diff --git a/CHANGELOG.md b/CHANGELOG.md index d847e4c7494..044cbff4b78 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -3800,6 +3800,7 @@ Released 2018-09-13 [`items_after_statements`]: https://rust-lang.github.io/rust-clippy/master/index.html#items_after_statements [`iter_cloned_collect`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_cloned_collect [`iter_count`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_count +[`iter_kv_map`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_kv_map [`iter_next_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_next_loop [`iter_next_slice`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_next_slice [`iter_not_returning_iterator`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_not_returning_iterator diff --git a/clippy_lints/src/lib.register_all.rs b/clippy_lints/src/lib.register_all.rs index 39ab175341f..ae57a9a24a7 100644 --- a/clippy_lints/src/lib.register_all.rs +++ b/clippy_lints/src/lib.register_all.rs @@ -171,6 +171,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![ LintId::of(methods::ITERATOR_STEP_BY_ZERO), LintId::of(methods::ITER_CLONED_COLLECT), LintId::of(methods::ITER_COUNT), + LintId::of(methods::ITER_KV_MAP), LintId::of(methods::ITER_NEXT_SLICE), LintId::of(methods::ITER_NTH), LintId::of(methods::ITER_NTH_ZERO), diff --git a/clippy_lints/src/lib.register_complexity.rs b/clippy_lints/src/lib.register_complexity.rs index aa247352f88..185189a6af5 100644 --- a/clippy_lints/src/lib.register_complexity.rs +++ b/clippy_lints/src/lib.register_complexity.rs @@ -40,6 +40,7 @@ store.register_group(true, "clippy::complexity", Some("clippy_complexity"), vec! LintId::of(methods::GET_LAST_WITH_LEN), LintId::of(methods::INSPECT_FOR_EACH), LintId::of(methods::ITER_COUNT), + LintId::of(methods::ITER_KV_MAP), LintId::of(methods::MANUAL_FILTER_MAP), LintId::of(methods::MANUAL_FIND_MAP), LintId::of(methods::MANUAL_SPLIT_ONCE), diff --git a/clippy_lints/src/lib.register_lints.rs b/clippy_lints/src/lib.register_lints.rs index c16f2d86ae0..02fcc8de507 100644 --- a/clippy_lints/src/lib.register_lints.rs +++ b/clippy_lints/src/lib.register_lints.rs @@ -313,6 +313,7 @@ store.register_lints(&[ methods::ITERATOR_STEP_BY_ZERO, methods::ITER_CLONED_COLLECT, methods::ITER_COUNT, + methods::ITER_KV_MAP, methods::ITER_NEXT_SLICE, methods::ITER_NTH, methods::ITER_NTH_ZERO, diff --git a/clippy_lints/src/methods/iter_kv_map.rs b/clippy_lints/src/methods/iter_kv_map.rs new file mode 100644 index 00000000000..a7eecabd684 --- /dev/null +++ b/clippy_lints/src/methods/iter_kv_map.rs @@ -0,0 +1,87 @@ +#![allow(unused_imports)] + +use super::ITER_KV_MAP; +use clippy_utils::diagnostics::{multispan_sugg, span_lint_and_sugg, span_lint_and_then}; +use clippy_utils::source::{snippet, snippet_with_applicability}; +use clippy_utils::sugg; +use clippy_utils::ty::is_type_diagnostic_item; +use clippy_utils::visitors::is_local_used; +use rustc_hir::{BindingAnnotation, Body, BorrowKind, Expr, ExprKind, Mutability, Pat, PatKind}; +use rustc_lint::{LateContext, LintContext}; +use rustc_middle::ty; +use rustc_span::sym; +use rustc_span::Span; + +/// lint use of: +/// - `hashmap.iter().map(|(_, v)| v)` +/// - `hashmap.into_iter().map(|(_, v)| v)` +/// on `HashMaps` and `BTreeMaps` in std + +pub(super) fn check<'tcx>( + cx: &LateContext<'tcx>, + map_type: &'tcx str, // iter / into_iter + expr: &'tcx Expr<'tcx>, // .iter().map(|(_, v_| v)) + recv: &'tcx Expr<'tcx>, // hashmap + m_arg: &'tcx Expr<'tcx>, // |(_, v)| v +) { + if_chain! { + if !expr.span.from_expansion(); + if let ExprKind::Closure(c) = m_arg.kind; + if let