1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
11 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
12 use crate::rustc::{declare_tool_lint, lint_array};
13 use if_chain::if_chain;
14 use crate::rustc::ty::{self, Ty};
15 use crate::rustc::hir::*;
17 use crate::syntax::ast;
18 use crate::utils::{last_path_segment, match_def_path, paths, snippet, span_lint, span_lint_and_then};
19 use crate::utils::{opt_def_id, sugg};
20 use crate::rustc_errors::Applicability;
22 /// **What it does:** Checks for transmutes that can't ever be correct on any
25 /// **Why is this bad?** It's basically guaranteed to be undefined behaviour.
27 /// **Known problems:** When accessing C, users might want to store pointer
28 /// sized objects in `extradata` arguments to save an allocation.
32 /// let ptr: *const T = core::intrinsics::transmute('x')
34 declare_clippy_lint! {
37 "transmutes that are confusing at best, undefined behaviour at worst and always useless"
40 /// **What it does:** Checks for transmutes to the original type of the object
41 /// and transmutes that could be a cast.
43 /// **Why is this bad?** Readability. The code tricks people into thinking that
44 /// something complex is going on.
46 /// **Known problems:** None.
50 /// core::intrinsics::transmute(t) // where the result type is the same as `t`'s
52 declare_clippy_lint! {
53 pub USELESS_TRANSMUTE,
55 "transmutes that have the same to and from types or could be a cast/coercion"
58 /// **What it does:** Checks for transmutes between a type `T` and `*T`.
60 /// **Why is this bad?** It's easy to mistakenly transmute between a type and a
61 /// pointer to that type.
63 /// **Known problems:** None.
67 /// core::intrinsics::transmute(t) // where the result type is the same as
70 declare_clippy_lint! {
71 pub CROSSPOINTER_TRANSMUTE,
73 "transmutes that have to or from types that are a pointer to the other"
76 /// **What it does:** Checks for transmutes from a pointer to a reference.
78 /// **Why is this bad?** This can always be rewritten with `&` and `*`.
80 /// **Known problems:** None.
84 /// let _: &T = std::mem::transmute(p); // where p: *const T
85 /// // can be written:
88 declare_clippy_lint! {
89 pub TRANSMUTE_PTR_TO_REF,
91 "transmutes from a pointer to a reference type"
94 /// **What it does:** Checks for transmutes from an integer to a `char`.
96 /// **Why is this bad?** Not every integer is a Unicode scalar value.
98 /// **Known problems:**
99 /// - [`from_u32`] which this lint suggests using is slower than `transmute`
100 /// as it needs to validate the input.
101 /// If you are certain that the input is always a valid Unicode scalar value,
102 /// use [`from_u32_unchecked`] which is as fast as `transmute`
103 /// but has a semantically meaningful name.
104 /// - You might want to handle `None` returned from [`from_u32`] instead of calling `unwrap`.
106 /// [`from_u32`]: https://doc.rust-lang.org/std/char/fn.from_u32.html
107 /// [`from_u32_unchecked`]: https://doc.rust-lang.org/std/char/fn.from_u32_unchecked.html
111 /// let _: char = std::mem::transmute(x); // where x: u32
113 /// let _ = std::char::from_u32(x).unwrap();
115 declare_clippy_lint! {
116 pub TRANSMUTE_INT_TO_CHAR,
118 "transmutes from an integer to a `char`"
121 /// **What it does:** Checks for transmutes from a `&[u8]` to a `&str`.
123 /// **Why is this bad?** Not every byte slice is a valid UTF-8 string.
125 /// **Known problems:**
126 /// - [`from_utf8`] which this lint suggests using is slower than `transmute`
127 /// as it needs to validate the input.
128 /// If you are certain that the input is always a valid UTF-8,
129 /// use [`from_utf8_unchecked`] which is as fast as `transmute`
130 /// but has a semantically meaningful name.
131 /// - You might want to handle errors returned from [`from_utf8`] instead of calling `unwrap`.
133 /// [`from_utf8`]: https://doc.rust-lang.org/std/str/fn.from_utf8.html
134 /// [`from_utf8_unchecked`]: https://doc.rust-lang.org/std/str/fn.from_utf8_unchecked.html
138 /// let _: &str = std::mem::transmute(b); // where b: &[u8]
140 /// let _ = std::str::from_utf8(b).unwrap();
142 declare_clippy_lint! {
143 pub TRANSMUTE_BYTES_TO_STR,
145 "transmutes from a `&[u8]` to a `&str`"
148 /// **What it does:** Checks for transmutes from an integer to a `bool`.
150 /// **Why is this bad?** This might result in an invalid in-memory representation of a `bool`.
152 /// **Known problems:** None.
156 /// let _: bool = std::mem::transmute(x); // where x: u8
158 /// let _: bool = x != 0;
160 declare_clippy_lint! {
161 pub TRANSMUTE_INT_TO_BOOL,
163 "transmutes from an integer to a `bool`"
166 /// **What it does:** Checks for transmutes from an integer to a float.
