From: Yusuke Tanaka Date: Wed, 10 Feb 2021 13:59:08 +0000 (+0900) Subject: Create transmute directory X-Git-Url: https://git.lizzy.rs/?a=commitdiff_plain;ds=sidebyside;h=306545ff9653a8e1d00c4f381c8e609d3ad49adb;p=rust.git Create transmute directory --- diff --git a/clippy_lints/src/transmute.rs b/clippy_lints/src/transmute.rs deleted file mode 100644 index dc938ed0238..00000000000 --- a/clippy_lints/src/transmute.rs +++ /dev/null @@ -1,763 +0,0 @@ -use crate::utils::{ - in_constant, is_normalizable, last_path_segment, match_def_path, paths, snippet, span_lint, span_lint_and_sugg, - span_lint_and_then, sugg, -}; -use if_chain::if_chain; -use rustc_ast as ast; -use rustc_errors::Applicability; -use rustc_hir::{Expr, ExprKind, GenericArg, Mutability, QPath, TyKind, UnOp}; -use rustc_lint::{LateContext, LateLintPass}; -use rustc_middle::ty::{self, cast::CastKind, Ty}; -use rustc_session::{declare_lint_pass, declare_tool_lint}; -use rustc_span::DUMMY_SP; -use rustc_typeck::check::{cast::CastCheck, FnCtxt, Inherited}; -use std::borrow::Cow; - -declare_clippy_lint! { - /// **What it does:** Checks for transmutes that can't ever be correct on any - /// architecture. - /// - /// **Why is this bad?** It's basically guaranteed to be undefined behaviour. - /// - /// **Known problems:** When accessing C, users might want to store pointer - /// sized objects in `extradata` arguments to save an allocation. - /// - /// **Example:** - /// ```ignore - /// let ptr: *const T = core::intrinsics::transmute('x') - /// ``` - pub WRONG_TRANSMUTE, - correctness, - "transmutes that are confusing at best, undefined behaviour at worst and always useless" -} - -// FIXME: Move this to `complexity` again, after #5343 is fixed -declare_clippy_lint! { - /// **What it does:** Checks for transmutes to the original type of the object - /// and transmutes that could be a cast. - /// - /// **Why is this bad?** Readability. The code tricks people into thinking that - /// something complex is going on. - /// - /// **Known problems:** None. - /// - /// **Example:** - /// ```rust,ignore - /// core::intrinsics::transmute(t); // where the result type is the same as `t`'s - /// ``` - pub USELESS_TRANSMUTE, - nursery, - "transmutes that have the same to and from types or could be a cast/coercion" -} - -// FIXME: Merge this lint with USELESS_TRANSMUTE once that is out of the nursery. -declare_clippy_lint! { - /// **What it does:**Checks for transmutes that could be a pointer cast. - /// - /// **Why is this bad?** Readability. The code tricks people into thinking that - /// something complex is going on. - /// - /// **Known problems:** None. - /// - /// **Example:** - /// - /// ```rust - /// # let p: *const [i32] = &[]; - /// unsafe { std::mem::transmute::<*const [i32], *const [u16]>(p) }; - /// ``` - /// Use instead: - /// ```rust - /// # let p: *const [i32] = &[]; - /// p as *const [u16]; - /// ``` - pub TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS, - complexity, - "transmutes that could be a pointer cast" -} - -declare_clippy_lint! { - /// **What it does:** Checks for transmutes between a type `T` and `*T`. - /// - /// **Why is this bad?** It's easy to mistakenly transmute between a type and a - /// pointer to that type. - /// - /// **Known problems:** None. - /// - /// **Example:** - /// ```rust,ignore - /// core::intrinsics::transmute(t) // where the result type is the same as - /// // `*t` or `&t`'s - /// ``` - pub CROSSPOINTER_TRANSMUTE, - complexity, - "transmutes that have to or from types that are a pointer to the other" -} - -declare_clippy_lint! { - /// **What it does:** Checks for transmutes from a pointer to a reference. - /// - /// **Why is this bad?** This can always be rewritten with `&` and `*`. - /// - /// **Known problems:** - /// - `mem::transmute` in statics and constants is stable from Rust 1.46.0, - /// while dereferencing raw pointer is not stable yet. - /// If you need to do this in those places, - /// you would have to use `transmute` instead. - /// - /// **Example:** - /// ```rust,ignore - /// unsafe { - /// let _: &T = std::mem::transmute(p); // where p: *const T - /// } - /// - /// // can be written: - /// let _: &T = &*p; - /// ``` - pub TRANSMUTE_PTR_TO_REF, - complexity, - "transmutes from a pointer to a reference type" -} - -declare_clippy_lint! { - /// **What it does:** Checks for transmutes from an integer to a `char`. - /// - /// **Why is this bad?** Not every integer is a Unicode scalar value. - /// - /// **Known problems:** - /// - [`from_u32`] which this lint suggests using is slower than `transmute` - /// as it needs to validate the input. - /// If you are certain that the input is always a valid Unicode scalar value, - /// use [`from_u32_unchecked`] which is as fast as `transmute` - /// but has a semantically meaningful name. - /// - You might want to handle `None` returned from [`from_u32`] instead of calling `unwrap`. - /// - /// [`from_u32`]: https://doc.rust-lang.org/std/char/fn.from_u32.html - /// [`from_u32_unchecked`]: https://doc.rust-lang.org/std/char/fn.from_u32_unchecked.html - /// - /// **Example:** - /// ```rust - /// let x = 1_u32; - /// unsafe { - /// let _: char = std::mem::transmute(x); // where x: u32 - /// } - /// - /// // should be: - /// let _ = std::char::from_u32(x).unwrap(); - /// ``` - pub TRANSMUTE_INT_TO_CHAR, - complexity, - "transmutes from an integer to a `char`" -} - -declare_clippy_lint! { - /// **What it does:** Checks for transmutes from a `&[u8]` to a `&str`. - /// - /// **Why is this bad?