Body {params: [p], value: body_expr, generator_kind: _ } = cx.tcx.hir().body(c.body); + if let PatKind::Tuple([key_pat, val_pat], _) = p.pat.kind; + + let (replacement_kind, binded_ident) = match (&key_pat.kind, &val_pat.kind) { + (key, PatKind::Binding(_, _, value, _)) if pat_is_wild(cx, key, m_arg) => ("value", value), + (PatKind::Binding(_, _, key, _), value) if pat_is_wild(cx, value, m_arg) => ("key", key), + _ => return, + }; + + let ty = cx.typeck_results().expr_ty(recv); + if is_type_diagnostic_item(cx, ty, sym::HashMap) || is_type_diagnostic_item(cx, ty, sym::BTreeMap); + + then { + let mut applicability = rustc_errors::Applicability::MachineApplicable; + let recv_snippet = snippet_with_applicability(cx, recv.span, "map", &mut applicability); + let into_prefix = if map_type == "into_iter" {"into_"} else {""}; + + if_chain! { + if let ExprKind::Path(rustc_hir::QPath::Resolved(_, path)) = body_expr.kind; + if let [local_ident] = path.segments; + if local_ident.ident.as_str() == binded_ident.as_str(); + + then { + span_lint_and_sugg( + cx, + ITER_KV_MAP, + expr.span, + &format!("iterating on a map's {}s", replacement_kind), + "try", + format!("{}.{}{}s()", recv_snippet, into_prefix, replacement_kind), + applicability, + ); + } else { + span_lint_and_sugg( + cx, + ITER_KV_MAP, + expr.span, + &format!("iterating on a map's {}s", replacement_kind), + "try", + format!("{}.{}{}s().map(|{}| {})", recv_snippet, into_prefix, replacement_kind, binded_ident, + snippet_with_applicability(cx, body_expr.span, "/* body */", &mut applicability)), + applicability, + ); + } + } + } + } +} + +/// Returns `true` if the pattern is a `PatWild`, or is an ident prefixed with `_` +/// that is not locally used. +fn pat_is_wild<'tcx>(cx: &LateContext<'tcx>, pat: &'tcx PatKind<'_>, body: &'tcx Expr<'_>) -> bool { + match *pat { + PatKind::Wild => true, + PatKind::Binding(_, id, ident, None) if ident.as_str().starts_with('_') => !is_local_used(cx, body, id), + _ => false, + } +} diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs index 41942b20ea1..cdde4c54d63 100644 --- a/clippy_lints/src/methods/mod.rs +++ b/clippy_lints/src/methods/mod.rs @@ -35,6 +35,7 @@ mod into_iter_on_ref; mod is_digit_ascii_radix; mod iter_cloned_collect; mod iter_count; +mod iter_kv_map; mod iter_next_slice; mod iter_nth; mod iter_nth_zero; @@ -3036,6 +3037,37 @@ declare_clippy_lint! { "use of `File::read_to_end` or `File::read_to_string`" } +declare_clippy_lint! { + /// ### What it does + /// + /// Checks for iterating a map (`HashMap` or `BTreeMap`) and + /// ignoring either the keys or values. + /// + /// ### Why is this bad? + /// + /// Readability. There are `keys` and `values` methods that + /// can be used to express that we only need the keys or the values. + /// + /// ### Example + /// + /// ``` + /// # use std::collections::HashMap; + /// let map: HashMap = HashMap::new(); + /// let values = map.iter().map(|(_, value)| value).collect::>(); + /// ``` + /// + /// Use instead: + /// ``` + /// # use std::collections::HashMap; + /// let map: HashMap = HashMap::new(); + /// let values = map.values().collect::>(); + /// ``` + #[clippy::version = "1.65.0"] + pub ITER_KV_MAP, + complexity, + "iterating on map using `iter` when `keys` or `values` would do" +} + pub struct Methods { avoid_breaking_exported_api: bool, msrv: Option, @@ -3159,6 +3191,7 @@ impl_lint_pass!