463 lines
20 KiB
Rust
463 lines
20 KiB
Rust
use rustc::lint::*;
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use rustc::ty::{self, Ty};
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use rustc::hir::*;
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use std::borrow::Cow;
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use syntax::ast;
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use utils::{last_path_segment, match_def_path, paths, snippet, span_lint, span_lint_and_then};
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use utils::{opt_def_id, sugg};
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/// **What it does:** Checks for transmutes that can't ever be correct on any
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/// architecture.
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///
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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
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/// sized objects in `extradata` arguments to save an allocation.
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///
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/// **Example:**
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/// ```rust
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/// let ptr: *const T = core::intrinsics::transmute('x')
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/// ```
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declare_clippy_lint! {
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pub WRONG_TRANSMUTE,
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correctness,
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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:** Checks for transmutes to the original type of the object
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/// 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
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/// 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:**
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/// ```rust
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/// core::intrinsics::transmute(t) // where the result type is the same as `t`'s
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/// ```
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declare_clippy_lint! {
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pub USELESS_TRANSMUTE,
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complexity,
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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:** Checks for transmutes between a type `T` and `*T`.
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///
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/// **Why is this bad?** It's easy to mistakenly transmute between a type and a
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/// pointer to that type.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// core::intrinsics::transmute(t) // where the result type is the same as
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/// // `*t` or `&t`'s
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/// ```
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declare_clippy_lint! {
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pub CROSSPOINTER_TRANSMUTE,
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complexity,
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"transmutes that have to or from types that are a pointer to the other"
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}
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/// **What it does:** Checks for transmutes from a pointer to a reference.
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///
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/// **Why is this bad?** This can always be rewritten with `&` and `*`.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let _: &T = std::mem::transmute(p); // where p: *const T
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/// // can be written:
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/// let _: &T = &*p;
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/// ```
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declare_clippy_lint! {
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pub TRANSMUTE_PTR_TO_REF,
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complexity,
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"transmutes from a pointer to a reference type"
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}
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/// **What it does:** Checks for transmutes from an integer to a `char`.
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///
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/// **Why is this bad?** Not every integer is a Unicode scalar value.
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///
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/// **Known problems:**
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/// - [`from_u32`] which this lint suggests using is slower than `transmute`
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/// as it needs to validate the input.
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/// If you are certain that the input is always a valid Unicode scalar value,
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/// use [`from_u32_unchecked`] which is as fast as `transmute`
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/// but has a semantically meaningful name.
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/// - You might want to handle `None` returned from [`from_u32`] instead of calling `unwrap`.
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///
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/// [`from_u32`]: https://doc.rust-lang.org/std/char/fn.from_u32.html
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/// [`from_u32_unchecked`]: https://doc.rust-lang.org/std/char/fn.from_u32_unchecked.html
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///
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/// **Example:**
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/// ```rust
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/// let _: char = std::mem::transmute(x); // where x: u32
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/// // should be:
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/// let _ = std::char::from_u32(x).unwrap();
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/// ```
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declare_clippy_lint! {
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pub TRANSMUTE_INT_TO_CHAR,
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complexity,
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"transmutes from an integer to a `char`"
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}
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/// **What it does:** Checks for transmutes from a `&[u8]` to a `&str`.
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///
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/// **Why is this bad?** Not every byte slice is a valid UTF-8 string.
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///
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/// **Known problems:**
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/// - [`from_utf8`] which this lint suggests using is slower than `transmute`
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/// as it needs to validate the input.
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/// If you are certain that the input is always a valid UTF-8,
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/// use [`from_utf8_unchecked`] which is as fast as `transmute`
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/// but has a semantically meaningful name.
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/// - You might want to handle errors returned from [`from_utf8`] instead of calling `unwrap`.
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///
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/// [`from_utf8`]: https://doc.rust-lang.org/std/str/fn.from_utf8.html
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/// [`from_utf8_unchecked`]: https://doc.rust-lang.org/std/str/fn.from_utf8_unchecked.html
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///
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/// **Example:**
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/// ```rust
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/// let _: &str = std::mem::transmute(b); // where b: &[u8]
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/// // should be:
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/// let _ = std::str::from_utf8(b).unwrap();
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/// ```
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declare_clippy_lint! {
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pub TRANSMUTE_BYTES_TO_STR,
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complexity,
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"transmutes from a `&[u8]` to a `&str`"
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}
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/// **What it does:** Checks for transmutes from an integer to a `bool`.
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///
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/// **Why is this bad?** This might result in an invalid in-memory representation of a `bool`.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let _: bool = std::mem::transmute(x); // where x: u8
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/// // should be:
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/// let _: bool = x != 0;
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/// ```
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declare_clippy_lint! {
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pub TRANSMUTE_INT_TO_BOOL,
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complexity,
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"transmutes from an integer to a `bool`"
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}
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/// **What it does:** Checks for transmutes from an integer to a float.
