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[cast_lossless]: Suggest type alias instead of the aliased type

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Catherine Flores 2023-08-02 14:36:25 -05:00 • committed by Centri3
parent 3a149111ba
commit 244d7da817
11 changed files with 127 additions and 59 deletions
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36
clippy_lints/src/casts/cast_lossless.rs
View file

@ -1,10 +1,10 @@
use clippy_config::msrvs::{self, Msrv};
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::in_constant;
use clippy_utils::source::snippet_opt;
use clippy_utils::source::{snippet_opt, snippet_with_applicability};
use clippy_utils::ty::is_isize_or_usize;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind};
use rustc_hir::{Expr, ExprKind, QPath, TyKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, FloatTy, Ty};
@ -16,6 +16,7 @@ pub(super) fn check(
cast_op: &Expr<'_>,
cast_from: Ty<'_>,
cast_to: Ty<'_>,
cast_to_hir: &rustc_hir::Ty<'_>,
msrv: &Msrv,
) {
if !should_lint(cx, expr, cast_from, cast_to, msrv) {
@ -24,11 +25,11 @@ pub(super) fn check(
// 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 mut app = Applicability::MachineApplicable;
let opt = snippet_opt(cx, cast_op.span.source_callsite());
let sugg = opt.as_ref().map_or_else(
|| {
applicability = Applicability::HasPlaceholders;
app = Applicability::HasPlaceholders;
".."
},
|snip| {
@ -40,10 +41,27 @@ pub(super) fn check(
},
);
let message = if cast_from.is_bool() {
format!("casting `{cast_from:}` to `{cast_to:}` is more cleanly stated with `{cast_to:}::from(_)`")
// Display the type alias instead of the aliased type. Fixes #11285
//
// FIXME: Once `lazy_type_alias` is stabilized(?) we should use `rustc_middle` types instead,
// this will allow us to display the right type with `cast_from` as well.
let cast_to_fmt = if let TyKind::Path(QPath::Resolved(None, path)) = cast_to_hir.kind
// It's a bit annoying but the turbofish is optional for types. A type in an `as` cast
// shouldn't have these if they're primitives, which are the only things we deal with.
//
// This could be removed for performance if this check is determined to have a pretty major
// effect.
&& path.segments.iter().all(|segment| segment.args.is_none())
{
snippet_with_applicability(cx, cast_to_hir.span, "..", &mut app)
} else {
format!("casting `{cast_from}` to `{cast_to}` may become silently lossy if you later change the type")
cast_to.to_string().into()
};
let message = if cast_from.is_bool() {
format!("casting `{cast_from}` to `{cast_to_fmt}` is more cleanly stated with `{cast_to_fmt}::from(_)`")
} else {
format!("casting `{cast_from}` to `{cast_to_fmt}` may become silently lossy if you later change the type")
};
span_lint_and_sugg(
@ -52,8 +70,8 @@ pub(super) fn check(
expr.span,
&message,
"try",
format!("{cast_to}::from({sugg})"),
applicability,
format!("{cast_to_fmt}::from({sugg})"),
app,
);
}

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

@ -791,7 +791,7 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
cast_abs_to_unsigned::check(cx, expr, cast_expr, cast_from, cast_to, &self.msrv);
cast_nan_to_int::check(cx, expr, cast_expr, cast_from, cast_to);
}
cast_lossless::check(cx, expr, cast_expr, cast_from, cast_to, &self.msrv);
cast_lossless::check(cx, expr, cast_expr, cast_from, cast_to, cast_to_hir, &self.msrv);
cast_enum_constructor::check(cx, expr, cast_expr, cast_from);
}