diff options
| -rw-r--r-- | CHANGELOG.md | 1 | ||||
| -rw-r--r-- | clippy_lints/src/lib.rs | 3 | ||||
| -rw-r--r-- | clippy_lints/src/ranges.rs | 112 | ||||
| -rw-r--r-- | tests/ui/reversed_empty_ranges_fixable.fixed | 24 | ||||
| -rw-r--r-- | tests/ui/reversed_empty_ranges_fixable.rs | 24 | ||||
| -rw-r--r-- | tests/ui/reversed_empty_ranges_fixable.stderr | 47 | ||||
| -rw-r--r-- | tests/ui/reversed_empty_ranges_unfixable.rs | 15 | ||||
| -rw-r--r-- | tests/ui/reversed_empty_ranges_unfixable.stderr | 34 |
8 files changed, 258 insertions, 2 deletions
diff --git a/CHANGELOG.md b/CHANGELOG.md index 8457d6ad05c..33b277fbd31 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -1546,6 +1546,7 @@ Released 2018-09-13 [`result_map_unwrap_or_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_map_unwrap_or_else [`result_unwrap_used`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_unwrap_used [`reverse_range_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#reverse_range_loop +[`reversed_empty_ranges`]: https://rust-lang.github.io/rust-clippy/master/index.html#reversed_empty_ranges [`same_functions_in_if_condition`]: https://rust-lang.github.io/rust-clippy/master/index.html#same_functions_in_if_condition [`search_is_some`]: https://rust-lang.github.io/rust-clippy/master/index.html#search_is_some [`serde_api_misuse`]: https://rust-lang.github.io/rust-clippy/master/index.html#serde_api_misuse diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index 51b5401da7d..e1cb10a4651 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -770,6 +770,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: &ranges::RANGE_MINUS_ONE, &ranges::RANGE_PLUS_ONE, &ranges::RANGE_ZIP_WITH_LEN, + &ranges::REVERSED_EMPTY_RANGES, &redundant_clone::REDUNDANT_CLONE, &redundant_field_names::REDUNDANT_FIELD_NAMES, &redundant_pattern_matching::REDUNDANT_PATTERN_MATCHING, @@ -1384,6 +1385,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&question_mark::QUESTION_MARK), LintId::of(&ranges::RANGE_MINUS_ONE), LintId::of(&ranges::RANGE_ZIP_WITH_LEN), + LintId::of(&ranges::REVERSED_EMPTY_RANGES), LintId::of(&redundant_clone::REDUNDANT_CLONE), LintId::of(&redundant_field_names::REDUNDANT_FIELD_NAMES), LintId::of(&redundant_pattern_matching::REDUNDANT_PATTERN_MATCHING), @@ -1675,6 +1677,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&open_options::NONSENSICAL_OPEN_OPTIONS), LintId::of(&option_env_unwrap::OPTION_ENV_UNWRAP), LintId::of(&ptr::MUT_FROM_REF), + LintId::of(&ranges::REVERSED_EMPTY_RANGES), LintId::of(®ex::INVALID_REGEX), LintId::of(&serde_api::SERDE_API_MISUSE), LintId::of(&suspicious_trait_impl::SUSPICIOUS_ARITHMETIC_IMPL), diff --git a/clippy_lints/src/ranges.rs b/clippy_lints/src/ranges.rs index d7ce2e66d69..86d55ccabb6 100644 --- a/clippy_lints/src/ranges.rs +++ b/clippy_lints/src/ranges.rs @@ -1,14 +1,17 @@ +use crate::consts::{constant, Constant}; use if_chain::if_chain; use rustc_ast::ast::RangeLimits; use rustc_errors::Applicability; use rustc_hir::{BinOpKind, Expr, ExprKind, QPath}; use rustc_lint::{LateContext, LateLintPass}; +use rustc_middle::ty; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::source_map::Spanned; +use std::cmp::Ordering; use crate::utils::sugg::Sugg; +use crate::utils::{get_parent_expr, is_integer_const, snippet, snippet_opt, span_lint, span_lint_and_then}; use crate::utils::{higher, SpanlessEq}; -use crate::utils::{is_integer_const, snippet, snippet_opt, span_lint, span_lint_and_then}; declare_clippy_lint! { /// **What it does:** Checks for zipping a collection with the range of @@ -84,10 +87,44 @@ declare_clippy_lint! { "`x..