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///
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/// **Why is this bad?** This might result in an invalid in-memory representation of a float.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let _: f32 = std::mem::transmute(x); // where x: u32
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/// // should be:
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/// let _: f32 = f32::from_bits(x);
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/// ```
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declare_clippy_lint! {
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pub TRANSMUTE_INT_TO_FLOAT,
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complexity,
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"transmutes from an integer to a float"
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}
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/// **What it does:** Checks for transmutes from a pointer to a pointer, or
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/// from a reference to a reference.
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///
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/// **Why is this bad?** Transmutes are dangerous, and these can instead be
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/// written as casts.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let ptr = &1u32 as *const u32;
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/// unsafe {
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/// // pointer-to-pointer transmute
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/// let _: *const f32 = std::mem::transmute(ptr);
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/// // ref-ref transmute
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/// let _: &f32 = std::mem::transmute(&1u32);
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/// }
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/// // These can be respectively written:
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/// let _ = ptr as *const f32
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/// let _ = unsafe{ &*(&1u32 as *const u32 as *const f32) };
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/// ```
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declare_clippy_lint! {
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pub TRANSMUTE_PTR_TO_PTR,
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complexity,
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"transmutes from a pointer to a reference type"
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}
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pub struct Transmute;
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impl LintPass for Transmute {
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fn get_lints(&self) -> LintArray {
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lint_array!(
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CROSSPOINTER_TRANSMUTE,
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TRANSMUTE_PTR_TO_REF,
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TRANSMUTE_PTR_TO_PTR,
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USELESS_TRANSMUTE,
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WRONG_TRANSMUTE,
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TRANSMUTE_INT_TO_CHAR,
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TRANSMUTE_BYTES_TO_STR,
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TRANSMUTE_INT_TO_BOOL,
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TRANSMUTE_INT_TO_FLOAT,
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)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Transmute {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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if let ExprCall(ref path_expr, ref args) = e.node {
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if let ExprPath(ref qpath) = path_expr.node {
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if let Some(def_id) = opt_def_id(cx.tables.qpath_def(qpath, path_expr.hir_id)) {
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if match_def_path(cx.tcx, def_id, &paths::TRANSMUTE) {
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let from_ty = cx.tables.expr_ty(&args[0]);
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let to_ty = cx.tables.expr_ty(e);
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match (&from_ty.sty, &to_ty.sty) {
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_ if from_ty == to_ty => span_lint(
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cx,
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USELESS_TRANSMUTE,
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e.span,
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&format!("transmute from a type (`{}`) to itself", from_ty),
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),
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(&ty::TyRef(_, rty), &ty::TyRawPtr(ptr_ty)) => 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 a reference to a pointer",
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|db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
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let sugg = if ptr_ty == rty {
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arg.as_ty(to_ty)
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} else {
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arg.as_ty(cx.tcx.mk_ptr(rty)).as_ty(to_ty)
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};
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db.span_suggestion(e.span, "try", sugg.to_string());
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},
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),
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(&ty::TyInt(_), &ty::TyRawPtr(_)) | (&ty::TyUint(_), &ty::TyRawPtr(_)) => {
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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| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
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db.span_suggestion(e.span, "try", arg.as_ty(&to_ty.to_string()).to_string());
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},
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)
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},
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(&ty::TyFloat(_), &ty::TyRef(..)) |
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(&ty::TyFloat(_), &ty::TyRawPtr(_)) |
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(&ty::TyChar, &ty::TyRef(..)) |
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(&ty::TyChar, &ty::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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(&ty::TyRawPtr(from_ptr), _) if from_ptr.ty == to_ty => span_lint(
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cx,
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CROSSPOINTER_TRANSMUTE,
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e.span,
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&format!(
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"transmute from a type (`{}`) to the type that it points to (`{}`)",
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from_ty,
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to_ty
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),
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),
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(_, &ty::TyRawPtr(to_ptr)) if to_ptr.ty == from_ty => span_lint(
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cx,
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CROSSPOINTER_TRANSMUTE,
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e.span,
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&format!(
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"transmute from a type (`{}`) to a pointer to that type (`{}`)",
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from_ty,
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to_ty
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),
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),
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(&ty::TyRawPtr(from_pty), &ty::TyRef(_, to_ref_ty)) => span_lint_and_then(
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cx,
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TRANSMUTE_PTR_TO_REF,
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e.span,
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&format!(
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"transmute from a pointer type (`{}`) to a reference type \
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(`{}`)",
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from_ty,
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to_ty
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),
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|db| {
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let arg = sugg::Sugg::hir(cx, &args[0], "..");
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let (deref, cast) = if to_ref_ty.mutbl == Mutability::MutMutable {
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("&mut *", "*mut")
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} else {
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("&*", "*const")
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};
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let arg = if from_pty.ty == to_ref_ty.ty {
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arg
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} else {
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arg.as_ty(&format!("{} {}", cast, get_type_snippet(cx, qpath, to_ref_ty.ty)))
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};
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db.span_suggestion(e.span, "try", sugg::make_unop(deref, arg).to_string());
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},
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),
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(&ty::TyInt(ast::IntTy::I32), &ty::TyChar) |
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(&ty::TyUint(ast::UintTy::U32), &ty::TyChar) => span_lint_and_then(
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cx,
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TRANSMUTE_INT_TO_CHAR,