(Methods => [ UNNECESSARY_SORT_BY, VEC_RESIZE_TO_ZERO, VERBOSE_FILE_READS, + ITER_KV_MAP, ]); /// Extracts a method call name, args, and `Span` of the method name. @@ -3498,6 +3531,9 @@ impl Methods { (name @ ("map" | "map_err"), [m_arg]) => { if name == "map" { map_clone::check(cx, expr, recv, m_arg, self.msrv); + if let Some((map_name @ ("iter" | "into_iter"), recv2, _, _)) = method_call(recv) { + iter_kv_map::check(cx, map_name, expr, recv2, m_arg); + } } else { map_err_ignore::check(cx, expr, m_arg); } diff --git a/src/docs.rs b/src/docs.rs index 9f6f1fb4727..6c89b4dde37 100644 --- a/src/docs.rs +++ b/src/docs.rs @@ -221,6 +221,7 @@ docs! { "items_after_statements", "iter_cloned_collect", "iter_count", + "iter_kv_map", "iter_next_loop", "iter_next_slice", "iter_not_returning_iterator", diff --git a/src/docs/iter_kv_map.txt b/src/docs/iter_kv_map.txt new file mode 100644 index 00000000000..a063c8195ef --- /dev/null +++ b/src/docs/iter_kv_map.txt @@ -0,0 +1,22 @@ +### What it does + +Checks for iterating a map (`HashMap` or `BTreeMap`) and +ignoring either the keys or values. + +### Why is this bad? + +Readability. There are `keys` and `values` methods that +can be used to express that we only need the keys or the values. + +### Example + +``` +let map: HashMap = HashMap::new(); +let values = map.iter().map(|(_, value)| value).collect::>(); +``` + +Use instead: +``` +let map: HashMap = HashMap::new(); +let values = map.values().collect::>(); +``` \ No newline at end of file diff --git a/tests/ui/iter_kv_map.fixed b/tests/ui/iter_kv_map.fixed new file mode 100644 index 00000000000..83fee04080f --- /dev/null +++ b/tests/ui/iter_kv_map.fixed @@ -0,0 +1,64 @@ +// run-rustfix + +#![warn(clippy::iter_kv_map)] +#![allow(clippy::redundant_clone)] +#![allow(clippy::suspicious_map)] +#![allow(clippy::map_identity)] + +use std::collections::{BTreeMap, HashMap}; + +fn main() { + let get_key = |(key, _val)| key; + + let map: HashMap = HashMap::new(); + + let _ = map.keys().collect::>(); + let _ = map.values().collect::>(); + let _ = map.values().map(|v| v + 2).collect::>(); + + let _ = map.clone().into_keys().collect::>(); + let _ = map.clone().into_keys().map(|key| key + 2).collect::>(); + + let _ = map.clone().into_values().collect::>(); + let _ = map.clone().into_values().map(|val| val + 2).collect::>(); + + let _ = map.clone().values().collect::>(); + let _ = map.keys().filter(|x| *x % 2 == 0).count(); + + // Don't lint + let _ = map.iter().filter(|(_, val)| *val % 2 == 0).map(|(key, _)| key).count(); + let _ = map.iter().map(get_key).collect::>(); + + // Linting the following could be an improvement to the lint + // map.iter().filter_map(|(_, val)| (val % 2 == 0).then(val * 17)).count(); + + // Lint + let _ = map.keys().map(|key| key * 9).count(); + let _ = map.values().map(|value| value * 17).count(); + + let map: BTreeMap = BTreeMap::new(); + + let _ = map.keys().collect::>(); + let _ = map.values().collect::>(); + let _ = map.values().map(|v| v + 2).collect::>(); + + let _ = map.clone().into_keys().collect::>(); + let _ = map.clone().into_keys().map(|key| key + 2).collect::>(); + + let _ = map.clone().into_values().collect::>(); + let _ = map.clone().into_values().map(|val| val + 2).collect::>(); + + let _ = map.clone().values().collect::>(); + let _ = map.keys().filter(|x| *x % 2 == 0).count(); + + // Don't lint + let _ = map.iter().filter(|(_, val)| *val % 2 == 0).map(|(key, _)| key).count(); + let _ = map.iter().map(get_key).collect::>(); + + // Linting the following could be an improvement to the lint + // map.iter().filter_map(|(_, val)| (val % 2 == 0).then(val * 17)).count(); + + // Lint + let _ = map.keys().map(|key| key * 9).count(); + let _ = map.values().map(|value| value * 17).count(); +} diff --git a/tests/ui/iter_kv_map.rs b/tests/ui/iter_kv_map.rs new file mode 