657 lines
27 KiB
Rust
657 lines
27 KiB
Rust
use crate::utils::{
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is_normalizable, last_path_segment, match_def_path, paths, snippet, span_lint, span_lint_and_then, sugg,
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};
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use if_chain::if_chain;
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use rustc::lint::{LateContext, LateLintPass};
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use rustc::ty::{self, Ty};
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use rustc_errors::Applicability;
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use rustc_hir::*;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use std::borrow::Cow;
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use syntax::ast;
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declare_clippy_lint! {
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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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/// ```ignore
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/// let ptr: *const T = core::intrinsics::transmute('x')
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/// ```
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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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declare_clippy_lint! {
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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,ignore
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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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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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declare_clippy_lint! {
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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,ignore
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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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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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declare_clippy_lint! {
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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,ignore
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/// unsafe {
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/// let _: &T = std::mem::transmute(p); // where p: *const T
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/// }
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///
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/// // can be written:
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/// let _: &T = &*p;
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/// ```
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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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declare_clippy_lint! {
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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 x = 1_u32;
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/// unsafe {
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/// let _: char = std::mem::transmute(x); // where x: u32
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/// }
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///
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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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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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declare_clippy_lint! {
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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 b: &[u8] = &[1_u8, 2_u8];
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/// unsafe {
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/// let _: &str = std::mem::transmute(b); // where b: &[u8]
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/// }
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///
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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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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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declare_clippy_lint! {
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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 x = 1_u8;
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/// unsafe {
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/// let _: bool = std::mem::transmute(x); // where x: u8
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/// }
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///
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/// // should be:
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/// let _: bool = x != 0;
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/// ```
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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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declare_clippy_lint! {
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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?** Transmutes are dangerous and error-prone, whereas `from_bits` is intuitive
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/// and safe.
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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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/// unsafe {
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/// let _: f32 = std::mem::transmute(1_u32); // where x: u32
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/// }
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///
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/// // should be:
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/// let _: f32 = f32::from_bits(1_u32);
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/// ```
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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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declare_clippy_lint! {
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/// **What it does:** Checks for transmutes from a float to an integer.
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///
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/// **Why is this bad?** Transmutes are dangerous and error-prone, whereas `to_bits` is intuitive
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/// and safe.
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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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/// unsafe {
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/// let _: u32 = std::mem::transmute(1f32);
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/// }
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///
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/// // should be:
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/// let _: u32 = 1f32.to_bits();
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/// ```
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pub TRANSMUTE_FLOAT_TO_INT,
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complexity,
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"transmutes from a float to an integer"
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}
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declare_clippy_lint! {
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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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pub TRANSMUTE_PTR_TO_PTR,
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complexity,
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"transmutes from a pointer to a pointer / a reference to a reference"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for transmutes between collections whose
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/// types have different ABI, size or alignment.
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///
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/// **Why is this bad?** This is undefined behavior.
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///
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/// **Known problems:** Currently, we cannot know whether a type is a
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/// collection, so we just lint the ones that come with `std`.
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///
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/// **Example:**
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/// ```rust
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/// // different size, therefore likely out-of-bounds memory access
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/// // You absolutely do not want this in your code!
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/// unsafe {
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/// std::mem::transmute::<_, Vec<u32>>(vec![2_u16])
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/// };
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/// ```
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///
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/// You must always iterate, map and collect the values:
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///
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/// ```rust
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/// vec![2_u16].into_iter().map(u32::from).collect::<Vec<_>>();
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/// ```
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pub UNSOUND_COLLECTION_TRANSMUTE,
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correctness,
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"transmute between collections of layout-incompatible types"
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}
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declare_lint_pass!(Transmute => [
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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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TRANSMUTE_FLOAT_TO_INT,
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UNSOUND_COLLECTION_TRANSMUTE,
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]);
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// used to check for UNSOUND_COLLECTION_TRANSMUTE
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static COLLECTIONS: &[&[&str]] = &[
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&paths::VEC,
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&paths::VEC_DEQUE,
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&paths::BINARY_HEAP,
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&paths::BTREESET,
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&paths::BTREEMAP,
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&paths::HASHSET,
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&paths::HASHMAP,
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];
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Transmute {
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#[allow(clippy::similar_names, clippy::too_many_lines)]
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) {
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if_chain! {
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if let ExprKind::Call(ref path_expr, ref args) = e.kind;
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if let ExprKind::Path(ref qpath) = path_expr.kind;
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if let Some(def_id) = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id();
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if match_def_path(cx, def_id, &paths::TRANSMUTE);
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then {
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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.kind, &to_ty.kind) {
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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::Ref(_, rty, rty_mutbl), &ty::RawPtr(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| {
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if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
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let rty_and_mut = ty::TypeAndMut {
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ty: rty,
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mutbl: rty_mutbl,
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};
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let sugg = if ptr_ty == rty_and_mut {
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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_and_mut)).as_ty(to_ty)
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};
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db.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified);
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}
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},
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),
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(&ty::Int(_), &ty::RawPtr(_)) | (&ty::Uint(_), &ty::RawPtr(_)) => 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) = sugg::Sugg::hir_opt(cx, &args[0]) {
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db.span_suggestion(
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e.span,
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"try",
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arg.as_ty(&to_ty.to_string()).to_string(),
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Applicability::Unspecified,
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);
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}
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},
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),
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(&ty::Float(_), &ty::Ref(..))
