Rollup merge of rust-lang#124957 - compiler-errors:builtin-deref, r=michaelwoerister

Make `Ty::builtin_deref` just return a `Ty`

Nowhere in the compiler are we using the mutability part of the `TyAndMut` that we used to return.

Author: matthiaskrgr

clippy_lints/src/matches/significant_drop_in_scrutinee.rs

@@ -6,7 +6,7 @@ use rustc_errors::{Applicability, Diag};
 use rustc_hir::intravisit::{walk_expr, Visitor};
 use rustc_hir::{Arm, Expr, ExprKind, MatchSource};
 use rustc_lint::{LateContext, LintContext};
-use rustc_middle::ty::{GenericArgKind, Ty, TypeAndMut};
+use rustc_middle::ty::{GenericArgKind, Ty};
 use rustc_span::Span;
 
 use super::SIGNIFICANT_DROP_IN_SCRUTINEE;
@@ -234,9 +234,9 @@ impl<'a, 'tcx> SigDropHelper<'a, 'tcx> {
         }
         let ty = self.sig_drop_checker.get_type(expr);
         if ty.is_ref() {
-            // We checked that the type was ref, so builtin_deref will return Some TypeAndMut,
-            // but let's avoid any chance of an ICE
-            if let Some(TypeAndMut { ty, .. }) = ty.builtin_deref(true) {
+            // We checked that the type was ref, so builtin_deref will return Some,
+            // but let's avoid any chance of an ICE.
+            if let Some(ty) = ty.builtin_deref(true) {
                 if ty.is_trivially_pure_clone_copy() {
                     self.replace_current_sig_drop(expr.span, false, LintSuggestion::MoveAndDerefToCopy);
                 } else if allow_move_and_clone {

clippy_lints/src/operators/cmp_owned.rs

@@ -70,7 +70,7 @@ fn check_op(cx: &LateContext<'_>, expr: &Expr<'_>, other: &Expr<'_>, left: bool)
     let without_deref = symmetric_partial_eq(cx, arg_ty, other_ty).unwrap_or_default();
     let with_deref = arg_ty
         .builtin_deref(true)
-        .and_then(|tam| symmetric_partial_eq(cx, tam.ty, other_ty))
+        .and_then(|ty| symmetric_partial_eq(cx, ty, other_ty))
         .unwrap_or_default();
 
     if !with_deref.is_implemented() && !without_deref.is_implemented() {

clippy_utils/src/qualify_min_const_fn.rs

@@ -134,7 +134,7 @@ fn check_rvalue<'tcx>(
         ) => Err((span, "function pointer casts are not allowed in const fn".into())),
         Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::Unsize), op, cast_ty) => {
             let pointee_ty = if let Some(deref_ty) = cast_ty.builtin_deref(true) {
-                deref_ty.ty
+                deref_ty
             } else {
                 // We cannot allow this for now.
                 return Err((span, "unsizing casts are only allowed for references right now".into()));