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fix [cast_possible_truncation] offering wrong suggestion for casting float to integer #10496

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Merged
merged 1 commit into from
Mar 25, 2023
Merged

fix [cast_possible_truncation] offering wrong suggestion for casting float to integer #10496

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42 changes: 29 additions & 13 deletions clippy_lints/src/casts/cast_possible_truncation.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,8 +2,9 @@ use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
use clippy_utils::expr_or_init;
use clippy_utils::source::snippet;
use clippy_utils::sugg::Sugg;
use clippy_utils::ty::{get_discriminant_value, is_isize_or_usize};
use rustc_errors::{Applicability, SuggestionStyle};
use rustc_errors::{Applicability, Diagnostic, SuggestionStyle};
use rustc_hir::def::{DefKind, Res};
use rustc_hir::{BinOpKind, Expr, ExprKind};
use rustc_lint::LateContext;
Expand Down Expand Up @@ -163,19 +164,34 @@ pub(super) fn check(
_ => return,
};

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_possible_truncation)]` ...");
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,
);
if !cast_from.is_floating_point() {
offer_suggestion(cx, expr, cast_expr, cast_to_span, diag);
}
});
}

fn offer_suggestion(
cx: &LateContext<'_>,
expr: &Expr<'_>,
cast_expr: &Expr<'_>,
cast_to_span: Span,
diag: &mut Diagnostic,
) {
let cast_to_snip = snippet(cx, cast_to_span, "..");
let suggestion = if cast_to_snip == "_" {
format!("{}.try_into()", Sugg::hir(cx, cast_expr, "..").maybe_par())
} else {
format!("{cast_to_snip}::try_from({})", Sugg::hir(cx, cast_expr, ".."))
};

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,
);
}
6 changes: 6 additions & 0 deletions tests/ui/cast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,12 @@ fn main() {
1f64 as isize;
1f64 as usize;
1f32 as u32 as u16;
{
let _x: i8 = 1i32 as _;
1f32 as i32;
1f64 as i32;
1f32 as u8;
}
// Test clippy::cast_possible_wrap
1u8 as i8;
1u16 as i16;
Expand Down
112 changes: 65 additions & 47 deletions tests/ui/cast.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -44,10 +44,6 @@ LL | 1f32 as i32;
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
= 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
Expand All @@ -56,10 +52,6 @@ LL | 1f32 as u32;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
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
Expand All @@ -76,10 +68,6 @@ LL | 1f64 as f32;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
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
Expand Down Expand Up @@ -112,10 +100,6 @@ LL | 1f64 as isize;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
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
Expand All @@ -124,10 +108,6 @@ LL | 1f64 as usize;
| ^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
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
Expand All @@ -154,63 +134,101 @@ LL | 1f32 as u32 as u16;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
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 `i32` to `i8` may truncate the value
--> $DIR/cast.rs:33:22
|
LL | let _x: i8 = 1i32 as _;
| ^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | let _x: i8 = 1i32.try_into();
| ~~~~~~~~~~~~~~~

error: casting `f32` to `i32` may truncate the value
--> $DIR/cast.rs:34:9
|
LL | 1f32 as i32;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...

error: casting `f64` to `i32` may truncate the value
--> $DIR/cast.rs:35:9
|
LL | 1f64 as i32;
| ^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...

error: casting `f32` to `u8` may truncate the value
--> $DIR/cast.rs:36:9
|
LL | 1f32 as u8;
| ^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...

error: casting `f32` to `u8` may lose the sign of the value
--> $DIR/cast.rs:36:9
|
LL | 1f32 as u8;
| ^^^^^^^^^^

error: casting `u8` to `i8` may wrap around the value
--> $DIR/cast.rs:33:5
--> $DIR/cast.rs:39:5
|
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:34:5
--> $DIR/cast.rs:40:5
|
LL | 1u16 as i16;
| ^^^^^^^^^^^

error: casting `u32` to `i32` may wrap around the value
--> $DIR/cast.rs:35:5
--> $DIR/cast.rs:41:5
|
LL | 1u32 as i32;
| ^^^^^^^^^^^

error: casting `u64` to `i64` may wrap around the value
--> $DIR/cast.rs:36:5
--> $DIR/cast.rs:42:5
|
LL | 1u64 as i64;
| ^^^^^^^^^^^

