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Auto merge of #4889 - krishna-veerareddy:issue-3993-float-to-int-transmute, r=llogiq

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Add lint to detect transmutes from float to integer

Add lint that detects transmutation from a float to an integer and suggests usage of `{f32, f64}.to_bits()` instead.

Fixes #3993

changelog: Add lint `transmute_float_to_int`
This commit is contained in:
bors 2019-12-08 02:23:23 +00:00
commit b245fbd0f2
7 changed files with 131 additions and 2 deletions
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1
CHANGELOG.md
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@ -1214,6 +1214,7 @@ Released 2018-09-13
[`too_many_lines`]: https://rust-lang.github.io/rust-clippy/master/index.html#too_many_lines
[`toplevel_ref_arg`]: https://rust-lang.github.io/rust-clippy/master/index.html#toplevel_ref_arg
[`transmute_bytes_to_str`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_bytes_to_str
[`transmute_float_to_int`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_float_to_int
[`transmute_int_to_bool`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_int_to_bool
[`transmute_int_to_char`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_int_to_char
[`transmute_int_to_float`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_int_to_float

2
README.md
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@ -6,7 +6,7 @@
A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
[There are 339 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
[There are 340 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:

2
clippy_lints/src/lib.rs
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@ -735,6 +735,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
&trait_bounds::TYPE_REPETITION_IN_BOUNDS,
&transmute::CROSSPOINTER_TRANSMUTE,
&transmute::TRANSMUTE_BYTES_TO_STR,
&transmute::TRANSMUTE_FLOAT_TO_INT,
&transmute::TRANSMUTE_INT_TO_BOOL,
&transmute::TRANSMUTE_INT_TO_CHAR,
&transmute::TRANSMUTE_INT_TO_FLOAT,
@ -1586,6 +1587,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
LintId::of(&mutex_atomic::MUTEX_INTEGER),
LintId::of(&needless_borrow::NEEDLESS_BORROW),
LintId::of(&path_buf_push_overwrite::PATH_BUF_PUSH_OVERWRITE),
LintId::of(&transmute::TRANSMUTE_FLOAT_TO_INT),
LintId::of(&use_self::USE_SELF),
]);
}

67
clippy_lints/src/transmute.rs
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@ -190,6 +190,28 @@ declare_clippy_lint! {
"transmutes from an integer to a float"
}
declare_clippy_lint! {
/// **What it does:** Checks for transmutes from a float to an integer.
///
/// **Why is this bad?** Transmutes are dangerous and error-prone, whereas `to_bits` is intuitive
/// and safe.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// unsafe {
/// let _: u32 = std::mem::transmute(1f32);
/// }
///
/// // should be:
/// let _: u32 = 1f32.to_bits();
/// ```
pub TRANSMUTE_FLOAT_TO_INT,
nursery,
"transmutes from a float to an integer"
}
declare_clippy_lint! {
/// **What it does:** Checks for transmutes from a pointer to a pointer, or
/// from a reference to a reference.
@ -254,6 +276,7 @@ declare_lint_pass!(Transmute => [
TRANSMUTE_BYTES_TO_STR,
TRANSMUTE_INT_TO_BOOL,
TRANSMUTE_INT_TO_FLOAT,
TRANSMUTE_FLOAT_TO_INT,
UNSOUND_COLLECTION_TRANSMUTE,
]);
@ -520,6 +543,50 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Transmute {
);
},
),
(&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)) {

9
src/lintlist/mod.rs
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@ -6,7 +6,7 @@ pub use lint::Lint;
pub use lint::LINT_LEVELS;
// begin lint list, do not remove this comment, it’s used in `update_lints`
pub const ALL_LINTS: [Lint; 339] = [
pub const ALL_LINTS: [Lint; 340] = [
Lint {
name: "absurd_extreme_comparisons",
group: "correctness",
@ -1953,6 +1953,13 @@ pub const ALL_LINTS: [Lint; 339] = [
deprecation: None,
module: "transmute",
},
Lint {
name: "transmute_float_to_int",
group: "nursery",
desc: "transmutes from a float to an integer",
deprecation: None,
module: "transmute",
},
Lint {
name: "transmute_int_to_bool",
group: "complexity",

12
tests/ui/transmute_float_to_int.rs Normal file
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@ -0,0 +1,12 @@
#[warn(clippy::transmute_float_to_int)]
fn float_to_int() {
let _: u32 = unsafe { std::mem::transmute(1f32) };
let _: i32 = unsafe { std::mem::transmute(1f32) };
let _: u64 = unsafe { std::mem::transmute(1f64) };
let _: i64 = unsafe { std::mem::transmute(1f64) };
let _: u64 = unsafe { std::mem::transmute(1.0) };
let _: u64 = unsafe { std::mem::transmute(-1.0) };
}
fn main() {}

40
tests/ui/transmute_float_to_int.stderr Normal file
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@ -0,0 +1,40 @@
error: transmute from a `f32` to a `u32`
--> $DIR/transmute_float_to_int.rs:4:27
|
LL | let _: u32 = unsafe { std::mem::transmute(1f32) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `1f32.to_bits()`
|
= note: `-D clippy::transmute-float-to-int` implied by `-D warnings`
error: transmute from a `f32` to a `i32`
--> $DIR/transmute_float_to_int.rs:5:27
|
LL | let _: i32 = unsafe { std::mem::transmute(1f32) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `1f32.to_bits() as i32`
error: transmute from a `f64` to a `u64`
--> $DIR/transmute_float_to_int.rs:6:27
|
LL | let _: u64 = unsafe { std::mem::transmute(1f64) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `1f64.to_bits()`
error: transmute from a `f64` to a `i64`
--> $DIR/transmute_float_to_int.rs:7:27
|
LL | let _: i64 = unsafe { std::mem::transmute(1f64) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `1f64.to_bits() as i64`
error: transmute from a `f64` to a `u64`
--> $DIR/transmute_float_to_int.rs:8:27
|
LL | let _: u64 = unsafe { std::mem::transmute(1.0) };
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `1.0f64.to_bits()`
error: transmute from a `f64` to a `u64`
--> $DIR/transmute_float_to_int.rs:9:27
|
LL | let _: u64 = unsafe { std::mem::transmute(-1.0) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `(-1.0f64).to_bits()`
error: aborting due to 6 previous errors