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Auto merge of #10038 - xFrednet:9231-sugg-try-from, r=Jarcho

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`cast_possible_truncation` Suggest TryFrom when truncation possible

This fixes the last issues from https://github.com/rust-lang/rust-clippy/pull/9664 as the author seems to be inactive. The PR author was sadly kept during the rebase, due to the conflict resolution.

IDK if it's worth it do to a full review, I only added the last commit, everything else remained the same, besides a rebase.

---

changelog: Sugg: [`cast_possible_truncation`]: Now suggests using `try_from` or allowing the lint
[#10038](https://github.com/rust-lang/rust-clippy/pull/10038)
<!-- changelog_checked -->

closes: https://github.com/rust-lang/rust-clippy/issues/9231
This commit is contained in:
bors 2023-01-14 16:04:51 +00:00
commit 483b7ac918
5 changed files with 244 additions and 25 deletions
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32
clippy_lints/src/casts/cast_possible_truncation.rs
View File

@ -1,11 +1,14 @@
use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint;
use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
use clippy_utils::expr_or_init;
use clippy_utils::source::snippet;
use clippy_utils::ty::{get_discriminant_value, is_isize_or_usize};
use rustc_errors::{Applicability, SuggestionStyle};
use rustc_hir::def::{DefKind, Res};
use rustc_hir::{BinOpKind, Expr, ExprKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, FloatTy, Ty};
use rustc_span::Span;
use rustc_target::abi::IntegerType;
use super::{utils, CAST_ENUM_TRUNCATION, CAST_POSSIBLE_TRUNCATION};
@ -74,7 +77,14 @@ fn apply_reductions(cx: &LateContext<'_>, nbits: u64, expr: &Expr<'_>, signed: b
}
}
pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
pub(super) fn check(
cx: &LateContext<'_>,
expr: &Expr<'_>,
cast_expr: &Expr<'_>,
cast_from: Ty<'_>,
cast_to: Ty<'_>,
cast_to_span: Span,
) {
let msg = match (cast_from.kind(), cast_to.is_integral()) {
(ty::Int(_) | ty::Uint(_), true) => {
let from_nbits = apply_reductions(
@ -139,7 +149,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
);
return;
}
format!("casting `{cast_from}` to `{cast_to}` may truncate the value{suffix}",)
format!("casting `{cast_from}` to `{cast_to}` may truncate the value{suffix}")
},
(ty::Float(_), true) => {
@ -153,5 +163,19 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
_ => return,
};
span_lint(cx, CAST_POSSIBLE_TRUNCATION, expr.span, &msg);
let name_of_cast_from = snippet(cx, cast_expr.span, "..");
let cast_to_snip = snippet(cx, cast_to_span, "..");
let suggestion = format!("{cast_to_snip}::try_from({name_of_cast_from})");
span_lint_and_then(cx, CAST_POSSIBLE_TRUNCATION, expr.span, &msg, |diag| {
diag.help("if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...");
diag.span_suggestion_with_style(
expr.span,
"... or use `try_from` and handle the error accordingly",
suggestion,
Applicability::Unspecified,
// always show the suggestion in a separate line
SuggestionStyle::ShowAlways,
);
});
}

20
clippy_lints/src/casts/mod.rs
View File

@ -80,7 +80,8 @@
/// ### What it does
/// Checks for casts between numerical types that may
/// truncate large values. This is expected behavior, so the cast is `Allow` by
/// default.
/// default. It suggests user either explicitly ignore the lint,
/// or use `try_from()` and handle the truncation, default, or panic explicitly.
///
/// ### Why is this bad?
/// In some problem domains, it is good practice to avoid
@ -93,6 +94,21 @@
/// x as u8
/// }
/// ```
/// Use instead:
/// ```
/// fn as_u8(x: u64) -> u8 {
/// if let Ok(x) = u8::try_from(x) {
/// x
/// } else {
/// todo!();
/// }
/// }
/// // Or
/// #[allow(clippy::cast_possible_truncation)]
/// fn as_u16(x: u64) -> u16 {
/// x as u16
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub CAST_POSSIBLE_TRUNCATION,
pedantic,
@ -712,7 +728,7 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
fn_to_numeric_cast_with_truncation::check(cx, expr, cast_expr, cast_from, cast_to);
if cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
cast_possible_truncation::check(cx, expr, cast_expr, cast_from, cast_to);
cast_possible_truncation::check(cx, expr, cast_expr, cast_from, cast_to, cast_to_hir.span);
if cast_from.is_numeric() {
cast_possible_wrap::check(cx, expr, cast_from, cast_to);
cast_precision_loss::check(cx, expr, cast_from, cast_to);

1
tests/ui/cast.rs
View File

@ -28,6 +28,7 @@ fn main() {
1i32 as u8;
1f64 as isize;
1f64 as usize;
1f32 as u32 as u16;
// Test clippy::cast_possible_wrap
1u8 as i8;
1u16 as i16;

