Auto merge of #5647 - ebroto:5644_allow_ptr_arg_in_arg_position, r=flip1995

ptr_arg: honor `allow` attribute on arguments

The `intravisit::Visitor` impl for `LateContextAndPass` only takes into account the attributes of a function parameter inside the `check_param` method. `ptr_arg` starts its heuristics at `check_item` / `check_impl_item` / `check_trait_item`, so the `allow` is not taken into account automatically.

changelog: ptr_arg: honor `allow` attribute on arguments

Fixes #5644

clippy_lints/src/ptr.rs

@@ -2,7 +2,7 @@
 
 use crate::utils::ptr::get_spans;
 use crate::utils::{
-    is_type_diagnostic_item, match_qpath, match_type, paths, snippet_opt, span_lint, span_lint_and_sugg,
+    is_allowed, is_type_diagnostic_item, match_qpath, match_type, paths, snippet_opt, span_lint, span_lint_and_sugg,
     span_lint_and_then, walk_ptrs_hir_ty,
 };
 use if_chain::if_chain;
@@ -150,8 +150,16 @@ fn check_fn(cx: &LateContext<'_, '_>, decl: &FnDecl<'_>, fn_id: HirId, opt_body_
     let fn_def_id = cx.tcx.hir().local_def_id(fn_id);
     let sig = cx.tcx.fn_sig(fn_def_id);
     let fn_ty = sig.skip_binder();
+    let body = opt_body_id.map(|id| cx.tcx.hir().body(id));
 
     for (idx, (arg, ty)) in decl.inputs.iter().zip(fn_ty.inputs()).enumerate() {
+        // Honor the allow attribute on parameters. See issue 5644.
+        if let Some(body) = &body {
+            if is_allowed(cx, PTR_ARG, body.params[idx].hir_id) {
+                continue;
+            }
+        }
+
         if let ty::Ref(_, ty, Mutability::Not) = ty.kind {
             if is_type_diagnostic_item(cx, ty, sym!(vec_type)) {
                 let mut ty_snippet = None;

clippy_lints/src/utils/sugg.rs

@@ -530,7 +530,7 @@ pub trait DiagnosticBuilderExt<'a, T: LintContext> {
 
     /// Suggest to add an item before another.
     ///
-    /// The item should not be indented (expect for inner indentation).
+    /// The item should not be indented (except for inner indentation).
     ///
     /// # Example
     ///

tests/ui/ptr_arg.rs

@@ -71,7 +71,6 @@ fn false_positive_capacity_too(x: &String) -> String {
 #[allow(dead_code)]
 fn test_cow_with_ref(c: &Cow<[i32]>) {}
 
-#[allow(dead_code)]
 fn test_cow(c: Cow<[i32]>) {
     let _c = c;
 }
@@ -84,3 +83,34 @@ trait Foo2 {
 impl Foo2 for String {
     fn do_string(&self) {}
 }
+
+// Check that the allow attribute on parameters is honored
+mod issue_5644 {
+    use std::borrow::Cow;
+
+    fn allowed(
+        #[allow(clippy::ptr_arg)] _v: &Vec<u32>,
+        #[allow(clippy::ptr_arg)] _s: &String,
+        #[allow(clippy::ptr_arg)] _c: &Cow<[i32]>,
+    ) {
+    }
+
+    struct S {}
+    impl S {
+        fn allowed(
+            #[allow(clippy::ptr_arg)] _v: &Vec<u32>,
+            #[allow(clippy::ptr_arg)] _s: &String,
+            #[allow(clippy::ptr_arg)] _c: &Cow<[i32]>,
+        ) {
+        }
+    }
+
+    trait T {
+        fn allowed(
+            #[allow(clippy::ptr_arg)] _v: &Vec<u32>,
+            #[allow(clippy::ptr_arg)] _s: &String,
+            #[allow(clippy::ptr_arg)] _c: &Cow<[i32]>,
+        ) {
+        }
+    }
+}