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e.span,
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&format!("transmute from a `{}` to a `char`", from_ty),
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|db| {
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let arg = sugg::Sugg::hir(cx, &args[0], "..");
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let arg = if let ty::TyInt(_) = from_ty.sty {
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arg.as_ty(ty::TyUint(ast::UintTy::U32))
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} else {
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arg
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};
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db.span_suggestion(
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e.span,
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"consider using",
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format!("std::char::from_u32({}).unwrap()", arg.to_string()),
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);
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},
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),
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(&ty::TyRef(_, ref ref_from), &ty::TyRef(_, ref ref_to)) => {
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if_chain! {
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if let (&ty::TySlice(slice_ty), &ty::TyStr) = (&ref_from.ty.sty, &ref_to.ty.sty);
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if let ty::TyUint(ast::UintTy::U8) = slice_ty.sty;
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if ref_from.mutbl == ref_to.mutbl;
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then {
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let postfix = if ref_from.mutbl == Mutability::MutMutable {
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"_mut"
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} else {
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""
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};
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span_lint_and_then(
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cx,
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TRANSMUTE_BYTES_TO_STR,
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e.span,
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&format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
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|db| {
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db.span_suggestion(
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e.span,
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"consider using",
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format!(
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"std::str::from_utf8{}({}).unwrap()",
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postfix,
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snippet(cx, args[0].span, ".."),
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),
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);
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}
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)
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} else {
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span_lint_and_then(
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cx,
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TRANSMUTE_PTR_TO_PTR,
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e.span,
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"transmute from a reference to a reference",
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|db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
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let sugg_paren = arg.as_ty(cx.tcx.mk_ptr(*ref_from)).as_ty(cx.tcx.mk_ptr(*ref_to));
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let sugg = if ref_to.mutbl == Mutability::MutMutable {
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sugg_paren.mut_addr_deref()
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} else {
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sugg_paren.addr_deref()
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};
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db.span_suggestion(e.span, "try", sugg.to_string());
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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::TyRawPtr(_), &ty::TyRawPtr(to_ty)) => span_lint_and_then(
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cx,
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TRANSMUTE_PTR_TO_PTR,
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e.span,
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"transmute from a pointer to a pointer",
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|db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
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let sugg = arg.as_ty(cx.tcx.mk_ptr(to_ty));
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db.span_suggestion(e.span, "try", sugg.to_string());
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},
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),
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(&ty::TyInt(ast::IntTy::I8), &ty::TyBool) | (&ty::TyUint(ast::UintTy::U8), &ty::TyBool) => {
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span_lint_and_then(
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cx,
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TRANSMUTE_INT_TO_BOOL,
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e.span,
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&format!("transmute from a `{}` to a `bool`", from_ty),
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|db| {
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let arg = sugg::Sugg::hir(cx, &args[0], "..");
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let zero = sugg::Sugg::NonParen(Cow::from("0"));
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db.span_suggestion(
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e.span,
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"consider using",
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sugg::make_binop(ast::BinOpKind::Ne, &arg, &zero).to_string(),
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);
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},
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)
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},
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(&ty::TyInt(_), &ty::TyFloat(_)) | (&ty::TyUint(_), &ty::TyFloat(_)) => {
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span_lint_and_then(
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cx,
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TRANSMUTE_INT_TO_FLOAT,
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e.span,
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&format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
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|db| {
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let arg = sugg::Sugg::hir(cx, &args[0], "..");
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let arg = if let ty::TyInt(int_ty) = from_ty.sty {
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arg.as_ty(format!(
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"u{}",
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int_ty
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.bit_width()
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.map_or_else(|| "size".to_string(), |v| v.to_string())
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))
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} else {
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arg
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};
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db.span_suggestion(
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e.span,
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"consider using",
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format!("{}::from_bits({})", to_ty, arg.to_string()),
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);
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},
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)
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},
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_ => return,
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};
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}
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}
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}
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}
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}
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}
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/// Get the snippet of `Bar` in `…::transmute<Foo, &Bar>`. If that snippet is
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/// not available , use
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/// the type's `ToString` implementation. In weird cases it could lead to types
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/// with invalid `'_`
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/// lifetime, but it should be rare.
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fn get_type_snippet(cx: &LateContext, path: &QPath, to_ref_ty: Ty) -> String {
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let seg = last_path_segment(path);
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if_chain! {
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if let Some(ref params) = seg.parameters;
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if !params.parenthesized;
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if let Some(to_ty) = params.types.get(1);
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if let TyRptr(_, ref to_ty) = to_ty.node;
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then {
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return snippet(cx, to_ty.ty.span, &to_ref_ty.to_string()).to_string();
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}
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}
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to_ref_ty.to_string()
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}
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