** Not every byte slice is a valid UTF-8 string. - /// - /// **Known problems:** - /// - [`from_utf8`] which this lint suggests using is slower than `transmute` - /// as it needs to validate the input. - /// If you are certain that the input is always a valid UTF-8, - /// use [`from_utf8_unchecked`] which is as fast as `transmute` - /// but has a semantically meaningful name. - /// - You might want to handle errors returned from [`from_utf8`] instead of calling `unwrap`. - /// - /// [`from_utf8`]: https://doc.rust-lang.org/std/str/fn.from_utf8.html - /// [`from_utf8_unchecked`]: https://doc.rust-lang.org/std/str/fn.from_utf8_unchecked.html - /// - /// **Example:** - /// ```rust - /// let b: &[u8] = &[1_u8, 2_u8]; - /// unsafe { - /// let _: &str = std::mem::transmute(b); // where b: &[u8] - /// } - /// - /// // should be: - /// let _ = std::str::from_utf8(b).unwrap(); - /// ``` - pub TRANSMUTE_BYTES_TO_STR, - complexity, - "transmutes from a `&[u8]` to a `&str`" -} - -declare_clippy_lint! { - /// **What it does:** Checks for transmutes from an integer to a `bool`. - /// - /// **Why is this bad?** This might result in an invalid in-memory representation of a `bool`. - /// - /// **Known problems:** None. - /// - /// **Example:** - /// ```rust - /// let x = 1_u8; - /// unsafe { - /// let _: bool = std::mem::transmute(x); // where x: u8 - /// } - /// - /// // should be: - /// let _: bool = x != 0; - /// ``` - pub TRANSMUTE_INT_TO_BOOL, - complexity, - "transmutes from an integer to a `bool`" -} - -declare_clippy_lint! { - /// **What it does:** Checks for transmutes from an integer to a float. - /// - /// **Why is this bad?** Transmutes are dangerous and error-prone, whereas `from_bits` is intuitive - /// and safe. - /// - /// **Known problems:** None. - /// - /// **Example:** - /// ```rust - /// unsafe { - /// let _: f32 = std::mem::transmute(1_u32); // where x: u32 - /// } - /// - /// // should be: - /// let _: f32 = f32::from_bits(1_u32); - /// ``` - pub TRANSMUTE_INT_TO_FLOAT, - complexity, - "transmutes from an integer to a float" -} - -declare_clippy_lint! { - /// **What it does:** Checks for transmutes from a float to an integer. - /// - /// **Why is this bad?** Transmutes are dangerous and error-prone, whereas `to_bits` is intuitive - /// and safe. - /// - /// **Known problems:** None. - /// - /// **Example:** - /// ```rust - /// unsafe { - /// let _: u32 = std::mem::transmute(1f32); - /// } - /// - /// // should be: - /// let _: u32 = 1f32.to_bits(); - /// ``` - pub TRANSMUTE_FLOAT_TO_INT, - complexity, - "transmutes from a float to an integer" -} - -declare_clippy_lint! { - /// **What it does:** Checks for transmutes from a pointer to a pointer, or - /// from a reference to a reference. - /// - /// **Why is this bad?** Transmutes are dangerous, and these can instead be - /// written as casts. - /// - /// **Known problems:** None. - /// - /// **Example:** - /// ```rust - /// let ptr = &1u32 as *const u32; - /// unsafe { - /// // pointer-to-pointer transmute - /// let _: *const f32 = std::mem::transmute(ptr); - /// // ref-ref transmute - /// let _: &f32 = std::mem::transmute(&1u32); - /// } - /// // These can be respectively written: - /// let _ = ptr as *const f32; - /// let _ = unsafe{ &*(&1u32 as *const u32 as *const f32) }; - /// ``` - pub TRANSMUTE_PTR_TO_PTR, - complexity, - "transmutes from a pointer to a pointer / a reference to a reference" -} - -declare_clippy_lint! { - /// **What it does:** Checks for transmutes between collections whose - /// types have different ABI, size or alignment. - /// - /// **Why is this bad?** This is undefined behavior. - /// - /// **Known problems:** Currently, we cannot know whether a type is a - /// collection, so we just lint the ones that come with `std`. - /// - /// **Example:** - /// ```rust - /// // different size, therefore likely out-of-bounds memory access - /// // You absolutely do not want this in your code! - /// unsafe { - /// std::mem::transmute::<_, Vec>(vec![2_u16]) - /// }; - /// ``` - /// - /// You must always iterate, map and collect the values: - /// - /// ```rust - /// vec![2_u16].into_iter().map(u32::from).collect::>(); - /// ``` - pub UNSOUND_COLLECTION_TRANSMUTE, - correctness, - "transmute between collections of layout-incompatible types" -} - -declare_lint_pass!(Transmute => [ - CROSSPOINTER_TRANSMUTE, - TRANSMUTE_PTR_TO_REF, - TRANSMUTE_PTR_TO_PTR, - USELESS_TRANSMUTE, - WRONG_TRANSMUTE, - TRANSMUTE_INT_TO_CHAR, - TRANSMUTE_BYTES_TO_STR, - TRANSMUTE_INT_TO_BOOL, - TRANSMUTE_INT_TO_FLOAT, - TRANSMUTE_FLOAT_TO_INT, - UNSOUND_COLLECTION_TRANSMUTE, - TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS, -]); - -// used to check for UNSOUND_COLLECTION_TRANSMUTE -static COLLECTIONS: &[&[&str]] = &[ - &paths::VEC, - &paths::VEC_DEQUE, - &paths::BINARY_HEAP, - &paths::BTREESET, - &paths::BTREEMAP, - &paths::HASHSET, - &paths::HASHMAP, -]; -impl<'tcx> LateLintPass<'tcx> for Transmute { - #[allow(clippy::similar_names, clippy::too_many_lines)] - fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) { - if_chain! { - if let ExprKind::Call(ref path_expr, ref args) = e.kind; - if let ExprKind::Path(ref qpath) = path_expr.kind; - if let Some(def_id) = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id(); - if match_def_path(cx, def_id, &paths::TRANSMUTE); - then { - // Avoid suggesting from/to bits and dereferencing raw pointers in const contexts. - // See https://github.com/rust-lang/rust/issues/73736 for progress on making them `const fn`. - // And see https://github.com/rust-lang/rust/issues/51911 for dereferencing raw pointers. - let const_context = in_constant(cx, e.hir_id); - - let from_ty = cx.typeck_results().expr_ty(&args[0]); - let to_ty = cx.typeck_results().expr_ty(e); - - match (&from_ty.kind(), &to_ty.kind()) { - _ if from_ty == to_ty => span_lint( - cx, - USELESS_TRANSMUTE, - e.span, - &format!