diff options
| -rw-r--r-- | clippy_lints/src/methods/iter_on_single_or_empty_collections.rs | 47 | ||||
| -rw-r--r-- | tests/ui/iter_on_empty_collections.fixed | 22 | ||||
| -rw-r--r-- | tests/ui/iter_on_empty_collections.rs | 22 | ||||
| -rw-r--r-- | tests/ui/iter_on_empty_collections.stderr | 8 |
4 files changed, 97 insertions, 2 deletions
diff --git a/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs b/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs index 6c9bdcff826..f4397212cf6 100644 --- a/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs +++ b/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs @@ -1,8 +1,12 @@ +use std::iter::once; + use clippy_utils::diagnostics::span_lint_and_sugg; use clippy_utils::source::snippet; use clippy_utils::{get_expr_use_or_unification_node, is_res_lang_ctor, path_res, std_or_core}; use rustc_errors::Applicability; +use rustc_hir::def_id::DefId; +use rustc_hir::hir_id::HirId; use rustc_hir::LangItem::{OptionNone, OptionSome}; use rustc_hir::{Expr, ExprKind, Node}; use rustc_lint::LateContext; @@ -25,7 +29,29 @@ impl IterType { } } -pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, method_name: &str, recv: &Expr<'_>) { +fn is_arg_ty_unified_in_fn<'tcx>( + cx: &LateContext<'tcx>, + fn_id: DefId, + arg_id: HirId, + args: impl IntoIterator<Item = &'tcx Expr<'tcx>>, +) -> bool { + let fn_sig = cx.tcx.fn_sig(fn_id).instantiate_identity(); + let arg_id_in_args = args.into_iter().position(|e| e.hir_id == arg_id).unwrap(); + let arg_ty_in_args = fn_sig.input(arg_id_in_args).skip_binder(); + + cx.tcx.predicates_of(fn_id).predicates.iter().any(|(clause, _)| { + clause + .as_projection_clause() + .and_then(|p| p.map_bound(|p| p.term.ty()).transpose()) + .is_some_and(|ty| ty.skip_binder() == arg_ty_in_args) + }) || fn_sig + .inputs() + .iter() + .enumerate() + .any(|(i, ty)| i != arg_id_in_args && ty.skip_binder().walk().any(|arg| arg.as_type() == Some(arg_ty_in_args))) +} + +pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, method_name: &str, recv: &'tcx Expr<'tcx>) { let item = match recv.kind { ExprKind::Array([]) => None, ExprKind::Array([e]) => Some(e), @@ -43,6 +69,25 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, method_name: &str, re 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::Call( + Expr { + kind: ExprKind::Path(path), + hir_id, + .. + }, + args, + ) => cx + .typeck_results() + .qpath_res(path, *hir_id) + .opt_def_id() + .filter(|fn_id| cx.tcx.def_kind(fn_id).is_fn_like()) + .is_some_and(|fn_id| is_arg_ty_unified_in_fn(cx, fn_id, child_id, args)), + ExprKind::MethodCall(_name, recv, args, _span) => is_arg_ty_unified_in_fn( + cx, + cx.typeck_results().type_dependent_def_id(parent.hir_id).unwrap(), + child_id, + once(recv).chain(args.iter()), + ), ExprKind::If(_, _, _) | ExprKind::Match(_, _, _) | ExprKind::Closure(_) diff --git a/tests/ui/iter_on_empty_collections.fixed b/tests/ui/iter_on_empty_collections.fixed index 794629f240e..0f28b48d9ab 100644 --- a/tests/ui/iter_on_empty_collections.fixed +++ b/tests/ui/iter_on_empty_collections.fixed @@ -20,6 +20,28 @@ fn array() { }; let _ = if false { ["test"].iter() } else { [].iter() }; + + let smth = Some(vec![1, 2, 3]); + + // Don't trigger when the empty collection iter is relied upon for its concrete type + // But do trigger if it is just an iterator, despite being an argument to a method + for i in smth.as_ref().map_or([].iter(), |s| s.iter()).chain(std::iter::empty()) { + println!("{i}"); + } + + // Same as above, but for empty collection iters with extra layers + for i in smth.as_ref().map_or({ [].iter() }, |s| s.iter()) { + println!("{y}", y = i + 1); + } + + // Same as above, but for regular function calls + for i in Option::map_or(smth.as_ref(), [].iter(), |s| s.iter()) { + println!("{i}"); + } + + // Same as above, but when there are no predicates that mention the collection iter type. + let mut iter = [34, 228, 35].iter(); + let _ = std::mem::replace(&mut iter, [].iter()); } macro_rules! in_macros { diff --git a/tests/ui/iter_on_empty_collections.rs b/tests/ui/iter_on_empty_collections.rs index a6461a702eb..702da514df7 100644 --- a/tests/ui/iter_on_empty_collections.rs +++ b/tests/ui/iter_on_empty_collections.rs @@ -20,6 +20,28 @@ fn array() { }; let _ = if false { ["test"].iter() } else { [].iter() }; + + let smth = Some(vec![1, 2, 3]); + + // Don't trigger when the empty collection iter is relied upon for its concrete type + // But do trigger if it is just an iterator, despite being an argument to a method + for i in smth.as_ref().map_or([].iter(), |s| s.iter()).chain([].iter()) { + println!("{i}"); + } + + // Same as above, but for empty collection iters with extra layers + for i in smth.as_ref().map_or({ [].iter() }, |s| s.iter()) { + println!("{y}", y = i + 1); + } + + // Same as above, but for regular function calls + for i in Option::map_or(smth.as_ref(), [].iter(), |s| s.iter()) { + println!("{i}"); + } + + // Same as above, but when there are no predicates that mention the collection iter type. + let mut iter = [34, 228, 35].iter(); + let _ = std::mem::replace(&mut iter, [].iter()); } macro_rules! in_macros { diff --git a/tests/ui/iter_on_empty_collections.stderr b/tests/ui/iter_on_empty_collections.stderr index ade20ff26a0..da9caa6925b 100644 --- a/tests/ui/iter_on_empty_collections.stderr +++ b/tests/ui/iter_on_empty_collections.stderr @@ -37,5 +37,11 @@ error: `iter` call on an empty collection LL | assert_eq!(None.iter().next(), Option::<&i32>::None); | ^^^^^^^^^^^ help: try: `std::iter::empty()` -error: aborting due to 6 previous errors +error: `iter` call on an empty collection + --> tests/ui/iter_on_empty_collections.rs:28:66 + | +LL | for i in smth.as_ref().map_or([].iter(), |s| s.iter()).chain([].iter()) { + | ^^^^^^^^^ help: try: `std::iter::empty()` + +error: aborting due to 7 previous errors |