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lint on unnecessary and plain wrong transmutes
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‎CHANGELOG.md

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# Change Log
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All notable changes to this project will be documented in this file.
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## 0.0.78 - TBA
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* New lints: [`wrong_transmute`]
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## 0.0.77 — 2016-06-21
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* Rustup to *rustc 1.11.0-nightly (5522e678b 2016-06-20)*
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* New lints: [`stutter`] and [`iter_nth`]
@@ -276,6 +279,7 @@ All notable changes to this project will be documented in this file.
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[`while_let_on_iterator`]: https://github.com/Manishearth/rust-clippy/wiki#while_let_on_iterator
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[`wrong_pub_self_convention`]: https://github.com/Manishearth/rust-clippy/wiki#wrong_pub_self_convention
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[`wrong_self_convention`]: https://github.com/Manishearth/rust-clippy/wiki#wrong_self_convention
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[`wrong_transmute`]: https://github.com/Manishearth/rust-clippy/wiki#wrong_transmute
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[`zero_divided_by_zero`]: https://github.com/Manishearth/rust-clippy/wiki#zero_divided_by_zero
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[`zero_width_space`]: https://github.com/Manishearth/rust-clippy/wiki#zero_width_space
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<!-- end autogenerated links to wiki -->

‎README.md

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@@ -17,7 +17,7 @@ Table of contents:
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## Lints
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There are 155 lints included in this crate:
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There are 156 lints included in this crate:
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name | default | meaning
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---------------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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[used_underscore_binding](https://github.com/Manishearth/rust-clippy/wiki#used_underscore_binding) | allow | using a binding which is prefixed with an underscore
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[useless_format](https://github.com/Manishearth/rust-clippy/wiki#useless_format) | warn | useless use of `format!`
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[useless_let_if_seq](https://github.com/Manishearth/rust-clippy/wiki#useless_let_if_seq) | warn | Checks for unidiomatic `let mut` declaration followed by initialization in `if`
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[useless_transmute](https://github.com/Manishearth/rust-clippy/wiki#useless_transmute) | warn | transmutes that have the same to and from types
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[useless_transmute](https://github.com/Manishearth/rust-clippy/wiki#useless_transmute) | warn | transmutes that have the same to and from types or could be a cast/coercion
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[useless_vec](https://github.com/Manishearth/rust-clippy/wiki#useless_vec) | warn | useless `vec!`
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[while_let_loop](https://github.com/Manishearth/rust-clippy/wiki#while_let_loop) | warn | `loop { if let { ... } else break }` can be written as a `while let` loop
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[while_let_on_iterator](https://github.com/Manishearth/rust-clippy/wiki#while_let_on_iterator) | warn | using a while-let loop instead of a for loop on an iterator
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[wrong_pub_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_pub_self_convention) | allow | defining a public method named with an established prefix (like "into_") that takes `self` with the wrong convention
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[wrong_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_self_convention) | warn | defining a method named with an established prefix (like "into_") that takes `self` with the wrong convention
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[wrong_transmute](https://github.com/Manishearth/rust-clippy/wiki#wrong_transmute) | warn | transmutes that are confusing at best, undefined behaviour at worst and always useless
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[zero_divided_by_zero](https://github.com/Manishearth/rust-clippy/wiki#zero_divided_by_zero) | warn | usage of `0.0 / 0.0` to obtain NaN instead of std::f32::NaN or std::f64::NaN
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[zero_width_space](https://github.com/Manishearth/rust-clippy/wiki#zero_width_space) | deny | using a zero-width space in a string literal, which is confusing
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‎clippy_lints/src/lib.rs

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@@ -403,6 +403,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
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transmute::CROSSPOINTER_TRANSMUTE,
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transmute::TRANSMUTE_PTR_TO_REF,
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transmute::USELESS_TRANSMUTE,
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transmute::WRONG_TRANSMUTE,
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types::ABSURD_EXTREME_COMPARISONS,
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types::BOX_VEC,
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types::CHAR_LIT_AS_U8,

