path>) {}
+   |
 
-error: usage of `Arc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer_arc.rs:27:17
+error: usage of `Arc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer_arc.rs:26:17
    |
 LL | fn func_bad3(_: Arc<Vec<u8>>) {}
-   |                 ^^^^^^^^^^^^ help: try: `Arc<[u8]>`
+   |                 ^^^^^^^^^^^^
+   |
+help: try
+   |
+LL - fn func_bad3(_: Arc<Vec<u8>>) {}
+LL + fn func_bad3(_: Arc<[u8]>) {}
+   |
 
-error: usage of `Arc<T>` when T is a buffer type
-  --> tests/ui/rc_buffer_arc.rs:29:17
+error: usage of `Arc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer_arc.rs:28:17
    |
 LL | fn func_bad4(_: Arc<OsString>) {}
-   |                 ^^^^^^^^^^^^^ help: try: `Arc<std::ffi::OsStr>`
+   |                 ^^^^^^^^^^^^^
+   |
+help: try
+   |
+LL - fn func_bad4(_: Arc<OsString>) {}
+LL + fn func_bad4(_: Arc<std::ffi::OsStr>) {}
+   |
 
-error: aborting due to 8 previous errors
+error: usage of `Arc<T>` when `T` is a buffer type
+  --> tests/ui/rc_buffer_arc.rs:34:15
+   |
+LL |     fn foo(_: std::sync::Arc<Vec<u8>>) {}
+   |               ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: try
+   |
+LL -     fn foo(_: std::sync::Arc<Vec<u8>>) {}
+LL +     fn foo(_: std::sync::Arc<[u8]>) {}
+   |
+
+error: aborting due to 9 previous errors