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Auto merge of #6716 - magurotuna:refactor-transmute-mod, r=flip1995

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Refactor: arrange transmute lints

This PR arranges `transmute` lints so that they can be accessed more easily.
Basically, I followed the instruction described in #6680 as to how to do the refactoring.

- `declare_clippy_lint!` and `impl LintPass` is placed in `transmute/mod.rs`
- Uitlity functions is placed in `transmute/utils.rs`
- Each lint function about `transmute` is moved into its own module, like `transmute/useless_transmute.rs`

For ease of review, I refactored step by step, keeping each commit small. For instance, all I did in
2451781 was to move  `useless_transmute` into its own module.

---

changelog: Refactor `transmute.rs` file into `transmute` module.
This commit is contained in:
bors 2021-03-02 09:44:03 +00:00
commit 3cd6ca051c
15 changed files with 1062 additions and 763 deletions
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763
clippy_lints/src/transmute.rs
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@ -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<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
}
})
}

37
clippy_lints/src/transmute/crosspointer_transmute.rs Normal file
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@ -0,0 +1,37 @@
use super::CROSSPOINTER_TRANSMUTE;
use crate::utils::span_lint;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
/// Checks for `crosspointer_transmute` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, from_ty: Ty<'tcx>, to_ty: Ty<'tcx>) -> bool {
match (&from_ty.kind(), &to_ty.kind()) {
(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
),
);
true
},
(_, 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
),
);
true
},
_ => false,
}
}

363
clippy_lints/src/transmute/mod.rs Normal file
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@ -0,0 +1,363 @@
mod crosspointer_transmute;
mod transmute_float_to_int;
mod transmute_int_to_bool;
mod transmute_int_to_char;
mod transmute_int_to_float;
mod transmute_ptr_to_ptr;
mod transmute_ptr_to_ref;
mod transmute_ref_to_ref;
mod transmutes_expressible_as_ptr_casts;
mod unsound_collection_transmute;
mod useless_transmute;
mod utils;
mod wrong_transmute;
use crate::utils::{in_constant, match_def_path, paths};
use if_chain::if_chain;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
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,
]);
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);
// If useless_transmute is triggered, the other lints can be skipped.
if useless_transmute::check(cx, e, from_ty, to_ty, args) {
return;
}
let mut linted = wrong_transmute::check(cx, e, from_ty, to_ty);
linted |= crosspointer_transmute::check(cx, e, from_ty, to_ty);
linted |= transmute_ptr_to_ref::check(cx, e, from_ty, to_ty, args, qpath);
linted |= transmute_int_to_char::check(cx, e, from_ty, to_ty, args);
linted |= transmute_ref_to_ref::check(cx, e, from_ty, to_ty, args, const_context);
linted |= transmute_ptr_to_ptr::check(cx, e, from_ty, to_ty, args);
linted |= transmute_int_to_bool::check(cx, e, from_ty, to_ty, args);
linted |= transmute_int_to_float::check(cx, e, from_ty, to_ty, args, const_context);
linted |= transmute_float_to_int::check(cx, e, from_ty, to_ty, args, const_context);
linted |= unsound_collection_transmute::check(cx, e, from_ty, to_ty);
if !linted {
transmutes_expressible_as_ptr_casts::check(cx, e, from_ty, to_ty, args);
}
}
}
}
}

65
clippy_lints/src/transmute/transmute_float_to_int.rs Normal file
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@ -0,0 +1,65 @@
use super::TRANSMUTE_FLOAT_TO_INT;
use crate::utils::{span_lint_and_then, sugg};
use if_chain::if_chain;
use rustc_ast as ast;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, UnOp};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
/// Checks for `transmute_float_to_int` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
args: &'tcx [Expr<'_>],
const_context: bool,
) -> bool {
match (&from_ty.kind(), &to_ty.kind()) {
(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);
},
);
true
},
_ => false,
}
}

41
clippy_lints/src/transmute/transmute_int_to_bool.rs Normal file
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@ -0,0 +1,41 @@
use super::TRANSMUTE_INT_TO_BOOL;
use crate::utils::{span_lint_and_then, sugg};
use rustc_ast as ast;
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
use std::borrow::Cow;
/// Checks for `transmute_int_to_bool` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
args: &'tcx [Expr<'_>],
) -> bool {
match (&from_ty.kind(), &to_ty.kind()) {
(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,
);
},
);
true
},
_ => false,
}
}

46
clippy_lints/src/transmute/transmute_int_to_char.rs Normal file
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@ -0,0 +1,46 @@
use super::TRANSMUTE_INT_TO_CHAR;
use crate::utils::{span_lint_and_then, sugg};
use rustc_ast as ast;
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
/// Checks for `transmute_int_to_char` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
args: &'tcx [Expr<'_>],
) -> bool {
match (&from_ty.kind(), &to_ty.kind()) {
(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,
);
},
)
};
true
},
_ => false,
}
}