‎clippy_lints/src/transmute.rs

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use rustc::lint::*;
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use rustc::ty::TypeVariants::{TyRawPtr, TyRef};
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use rustc::ty;
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use rustc::hir::*;
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use utils::{match_def_path, paths, snippet_opt, span_lint, span_lint_and_then};
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/// **What it does:** This lint checks for transmutes to the original type of the object.
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/// **What it does:** This lint checks for transmutes that can't ever be correct on any architecture
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///
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/// **Why is this bad?** Readability. The code tricks people into thinking that the original value was of some other type.
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/// **Why is this bad?** It's basically guaranteed to be undefined behaviour
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///
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/// **Known problems:** When accessing C, users might want to store pointer sized objects in `extradata` arguments to save an allocation.
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///
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/// **Example:** `let ptr: *const T = core::intrinsics::transmute('x')`.
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declare_lint! {
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pub WRONG_TRANSMUTE,
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Warn,
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"transmutes that are confusing at best, undefined behaviour at worst and always useless"
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}
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/// **What it does:** This lint checks for transmutes to the original type of the object and transmutes that could be a cast.
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///
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/// **Why is this bad?** Readability. The code tricks people into thinking that something complex is going on
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///
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/// **Known problems:** None.
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///
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/// **Example:** `core::intrinsics::transmute(t)` where the result type is the same as `t`'s.
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declare_lint! {
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pub USELESS_TRANSMUTE,
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Warn,
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"transmutes that have the same to and from types"
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"transmutes that have the same to and from types or could be a cast/coercion"
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}
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/// **What it does:*** This lint checks for transmutes between a type `T` and `*T`.
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impl LintPass for Transmute {
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fn get_lints(&self) -> LintArray {
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lint_array![CROSSPOINTER_TRANSMUTE, TRANSMUTE_PTR_TO_REF, USELESS_TRANSMUTE]
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lint_array![CROSSPOINTER_TRANSMUTE, TRANSMUTE_PTR_TO_REF, USELESS_TRANSMUTE, WRONG_TRANSMUTE]
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}
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}
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}
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},
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),
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(&ty::TyInt(_), &TyRawPtr(_)) |
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(&ty::TyUint(_), &TyRawPtr(_)) => span_lint_and_then(
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cx,
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USELESS_TRANSMUTE,
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e.span,
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"transmute from an integer to a pointer",
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|db| {
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if let Some(arg) = snippet_opt(cx, args[0].span) {
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db.span_suggestion(e.span, "try", format!("{} as {}", arg, to_ty));
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}
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},
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),
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(&ty::TyFloat(_), &TyRef(..)) |
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(&ty::TyFloat(_), &TyRawPtr(_)) |
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(&ty::TyChar, &TyRef(..)) |
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(&ty::TyChar, &TyRawPtr(_)) => span_lint(
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cx,
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WRONG_TRANSMUTE,
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e.span,
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&format!("transmute from a `{}` to a pointer", from_ty),
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),
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(&TyRawPtr(from_ptr), _) if from_ptr.ty == to_ty => span_lint(
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cx,
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CROSSPOINTER_TRANSMUTE,

‎tests/compile-fail/transmute.rs

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use std::mem::transmute as my_transmute;
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use std::vec::Vec as MyVec;
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fn my_int() -> usize {
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fn my_int() -> Usize {
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Usize(42)
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}
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fn my_vec() -> MyVec<i32> {
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let _: Vec<u32> = std::intrinsics::transmute(my_vec());
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let _: Vec<u32> = std::mem::transmute(my_vec());
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let _: Vec<u32> = my_transmute(my_vec());
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let _: *const usize = std::mem::transmute(5_isize);
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//~^ ERROR transmute from an integer to a pointer
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//~| HELP try
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//~| SUGGESTION 5_isize as *const usize
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}
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}
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struct Usize(usize);
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#[deny(crosspointer_transmute)]
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fn crosspointer() {
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let mut int: usize = 0;
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let int_const_ptr: *const usize = &int as *const usize;
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let int_mut_ptr: *mut usize = &mut int as *mut usize;
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let mut int: Usize = Usize(0);
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let int_const_ptr: *const Usize = &int as *const Usize;
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let int_mut_ptr: *mut Usize = &mut int as *mut Usize;
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unsafe {
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let _: usize = core::intrinsics::transmute(int_const_ptr);
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//~^ ERROR transmute from a type (`*const usize`) to the type that it points to (`usize`)
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let _: Usize = core::intrinsics::transmute(int_const_ptr);
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//~^ ERROR transmute from a type (`*const Usize`) to the type that it points to (`Usize`)
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let _: usize = core::intrinsics::transmute(int_mut_ptr);
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//~^ ERROR transmute from a type (`*mut usize`) to the type that it points to (`usize`)
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let _: Usize = core::intrinsics::transmute(int_mut_ptr);
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//~^ ERROR transmute from a type (`*mut Usize`) to the type that it points to (`Usize`)
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let _: *const usize = core::intrinsics::transmute(my_int());
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//~^ ERROR transmute from a type (`usize`) to a pointer to that type (`*const usize`)
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let _: *const Usize = core::intrinsics::transmute(my_int());
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//~^ ERROR transmute from a type (`Usize`) to a pointer to that type (`*const Usize`)
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let _: *mut usize = core::intrinsics::transmute(my_int());
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//~^ ERROR transmute from a type (`usize`) to a pointer to that type (`*mut usize`)
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let _: *mut Usize = core::intrinsics::transmute(my_int());
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//~^ ERROR transmute from a type (`Usize`) to a pointer to that type (`*mut Usize`)
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}
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}
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‎tests/compile-fail/transmute_32bit.rs

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//ignore-x86_64
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#![feature(plugin)]
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#![plugin(clippy)]
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#[deny(wrong_transmute)]
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fn main() {
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unsafe {
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let _: *const usize = std::mem::transmute(6.0f32);
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//~^ ERROR transmute from a `f32` to a pointer
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let _: *mut usize = std::mem::transmute(6.0f32);
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//~^ ERROR transmute from a `f32` to a pointer
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let _: *const usize = std::mem::transmute('x');
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//~^ ERROR transmute from a `char` to a pointer
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let _: *mut usize = std::mem::transmute('x');
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//~^ ERROR transmute from a `char` to a pointer
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}
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}

‎tests/compile-fail/transmute_64bit.rs

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//ignore-x86
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//no-ignore-x86_64
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#![feature(plugin)]
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#![plugin(clippy)]
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6+
#[deny(wrong_transmute)]
7+
fn main() {
8+
unsafe {
9+
let _: *const usize = std::mem::transmute(6.0f64);
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//~^ ERROR transmute from a `f64` to a pointer
11+
12+
let _: *mut usize = std::mem::transmute(6.0f64);
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//~^ ERROR transmute from a `f64` to a pointer
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}
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}

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