error: casting `usize` to `isize` may wrap around the value
--> $DIR/cast.rs:37:5
--> $DIR/cast.rs:43:5
|
LL | 1usize as isize;
| ^^^^^^^^^^^^^^^

error: casting `i32` to `u32` may lose the sign of the value
--> $DIR/cast.rs:40:5
--> $DIR/cast.rs:46:5
|
LL | -1i32 as u32;
| ^^^^^^^^^^^^

error: casting `isize` to `usize` may lose the sign of the value
--> $DIR/cast.rs:42:5
--> $DIR/cast.rs:48:5
|
LL | -1isize as usize;
| ^^^^^^^^^^^^^^^^

error: casting `i64` to `i8` may truncate the value
--> $DIR/cast.rs:109:5
--> $DIR/cast.rs:115:5
|
LL | (-99999999999i64).min(1) as i8; // should be linted because signed
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -222,7 +240,7 @@ LL | i8::try_from((-99999999999i64).min(1)); // should be linted because sig
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: casting `u64` to `u8` may truncate the value
--> $DIR/cast.rs:121:5
--> $DIR/cast.rs:127:5
|
LL | 999999u64.clamp(0, 256) as u8; // should still be linted
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -234,7 +252,7 @@ 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:142:21
--> $DIR/cast.rs:148:21
|
LL | let _ = self as u8;
| ^^^^^^^^^^
Expand All @@ -246,15 +264,15 @@ LL | let _ = u8::try_from(self);
| ~~~~~~~~~~~~~~~~~~

error: casting `main::E2::B` to `u8` will truncate the value
--> $DIR/cast.rs:143:21
--> $DIR/cast.rs:149:21
|
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:179:21
--> $DIR/cast.rs:185:21
|
LL | let _ = self as i8;
| ^^^^^^^^^^
Expand All @@ -266,13 +284,13 @@ LL | let _ = i8::try_from(self);
| ~~~~~~~~~~~~~~~~~~

error: casting `main::E5::A` to `i8` will truncate the value
--> $DIR/cast.rs:180:21
--> $DIR/cast.rs:186:21
|
LL | let _ = Self::A as i8;
| ^^^^^^^^^^^^^

error: casting `main::E6` to `i16` may truncate the value
--> $DIR/cast.rs:194:21
--> $DIR/cast.rs:200:21
|
LL | let _ = self as i16;
| ^^^^^^^^^^^
Expand All @@ -284,7 +302,7 @@ 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:209:21
--> $DIR/cast.rs:215:21
|
LL | let _ = self as usize;
| ^^^^^^^^^^^^^
Expand All @@ -296,7 +314,7 @@ LL | let _ = usize::try_from(self);
| ~~~~~~~~~~~~~~~~~~~~~

error: casting `main::E10` to `u16` may truncate the value
--> $DIR/cast.rs:250:21
--> $DIR/cast.rs:256:21
|
LL | let _ = self as u16;
| ^^^^^^^^^^^
Expand All @@ -308,28 +326,28 @@ LL | let _ = u16::try_from(self);
| ~~~~~~~~~~~~~~~~~~~

error: casting `u32` to `u8` may truncate the value
--> $DIR/cast.rs:258:13
--> $DIR/cast.rs:264:13
|
LL | let c = (q >> 16) as u8;
| ^^^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | let c = u8::try_from((q >> 16));
| ~~~~~~~~~~~~~~~~~~~~~~~
LL | let c = u8::try_from(q >> 16);
| ~~~~~~~~~~~~~~~~~~~~~

error: casting `u32` to `u8` may truncate the value
--> $DIR/cast.rs:261:13
--> $DIR/cast.rs:267:13
|
LL | let c = (q / 1000) as u8;
| ^^^^^^^^^^^^^^^^
|
= help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
help: ... or use `try_from` and handle the error accordingly
|
LL | let c = u8::try_from((q / 1000));
| ~~~~~~~~~~~~~~~~~~~~~~~~
LL | let c = u8::try_from(q / 1000);
| ~~~~~~~~~~~~~~~~~~~~~~

error: aborting due to 36 previous errors
error: aborting due to 41 previous errors