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|
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::is_isize_or_usize;
use clippy_utils::{in_constant, meets_msrv, msrvs};
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, FloatTy, Ty};
use rustc_semver::RustcVersion;
use super::{utils, CAST_LOSSLESS};
pub(super) fn check(
cx: &LateContext<'_>,
expr: &Expr<'_>,
cast_op: &Expr<'_>,
cast_from: Ty<'_>,
cast_to: Ty<'_>,
msrv: &Option<RustcVersion>,
) {
if !should_lint(cx, expr, cast_from, cast_to, msrv) {
return;
}
// The suggestion is to use a function call, so if the original expression
// has parens on the outside, they are no longer needed.
let mut applicability = Applicability::MachineApplicable;
let opt = snippet_opt(cx, cast_op.span);
let sugg = opt.as_ref().map_or_else(
|| {
applicability = Applicability::HasPlaceholders;
".."
},
|snip| {
if should_strip_parens(cast_op, snip) {
&snip[1..snip.len() - 1]
} else {
snip.as_str()
}
},
);
let message = if cast_from.is_bool() {
format!(
"casting `{0:}` to `{1:}` is more cleanly stated with `{1:}::from(_)`",
cast_from, cast_to
)
} else {
format!(
"casting `{}` to `{}` may become silently lossy if you later change the type",
cast_from, cast_to
)
};
span_lint_and_sugg(
cx,
CAST_LOSSLESS,
expr.span,
&message,
"try",
format!("{}::from({})", cast_to, sugg),
applicability,
);
}
fn should_lint(
cx: &LateContext<'_>,
expr: &Expr<'_>,
cast_from: Ty<'_>,
cast_to: Ty<'_>,
msrv: &Option<RustcVersion>,
) -> bool {
// Do not suggest using From in consts/statics until it is valid to do so (see #2267).
if in_constant(cx, expr.hir_id) {
return false;
}
match (cast_from.is_integral(), cast_to.is_integral()) {
(true, true) => {
let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
let from_nbits = utils::int_ty_to_nbits(cast_from, cx.tcx);
let to_nbits = utils::int_ty_to_nbits(cast_to, cx.tcx);
!is_isize_or_usize(cast_from)
&& !is_isize_or_usize(cast_to)
&& from_nbits < to_nbits
&& !cast_signed_to_unsigned
},
(true, false) => {
let from_nbits = utils::int_ty_to_nbits(cast_from, cx.tcx);
let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.kind() {
32
} else {
64
};
from_nbits < to_nbits
},
(false, true) if matches!(cast_from.kind(), ty::Bool) && meets_msrv(msrv.as_ref(), &msrvs::FROM_BOOL) => true,
(_, _) => {
matches!(cast_from.kind(), ty::Float(FloatTy::F32)) && matches!(cast_to.kind(), ty::Float(FloatTy::F64))
},
}
}
fn should_strip_parens(cast_expr: &Expr<'_>, snip: &str) -> bool {
if let ExprKind::Binary(_, _, _) = cast_expr.kind {
if snip.starts_with('(') && snip.ends_with(')') {
return true;
}
}
false
}
|