("transmute from a type (`{}`) to itself", from_ty), - ), - (ty::Ref(_, rty, rty_mutbl), ty::RawPtr(ptr_ty)) => span_lint_and_then( - cx, - USELESS_TRANSMUTE, - e.span, - "transmute from a reference to a pointer", - |diag| { - if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { - let rty_and_mut = ty::TypeAndMut { - ty: rty, - mutbl: *rty_mutbl, - }; - - let sugg = if *ptr_ty == rty_and_mut { - arg.as_ty(to_ty) - } else { - arg.as_ty(cx.tcx.mk_ptr(rty_and_mut)).as_ty(to_ty) - }; - - diag.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified); - } - }, - ), - (ty::Int(_) | ty::Uint(_), ty::RawPtr(_)) => span_lint_and_then( - cx, - USELESS_TRANSMUTE, - e.span, - "transmute from an integer to a pointer", - |diag| { - if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { - diag.span_suggestion( - e.span, - "try", - arg.as_ty(&to_ty.to_string()).to_string(), - Applicability::Unspecified, - ); - } - }, - ), - (ty::Float(_) | ty::Char, ty::Ref(..) | ty::RawPtr(_)) => span_lint( - cx, - WRONG_TRANSMUTE, - e.span, - &format!("transmute from a `{}` to a pointer", from_ty), - ), - (ty::RawPtr(from_ptr), _) if from_ptr.ty == to_ty => span_lint( - cx, - CROSSPOINTER_TRANSMUTE, - e.span, - &format!( - "transmute from a type (`{}`) to the type that it points to (`{}`)", - from_ty, to_ty - ), - ), - (_, ty::RawPtr(to_ptr)) if to_ptr.ty == from_ty => span_lint( - cx, - CROSSPOINTER_TRANSMUTE, - e.span, - &format!( - "transmute from a type (`{}`) to a pointer to that type (`{}`)", - from_ty, to_ty - ), - ), - (ty::RawPtr(from_pty), ty::Ref(_, to_ref_ty, mutbl)) => span_lint_and_then( - cx, - TRANSMUTE_PTR_TO_REF, - e.span, - &format!( - "transmute from a pointer type (`{}`) to a reference type \ - (`{}`)", - from_ty, to_ty - ), - |diag| { - let arg = sugg::Sugg::hir(cx, &args[0], ".."); - let (deref, cast) = if *mutbl == Mutability::Mut { - ("&mut *", "*mut") - } else { - ("&*", "*const") - }; - - let arg = if from_pty.ty == *to_ref_ty { - arg - } else { - arg.as_ty(&format!("{} {}", cast, get_type_snippet(cx, qpath, to_ref_ty))) - }; - - diag.span_suggestion( - e.span, - "try", - sugg::make_unop(deref, arg).to_string(), - Applicability::Unspecified, - ); - }, - ), - (ty::Int(ty::IntTy::I32) | ty::Uint(ty::UintTy::U32), &ty::Char) => { - span_lint_and_then( - cx, - TRANSMUTE_INT_TO_CHAR, - e.span, - &format!("transmute from a `{}` to a `char`", from_ty), - |diag| { - let arg = sugg::Sugg::hir(cx, &args[0], ".."); - let arg = if let ty::Int(_) = from_ty.kind() { - arg.as_ty(ast::UintTy::U32.name_str()) - } else { - arg - }; - diag.span_suggestion( - e.span, - "consider using", - format!("std::char::from_u32({}).unwrap()", arg.to_string()), - Applicability::Unspecified, - ); - }, - ) - }, - (ty::Ref(_, ty_from, from_mutbl), ty::Ref(_, ty_to, to_mutbl)) => { - if_chain! { - if let (&ty::Slice(slice_ty), &ty::Str) = (&ty_from.kind(), &ty_to.kind()); - if let ty::Uint(ty::UintTy::U8) = slice_ty.kind(); - if from_mutbl == to_mutbl; - then { - let postfix = if *from_mutbl == Mutability::Mut { - "_mut" - } else { - "" - }; - - span_lint_and_sugg( - cx, - TRANSMUTE_BYTES_TO_STR, - e.span, - &format!("transmute from a `{}` to a `{}`", from_ty, to_ty), - "consider using", - format!( - "std::str::from_utf8{}({}).unwrap()", - postfix, - snippet(cx, args[0].span, ".."), - ), - Applicability::Unspecified, - ); - } else { - if (cx.tcx.erase_regions(from_ty) != cx.tcx.erase_regions(to_ty)) - && !const_context { - span_lint_and_then( - cx, - TRANSMUTE_PTR_TO_PTR, - e.span, - "transmute from a reference to a reference", - |diag| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { - let ty_from_and_mut = ty::TypeAndMut { - ty: ty_from, - mutbl: *from_mutbl - }; - let ty_to_and_mut = ty::TypeAndMut { ty: ty_to, mutbl: *to_mutbl }; - let sugg_paren = arg - .as_ty(cx.tcx.mk_ptr(ty_from_and_mut)) - .as_ty(cx.tcx.mk_ptr(ty_to_and_mut)); - let sugg = if *to_mutbl == Mutability::Mut { - sugg_paren.mut_addr_deref() - } else { - sugg_paren.addr_deref() - }; - diag.span_suggestion( - e.span, - "try", - sugg.to_string(), - Applicability::Unspecified, - ); - }, - ) - } - } - } - }, - (ty::RawPtr(_), ty::RawPtr(to_ty)) => span_lint_and_then( - cx, - TRANSMUTE_PTR_TO_PTR, - e.span, - "transmute from a pointer to a pointer", - |diag| { - if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { - let sugg = arg.as_ty(cx.tcx.mk_ptr(*to_ty)); - diag.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified); - } - }, - ), - (ty::Int(ty::IntTy::I8) | ty::Uint(ty::UintTy::U8), ty::Bool) => { - span_lint_and_then( - cx, - TRANSMUTE_INT_TO_BOOL, - e.span, - &format!("transmute from a `{}` to a `bool`", from_ty), - |diag| { - let arg = sugg::Sugg::hir(cx, &args[0], ".."); - let zero = sugg::Sugg::NonParen(Cow::from("0")); - diag.span_suggestion( - e.span, - "consider using", - sugg::make_binop(ast::BinOpKind::Ne, &arg, &zero).to_string(), - Applicability::Unspecified, - ); - }, - ) - }, - (ty::Int(_) | ty::Uint(_), ty::Float(_)) if !const_context => span_lint_and_then( - cx, - TRANSMUTE_INT_TO_FLOAT, - e.span, - &format!("transmute from a `{}` to a `{}`", from_ty, to_ty), - |diag| { - let arg = sugg::Sugg::hir(cx, &args[0], ".."); - let arg = if let ty::Int(int_ty) = from_ty.kind() { - arg.as_ty(format!( - "u{}", - int_ty.bit_width().map_or_else(|| "size".to_string(), |v| v.to_string()) - )) - } else { - arg - }; - diag.span_suggestion( - e.span, - "consider using", - format!("{}::from_bits({})", to_ty, arg.to_string()), - Applicability::Unspecified, - ); - }, - ), - (ty::Float(float_ty), ty::Int(_) | ty::Uint(_)) if !const_context => span_lint_and_then( - cx, - TRANSMUTE_FLOAT_TO_INT, - e.span, - &format!