100644 index 00000000000..7a1f1fb0198 --- /dev/null +++ b/tests/ui/iter_kv_map.rs @@ -0,0 +1,64 @@ +// run-rustfix + +#![warn(clippy::iter_kv_map)] +#![allow(clippy::redundant_clone)] +#![allow(clippy::suspicious_map)] +#![allow(clippy::map_identity)] + +use std::collections::{BTreeMap, HashMap}; + +fn main() { + let get_key = |(key, _val)| key; + + let map: HashMap = HashMap::new(); + + let _ = map.iter().map(|(key, _)| key).collect::>(); + let _ = map.iter().map(|(_, value)| value).collect::>(); + let _ = map.iter().map(|(_, v)| v + 2).collect::>(); + + let _ = map.clone().into_iter().map(|(key, _)| key).collect::>(); + let _ = map.clone().into_iter().map(|(key, _)| key + 2).collect::>(); + + let _ = map.clone().into_iter().map(|(_, val)| val).collect::>(); + let _ = map.clone().into_iter().map(|(_, val)| val + 2).collect::>(); + + let _ = map.clone().iter().map(|(_, val)| val).collect::>(); + let _ = map.iter().map(|(key, _)| key).filter(|x| *x % 2 == 0).count(); + + // Don't lint + let _ = map.iter().filter(|(_, val)| *val % 2 == 0).map(|(key, _)| key).count(); + let _ = map.iter().map(get_key).collect::>(); + + // Linting the following could be an improvement to the lint + // map.iter().filter_map(|(_, val)| (val % 2 == 0).then(val * 17)).count(); + + // Lint + let _ = map.iter().map(|(key, _value)| key * 9).count(); + let _ = map.iter().map(|(_key, value)| value * 17).count(); + + let map: BTreeMap = BTreeMap::new(); + + let _ = map.iter().map(|(key, _)| key).collect::>(); + let _ = map.iter().map(|(_, value)| value).collect::>(); + let _ = map.iter().map(|(_, v)| v + 2).collect::>(); + + let _ = map.clone().into_iter().map(|(key, _)| key).collect::>(); + let _ = map.clone().into_iter().map(|(key, _)| key + 2).collect::>(); + + let _ = map.clone().into_iter().map(|(_, val)| val).collect::>(); + let _ = map.clone().into_iter().map(|(_, val)| val + 2).collect::>(); + + let _ = map.clone().iter().map(|(_, val)| val).collect::>(); + let _ = map.iter().map(|(key, _)| key).filter(|x| *x % 2 == 0).count(); + + // Don't lint + let _ = map.iter().filter(|(_, val)| *val % 2 == 0).map(|(key, _)| key).count(); + let _ = map.iter().map(get_key).collect::>(); + + // Linting the following could be an improvement to the lint + // map.iter().filter_map(|(_, val)| (val % 2 == 0).then(val * 17)).count(); + + // Lint + let _ = map.iter().map(|(key, _value)| key * 9).count(); + let _ = map.iter().map(|(_key, value)| value * 17).count(); +} diff --git a/tests/ui/iter_kv_map.stderr b/tests/ui/iter_kv_map.stderr new file mode 100644 index 00000000000..9b9b04c97d8 --- /dev/null +++ b/tests/ui/iter_kv_map.stderr @@ -0,0 +1,136 @@ +error: iterating on a map's keys + --> $DIR/iter_kv_map.rs:15:13 + | +LL | let _ = map.iter().map(|(key, _)| key).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.keys()` + | + = note: `-D clippy::iter-kv-map` implied by `-D warnings` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:16:13 + | +LL | let _ = map.iter().map(|(_, value)| value).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.values()` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:17:13 + | +LL | let _ = map.iter().map(|(_, v)| v + 2).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.values().map(|v| v + 2)` + +error: iterating on a map's keys + --> $DIR/iter_kv_map.rs:19:13 + | +LL | let _ = map.clone().into_iter().map(|(key, _)| key).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.clone().into_keys()` + +error: iterating on a map's keys + --> $DIR/iter_kv_map.rs:20:13 + | +LL | let _ = map.clone().into_iter().map(|(key, _)| key + 2).