Properly handle Self type for trivially_copy_pass_by_ref

Author: LeSeulArtichaut

clippy_lints/src/pass_by_ref_or_value.rs

@@ -2,9 +2,9 @@ use std::cmp;
 use std::iter;
 
 use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::is_self_ty;
 use clippy_utils::source::snippet;
 use clippy_utils::ty::is_copy;
+use clippy_utils::{is_self, is_self_ty};
 use if_chain::if_chain;
 use rustc_ast::attr;
 use rustc_errors::Applicability;
@@ -170,7 +170,7 @@ impl<'tcx> PassByRefOrValue {
                         if size <= self.ref_min_size;
                         if let hir::TyKind::Rptr(_, MutTy { ty: decl_ty, .. }) = input.kind;
                         then {
-                            let value_type = if is_self_ty(decl_ty) {
+                            let value_type = if fn_body.and_then(|body| body.params.get(index)).map_or(false, is_self) {
                                 "self".into()
                             } else {
                                 snippet(cx, decl_ty.span, "_").into()

tests/ui/trivially_copy_pass_by_ref.rs

@@ -58,6 +58,8 @@ impl Foo {
     fn bad(&self, x: &u32, y: &Foo, z: &Baz) {}
 
     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
+
+    fn bad_issue7518(self, other: &Self) {}
 }
 
 impl AsRef<u32> for Foo {

tests/ui/trivially_copy_pass_by_ref.stderr

@@ -65,40 +65,46 @@ LL |     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
    |                                  ^^^^ help: consider passing by value instead: `Baz`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> $DIR/trivially_copy_pass_by_ref.rs:72:16
+  --> $DIR/trivially_copy_pass_by_ref.rs:62:35
+   |
+LL |     fn bad_issue7518(self, other: &Self) {}
+   |                                   ^^^^^ help: consider passing by value instead: `Self`
+
+error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
+  --> $DIR/trivially_copy_pass_by_ref.rs:74:16
    |
 LL |     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
    |                ^^^^ help: consider passing by value instead: `u32`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> $DIR/trivially_copy_pass_by_ref.rs:72:25
+  --> $DIR/trivially_copy_pass_by_ref.rs:74:25
    |
 LL |     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
    |                         ^^^^ help: consider passing by value instead: `Foo`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> $DIR/trivially_copy_pass_by_ref.rs:72:34
+  --> $DIR/trivially_copy_pass_by_ref.rs:74:34
    |
 LL |     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
    |                                  ^^^^ help: consider passing by value instead: `Baz`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> $DIR/trivially_copy_pass_by_ref.rs:76:34
+  --> $DIR/trivially_copy_pass_by_ref.rs:78:34
    |
 LL |     fn trait_method(&self, _foo: &Foo);
    |                                  ^^^^ help: consider passing by value instead: `Foo`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> $DIR/trivially_copy_pass_by_ref.rs:108:21
+  --> $DIR/trivially_copy_pass_by_ref.rs:110:21
    |
 LL |     fn foo_never(x: &i32) {
    |                     ^^^^ help: consider passing by value instead: `i32`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> $DIR/trivially_copy_pass_by_ref.rs:113:15
+  --> $DIR/trivially_copy_pass_by_ref.rs:115:15
    |
 LL |     fn foo(x: &i32) {
    |               ^^^^ help: consider passing by value instead: `i32`
 
-error: aborting due to 16 previous errors
+error: aborting due to 17 previous errors