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cast_possible_truncation Suggest TryFrom when truncation possible

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navh 2022-12-06 19:05:22 +01:00 committed by xFrednet
parent a95286b852
commit 51aaba6e8c
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GPG Key ID: F5C59D0E669E5302
4 changed files with 170 additions and 4 deletions
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24
clippy_lints/src/casts/cast_possible_truncation.rs
View File

@ -1,7 +1,11 @@
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_ast::ast;
use rustc_attr::IntType;
use rustc_errors::{Applicability, SuggestionStyle};
use rustc_hir::def::{DefKind, Res};
use rustc_hir::{BinOpKind, Expr, ExprKind};
use rustc_lint::LateContext;
@ -139,7 +143,7 @@ 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 +157,19 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
_ => return,
};
span_lint(cx, CAST_POSSIBLE_TRUNCATION, expr.span, &msg);
let snippet = snippet(cx, expr.span, "x");
let name_of_cast_from = snippet.split(" as").next().unwrap_or("x");
let suggestion = format!("{cast_to}::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,
);
});
}

2
clippy_lints/src/casts/mod.rs
View File

@ -85,7 +85,7 @@ declare_clippy_lint! {
/// ### Why is this bad?
/// In some problem domains, it is good practice to avoid
/// truncation. This lint can be activated to help assess where additional
/// checks could be beneficial.
/// checks could be beneficial, and suggests implementing TryFrom trait.
///
/// ### Example
/// ```rust

95
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
@ -143,18 +184,36 @@ error: casting `i64` to `i8` may truncate the value
|
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
|
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
|
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
@ -169,6 +228,12 @@ error: casting `main::E5` to `i8` may truncate the value
|
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
@ -181,30 +246,60 @@ error: casting `main::E6` to `i16` may truncate the value
|
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
|
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
|
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
|
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
|
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

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