diff --git a/CHANGELOG.md b/CHANGELOG.md index 2ac9057199ff..f7dae3dcfff0 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -1630,6 +1630,7 @@ Released 2018-09-13 [`useless_transmute`]: https://rust-lang.github.io/rust-clippy/master/index.html#useless_transmute [`useless_vec`]: https://rust-lang.github.io/rust-clippy/master/index.html#useless_vec [`vec_box`]: https://rust-lang.github.io/rust-clippy/master/index.html#vec_box +[`vec_resize_to_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#vec_resize_to_zero [`verbose_bit_mask`]: https://rust-lang.github.io/rust-clippy/master/index.html#verbose_bit_mask [`verbose_file_reads`]: https://rust-lang.github.io/rust-clippy/master/index.html#verbose_file_reads [`vtable_address_comparisons`]: https://rust-lang.github.io/rust-clippy/master/index.html#vtable_address_comparisons diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index 057d39d4c825..119501d90924 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -325,6 +325,7 @@ mod unwrap; mod use_self; mod useless_conversion; mod vec; +mod vec_resize_to_zero; mod verbose_file_reads; mod wildcard_dependencies; mod wildcard_imports; @@ -852,6 +853,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: &utils::internal_lints::OUTER_EXPN_EXPN_DATA, &utils::internal_lints::PRODUCE_ICE, &vec::USELESS_VEC, + &vec_resize_to_zero::VEC_RESIZE_TO_ZERO, &verbose_file_reads::VERBOSE_FILE_READS, &wildcard_dependencies::WILDCARD_DEPENDENCIES, &wildcard_imports::ENUM_GLOB_USE, @@ -1066,6 +1068,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: store.register_late_pass(|| box match_on_vec_items::MatchOnVecItems); store.register_early_pass(|| box manual_non_exhaustive::ManualNonExhaustive); store.register_late_pass(|| box manual_async_fn::ManualAsyncFn); + store.register_late_pass(|| box vec_resize_to_zero::VecResizeToZero); store.register_group(true, "clippy::restriction", Some("clippy_restriction"), vec![ LintId::of(&arithmetic::FLOAT_ARITHMETIC), @@ -1430,6 +1433,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&unwrap::UNNECESSARY_UNWRAP), LintId::of(&useless_conversion::USELESS_CONVERSION), LintId::of(&vec::USELESS_VEC), + LintId::of(&vec_resize_to_zero::VEC_RESIZE_TO_ZERO), LintId::of(&write::PRINTLN_EMPTY_STRING), LintId::of(&write::PRINT_LITERAL), LintId::of(&write::PRINT_WITH_NEWLINE), @@ -1677,6 +1681,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&unnamed_address::VTABLE_ADDRESS_COMPARISONS), LintId::of(&unused_io_amount::UNUSED_IO_AMOUNT), LintId::of(&unwrap::PANICKING_UNWRAP), + LintId::of(&vec_resize_to_zero::VEC_RESIZE_TO_ZERO), ]); store.register_group(true, "clippy::perf", Some("clippy_perf"), vec![ diff --git a/clippy_lints/src/utils/paths.rs b/clippy_lints/src/utils/paths.rs index b3ad2ad9d998..bc7dccc8fe58 100644 --- a/clippy_lints/src/utils/paths.rs +++ b/clippy_lints/src/utils/paths.rs @@ -136,5 +136,6 @@ pub const VEC_AS_SLICE: [&str; 4] = ["alloc", "vec", "Vec", "as_slice"]; pub const VEC_DEQUE: [&str; 4] = ["alloc", "collections", "vec_deque", "VecDeque"]; pub const VEC_FROM_ELEM: [&str; 3] = ["alloc", "vec", "from_elem"]; pub const VEC_NEW: [&str; 4] = ["alloc", "vec", "Vec", "new"]; +pub const VEC_RESIZE: [&str; 4] = ["alloc", "vec", "Vec", "resize"]; pub const WEAK_ARC: [&str; 3] = ["alloc", "sync", "Weak"]; pub const WEAK_RC: [&str; 3] = ["alloc", "rc", "Weak"]; diff --git a/clippy_lints/src/vec_resize_to_zero.rs b/clippy_lints/src/vec_resize_to_zero.rs new file mode 100644 index 000000000000..8fb1dc6bb929 --- /dev/null +++ b/clippy_lints/src/vec_resize_to_zero.rs @@ -0,0 +1,43 @@ +use crate::utils::span_lint; +use if_chain::if_chain; +use rustc_hir::{Expr, ExprKind}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_session::{declare_lint_pass, declare_tool_lint}; +use rustc_span::source_map::Spanned; + +use crate::utils::{match_def_path, paths}; +use rustc_ast::ast::LitKind; +use rustc_hir as hir; + +declare_clippy_lint! { + /// **What it does:** Finds occurences of `Vec::resize(0, an_int)` + /// + /// **Why is this bad?