168 /// **Why is this bad?** This might result in an invalid in-memory representation of a float.
170 /// **Known problems:** None.
174 /// let _: f32 = std::mem::transmute(x); // where x: u32
176 /// let _: f32 = f32::from_bits(x);
178 declare_clippy_lint! {
179 pub TRANSMUTE_INT_TO_FLOAT,
181 "transmutes from an integer to a float"
184 /// **What it does:** Checks for transmutes from a pointer to a pointer, or
185 /// from a reference to a reference.
187 /// **Why is this bad?** Transmutes are dangerous, and these can instead be
188 /// written as casts.
190 /// **Known problems:** None.
194 /// let ptr = &1u32 as *const u32;
196 /// // pointer-to-pointer transmute
197 /// let _: *const f32 = std::mem::transmute(ptr);
198 /// // ref-ref transmute
199 /// let _: &f32 = std::mem::transmute(&1u32);
201 /// // These can be respectively written:
202 /// let _ = ptr as *const f32
203 /// let _ = unsafe{ &*(&1u32 as *const u32 as *const f32) };
205 declare_clippy_lint! {
206 pub TRANSMUTE_PTR_TO_PTR,
208 "transmutes from a pointer to a pointer / a reference to a reference"
211 pub struct Transmute;
213 impl LintPass for Transmute {
214 fn get_lints(&self) -> LintArray {
216 CROSSPOINTER_TRANSMUTE,
217 TRANSMUTE_PTR_TO_REF,
218 TRANSMUTE_PTR_TO_PTR,
221 TRANSMUTE_INT_TO_CHAR,
222 TRANSMUTE_BYTES_TO_STR,
223 TRANSMUTE_INT_TO_BOOL,
224 TRANSMUTE_INT_TO_FLOAT,
229 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Transmute {
230 #[allow(clippy::similar_names)]
231 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
232 if let ExprKind::Call(ref path_expr, ref args) = e.node {
233 if let ExprKind::Path(ref qpath) = path_expr.node {
234 if let Some(def_id) = opt_def_id(cx.tables.qpath_def(qpath, path_expr.hir_id)) {
235 if match_def_path(cx.tcx, def_id, &paths::TRANSMUTE) {
236 let from_ty = cx.tables.expr_ty(&args[0]);
237 let to_ty = cx.tables.expr_ty(e);
239 match (&from_ty.sty, &to_ty.sty) {
240 _ if from_ty == to_ty => span_lint(
244 &format!("transmute from a type (`{}`) to itself", from_ty),
246 (&ty::Ref(_, rty, rty_mutbl), &ty::RawPtr(ptr_ty)) => span_lint_and_then(
250 "transmute from a reference to a pointer",
251 |db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
252 let rty_and_mut = ty::TypeAndMut { ty: rty, mutbl: rty_mutbl };
254 let sugg = if ptr_ty == rty_and_mut {
257 arg.as_ty(cx.tcx.mk_ptr(rty_and_mut)).as_ty(to_ty)
260 db.span_suggestion_with_applicability(
264 Applicability::Unspecified,
268 (&ty::Int(_), &ty::RawPtr(_)) | (&ty::Uint(_), &ty::RawPtr(_)) => {
273 "transmute from an integer to a pointer",
274 |db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
275 db.span_suggestion_with_applicability(
278 arg.as_ty(&to_ty.to_string()).to_string(),
279 Applicability::Unspecified,
284 (&ty::Float(_), &ty::Ref(..)) |
285 (&ty::Float(_), &ty::RawPtr(_)) |
286 (&ty::Char, &ty::Ref(..)) |
287 (&ty::Char, &ty::RawPtr(_)) => span_lint(
291 &format!("transmute from a `{}` to a pointer", from_ty),
293 (&ty::RawPtr(from_ptr), _) if from_ptr.ty == to_ty => span_lint(
295 CROSSPOINTER_TRANSMUTE,
298 "transmute from a type (`{}`) to the type that it points to (`{}`)",
303 (_, &ty::RawPtr(to_ptr)) if to_ptr.ty == from_ty => span_lint(
305 CROSSPOINTER_TRANSMUTE,
308 "transmute from a type (`{}`) to a pointer to that type (`{}`)",
313 (&ty::RawPtr(from_pty), &ty::Ref(_, to_ref_ty, mutbl)) => span_lint_and_then(
315 TRANSMUTE_PTR_TO_REF,
318 "transmute from a pointer type (`{}`) to a reference type \
324 let arg = sugg::Sugg::hir(cx, &args[0], "..");
325 let (deref, cast) = if mutbl == Mutability::MutMutable {
331 let arg = if from_pty.ty == to_ref_ty {
334 arg.as_ty(&format!("{} {}", cast, get_type_snippet(cx, qpath, to_ref_ty)))
