From acff51187115444038662ff4e9e23403a96d085d Mon Sep 17 00:00:00 2001 From: Samuel Tardieu Date: Sat, 21 Sep 2024 19:13:37 +0200 Subject: [PATCH] Lint comparison to empty slice using `PartialEq` methods --- clippy_lints/src/len_zero.rs | 15 ++++++++++++++- tests/ui/comparison_to_empty.fixed | 8 ++++++++ tests/ui/comparison_to_empty.rs | 8 ++++++++ tests/ui/comparison_to_empty.stderr | 26 +++++++++++++++++++++++++- 4 files changed, 55 insertions(+), 2 deletions(-) diff --git a/clippy_lints/src/len_zero.rs b/clippy_lints/src/len_zero.rs index c1ba66de57e5..3cd5f76e6b67 100644 --- a/clippy_lints/src/len_zero.rs +++ b/clippy_lints/src/len_zero.rs @@ -1,7 +1,7 @@ use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then}; use clippy_utils::source::{SpanRangeExt, snippet_with_context}; use clippy_utils::sugg::{Sugg, has_enclosing_paren}; -use clippy_utils::{get_item_name, get_parent_as_impl, is_lint_allowed, peel_ref_operators}; +use clippy_utils::{get_item_name, get_parent_as_impl, is_lint_allowed, is_trait_method, peel_ref_operators}; use rustc_ast::ast::LitKind; use rustc_errors::Applicability; use rustc_hir::def::Res; @@ -185,6 +185,19 @@ impl<'tcx> LateLintPass<'tcx> for LenZero { ); } + if let ExprKind::MethodCall(method, lhs_expr, [rhs_expr], _) = expr.kind + && is_trait_method(cx, expr, sym::PartialEq) + && !expr.span.from_expansion() + { + check_empty_expr( + cx, + expr.span, + lhs_expr, + peel_ref_operators(cx, rhs_expr), + (method.ident.name == sym::ne).then_some("!").unwrap_or_default(), + ); + } + if let ExprKind::Binary(Spanned { node: cmp, .. }, left, right) = expr.kind && !expr.span.from_expansion() { diff --git a/tests/ui/comparison_to_empty.fixed b/tests/ui/comparison_to_empty.fixed index e102b13a7618..a2a3dd9086d4 100644 --- a/tests/ui/comparison_to_empty.fixed +++ b/tests/ui/comparison_to_empty.fixed @@ -33,4 +33,12 @@ fn main() { if let [0] = &*s && s == [0] {} + + // Also lint the `PartialEq` methods + let s = String::new(); + let _ = s.is_empty(); + let _ = !s.is_empty(); + let v = vec![0]; + let _ = v.is_empty(); + let _ = !v.is_empty(); } diff --git a/tests/ui/comparison_to_empty.rs b/tests/ui/comparison_to_empty.rs index 69a6c967d382..7c5689a4bbec 100644 --- a/tests/ui/comparison_to_empty.rs +++ b/tests/ui/comparison_to_empty.rs @@ -33,4 +33,12 @@ fn main() { if let [0] = &*s && s == [0] {} + + // Also lint the `PartialEq` methods + let s = String::new(); + let _ = s.eq(""); + let _ = s.ne(""); + let v = vec![0]; + let _ = v.eq(&[]); + let _ = v.ne(&[]); } diff --git a/tests/ui/comparison_to_empty.stderr b/tests/ui/comparison_to_empty.stderr index 6b027459ed34..2ee0efc7dbb1 100644 --- a/tests/ui/comparison_to_empty.stderr +++ b/tests/ui/comparison_to_empty.stderr @@ -55,5 +55,29 @@ error: comparison to empty slice LL | && s == [] | ^^^^^^^ help: using `is_empty` is clearer and more explicit: `s.is_empty()` -error: aborting due to 9 previous errors +error: comparison to empty slice + --> tests/ui/comparison_to_empty.rs:39:13 + | +LL | let _ = s.eq(""); + | ^^^^^^^^ help: using `is_empty` is clearer and more explicit: `s.is_empty()` + +error: comparison to empty slice + --> tests/ui/comparison_to_empty.rs:40:13 + | +LL | let _ = s.ne(""); + | ^^^^^^^^ help: using `!is_empty` is clearer and more explicit: `!s.is_empty()` + +error: comparison to empty slice + --> tests/ui/comparison_to_empty.rs:42:13 + | +LL | let _ = v.eq(&[]); + | ^^^^^^^^^ help: using `is_empty` is clearer and more explicit: `v.is_empty()` + +error: comparison to empty slice + --> tests/ui/comparison_to_empty.rs:43:13 + | +LL | let _ = v.ne(&[]); + | ^^^^^^^^^ help: using `!is_empty` is clearer and more explicit: `!v.is_empty()` + +error: aborting due to 13 previous errors