("transmute from a `{}` to a `{}`", from_ty, to_ty), - |diag| { - let mut expr = &args[0]; - let mut arg = sugg::Sugg::hir(cx, expr, ".."); - - if let ExprKind::Unary(UnOp::Neg, inner_expr) = &expr.kind { - expr = &inner_expr; - } - - if_chain! { - // if the expression is a float literal and it is unsuffixed then - // add a suffix so the suggestion is valid and unambiguous - let op = format!("{}{}", arg, float_ty.name_str()).into(); - if let ExprKind::Lit(lit) = &expr.kind; - if let ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) = lit.node; - then { - match arg { - sugg::Sugg::MaybeParen(_) => arg = sugg::Sugg::MaybeParen(op), - _ => arg = sugg::Sugg::NonParen(op) - } - } - } - - arg = sugg::Sugg::NonParen(format!("{}.to_bits()", arg.maybe_par()).into()); - - // cast the result of `to_bits` if `to_ty` is signed - arg = if let ty::Int(int_ty) = to_ty.kind() { - arg.as_ty(int_ty.name_str().to_string()) - } else { - arg - }; - - diag.span_suggestion( - e.span, - "consider using", - arg.to_string(), - Applicability::Unspecified, - ); - }, - ), - (ty::Adt(from_adt, from_substs), ty::Adt(to_adt, to_substs)) => { - if from_adt.did != to_adt.did || - !COLLECTIONS.iter().any(|path| match_def_path(cx, to_adt.did, path)) { - return; - } - if from_substs.types().zip(to_substs.types()) - .any(|(from_ty, to_ty)| is_layout_incompatible(cx, from_ty, to_ty)) { - span_lint( - cx, - UNSOUND_COLLECTION_TRANSMUTE, - e.span, - &format!( - "transmute from `{}` to `{}` with mismatched layout is unsound", - from_ty, - to_ty - ) - ); - } - }, - (_, _) if can_be_expressed_as_pointer_cast(cx, e, from_ty, to_ty) => span_lint_and_then( - cx, - TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS, - e.span, - &format!( - "transmute from `{}` to `{}` which could be expressed as a pointer cast instead", - from_ty, - to_ty - ), - |diag| { - if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { - let sugg = arg.as_ty(&to_ty.to_string()).to_string(); - diag.span_suggestion(e.span, "try", sugg, Applicability::MachineApplicable); - } - } - ), - _ => { - return; - }, - } - } - } - } -} - -/// Gets the snippet of `Bar` in `…::transmute`. If that snippet is -/// not available , use -/// the type's `ToString` implementation. In weird cases it could lead to types -/// with invalid `'_` -/// lifetime, but it should be rare. -fn get_type_snippet(cx: &LateContext<'_>, path: &QPath<'_>, to_ref_ty: Ty<'_>) -> String { - let seg = last_path_segment(path); - if_chain! { - if let Some(ref params) = seg.args; - if !params.parenthesized; - if let Some(to_ty) = params.args.iter().filter_map(|arg| match arg { - GenericArg::Type(ty) => Some(ty), - _ => None, - }).nth(1); - if let TyKind::Rptr(_, ref to_ty) = to_ty.kind; - then { - return snippet(cx, to_ty.ty.span, &to_ref_ty.to_string()).to_string(); - } - } - - to_ref_ty.to_string() -} - -// check if the component types of the transmuted collection and the result have different ABI, -// size or alignment -fn is_layout_incompatible<'tcx>(cx: &LateContext<'tcx>, from: Ty<'tcx>, to: Ty<'tcx>) -> bool { - let empty_param_env = ty::ParamEnv::empty(); - // check if `from` and `to` are normalizable to avoid ICE (#4968) - if !(is_normalizable(cx, empty_param_env, from) && is_normalizable(cx, empty_param_env, to)) { - return false; - } - let from_ty_layout = cx.tcx.layout_of(empty_param_env.and(from)); - let to_ty_layout = cx.tcx.layout_of(empty_param_env.and(to)); - if let (Ok(from_layout), Ok(to_layout)) = (from_ty_layout, to_ty_layout) { - from_layout.size != to_layout.size || from_layout.align != to_layout.align || from_layout.abi != to_layout.abi - } else { - // no idea about layout, so don't lint - false - } -} - -/// Check if the type conversion can be expressed as a pointer cast, instead of -/// a transmute. In certain cases, including some invalid casts from array -/// references to pointers, this may cause additional errors to be emitted and/or -/// ICE error messages. This function will panic if that occurs. -fn can_be_expressed_as_pointer_cast<'tcx>( - cx: &LateContext<'tcx>, - e: &'tcx Expr<'_>, - from_ty: Ty<'tcx>, - to_ty: Ty<'tcx>, -) -> bool { - use CastKind::{AddrPtrCast, ArrayPtrCast, FnPtrAddrCast, FnPtrPtrCast, PtrAddrCast, PtrPtrCast}; - matches!( - check_cast(cx, e, from_ty, to_ty), - Some(PtrPtrCast | PtrAddrCast | AddrPtrCast | ArrayPtrCast | FnPtrPtrCast | FnPtrAddrCast) - ) -} - -/// If a cast from `from_ty` to `to_ty` is valid, returns an Ok containing the kind of -/// the cast. In certain cases, including some invalid casts from array references -/// to pointers, this may cause additional errors to be emitted and/or ICE error -/// messages. This function will panic if that occurs. -fn check_cast<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, from_ty: Ty<'tcx>, to_ty: Ty<'tcx>) -> Option { - let hir_id = e.hir_id; - let local_def_id = hir_id.owner; - - Inherited::build(cx.tcx, local_def_id).enter(|inherited| { - let fn_ctxt = FnCtxt::new(&inherited, cx.param_env, hir_id); - - // If we already have errors, we can't be sure we can pointer cast. - assert!( - !fn_ctxt.errors_reported_since_creation(), - "Newly created FnCtxt contained errors" - ); - - if let Ok(check) = CastCheck::new( - &fn_ctxt, e, from_ty, to_ty, - // We won't show any error to the user, so we don't care what the span is here. - DUMMY_SP, DUMMY_SP, - ) { - let res = check.do_check(&fn_ctxt); - - // do_check's documentation says that it might return Ok and create - // errors in the fcx instead of returing Err in some cases. Those cases - // should be filtered out before getting here. - assert!