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| (&ty::Float(_), &ty::RawPtr(_))
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| (&ty::Char, &ty::Ref(..))
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| (&ty::Char, &ty::RawPtr(_)) => 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::RawPtr(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, to_ty
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),
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),
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(_, &ty::RawPtr(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, to_ty
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),
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),
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(&ty::RawPtr(from_pty), &ty::Ref(_, to_ref_ty, mutbl)) => 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, 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 mutbl == Mutability::Mut {
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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 {
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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)))
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};
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db.span_suggestion(
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e.span,
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"try",
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sugg::make_unop(deref, arg).to_string(),
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Applicability::Unspecified,
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);
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},
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),
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(&ty::Int(ast::IntTy::I32), &ty::Char) | (&ty::Uint(ast::UintTy::U32), &ty::Char) => {
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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::Int(_) = from_ty.kind {
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arg.as_ty(ast::UintTy::U32.name_str())
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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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Applicability::Unspecified,
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);
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},
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)
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},
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(&ty::Ref(_, ty_from, from_mutbl), &ty::Ref(_, ty_to, to_mutbl)) => {
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if_chain! {
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if let (&ty::Slice(slice_ty), &ty::Str) = (&ty_from.kind, &ty_to.kind);
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if let ty::Uint(ast::UintTy::U8) = slice_ty.kind;
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if from_mutbl == to_mutbl;
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then {
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let postfix = if from_mutbl == Mutability::Mut {
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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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Applicability::Unspecified,
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);
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}
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)
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} else {
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if cx.tcx.erase_regions(&from_ty) != cx.tcx.erase_regions(&to_ty) {
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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 ty_from_and_mut = ty::TypeAndMut {
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ty: ty_from,
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mutbl: from_mutbl
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};
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let ty_to_and_mut = ty::TypeAndMut { ty: ty_to, mutbl: to_mutbl };
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let sugg_paren = arg
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.as_ty(cx.tcx.mk_ptr(ty_from_and_mut))
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.as_ty(cx.tcx.mk_ptr(ty_to_and_mut));
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let sugg = if to_mutbl == Mutability::Mut {
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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(
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e.span,
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"try",
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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",
|
|
|db| {
|
|
if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
|
|
let sugg = arg.as_ty(cx.tcx.mk_ptr(to_ty));
|
|
db.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified);
|
|
}
|
|
},
|
|
),
|
|
(&ty::Int(ast::IntTy::I8), &ty::Bool) | (&ty::Uint(ast::UintTy::U8), &ty::Bool) => {
|
|
span_lint_and_then(
|
|
cx,
|
|
TRANSMUTE_INT_TO_BOOL,
|
|
e.span,
|
|
&format!("transmute from a `{}` to a `bool`", from_ty),
|
|
|db| {
|
|
let arg = sugg::Sugg::hir(cx, &args[0], "..");
|
|
let zero = sugg::Sugg::NonParen(Cow::from("0"));
|
|
db.span_suggestion(
|
|
e.span,
|
|
"consider using",
|
|
sugg::make_binop(ast::BinOpKind::Ne, &arg, &zero).to_string(),
|
|
Applicability::Unspecified,
|
|
);
|
|
},
|
|
)
|
|
},
|
|
(&ty::Int(_), &ty::Float(_)) | (&ty::Uint(_), &ty::Float(_)) => span_lint_and_then(
|
|
cx,
|
|
TRANSMUTE_INT_TO_FLOAT,
|
|
e.span,
|
|
&format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
|
|
|db| {
|
|
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
|
|
};
|
|
db.span_suggestion(
|
|
e.span,
|
|
"consider using",
|
|
format!("{}::from_bits({})", to_ty, arg.to_string()),
|
|
Applicability::Unspecified,
|
|
);
|
|
},
|
|
),
|
|
(&ty::Float(float_ty), &ty::Int(_)) | (&ty::Float(float_ty), &ty::Uint(_)) => span_lint_and_then(
|
|
cx,
|
|
TRANSMUTE_FLOAT_TO_INT,
|
|
e.span,
|
|
&format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
|
|
|db| {
|
|
let mut expr = &args[0];
|
|
let mut arg = sugg::Sugg::hir(cx, expr, "..");
|
|
|
|
if let ExprKind::Unary(UnOp::UnNeg, 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
|
|
};
|
|
|
|
db.span_suggestion(
|
|
e.span,
|
|
"consider using",
|
|
arg.to_string(),
|
|
Applicability::Unspecified,
|
|
);
|
|
},
|
|
),
|
|
(&ty::Adt(ref from_adt, ref from_substs), &ty::Adt(ref to_adt, ref 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
|
|
)
|
|
);
|
|
}
|
|
},
|
|
_ => 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<'a, 'tcx>(cx: &LateContext<'a, '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
|
|
}
|
|
}
|