+++ /dev/null
-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<u32>>(vec![2_u16])
- /// };
- /// ```
- ///
- /// You must always iterate, map and collect the values:
- ///
- /// ```rust
- /// vec![2_u16].into_iter().map(u32::from).collect::<Vec<_>>();
- /// ```
- 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<Foo, &Bar>`. 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<CastKind> {
- 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
- }
- })
-}
--- /dev/null
+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<u32>>(vec![2_u16])
+ /// };
+ /// ```
+ ///
+ /// You must always iterate, map and collect the values:
+ ///
+ /// ```rust
+ /// vec![2_u16].into_iter().map(u32::from).collect::<Vec<_>>();
+ /// ```
+ 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<Foo, &Bar>`. 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<CastKind> {
+ 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
+ }
+ })
+}
projects / rust.git / commitdiff