( - !fn_ctxt.errors_reported_since_creation(), - "`fn_ctxt` contained errors after cast check!" - ); - - res.ok() - } else { - None - } - }) -} diff --git a/clippy_lints/src/transmute/mod.rs b/clippy_lints/src/transmute/mod.rs new file mode 100644 index 00000000000..dc938ed0238 --- /dev/null +++ b/clippy_lints/src/transmute/mod.rs @@ -0,0 +1,763 @@ +use crate::utils::{ + in_constant, is_normalizable, last_path_segment, match_def_path, paths, snippet, span_lint, span_lint_and_sugg, + span_lint_and_then, sugg, +}; +use if_chain::if_chain; +use rustc_ast as ast; +use rustc_errors::Applicability; +use rustc_hir::{Expr, ExprKind, GenericArg, Mutability, QPath, TyKind, UnOp}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_middle::ty::{self, cast::CastKind, Ty}; +use rustc_session::{declare_lint_pass, declare_tool_lint}; +use rustc_span::DUMMY_SP; +use rustc_typeck::check::{cast::CastCheck, FnCtxt, Inherited}; +use std::borrow::Cow; + +declare_clippy_lint! { + /// **What it does:** Checks for transmutes that can't ever be correct on any + /// architecture. + /// + /// **Why is this bad?** It's basically guaranteed to be undefined behaviour. + /// + /// **Known problems:** When accessing C, users might want to store pointer + /// sized objects in `extradata` arguments to save an allocation. + /// + /// **Example:** + /// ```ignore + /// let ptr: *const T = core::intrinsics::transmute('x') + /// ``` + pub WRONG_TRANSMUTE, + correctness, + "transmutes that are confusing at best, undefined behaviour at worst and always useless" +} + +// FIXME: Move this to `complexity` again, after #5343 is fixed +declare_clippy_lint! { + /// **What it does:** Checks for transmutes to the original type of the object + /// and transmutes that could be a cast. + /// + /// **Why is this bad?** Readability. The code tricks people into thinking that + /// something complex is going on. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// ```rust,ignore + /// core::intrinsics::transmute(t); // where the result type is the same as `t`'s + /// ``` + pub USELESS_TRANSMUTE, + nursery, + "transmutes that have the same to and from types or could be a cast/coercion" +} + +// FIXME: Merge this lint with USELESS_TRANSMUTE once that is out of the nursery. +declare_clippy_lint! { + /// **What it does:**Checks for transmutes that could be a pointer cast. + /// + /// **Why is this bad?** Readability. The code tricks people into thinking that + /// something complex is going on. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// + /// ```rust + /// # let p: *const [i32] = &[]; + /// unsafe { std::mem::transmute::<*const [i32], *const [u16]>(p) }; + /// ``` + /// Use instead: + /// ```rust + /// # let p: *const [i32] = &[]; + /// p as *const [u16]; + /// ``` + pub TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS, + complexity, + "transmutes that could be a pointer cast" +} + +declare_clippy_lint! { + /// **What it does:** Checks for transmutes between a type `T` and `*T`. + /// + /// **Why is this bad?** It's easy to mistakenly transmute between a type and a + /// pointer to that type. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// ```rust,ignore + /// core::intrinsics::transmute(t) // where the result type is the same as + /// // `*t` or `&t`'s + /// ``` + pub CROSSPOINTER_TRANSMUTE, + complexity, + "transmutes that have to or from types that are a pointer to the other" +} + +declare_clippy_lint! { + /// **What it does:** Checks for transmutes from a pointer to a reference. + /// + /// **Why is this bad?** This can always be rewritten with `&` and `*`. + /// + /// **Known problems:** + /// - `mem::transmute` in statics and constants is stable from Rust 1.46.0, + /// while dereferencing raw pointer is not stable yet. + /// If you need to do this in those places, + /// you would have to use `transmute` instead. + /// + /// **Example:** + /// ```rust,ignore + /// unsafe { + /// let _: &T = std::mem::transmute(p); // where p: *const T + /// } + /// + /// // can be written: + /// let _: &T = &*p; + /// ``` + pub TRANSMUTE_PTR_TO_REF, + complexity, + "transmutes from a pointer to a reference type" +} + +declare_clippy_lint! { + /// **What it does:** Checks for transmutes from an integer to a `char`. + /// + /// **Why is this bad?** Not every integer is a Unicode scalar value. + /// + /// **Known problems:** + /// - [`from_u32`] which this lint suggests using is slower than `transmute` + /// as it needs to validate the input. + /// If you are certain that the input is always a valid Unicode scalar value, + /// use [`from_u32_unchecked`] which is as fast as `transmute` + /// but has a semantically meaningful name. + /// - You might want to handle `None` returned from [`from_u32`] instead of calling `unwrap`. + /// + /// [`from_u32`]: https://doc.rust-lang.org/std/char/fn.from_u32.html + /// [`from_u32_unchecked`]: https://doc.rust-lang.org/std/char/fn.from_u32_unchecked.html + /// + /// **Example:** + /// ```rust + /// let x = 1_u32; + /// unsafe { + /// let _: char = std::mem::transmute(x); // where x: u32 + /// } + /// + /// // should be: + /// let _ = std::char::from_u32(x).unwrap(); + /// ``` + pub TRANSMUTE_INT_TO_CHAR, + complexity, + "transmutes from an integer to a `char`" +} + +declare_clippy_lint! { + /// **What it does:** Checks for transmutes from a `&[u8]` to a `&str`. + /// + /// **Why is this bad?