diff options
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs b/src/tools/clippy/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs new file mode 100644 index 000000000..4f73b3ec4 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs @@ -0,0 +1,92 @@ +use clippy_utils::diagnostics::span_lint_and_sugg; +use clippy_utils::source::snippet; +use clippy_utils::{get_expr_use_or_unification_node, is_no_std_crate, is_res_lang_ctor, path_res}; + +use rustc_errors::Applicability; +use rustc_hir::LangItem::{OptionNone, OptionSome}; +use rustc_hir::{Expr, ExprKind, Node}; +use rustc_lint::LateContext; + +use super::{ITER_ON_EMPTY_COLLECTIONS, ITER_ON_SINGLE_ITEMS}; + +enum IterType { + Iter, + IterMut, + IntoIter, +} + +impl IterType { + fn ref_prefix(&self) -> &'static str { + match self { + Self::Iter => "&", + Self::IterMut => "&mut ", + Self::IntoIter => "", + } + } +} + +pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, method_name: &str, recv: &Expr<'_>) { + let item = match recv.kind { + ExprKind::Array([]) => None, + ExprKind::Array([e]) => Some(e), + ExprKind::Path(ref p) if is_res_lang_ctor(cx, cx.qpath_res(p, recv.hir_id), OptionNone) => None, + ExprKind::Call(f, [arg]) if is_res_lang_ctor(cx, path_res(cx, f), OptionSome) => Some(arg), + _ => return, + }; + let iter_type = match method_name { + "iter" => IterType::Iter, + "iter_mut" => IterType::IterMut, + "into_iter" => IterType::IntoIter, + _ => return, + }; + + let is_unified = match get_expr_use_or_unification_node(cx.tcx, expr) { + Some((Node::Expr(parent), child_id)) => match parent.kind { + ExprKind::If(e, _, _) | ExprKind::Match(e, _, _) if e.hir_id == child_id => false, + ExprKind::If(_, _, _) + | ExprKind::Match(_, _, _) + | ExprKind::Closure(_) + | ExprKind::Ret(_) + | ExprKind::Break(_, _) => true, + _ => false, + }, + Some((Node::Stmt(_) | Node::Local(_), _)) => false, + _ => true, + }; + + if is_unified { + return; + } + + if let Some(i) = item { + let sugg = format!( + "{}::iter::once({}{})", + if is_no_std_crate(cx) { "core" } else { "std" }, + iter_type.ref_prefix(), + snippet(cx, i.span, "...") + ); + span_lint_and_sugg( + cx, + ITER_ON_SINGLE_ITEMS, + expr.span, + &format!("`{method_name}` call on a collection with only one item"), + "try", + sugg, + Applicability::MaybeIncorrect, + ); + } else { + span_lint_and_sugg( + cx, + ITER_ON_EMPTY_COLLECTIONS, + expr.span, + &format!("`{method_name}` call on an empty collection"), + "try", + if is_no_std_crate(cx) { + "core::iter::empty()".to_string() + } else { + "std::iter::empty()".to_string() + }, + Applicability::MaybeIncorrect, + ); + } +} |