=(y-1)` reads better as `x..y`" } +declare_clippy_lint! { + /// **What it does:** Checks for range expressions `x..y` where both `x` and `y` + /// are constant and `x` is greater or equal to `y`. + /// + /// **Why is this bad?** Empty ranges yield no values so iterating them is a no-op. + /// Moreover, trying to use a reversed range to index a slice will panic at run-time. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// + /// ```rust + /// fn main() { + /// (10..=0).for_each(|x| println!("{}", x)); + /// + /// let arr = [1, 2, 3, 4, 5]; + /// let sub = &arr[3..1]; + /// } + /// ``` + /// Use instead: + /// ```rust + /// fn main() { + /// (0..=10).rev().for_each(|x| println!("{}", x)); + /// + /// let arr = [1, 2, 3, 4, 5]; + /// let sub = &arr[1..3]; + /// } + /// ``` + pub REVERSED_EMPTY_RANGES, + correctness, + "reversing the limits of range expressions, resulting in empty ranges" +} + declare_lint_pass!(Ranges => [ RANGE_ZIP_WITH_LEN, RANGE_PLUS_ONE, - RANGE_MINUS_ONE + RANGE_MINUS_ONE, + REVERSED_EMPTY_RANGES, ]); impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Ranges { @@ -124,6 +161,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Ranges { check_exclusive_range_plus_one(cx, expr); check_inclusive_range_minus_one(cx, expr); + check_reversed_empty_range(cx, expr); } } @@ -202,6 +240,76 @@ fn check_inclusive_range_minus_one(cx: &LateContext<'_, '_>, expr: &Expr<'_>) { } } +fn check_reversed_empty_range(cx: &LateContext<'_, '_>, expr: &Expr<'_>) { + fn inside_indexing_expr(cx: &LateContext<'_, '_>, expr: &Expr<'_>) -> bool { + matches!( + get_parent_expr(cx, expr), + Some(Expr { + kind: ExprKind::Index(..), + .. + }) + ) + } + + fn is_empty_range(limits: RangeLimits, ordering: Ordering) -> bool { + match limits { + RangeLimits::HalfOpen => ordering != Ordering::Less, + RangeLimits::Closed => ordering == Ordering::Greater, + } + } + + if_chain! { + if let Some(higher::Range { start: Some(start), end: Some(end), limits }) = higher::range(cx, expr); + let ty = cx.tables.expr_ty(start); + if let ty::Int(_) | ty::Uint(_) = ty.kind; + if let Some((start_idx, _)) = constant(cx, cx.tables, start); + if let Some((end_idx, _)) = constant(cx, cx.tables, end); + if let Some(ordering) = Constant::partial_cmp(cx.tcx, ty, &start_idx, &end_idx); + if is_empty_range(limits, ordering); + then { + if inside_indexing_expr(cx, expr) { + let (reason, outcome) = if ordering == Ordering::Equal { + ("empty", "always yield an empty slice") + } else { + ("reversed", "panic at run-time") + }; + + span_lint( + cx, + REVERSED_EMPTY_RANGES, + expr.span, + &format!