clippy_lints/src/casts/ptr_as_ptr.rs

   1 use std::borrow::Cow;
   2
   3 use rustc_errors::Applicability;
   4 use rustc_hir::{Expr, ExprKind, Mutability, TyKind};
   5 use rustc_lint::LateContext;
   6 use rustc_middle::ty::{self, TypeAndMut};
   7 use rustc_semver::RustcVersion;
   8
   9 use if_chain::if_chain;
  10
  11 use crate::utils::meets_msrv;
  12 use crate::utils::sugg::Sugg;
  13 use clippy_utils::diagnostics::span_lint_and_sugg;
  14
  15 use super::PTR_AS_PTR;
  16
  17 const PTR_AS_PTR_MSRV: RustcVersion = RustcVersion::new(1, 38, 0);
  18
  19 pub(super) fn check(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, msrv: &Option<RustcVersion>) {
  20     if !meets_msrv(msrv.as_ref(), &PTR_AS_PTR_MSRV) {
  21         return;
  22     }
  23
  24     if_chain! {
  25         if let ExprKind::Cast(cast_expr, cast_to_hir_ty) = expr.kind;
  26         let (cast_from, cast_to) = (cx.typeck_results().expr_ty(cast_expr), cx.typeck_results().expr_ty(expr));
  27         if let ty::RawPtr(TypeAndMut { mutbl: from_mutbl, .. }) = cast_from.kind();
  28         if let ty::RawPtr(TypeAndMut { ty: to_pointee_ty, mutbl: to_mutbl }) = cast_to.kind();
  29         if matches!((from_mutbl, to_mutbl),
  30             (Mutability::Not, Mutability::Not) | (Mutability::Mut, Mutability::Mut));
  31         // The `U` in `pointer::cast` have to be `Sized`
  32         // as explained here: https://github.com/rust-lang/rust/issues/60602.
  33         if to_pointee_ty.is_sized(cx.tcx.at(expr.span), cx.param_env);
  34         then {
  35             let mut applicability = Applicability::MachineApplicable;
  36             let cast_expr_sugg = Sugg::hir_with_applicability(cx, cast_expr, "_", &mut applicability);
  37             let turbofish = match &cast_to_hir_ty.kind {
  38                     TyKind::Infer => Cow::Borrowed(""),
  39                     TyKind::Ptr(mut_ty) if matches!(mut_ty.ty.kind, TyKind::Infer) => Cow::Borrowed(""),
  40                     _ => Cow::Owned(format!("::<{}>", to_pointee_ty)),
  41                 };
  42             span_lint_and_sugg(
  43                 cx,
  44                 PTR_AS_PTR,
  45                 expr.span,
  46                 "`as` casting between raw pointers without changing its mutability",
  47                 "try `pointer::cast`, a safer alternative",
  48                 format!("{}.cast{}()", cast_expr_sugg.maybe_par(), turbofish),
  49                 applicability,
  50             );
  51         }
  52     }
  53 }