** Not every byte slice is a valid UTF-8 string. + /// + /// **Known problems:** + /// - [`from_utf8`] which this lint suggests using is slower than `transmute` + /// as it needs to validate the input. + /// If you are certain that the input is always a valid UTF-8, + /// use [`from_utf8_unchecked`] which is as fast as `transmute` + /// but has a semantically meaningful name. + /// - You might want to handle errors returned from [`from_utf8`] instead of calling `unwrap`. + /// + /// [`from_utf8`]: https://doc.rust-lang.org/std/str/fn.from_utf8.html + /// [`from_utf8_unchecked`]: https://doc.rust-lang.org/std/str/fn.from_utf8_unchecked.html + /// + /// **Example:** + /// ```rust + /// let b: &[u8] = &[1_u8, 2_u8]; + /// unsafe { + /// let _: &str = std::mem::transmute(b); // where b: &[u8] + /// } + /// + /// // should be: + /// let _ = std::str::from_utf8(b).unwrap(); + /// ``` + pub TRANSMUTE_BYTES_TO_STR, + complexity, + "transmutes from a `&[u8]` to a `&str`" +} + +declare_clippy_lint! { + /// **What it does:** Checks for transmutes from an integer to a `bool`. + /// + /// **Why is this bad?** This might result in an invalid in-memory representation of a `bool`. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// ```rust + /// let x = 1_u8; + /// unsafe { + /// let _: bool = std::mem::transmute(x); // where x: u8 + /// } + /// + /// // should be: + /// let _: bool = x != 0; + /// ``` + pub TRANSMUTE_INT_TO_BOOL, + complexity, + "transmutes from an integer to a `bool`" +} + +declare_clippy_lint! { + /// **What it does:** Checks for transmutes from an integer to a float. + /// + /// **Why is this bad?** Transmutes are dangerous and error-prone, whereas `from_bits` is intuitive + /// and safe. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// ```rust + /// unsafe { + /// let _: f32 = std::mem::transmute(1_u32); // where x: u32 + /// } + /// + /// // should be: + /// let _: f32 = f32::from_bits(1_u32); + /// ``` + pub TRANSMUTE_INT_TO_FLOAT, + complexity, + "transmutes from an integer to a float" +} + +declare_clippy_lint! { + /// **What it does:** Checks for transmutes from a float to an integer. + /// + /// **Why is this bad?** Transmutes are dangerous and error-prone, whereas `to_bits` is intuitive + /// and safe. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// ```rust + /// unsafe { + /// let _: u32 = std::mem::transmute(1f32); + /// } + /// + /// // should be: + /// let _: u32 = 1f32.to_bits(); + /// ``` + pub TRANSMUTE_FLOAT_TO_INT, + complexity, + "transmutes from a float to an integer" +} + +declare_clippy_lint! { + /// **What it does:** Checks for transmutes from a pointer to a pointer, or + /// from a reference to a reference. + /// + /// **Why is this bad?** Transmutes are dangerous, and these can instead be + /// written as casts. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// ```rust + /// let ptr = &1u32 as *const u32; + /// unsafe { + /// // pointer-to-pointer transmute + /// let _: *const f32 = std::mem::transmute(ptr); + /// // ref-ref transmute + /// let _: &f32 = std::mem::transmute(&1u32); + /// } + /// // These can be respectively written: + /// let _ = ptr as *const f32; + /// let _ = unsafe{ &*(&1u32 as *const u32 as *const f32) }; + /// ``` + pub TRANSMUTE_PTR_TO_PTR, + complexity, + "transmutes from a pointer to a pointer / a reference to a reference" +} + +declare_clippy_lint! { + /// **What it does:** Checks for transmutes between collections whose + /// types have different ABI, size or alignment. + /// + /// **Why is this bad?** This is undefined behavior. + /// + /// **Known problems:** Currently, we cannot know whether a type is a + /// collection, so we just lint the ones that come with `std`. + /// + /// **Example:** + /// ```rust + /// // different size, therefore likely out-of-bounds memory access + /// // You absolutely do not want this in your code! + /// unsafe { + /// std::mem::transmute::<_, Vec>(vec![2_u16]) + /// }; + /// ``` + /// + /// You must always iterate, map and collect the values: + /// + /// ```rust + /// vec![2_u16].into_iter().map(u32::from).collect::>(); + /// ``` + pub UNSOUND_COLLECTION_TRANSMUTE, + correctness, + "transmute between collections of layout-incompatible types" +} + +declare_lint_pass!(Transmute => [ + CROSSPOINTER_TRANSMUTE, + TRANSMUTE_PTR_TO_REF, + TRANSMUTE_PTR_TO_PTR, + USELESS_TRANSMUTE, + WRONG_TRANSMUTE, + TRANSMUTE_INT_TO_CHAR, + TRANSMUTE_BYTES_TO_STR, + TRANSMUTE_INT_TO_BOOL, + TRANSMUTE_INT_TO_FLOAT, + TRANSMUTE_FLOAT_TO_INT, + UNSOUND_COLLECTION_TRANSMUTE, + TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS, +]); + +// used to check for UNSOUND_COLLECTION_TRANSMUTE +static COLLECTIONS: &[&[&str]] = &[ + &paths::VEC, + &paths::VEC_DEQUE, + &paths::BINARY_HEAP, + &paths::BTREESET, + &paths::BTREEMAP, + &paths::HASHSET, + &paths::HASHMAP, +]; +impl<'tcx> LateLintPass<'tcx> for Transmute { + #[allow(clippy::similar_names, clippy::too_many_lines)] + fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) { + if_chain! { + if let ExprKind::Call(ref path_expr, ref args) = e.kind; + if let ExprKind::Path(ref qpath) = path_expr.kind; + if let Some(def_id) = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id(); + if match_def_path(cx, def_id, &paths::TRANSMUTE); + then { + // Avoid suggesting from/to bits and dereferencing raw pointers in const contexts. + // See https://github.com/rust-lang/rust/issues/73736 for progress on making them `const fn`. + // And see https://github.com/rust-lang/rust/issues/51911 for dereferencing raw pointers. + let const_context = in_constant(cx, e.hir_id); + + let from_ty = cx.typeck_results().expr_ty(&args[0]); + let to_ty = cx.typeck_results().expr_ty(e); + + match (&from_ty.kind(), &to_ty.kind()) { + _ if from_ty == to_ty => span_lint( + cx, + USELESS_TRANSMUTE, + e.span, + &format!