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.clone().into_keys().map(|key| key + 2)` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:22:13 + | +LL | let _ = map.clone().into_iter().map(|(_, val)| val).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.clone().into_values()` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:23:13 + | +LL | let _ = map.clone().into_iter().map(|(_, val)| val + 2).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.clone().into_values().map(|val| val + 2)` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:25:13 + | +LL | let _ = map.clone().iter().map(|(_, val)| val).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.clone().values()` + +error: iterating on a map's keys + --> $DIR/iter_kv_map.rs:26:13 + | +LL | let _ = map.iter().map(|(key, _)| key).filter(|x| *x % 2 == 0).count(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.keys()` + +error: iterating on a map's keys + --> $DIR/iter_kv_map.rs:36:13 + | +LL | let _ = map.iter().map(|(key, _value)| key * 9).count(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.keys().map(|key| key * 9)` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:37:13 + | +LL | let _ = map.iter().map(|(_key, value)| value * 17).count(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.values().map(|value| value * 17)` + +error: iterating on a map's keys + --> $DIR/iter_kv_map.rs:41:13 + | +LL | let _ = map.iter().map(|(key, _)| key).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.keys()` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:42:13 + | +LL | let _ = map.iter().map(|(_, value)| value).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.values()` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:43:13 + | +LL | let _ = map.iter().map(|(_, v)| v + 2).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.values().map(|v| v + 2)` + +error: iterating on a map's keys + --> $DIR/iter_kv_map.rs:45:13 + | +LL | let _ = map.clone().into_iter().map(|(key, _)| key).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.clone().into_keys()` + +error: iterating on a map's keys + --> $DIR/iter_kv_map.rs:46:13 + | +LL | let _ = map.clone().into_iter().map(|(key, _)| key + 2).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.clone().into_keys().map(|key| key + 2)` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:48:13 + | +LL | let _ = map.clone().into_iter().map(|(_, val)| val).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.clone().into_values()` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:49:13 + | +LL | let _ = map.clone().into_iter().map(|(_, val)| val + 2).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.clone().into_values().map(|val| val + 2)` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:51:13 + | +LL | let _ = map.clone().iter().map(|(_, val)| val).collect::>(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.clone().values()` + +error: iterating on a map's keys + --> $DIR/iter_kv_map.rs:52:13 + | +LL | let _ = map.iter().map(|(key, _)| key).filter(|x| *x % 2 == 0).count(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.keys()` + +error: iterating on a map's keys + --> $DIR/iter_kv_map.rs:62:13 + | +LL | let _ = map.iter().map(|(key, _value)| key * 9).count(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.keys().map(|key| key * 9)` + +error: iterating on a map's values + --> $DIR/iter_kv_map.rs:63:13 + | +LL | let _ = map.iter().map(|(_key, value)| value * 17).count(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map.values().map(|value| value * 17)` + +error: aborting due to 22 previous errors +