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Improve string_to_string lint in case it is in a map call

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This commit is contained in:
Guillaume Gomez 2025-03-12 15:38:43 +01:00
parent 0730678e26
commit 21601fd042
1 changed files with 74 additions and 16 deletions
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90
clippy_lints/src/strings.rs
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@ -1,4 +1,4 @@
use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then};
use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then};
use clippy_utils::source::{snippet, snippet_with_applicability};
use clippy_utils::ty::is_type_lang_item;
use clippy_utils::{
@ -438,27 +438,85 @@ declare_clippy_lint! {
declare_lint_pass!(StringToString => [STRING_TO_STRING]);
fn is_parent_map_like(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<rustc_span::Span> {
if let Some(parent_expr) = get_parent_expr(cx, expr)
&& let ExprKind::MethodCall(name, ..) = parent_expr.kind
&& name.ident.name == sym::map
&& let Some(caller_def_id) = cx.typeck_results().type_dependent_def_id(parent_expr.hir_id)
&& (clippy_utils::is_diag_item_method(cx, caller_def_id, sym::Result)
|| clippy_utils::is_diag_item_method(cx, caller_def_id, sym::Option)
|| clippy_utils::is_diag_trait_item(cx, caller_def_id, sym::Iterator))
{
Some(parent_expr.span)
} else {
None
}
}
fn is_called_from_map_like(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<rustc_span::Span> {
let parent = get_parent_expr(cx, expr)?;
if matches!(parent.kind, ExprKind::Closure(_)) {
is_parent_map_like(cx, parent)
} else {
None
}
}
fn suggest_cloned_string_to_string(cx: &LateContext<'_>, span: rustc_span::Span) {
span_lint_and_help(
cx,
STRING_TO_STRING,
span,
"`to_string()` called on a `String`",
None,
"consider using `.cloned()`",
);
}
impl<'tcx> LateLintPass<'tcx> for StringToString {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'_>) {
if expr.span.from_expansion() {
return;
}
if let ExprKind::MethodCall(path, self_arg, [], _) = &expr.kind
&& path.ident.name == sym::to_string
&& let ty = cx.typeck_results().expr_ty(self_arg)
&& is_type_lang_item(cx, ty, LangItem::String)
{
#[expect(clippy::collapsible_span_lint_calls, reason = "rust-clippy#7797")]
span_lint_and_then(
cx,
STRING_TO_STRING,
expr.span,
"`to_string()` called on a `String`",
|diag| {
diag.help("consider using `.clone()`");
},
);
match &expr.kind {
ExprKind::MethodCall(path, self_arg, [], _) => {
if path.ident.name == sym::to_string
&& let ty = cx.typeck_results().expr_ty(self_arg)
&& is_type_lang_item(cx, ty.peel_refs(), LangItem::String)
{
if let Some(parent_span) = is_called_from_map_like(cx, expr) {
suggest_cloned_string_to_string(cx, parent_span);
} else {
#[expect(clippy::collapsible_span_lint_calls, reason = "rust-clippy#7797")]
span_lint_and_then(
cx,
STRING_TO_STRING,
expr.span,
"`to_string()` called on a `String`",
|diag| {
diag.help("consider using `.clone()`");
},
);
}
}
},
ExprKind::Path(QPath::TypeRelative(ty, segment)) => {
if segment.ident.name == sym::to_string
&& let rustc_hir::TyKind::Path(QPath::Resolved(_, path)) = ty.peel_refs().kind
&& let rustc_hir::def::Res::Def(_, def_id) = path.res
&& cx
.tcx
.lang_items()
.get(LangItem::String)
.is_some_and(|lang_id| lang_id == def_id)
&& let Some(parent_span) = is_parent_map_like(cx, expr)
{
suggest_cloned_string_to_string(cx, parent_span);
}
},
_ => {},
}
}
}