src/tools/clippy/clippy_lints/src/casts/ptr_as_ptr.rs

   1 use std::borrow::Cow;
   2
   3 use clippy_utils::diagnostics::span_lint_and_sugg;
   4 use clippy_utils::msrvs::{self, Msrv};
   5 use clippy_utils::sugg::Sugg;
   6 use if_chain::if_chain;
   7 use rustc_errors::Applicability;
   8 use rustc_hir::{Expr, ExprKind, Mutability, TyKind};
   9 use rustc_lint::LateContext;
  10 use rustc_middle::ty::{self, TypeAndMut};
  11
  12 use super::PTR_AS_PTR;
  13
  14 pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, msrv: &Msrv) {
  15     if !msrv.meets(msrvs::POINTER_CAST) {
  16         return;
  17     }
  18
  19     if_chain! {
  20         if let ExprKind::Cast(cast_expr, cast_to_hir_ty) = expr.kind;
  21         let (cast_from, cast_to) = (cx.typeck_results().expr_ty(cast_expr), cx.typeck_results().expr_ty(expr));
  22         if let ty::RawPtr(TypeAndMut { mutbl: from_mutbl, .. }) = cast_from.kind();
  23         if let ty::RawPtr(TypeAndMut { ty: to_pointee_ty, mutbl: to_mutbl }) = cast_to.kind();
  24         if matches!((from_mutbl, to_mutbl),
  25             (Mutability::Not, Mutability::Not) | (Mutability::Mut, Mutability::Mut));
  26         // The `U` in `pointer::cast` have to be `Sized`
  27         // as explained here: https://github.com/rust-lang/rust/issues/60602.
  28         if to_pointee_ty.is_sized(cx.tcx, cx.param_env);
  29         then {
  30             let mut applicability = Applicability::MachineApplicable;
  31             let cast_expr_sugg = Sugg::hir_with_applicability(cx, cast_expr, "_", &mut applicability);
  32             let turbofish = match &cast_to_hir_ty.kind {
  33                     TyKind::Infer => Cow::Borrowed(""),
  34                     TyKind::Ptr(mut_ty) if matches!(mut_ty.ty.kind, TyKind::Infer) => Cow::Borrowed(""),
  35                     _ => Cow::Owned(format!("::<{to_pointee_ty}>")),
  36                 };
  37             span_lint_and_sugg(
  38                 cx,
  39                 PTR_AS_PTR,
  40                 expr.span,
  41                 "`as` casting between raw pointers without changing its mutability",
  42                 "try `pointer::cast`, a safer alternative",
  43                 format!("{}.cast{turbofish}()", cast_expr_sugg.maybe_par()),
  44                 applicability,
  45             );
  46         }
  47     }
  48 }