** This is probably an argument inversion mistake. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// ```rust + /// vec!(1, 2, 3, 4, 5).resize(0, 5) + /// ``` + pub VEC_RESIZE_TO_ZERO, + correctness, + "emptying a vector with `resize(0, an_int)` instead of `clear()` is probably an argument inversion mistake" +} + +declare_lint_pass!(VecResizeToZero => [VEC_RESIZE_TO_ZERO]); + +impl<'a, 'tcx> LateLintPass<'a, 'tcx> for VecResizeToZero { + fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) { + if_chain! { + if let hir::ExprKind::MethodCall(_, _, ref args) = expr.kind; + if let Some(method_def_id) = cx.tables.type_dependent_def_id(expr.hir_id); + if match_def_path(cx, method_def_id, &paths::VEC_RESIZE) && args.len() == 3; + if let ExprKind::Lit(Spanned { node: LitKind::Int(0, _), .. }) = args[1].kind; + if let ExprKind::Lit(Spanned { node: LitKind::Int(..), .. }) = args[2].kind; + then { + span_lint(cx, VEC_RESIZE_TO_ZERO, expr.span, "this empties the vector. It could be an argument inversion mistake. If not, call `clear()` instead."); + } + } + } +} diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs index 8211a57b5643..05e40b11afb5 100644 --- a/src/lintlist/mod.rs +++ b/src/lintlist/mod.rs @@ -2460,6 +2460,13 @@ pub static ref ALL_LINTS: Vec = vec![ deprecation: None, module: "types", }, + Lint { + name: "vec_resize_to_zero", + group: "correctness", + desc: "emptying a vector with `resize(0, an_int)` instead of `clear()` is probably an argument inversion mistake", + deprecation: None, + module: "vec_resize_to_zero", + }, Lint { name: "verbose_bit_mask", group: "style", diff --git a/tests/ui/vec_resize_to_zero.rs b/tests/ui/vec_resize_to_zero.rs new file mode 100644 index 000000000000..0263e2f5f20c --- /dev/null +++ b/tests/ui/vec_resize_to_zero.rs @@ -0,0 +1,15 @@ +#![warn(clippy::vec_resize_to_zero)] + +fn main() { + // applicable here + vec![1, 2, 3, 4, 5].resize(0, 5); + + // not applicable + vec![1, 2, 3, 4, 5].resize(2, 5); + + // applicable here, but only implemented for integer litterals for now + vec!["foo", "bar", "baz"].resize(0, "bar"); + + // not applicable + vec!["foo", "bar", "baz"].resize(2, "bar") +} diff --git a/tests/ui/vec_resize_to_zero.stderr b/tests/ui/vec_resize_to_zero.stderr new file mode 100644 index 000000000000..3f47c2f2568c --- /dev/null +++ b/tests/ui/vec_resize_to_zero.stderr @@ -0,0 +1,18 @@ +error: this empties the vector. This is probably an argument inversion mistake. If not, call `clear()` instead. + --> $DIR/vec_resize_to_zero.rs:5:5 + | +LL | vec![1, 2, 3, 4, 5].resize(0, 5); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: `#[deny(clippy::vec_resize_to_zero)]` on by default + +error: unknown clippy lint: clippy::vec_resize_to_zero + --> $DIR/vec_resize_to_zero.rs:1:9 + | +LL | #![warn(clippy::vec_resize_to_zero)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: `-D clippy::unknown-clippy-lints` implied by `-D warnings` + +error: aborting due to 2 previous errors +