Rollup merge of #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

src/borrow_tracker/stacked_borrows/mod.rs

@@ -136,7 +136,7 @@ impl NewPermission {
         cx: &crate::MiriInterpCx<'_, 'tcx>,
     ) -> Self {
         // `ty` is not the `Box` but the field of the Box with this pointer (due to allocator handling).
-        let pointee = ty.builtin_deref(true).unwrap().ty;
+        let pointee = ty.builtin_deref(true).unwrap();
         if pointee.is_unpin(*cx.tcx, cx.param_env()) {
             // A regular box. On `FnEntry` this is `noalias`, but not `dereferenceable` (hence only
             // a weak protector).

src/borrow_tracker/tree_borrows/mod.rs

@@ -173,7 +173,7 @@ impl<'tcx> NewPermission {
         cx: &crate::MiriInterpCx<'_, 'tcx>,
         zero_size: bool,
     ) -> Option<Self> {
-        let pointee = ty.builtin_deref(true).unwrap().ty;
+        let pointee = ty.builtin_deref(true).unwrap();
         pointee.is_unpin(*cx.tcx, cx.param_env()).then_some(()).map(|()| {
             // Regular `Unpin` box, give it `noalias` but only a weak protector
             // because it is valid to deallocate it within the function.

src/intrinsics/mod.rs

@@ -117,7 +117,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
 
             "write_bytes" | "volatile_set_memory" => {
                 let [ptr, val_byte, count] = check_arg_count(args)?;
-                let ty = ptr.layout.ty.builtin_deref(true).unwrap().ty;
+                let ty = ptr.layout.ty.builtin_deref(true).unwrap();
                 let ty_layout = this.layout_of(ty)?;
                 let val_byte = this.read_scalar(val_byte)?.to_u8()?;
                 let ptr = this.read_pointer(ptr)?;

src/intrinsics/simd.rs

@@ -267,7 +267,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                         Op::WrappingOffset => {
                             let ptr = left.to_scalar().to_pointer(this)?;
                             let offset_count = right.to_scalar().to_target_isize(this)?;
-                            let pointee_ty = left.layout.ty.builtin_deref(true).unwrap().ty;
+                            let pointee_ty = left.layout.ty.builtin_deref(true).unwrap();
 
                             let pointee_size = i64::try_from(this.layout_of(pointee_ty)?.size.bytes()).unwrap();
                             let offset_bytes = offset_count.wrapping_mul(pointee_size);

src/shims/unix/foreign_items.rs

@@ -378,8 +378,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                     .builtin_deref(true)
                     .ok_or_else(|| err_ub_format!(
                         "wrong signature used for `pthread_key_create`: first argument must be a raw pointer."
-                    ))?
-                    .ty;
+                    ))?;
                 let key_layout = this.layout_of(key_type)?;
 
                 // Create key and write it into the memory where `key_ptr` wants it.