("transmute from a type (`{}`) to itself", from_ty), + ), + (ty::Ref(_, rty, rty_mutbl), ty::RawPtr(ptr_ty)) => span_lint_and_then( + cx, + USELESS_TRANSMUTE, + e.span, + "transmute from a reference to a pointer", + |diag| { + if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { + let rty_and_mut = ty::TypeAndMut { + ty: rty, + mutbl: *rty_mutbl, + }; + + let sugg = if *ptr_ty == rty_and_mut { + arg.as_ty(to_ty) + } else { + arg.as_ty(cx.tcx.mk_ptr(rty_and_mut)).as_ty(to_ty) + }; + + diag.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified); + } + }, + ), + (ty::Int(_) | ty::Uint(_), ty::RawPtr(_)) => span_lint_and_then( + cx, + USELESS_TRANSMUTE, + e.span, + "transmute from an integer to a pointer", + |diag| { + if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { + diag.span_suggestion( + e.span, + "try", + arg.as_ty(&to_ty.to_string()).to_string(), + Applicability::Unspecified, + ); + } + }, + ), + (ty::Float(_) | ty::Char, ty::Ref(..) | ty::RawPtr(_)) => span_lint( + cx, + WRONG_TRANSMUTE, + e.span, + &format!("transmute from a `{}` to a pointer", from_ty), + ), + (ty::RawPtr(from_ptr), _) if from_ptr.ty == to_ty => span_lint( + cx, + CROSSPOINTER_TRANSMUTE, + e.span, + &format!( + "transmute from a type (`{}`) to the type that it points to (`{}`)", + from_ty, to_ty + ), + ), + (_, ty::RawPtr(to_ptr)) if to_ptr.ty == from_ty => span_lint( + cx, + CROSSPOINTER_TRANSMUTE, + e.span, + &format!( + "transmute from a type (`{}`) to a pointer to that type (`{}`)", + from_ty, to_ty + ), + ), + (ty::RawPtr(from_pty), ty::Ref(_, to_ref_ty, mutbl)) => span_lint_and_then( + cx, + TRANSMUTE_PTR_TO_REF, + e.span, + &format!( + "transmute from a pointer type (`{}`) to a reference type \ + (`{}`)", + from_ty, to_ty + ), + |diag| { + let arg = sugg::Sugg::hir(cx, &args[0], ".."); + let (deref, cast) = if *mutbl == Mutability::Mut { + ("&mut *", "*mut") + } else { + ("&*", "*const") + }; + + let arg = if from_pty.ty == *to_ref_ty { + arg + } else { + arg.as_ty(&format!("{} {}", cast, get_type_snippet(cx, qpath, to_ref_ty))) + }; + + diag.span_suggestion( + e.span, + "try", + sugg::make_unop(deref, arg).to_string(), + Applicability::Unspecified, + ); + }, + ), + (ty::Int(ty::IntTy::I32) | ty::Uint(ty::UintTy::U32), &ty::Char) => { + span_lint_and_then( + cx, + TRANSMUTE_INT_TO_CHAR, + e.span, + &format!("transmute from a `{}` to a `char`", from_ty), + |diag| { + let arg = sugg::Sugg::hir(cx, &args[0], ".."); + let arg = if let ty::Int(_) = from_ty.kind() { + arg.as_ty(ast::UintTy::U32.name_str()) + } else { + arg + }; + diag.span_suggestion( + e.span, + "consider using", + format!("std::char::from_u32({}).unwrap()", arg.to_string()), + Applicability::Unspecified, + ); + }, + ) + }, + (ty::Ref(_, ty_from, from_mutbl), ty::Ref(_, ty_to, to_mutbl)) => { + if_chain! { + if let (&ty::Slice(slice_ty), &ty::Str) = (&ty_from.kind(), &ty_to.kind()); + if let ty::Uint(ty::UintTy::U8) = slice_ty.kind(); + if from_mutbl == to_mutbl; + then { + let postfix = if *from_mutbl == Mutability::Mut { + "_mut" + } else { + "" + }; + + span_lint_and_sugg( + cx, + TRANSMUTE_BYTES_TO_STR, + e.span, + &format!("transmute from a `{}` to a `{}`", from_ty, to_ty), + "consider using", + format!( + "std::str::from_utf8{}({}).unwrap()", + postfix, + snippet(cx, args[0].span, ".."), + ), + Applicability::Unspecified, + ); + } else { + if (cx.tcx.erase_regions(from_ty) != cx.tcx.erase_regions(to_ty)) + && !const_context { + span_lint_and_then( + cx, + TRANSMUTE_PTR_TO_PTR, + e.span, + "transmute from a reference to a reference", + |diag| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { + let ty_from_and_mut = ty::TypeAndMut { + ty: ty_from, + mutbl: *from_mutbl + }; + let ty_to_and_mut = ty::TypeAndMut { ty: ty_to, mutbl: *to_mutbl }; + let sugg_paren = arg + .as_ty(cx.tcx.mk_ptr(ty_from_and_mut)) + .as_ty(cx.tcx.mk_ptr(ty_to_and_mut)); + let sugg = if *to_mutbl == Mutability::Mut { + sugg_paren.mut_addr_deref() + } else { + sugg_paren.addr_deref() + }; + diag.span_suggestion( + e.span, + "try", + sugg.to_string(), + Applicability::Unspecified, + ); + }, + ) + } + } + } + }, + (ty::RawPtr(_), ty::RawPtr(to_ty)) => span_lint_and_then( + cx, + TRANSMUTE_PTR_TO_PTR, + e.span, + "transmute from a pointer to a pointer", + |diag| { + if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { + let sugg = arg.as_ty(cx.tcx.mk_ptr(*to_ty)); + diag.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified); + } + }, + ), + (ty::Int(ty::IntTy::I8) | ty::Uint(ty::UintTy::U8), ty::Bool) => { + span_lint_and_then( + cx, + TRANSMUTE_INT_TO_BOOL, + e.span, + &format!("transmute from a `{}` to a `bool`", from_ty), + |diag| { + let arg = sugg::Sugg::hir(cx, &args[0], ".."); + let zero = sugg::Sugg::NonParen(Cow::from("0")); + diag.span_suggestion( + e.span, + "consider using", + sugg::make_binop(ast::BinOpKind::Ne, &arg, &zero).to_string(), + Applicability::Unspecified, + ); + }, + ) + }, + (ty::Int(_) | ty::Uint(_), ty::Float(_)) if !const_context => span_lint_and_then( + cx, + TRANSMUTE_INT_TO_FLOAT, + e.span, + &format!("transmute from a `{}` to a `{}`", from_ty, to_ty), + |diag| { + let arg = sugg::Sugg::hir(cx, &args[0], ".."); + let arg = if let ty::Int(int_ty) = from_ty.kind() { + arg.as_ty(format!( + "u{}", + int_ty.bit_width().map_or_else(|| "size".to_string(), |v| v.to_string()) + )) + } else { + arg + }; + diag.span_suggestion( + e.span, + "consider using", + format!("{}::from_bits({})", to_ty, arg.to_string()), + Applicability::Unspecified, + ); + }, + ), + (ty::Float(float_ty), ty::Int(_) | ty::Uint(_)) if !const_context => span_lint_and_then( + cx, + TRANSMUTE_FLOAT_TO_INT, + e.span, + &format!