163
tests/ui/cast.stderr
View File

@ -42,13 +42,24 @@ error: casting `f32` to `i32` may truncate the value
LL | 1f32 as i32;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
= note: `-D clippy::cast-possible-truncation` implied by `-D warnings`
help: ... or use `try_from` and handle the error accordingly
|
LL | i32::try_from(1f32);
| ~~~~~~~~~~~~~~~~~~~
error: casting `f32` to `u32` may truncate the value
--> $DIR/cast.rs:25:5
|
LL | 1f32 as u32;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | u32::try_from(1f32);
| ~~~~~~~~~~~~~~~~~~~
error: casting `f32` to `u32` may lose the sign of the value
--> $DIR/cast.rs:25:5
@ -63,30 +74,60 @@ error: casting `f64` to `f32` may truncate the value
|
LL | 1f64 as f32;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | f32::try_from(1f64);
| ~~~~~~~~~~~~~~~~~~~
error: casting `i32` to `i8` may truncate the value
--> $DIR/cast.rs:27:5
|
LL | 1i32 as i8;
| ^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | i8::try_from(1i32);
| ~~~~~~~~~~~~~~~~~~
error: casting `i32` to `u8` may truncate the value
--> $DIR/cast.rs:28:5
|
LL | 1i32 as u8;
| ^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | u8::try_from(1i32);
| ~~~~~~~~~~~~~~~~~~
error: casting `f64` to `isize` may truncate the value
--> $DIR/cast.rs:29:5
|
LL | 1f64 as isize;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | isize::try_from(1f64);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `f64` to `usize` may truncate the value
--> $DIR/cast.rs:30:5
|
LL | 1f64 as usize;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | usize::try_from(1f64);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `f64` to `usize` may lose the sign of the value
--> $DIR/cast.rs:30:5
@ -94,8 +135,38 @@ error: casting `f64` to `usize` may lose the sign of the value
LL | 1f64 as usize;
| ^^^^^^^^^^^^^
error: casting `u32` to `u16` may truncate the value
--> $DIR/cast.rs:31:5
|
LL | 1f32 as u32 as u16;
| ^^^^^^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | u16::try_from(1f32 as u32);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~
error: casting `f32` to `u32` may truncate the value
--> $DIR/cast.rs:31:5
|
LL | 1f32 as u32 as u16;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | u32::try_from(1f32) as u16;
| ~~~~~~~~~~~~~~~~~~~
error: casting `f32` to `u32` may lose the sign of the value
--> $DIR/cast.rs:31:5
|
LL | 1f32 as u32 as u16;
| ^^^^^^^^^^^
error: casting `u8` to `i8` may wrap around the value
--> $DIR/cast.rs:32:5
--> $DIR/cast.rs:33:5
|
LL | 1u8 as i8;
| ^^^^^^^^^
@ -103,61 +174,79 @@ LL | 1u8 as i8;
= note: `-D clippy::cast-possible-wrap` implied by `-D warnings`
error: casting `u16` to `i16` may wrap around the value
--> $DIR/cast.rs:33:5
--> $DIR/cast.rs:34:5
|
LL | 1u16 as i16;
| ^^^^^^^^^^^
error: casting `u32` to `i32` may wrap around the value
--> $DIR/cast.rs:34:5
--> $DIR/cast.rs:35:5
|
LL | 1u32 as i32;
| ^^^^^^^^^^^
error: casting `u64` to `i64` may wrap around the value
--> $DIR/cast.rs:35:5
--> $DIR/cast.rs:36:5
|
LL | 1u64 as i64;
| ^^^^^^^^^^^
error: casting `usize` to `isize` may wrap around the value
--> $DIR/cast.rs:36:5
--> $DIR/cast.rs:37:5
|
LL | 1usize as isize;
| ^^^^^^^^^^^^^^^
error: casting `i32` to `u32` may lose the sign of the value
--> $DIR/cast.rs:39:5
--> $DIR/cast.rs:40:5
|
LL | -1i32 as u32;
| ^^^^^^^^^^^^
error: casting `isize` to `usize` may lose the sign of the value
--> $DIR/cast.rs:41:5
--> $DIR/cast.rs:42:5
|
LL | -1isize as usize;
| ^^^^^^^^^^^^^^^^
error: casting `i64` to `i8` may truncate the value
--> $DIR/cast.rs:108:5
--> $DIR/cast.rs:109:5
|
LL | (-99999999999i64).min(1) as i8; // should be linted because signed
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | i8::try_from((-99999999999i64).min(1)); // should be linted because signed
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
error: casting `u64` to `u8` may truncate the value
--> $DIR/cast.rs:120:5
--> $DIR/cast.rs:121:5
|
LL | 999999u64.clamp(0, 256) as u8; // should still be linted
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | u8::try_from(999999u64.clamp(0, 256)); // should still be linted
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
error: casting `main::E2` to `u8` may truncate the value
--> $DIR/cast.rs:141:21
--> $DIR/cast.rs:142:21
|
LL | let _ = self as u8;
| ^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | let _ = u8::try_from(self);
| ~~~~~~~~~~~~~~~~~~
error: casting `main::E2::B` to `u8` will truncate the value
--> $DIR/cast.rs:142:21
--> $DIR/cast.rs:143:21
|
LL | let _ = Self::B as u8;
| ^^^^^^^^^^^^^
@ -165,46 +254,82 @@ LL | let _ = Self::B as u8;
= note: `-D clippy::cast-enum-truncation` implied by `-D warnings`
error: casting `main::E5` to `i8` may truncate the value
--> $DIR/cast.rs:178:21
--> $DIR/cast.rs:179:21
|
LL | let _ = self as i8;
| ^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | let _ = i8::try_from(self);
| ~~~~~~~~~~~~~~~~~~
error: casting `main::E5::A` to `i8` will truncate the value
--> $DIR/cast.rs:179:21
--> $DIR/cast.rs:180:21
|
LL | let _ = Self::A as i8;
| ^^^^^^^^^^^^^
error: casting `main::E6` to `i16` may truncate the value
--> $DIR/cast.rs:193:21
--> $DIR/cast.rs:194:21
|
LL | let _ = self as i16;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | let _ = i16::try_from(self);
| ~~~~~~~~~~~~~~~~~~~
error: casting `main::E7` to `usize` may truncate the value on targets with 32-bit wide pointers
--> $DIR/cast.rs:208:21
--> $DIR/cast.rs:209:21
|
LL | let _ = self as usize;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | let _ = usize::try_from(self);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `main::E10` to `u16` may truncate the value
--> $DIR/cast.rs:249:21
--> $DIR/cast.rs:250:21
|
LL | let _ = self as u16;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | let _ = u16::try_from(self);
| ~~~~~~~~~~~~~~~~~~~
error: casting `u32` to `u8` may truncate the value
--> $DIR/cast.rs:257:13
--> $DIR/cast.rs:258:13
|
LL | let c = (q >> 16) as u8;
| ^^^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | let c = u8::try_from((q >> 16));
| ~~~~~~~~~~~~~~~~~~~~~~~
error: casting `u32` to `u8` may truncate the value
--> $DIR/cast.rs:260:13
--> $DIR/cast.rs:261:13
|
LL | let c = (q / 1000) as u8;
| ^^^^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | let c = u8::try_from((q / 1000));
| ~~~~~~~~~~~~~~~~~~~~~~~~
error: aborting due to 33 previous errors
error: aborting due to 36 previous errors