337 db.span_suggestion_with_applicability(
340 sugg::make_unop(deref, arg).to_string(),
341 Applicability::Unspecified,
345 (&ty::Int(ast::IntTy::I32), &ty::Char) |
346 (&ty::Uint(ast::UintTy::U32), &ty::Char) => span_lint_and_then(
348 TRANSMUTE_INT_TO_CHAR,
350 &format!("transmute from a `{}` to a `char`", from_ty),
352 let arg = sugg::Sugg::hir(cx, &args[0], "..");
353 let arg = if let ty::Int(_) = from_ty.sty {
354 arg.as_ty(ty::Uint(ast::UintTy::U32))
358 db.span_suggestion_with_applicability(
361 format!("std::char::from_u32({}).unwrap()", arg.to_string()),
362 Applicability::Unspecified,
366 (&ty::Ref(_, ty_from, from_mutbl), &ty::Ref(_, ty_to, to_mutbl)) => {
368 if let (&ty::Slice(slice_ty), &ty::Str) = (&ty_from.sty, &ty_to.sty);
369 if let ty::Uint(ast::UintTy::U8) = slice_ty.sty;
370 if from_mutbl == to_mutbl;
372 let postfix = if from_mutbl == Mutability::MutMutable {
380 TRANSMUTE_BYTES_TO_STR,
382 &format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
384 db.span_suggestion_with_applicability(
388 "std::str::from_utf8{}({}).unwrap()",
390 snippet(cx, args[0].span, ".."),
392 Applicability::Unspecified,
397 if cx.tcx.erase_regions(&from_ty) != cx.tcx.erase_regions(&to_ty) {
400 TRANSMUTE_PTR_TO_PTR,
402 "transmute from a reference to a reference",
403 |db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
404 let ty_from_and_mut = ty::TypeAndMut { ty: ty_from, mutbl: from_mutbl };
405 let ty_to_and_mut = ty::TypeAndMut { ty: ty_to, mutbl: to_mutbl };
406 let sugg_paren = arg.as_ty(cx.tcx.mk_ptr(ty_from_and_mut)).as_ty(cx.tcx.mk_ptr(ty_to_and_mut));
407 let sugg = if to_mutbl == Mutability::MutMutable {
408 sugg_paren.mut_addr_deref()
410 sugg_paren.addr_deref()
412 db.span_suggestion_with_applicability(
416 Applicability::Unspecified,
424 (&ty::RawPtr(_), &ty::RawPtr(to_ty)) => span_lint_and_then(
426 TRANSMUTE_PTR_TO_PTR,
428 "transmute from a pointer to a pointer",
429 |db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
430 let sugg = arg.as_ty(cx.tcx.mk_ptr(to_ty));
431 db.span_suggestion_with_applicability(
435 Applicability::Unspecified,
439 (&ty::Int(ast::IntTy::I8), &ty::Bool) | (&ty::Uint(ast::UintTy::U8), &ty::Bool) => {
442 TRANSMUTE_INT_TO_BOOL,
444 &format!("transmute from a `{}` to a `bool`", from_ty),
446 let arg = sugg::Sugg::hir(cx, &args[0], "..");
447 let zero = sugg::Sugg::NonParen(Cow::from("0"));
448 db.span_suggestion_with_applicability(
451 sugg::make_binop(ast::BinOpKind::Ne, &arg, &zero).to_string(),
452 Applicability::Unspecified,
457 (&ty::Int(_), &ty::Float(_)) | (&ty::Uint(_), &ty::Float(_)) => {
460 TRANSMUTE_INT_TO_FLOAT,
462 &format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
464 let arg = sugg::Sugg::hir(cx, &args[0], "..");
465 let arg = if let ty::Int(int_ty) = from_ty.sty {
470 .map_or_else(|| "size".to_string(), |v| v.to_string())
475 db.span_suggestion_with_applicability(
478 format!("{}::from_bits({})", to_ty, arg.to_string()),
479 Applicability::Unspecified,
493 /// Get the snippet of `Bar` in `…::transmute<Foo, &Bar>`. If that snippet is
494 /// not available , use
495 /// the type's `ToString` implementation. In weird cases it could lead to types
496 /// with invalid `'_`
497 /// lifetime, but it should be rare.
498 fn get_type_snippet(cx: &LateContext<'_, '_>, path: &QPath, to_ref_ty: Ty<'_>) -> String {
499 let seg = last_path_segment(path);
501 if let Some(ref params) = seg.args;
502 if !params.parenthesized;
503 if let Some(to_ty) = params.args.iter().filter_map(|arg| match arg {
504 GenericArg::Type(ty) => Some(ty),
505 GenericArg::Lifetime(_) => None,
507 if let TyKind::Rptr(_, ref to_ty) = to_ty.node;
509 return snippet(cx, to_ty.ty.span, &to_ref_ty.to_string()).to_string();
513 to_ref_ty.to_string()