82 lines
2.8 KiB
Rust
82 lines
2.8 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::snippet_with_context;
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use clippy_utils::{last_path_segment, std_or_core};
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use rustc_errors::Applicability;
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use rustc_hir::{def, Expr, ExprKind, GenericArg, QPath, TyKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::declare_lint_pass;
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use rustc_span::{sym, SyntaxContext};
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declare_clippy_lint! {
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/// ### What it does
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/// It checks for `std::iter::Empty::default()` and suggests replacing it with
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/// `std::iter::empty()`.
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/// ### Why is this bad?
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/// `std::iter::empty()` is the more idiomatic way.
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/// ### Example
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/// ```no_run
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/// let _ = std::iter::Empty::<usize>::default();
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/// let iter: std::iter::Empty<usize> = std::iter::Empty::default();
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/// ```
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/// Use instead:
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/// ```no_run
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/// let _ = std::iter::empty::<usize>();
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/// let iter: std::iter::Empty<usize> = std::iter::empty();
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/// ```
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#[clippy::version = "1.64.0"]
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pub DEFAULT_INSTEAD_OF_ITER_EMPTY,
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style,
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"check `std::iter::Empty::default()` and replace with `std::iter::empty()`"
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}
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declare_lint_pass!(DefaultIterEmpty => [DEFAULT_INSTEAD_OF_ITER_EMPTY]);
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impl<'tcx> LateLintPass<'tcx> for DefaultIterEmpty {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if let ExprKind::Call(iter_expr, []) = &expr.kind
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&& let ExprKind::Path(QPath::TypeRelative(ty, _)) = &iter_expr.kind
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&& let TyKind::Path(ty_path) = &ty.kind
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&& let QPath::Resolved(None, path) = ty_path
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&& let def::Res::Def(_, def_id) = &path.res
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&& cx.tcx.is_diagnostic_item(sym::IterEmpty, *def_id)
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&& let ctxt = expr.span.ctxt()
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&& ty.span.ctxt() == ctxt
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{
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let mut applicability = Applicability::MachineApplicable;
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let Some(path) = std_or_core(cx) else { return };
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let path = format!("{path}::iter::empty");
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let sugg = make_sugg(cx, ty_path, ctxt, &mut applicability, &path);
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span_lint_and_sugg(
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cx,
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DEFAULT_INSTEAD_OF_ITER_EMPTY,
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expr.span,
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format!("`{path}()` is the more idiomatic way"),
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"try",
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sugg,
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applicability,
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);
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}
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}
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}
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fn make_sugg(
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cx: &LateContext<'_>,
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ty_path: &QPath<'_>,
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ctxt: SyntaxContext,
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applicability: &mut Applicability,
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path: &str,
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) -> String {
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if let Some(last) = last_path_segment(ty_path).args
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&& let Some(iter_ty) = last.args.iter().find_map(|arg| match arg {
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GenericArg::Type(ty) => Some(ty),
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_ => None,
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})
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{
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format!(
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"{path}::<{}>()",
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snippet_with_context(cx, iter_ty.span, ctxt, "..", applicability).0
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)
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} else {
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format!("{path}()")
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}
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}
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