53
tests/ui/cast_size.stderr
View File

@ -4,7 +4,12 @@ error: casting `isize` to `i8` may truncate the value
LL | 1isize as i8;
| ^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
= note: `-D clippy::cast-possible-truncation` implied by `-D warnings`
help: ... or use `try_from` and handle the error accordingly
|
LL | i8::try_from(1isize);
| ~~~~~~~~~~~~~~~~~~~~
error: casting `isize` to `f64` causes a loss of precision on targets with 64-bit wide pointers (`isize` is 64 bits wide, but `f64`'s mantissa is only 52 bits wide)
--> $DIR/cast_size.rs:15:5
@ -37,24 +42,48 @@ error: casting `isize` to `i32` may truncate the value on targets with 64-bit wi
|
LL | 1isize as i32;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | i32::try_from(1isize);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `isize` to `u32` may truncate the value on targets with 64-bit wide pointers
--> $DIR/cast_size.rs:20:5
|
LL | 1isize as u32;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | u32::try_from(1isize);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `usize` to `u32` may truncate the value on targets with 64-bit wide pointers
--> $DIR/cast_size.rs:21:5
|
LL | 1usize as u32;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | u32::try_from(1usize);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `usize` to `i32` may truncate the value on targets with 64-bit wide pointers
--> $DIR/cast_size.rs:22:5
|
LL | 1usize as i32;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | i32::try_from(1usize);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `usize` to `i32` may wrap around the value on targets with 32-bit wide pointers
--> $DIR/cast_size.rs:22:5
@ -69,18 +98,36 @@ error: casting `i64` to `isize` may truncate the value on targets with 32-bit wi
|
LL | 1i64 as isize;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | isize::try_from(1i64);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `i64` to `usize` may truncate the value on targets with 32-bit wide pointers
--> $DIR/cast_size.rs:25:5
|
LL | 1i64 as usize;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | usize::try_from(1i64);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `u64` to `isize` may truncate the value on targets with 32-bit wide pointers
--> $DIR/cast_size.rs:26:5
|
LL | 1u64 as isize;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | isize::try_from(1u64);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `u64` to `isize` may wrap around the value on targets with 64-bit wide pointers
--> $DIR/cast_size.rs:26:5
@ -93,6 +140,12 @@ error: casting `u64` to `usize` may truncate the value on targets with 32-bit wi
|
LL | 1u64 as usize;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | usize::try_from(1u64);
| ~~~~~~~~~~~~~~~~~~~~~
error: casting `u32` to `isize` may wrap around the value on targets with 32-bit wide pointers
--> $DIR/cast_size.rs:28:5