47
clippy_lints/src/transmute/transmute_int_to_float.rs Normal file
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@ -0,0 +1,47 @@
use super::TRANSMUTE_INT_TO_FLOAT;
use crate::utils::{span_lint_and_then, sugg};
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
/// Checks for `transmute_int_to_float` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
args: &'tcx [Expr<'_>],
const_context: bool,
) -> bool {
match (&from_ty.kind(), &to_ty.kind()) {
(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,
);
},
);
true
},
_ => false,
}
}

35
clippy_lints/src/transmute/transmute_ptr_to_ptr.rs Normal file
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@ -0,0 +1,35 @@
use super::TRANSMUTE_PTR_TO_PTR;
use crate::utils::{span_lint_and_then, sugg};
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
/// Checks for `transmute_ptr_to_ptr` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
args: &'tcx [Expr<'_>],
) -> bool {
match (&from_ty.kind(), &to_ty.kind()) {
(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);
}
},
);
true
},
_ => false,
}
}

55
clippy_lints/src/transmute/transmute_ptr_to_ref.rs Normal file
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use super::utils::get_type_snippet;
use super::TRANSMUTE_PTR_TO_REF;
use crate::utils::{span_lint_and_then, sugg};
use rustc_errors::Applicability;
use rustc_hir::{Expr, Mutability, QPath};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
/// Checks for `transmute_ptr_to_ref` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
args: &'tcx [Expr<'_>],
qpath: &'tcx QPath<'_>,
) -> bool {
match (&from_ty.kind(), &to_ty.kind()) {
(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,
);
},
);
true
},
_ => false,
}
}

88
clippy_lints/src/transmute/transmute_ref_to_ref.rs Normal file
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use super::{TRANSMUTE_BYTES_TO_STR, TRANSMUTE_PTR_TO_PTR};
use crate::utils::{snippet, span_lint_and_sugg, span_lint_and_then, sugg};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Expr, Mutability};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
/// Checks for `transmute_bytes_to_str` and `transmute_ptr_to_ptr` lints.
/// Returns `true` if either one triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
args: &'tcx [Expr<'_>],
const_context: bool,
) -> bool {
let mut triggered = false;
match (&from_ty.kind(), &to_ty.kind()) {
(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,
);
triggered = true;
} 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,
);
},
);
triggered = true;
}
}
}
},
_ => {},
}
triggered
}

38
clippy_lints/src/transmute/transmutes_expressible_as_ptr_casts.rs Normal file
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use super::utils::can_be_expressed_as_pointer_cast;
use super::TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS;
use crate::utils::{span_lint_and_then, sugg};
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::Ty;
/// Checks for `transmutes_expressible_as_ptr_casts` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
args: &'tcx [Expr<'_>],
) -> bool {
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);
}
},
);
true
} else {
false
}
}

48
clippy_lints/src/transmute/unsound_collection_transmute.rs Normal file
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use super::utils::is_layout_incompatible;
use super::UNSOUND_COLLECTION_TRANSMUTE;
use crate::utils::{match_def_path, paths, span_lint};
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
// 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,
];
/// Checks for `unsound_collection_transmute` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, from_ty: Ty<'tcx>, to_ty: Ty<'tcx>) -> bool {
match (&from_ty.kind(), &to_ty.kind()) {
(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 false;
}
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
),
);
true
} else {
false
}
},
_ => false,
}
}

73
clippy_lints/src/transmute/useless_transmute.rs Normal file
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use super::USELESS_TRANSMUTE;
use crate::utils::{span_lint, span_lint_and_then, sugg};
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
/// Checks for `useless_transmute` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
args: &'tcx [Expr<'_>],
) -> bool {
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),
);
true
},
(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);
}
},
);
true
},
(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,
);
}
},
);
true
},
_ => false,
}
}

104
clippy_lints/src/transmute/utils.rs Normal file
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use crate::utils::{is_normalizable, last_path_segment, snippet};
use if_chain::if_chain;
use rustc_hir::{Expr, GenericArg, QPath, TyKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, cast::CastKind, Ty};
use rustc_span::DUMMY_SP;
use rustc_typeck::check::{cast::CastCheck, FnCtxt, Inherited};
/// 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.
pub(super) 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
pub(super) 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.
pub(super) 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
}
})
}

22
clippy_lints/src/transmute/wrong_transmute.rs Normal file
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use super::WRONG_TRANSMUTE;
use crate::utils::span_lint;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
/// Checks for `wrong_transmute` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, from_ty: Ty<'tcx>, to_ty: Ty<'tcx>) -> bool {
match (&from_ty.kind(), &to_ty.kind()) {
(ty::Float(_) | ty::Char, ty::Ref(..) | ty::RawPtr(_)) => {
span_lint(
cx,
WRONG_TRANSMUTE,
e.span,
&format!("transmute from a `{}` to a pointer", from_ty),
);
true
},
_ => false,
}
}