("transmute from a `{}` to a `{}`", from_ty, to_ty), + |diag| { + let mut expr = &args[0]; + let mut arg = sugg::Sugg::hir(cx, expr, ".."); + + if let ExprKind::Unary(UnOp::Neg, inner_expr) = &expr.kind { + expr = &inner_expr; + } + + if_chain! { + // if the expression is a float literal and it is unsuffixed then + // add a suffix so the suggestion is valid and unambiguous + let op = format!("{}{}", arg, float_ty.name_str()).into(); + if let ExprKind::Lit(lit) = &expr.kind; + if let ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) = lit.node; + then { + match arg { + sugg::Sugg::MaybeParen(_) => arg = sugg::Sugg::MaybeParen(op), + _ => arg = sugg::Sugg::NonParen(op) + } + } + } + + arg = sugg::Sugg::NonParen(format!("{}.to_bits()", arg.maybe_par()).into()); + + // cast the result of `to_bits` if `to_ty` is signed + arg = if let ty::Int(int_ty) = to_ty.kind() { + arg.as_ty(int_ty.name_str().to_string()) + } else { + arg + }; + + diag.span_suggestion( + e.span, + "consider using", + arg.to_string(), + Applicability::Unspecified, + ); + }, + ), + (ty::Adt(from_adt, from_substs), ty::Adt(to_adt, to_substs)) => { + if from_adt.did != to_adt.did || + !COLLECTIONS.iter().any(|path| match_def_path(cx, to_adt.did, path)) { + return; + } + if from_substs.types().zip(to_substs.types()) + .any(|(from_ty, to_ty)| is_layout_incompatible(cx, from_ty, to_ty)) { + span_lint( + cx, + UNSOUND_COLLECTION_TRANSMUTE, + e.span, + &format!( + "transmute from `{}` to `{}` with mismatched layout is unsound", + from_ty, + to_ty + ) + ); + } + }, + (_, _) if can_be_expressed_as_pointer_cast(cx, e, from_ty, to_ty) => span_lint_and_then( + cx, + TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS, + e.span, + &format!( + "transmute from `{}` to `{}` which could be expressed as a pointer cast instead", + from_ty, + to_ty + ), + |diag| { + if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { + let sugg = arg.as_ty(&to_ty.to_string()).to_string(); + diag.span_suggestion(e.span, "try", sugg, Applicability::MachineApplicable); + } + } + ), + _ => { + return; + }, + } + } + } + } +} + +/// Gets the snippet of `Bar` in `…::transmute`. If that snippet is +/// not available , use +/// the type's `ToString` implementation. In weird cases it could lead to types +/// with invalid `'_` +/// lifetime, but it should be rare. +fn get_type_snippet(cx: &LateContext<'_>, path: &QPath<'_>, to_ref_ty: Ty<'_>) -> String { + let seg = last_path_segment(path); + if_chain! { + if let Some(ref params) = seg.args; + if !params.parenthesized; + if let Some(to_ty) = params.args.iter().filter_map(|arg| match arg { + GenericArg::Type(ty) => Some(ty), + _ => None, + }).nth(1); + if let TyKind::Rptr(_, ref to_ty) = to_ty.kind; + then { + return snippet(cx, to_ty.ty.span, &to_ref_ty.to_string()).to_string(); + } + } + + to_ref_ty.to_string() +} + +// check if the component types of the transmuted collection and the result have different ABI, +// size or alignment +fn is_layout_incompatible<'tcx>(cx: &LateContext<'tcx>, from: Ty<'tcx>, to: Ty<'tcx>) -> bool { + let empty_param_env = ty::ParamEnv::empty(); + // check if `from` and `to` are normalizable to avoid ICE (#4968) + if !(is_normalizable(cx, empty_param_env, from) && is_normalizable(cx, empty_param_env, to)) { + return false; + } + let from_ty_layout = cx.tcx.layout_of(empty_param_env.and(from)); + let to_ty_layout = cx.tcx.layout_of(empty_param_env.and(to)); + if let (Ok(from_layout), Ok(to_layout)) = (from_ty_layout, to_ty_layout) { + from_layout.size != to_layout.size || from_layout.align != to_layout.align || from_layout.abi != to_layout.abi + } else { + // no idea about layout, so don't lint + false + } +} + +/// Check if the type conversion can be expressed as a pointer cast, instead of +/// a transmute. In certain cases, including some invalid casts from array +/// references to pointers, this may cause additional errors to be emitted and/or +/// ICE error messages. This function will panic if that occurs. +fn can_be_expressed_as_pointer_cast<'tcx>( + cx: &LateContext<'tcx>, + e: &'tcx Expr<'_>, + from_ty: Ty<'tcx>, + to_ty: Ty<'tcx>, +) -> bool { + use CastKind::{AddrPtrCast, ArrayPtrCast, FnPtrAddrCast, FnPtrPtrCast, PtrAddrCast, PtrPtrCast}; + matches!( + check_cast(cx, e, from_ty, to_ty), + Some(PtrPtrCast | PtrAddrCast | AddrPtrCast | ArrayPtrCast | FnPtrPtrCast | FnPtrAddrCast) + ) +} + +/// If a cast from `from_ty` to `to_ty` is valid, returns an Ok containing the kind of +/// the cast. In certain cases, including some invalid casts from array references +/// to pointers, this may cause additional errors to be emitted and/or ICE error +/// messages. This function will panic if that occurs. +fn check_cast<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, from_ty: Ty<'tcx>, to_ty: Ty<'tcx>) -> Option { + let hir_id = e.hir_id; + let local_def_id = hir_id.owner; + + Inherited::build(cx.tcx, local_def_id).enter(|inherited| { + let fn_ctxt = FnCtxt::new(&inherited, cx.param_env, hir_id); + + // If we already have errors, we can't be sure we can pointer cast. + assert!( + !fn_ctxt.errors_reported_since_creation(), + "Newly created FnCtxt contained errors" + ); + + if let Ok(check) = CastCheck::new( + &fn_ctxt, e, from_ty, to_ty, + // We won't show any error to the user, so we don't care what the span is here. + DUMMY_SP, DUMMY_SP, + ) { + let res = check.do_check(&fn_ctxt); + + // do_check's documentation says that it might return Ok and create + // errors in the fcx instead of returing Err in some cases. Those cases + // should be filtered out before getting here. + assert!( + !fn_ctxt.errors_reported_since_creation(), + "`fn_ctxt` contained errors after cast check!" + ); + + res.ok() + } else { + None + } + }) +}