1 use crate::utils::paths::INTO;
2 use crate::utils::{match_def_path, meets_msrv, span_lint_and_help};
3 use if_chain::if_chain;
5 use rustc_lint::{LateContext, LateLintPass, LintContext};
6 use rustc_semver::RustcVersion;
7 use rustc_session::{declare_tool_lint, impl_lint_pass};
9 const FROM_OVER_INTO_MSRV: RustcVersion = RustcVersion::new(1, 41, 0);
11 declare_clippy_lint! {
12 /// **What it does:** Searches for implementations of the `Into<..>` trait and suggests to implement `From<..>` instead.
14 /// **Why is this bad?** According the std docs implementing `From<..>` is preferred since it gives you `Into<..>` for free where the reverse isn't true.
16 /// **Known problems:** None.
21 /// struct StringWrapper(String);
23 /// impl Into<StringWrapper> for String {
24 /// fn into(self) -> StringWrapper {
25 /// StringWrapper(self)
31 /// struct StringWrapper(String);
33 /// impl From<String> for StringWrapper {
34 /// fn from(s: String) -> StringWrapper {
41 "Warns on implementations of `Into<..>` to use `From<..>`"
44 pub struct FromOverInto {
45 msrv: Option<RustcVersion>,
50 pub fn new(msrv: Option<RustcVersion>) -> Self {
55 impl_lint_pass!(FromOverInto => [FROM_OVER_INTO]);
57 impl LateLintPass<'_> for FromOverInto {
58 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
59 if !meets_msrv(self.msrv.as_ref(), &FROM_OVER_INTO_MSRV) {
63 let impl_def_id = cx.tcx.hir().local_def_id(item.hir_id);
65 if let hir::ItemKind::Impl{ .. } = &item.kind;
66 if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_def_id);
67 if match_def_path(cx, impl_trait_ref.def_id, &INTO);
74 "an implementation of `From` is preferred since it gives you `Into<_>` for free where the reverse isn't true",
76 "consider to implement `From` instead",
82 extract_msrv_attr!(LateContext);