81 lines
2.4 KiB
Rust
81 lines
2.4 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::{meets_msrv, msrvs};
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use if_chain::if_chain;
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use rustc_hir as hir;
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use rustc_lint::{LateContext, LateLintPass, LintContext};
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use rustc_semver::RustcVersion;
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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use rustc_span::symbol::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// Searches for implementations of the `Into<..>` trait and suggests to implement `From<..>` instead.
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///
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/// ### Why is this bad?
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/// According the std docs implementing `From<..>` is preferred since it gives you `Into<..>` for free where the reverse isn't true.
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///
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/// ### Example
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/// ```rust
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/// struct StringWrapper(String);
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///
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/// impl Into<StringWrapper> for String {
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/// fn into(self) -> StringWrapper {
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/// StringWrapper(self)
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/// }
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/// }
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/// ```
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/// Use instead:
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/// ```rust
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/// struct StringWrapper(String);
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///
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/// impl From<String> for StringWrapper {
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/// fn from(s: String) -> StringWrapper {
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/// StringWrapper(s)
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/// }
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/// }
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/// ```
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pub FROM_OVER_INTO,
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style,
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"Warns on implementations of `Into<..>` to use `From<..>`"
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}
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pub struct FromOverInto {
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msrv: Option<RustcVersion>,
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}
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impl FromOverInto {
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#[must_use]
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pub fn new(msrv: Option<RustcVersion>) -> Self {
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FromOverInto { msrv }
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}
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}
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impl_lint_pass!(FromOverInto => [FROM_OVER_INTO]);
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impl LateLintPass<'_> for FromOverInto {
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fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
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if !meets_msrv(self.msrv.as_ref(), &msrvs::RE_REBALANCING_COHERENCE) {
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return;
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}
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if_chain! {
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if let hir::ItemKind::Impl{ .. } = &item.kind;
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if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(item.def_id);
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if cx.tcx.is_diagnostic_item(sym::into_trait, impl_trait_ref.def_id);
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then {
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span_lint_and_help(
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cx,
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FROM_OVER_INTO,
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cx.tcx.sess.source_map().guess_head_span(item.span),
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"an implementation of `From` is preferred since it gives you `Into<_>` for free where the reverse isn't true",
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None,
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&format!("consider to implement `From<{}>` instead", impl_trait_ref.self_ty()),
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);
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}
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}
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}
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extract_msrv_attr!(LateContext);
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}
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