("this range is {} and using it to index a slice will {}", reason, outcome), + ); + } else { + span_lint_and_then( + cx, + REVERSED_EMPTY_RANGES, + expr.span, + "this range is empty so it will yield no values", + |diag| { + if ordering != Ordering::Equal { + let start_snippet = snippet(cx, start.span, "_"); + let end_snippet = snippet(cx, end.span, "_"); + let dots = match limits { + RangeLimits::HalfOpen => "..", + RangeLimits::Closed => "..=" + }; + + diag.span_suggestion( + expr.span, + "consider using the following if you are attempting to iterate over this \ + range in reverse", + format!("({}{}{}).rev()", end_snippet, dots, start_snippet), + Applicability::MaybeIncorrect, + ); + } + }, + ); + } + } + } +} + fn y_plus_one<'t>(cx: &LateContext<'_, '_>, expr: &'t Expr<'_>) -> Option<&'t Expr<'t>> { match expr.kind { ExprKind::Binary( diff --git a/tests/ui/reversed_empty_ranges_fixable.fixed b/tests/ui/reversed_empty_ranges_fixable.fixed new file mode 100644 index 00000000000..ee2cbc3cf54 --- /dev/null +++ b/tests/ui/reversed_empty_ranges_fixable.fixed @@ -0,0 +1,24 @@ +// run-rustfix +#![warn(clippy::reversed_empty_ranges)] + +const ANSWER: i32 = 42; + +fn main() { + (21..=42).rev().for_each(|x| println!("{}", x)); + let _ = (21..ANSWER).rev().filter(|x| x % 2 == 0).take(10).collect::<Vec<_>>(); + + for _ in (-42..=-21).rev() {} + for _ in (21u32..42u32).rev() {} + + // These should be ignored as they are not empty ranges: + + (21..=42).for_each(|x| println!("{}", x)); + (21..42).for_each(|x| println!("{}", x)); + + let arr = [1, 2, 3, 4, 5]; + let _ = &arr[1..=3]; + let _ = &arr[1..3]; + + for _ in 21..=42 {} + for _ in 21..42 {} +} diff --git a/tests/ui/reversed_empty_ranges_fixable.rs b/tests/ui/reversed_empty_ranges_fixable.rs new file mode 100644 index 00000000000..6ed5ca6daa0 --- /dev/null +++ b/tests/ui/reversed_empty_ranges_fixable.rs @@ -0,0 +1,24 @@ +// run-rustfix +#![warn(clippy::reversed_empty_ranges)] + +const ANSWER: i32 = 42; + +fn main() { + (42..=21).for_each(|x| println!("{}", x)); + let _ = (ANSWER..21).filter(|x| x % 2 == 0).take(10).collect::<Vec<_>>(); + + for _ in -21..=-42 {} + for _ in 42u32..21u32 {} + + // These should be ignored as they are not empty ranges: + + (21..=42).for_each(|x| println!("{}", x)); + (21..42).for_each(|x| println!("{}", x)); + + let arr = [1, 2, 3, 4, 5]; + let _ = &arr[1..=3]; + let _ = &arr[1..3]; + + for _ in 21..=42 {} + for _ in 21..42 {} +} diff --git a/tests/ui/reversed_empty_ranges_fixable.stderr b/tests/ui/reversed_empty_ranges_fixable.stderr new file mode 100644 index 00000000000..97933b8ff85 --- /dev/null +++ b/tests/ui/reversed_empty_ranges_fixable.stderr @@ -0,0 +1,47 @@ +error: this range is empty so it will yield no values + --> $DIR/reversed_empty_ranges_fixable.rs:7:5 + | +LL | (42..=21).for_each(|x| println!("{}", x)); + | ^^^^^^^^^ + | + = note: `-D clippy::reversed-empty-ranges` implied by `-D warnings` +help: consider using the following if you are attempting to iterate over this range in reverse + | +LL | (21..=42).rev().for_each(|x| println!("{}", x)); + | ^^^^^^^^^^^^^^^ + +error: this range is empty so it will yield no values + --> $DIR/reversed_empty_ranges_fixable.rs:8:13 + | +LL | let _ = (ANSWER..21).filter(|x| x % 2 == 0).take(10).collect::<Vec<_>>(); + | ^^^^^^^^^^^^ + | +help: consider using the following if you are attempting to iterate over this range in reverse + | +LL | let _ = (21..ANSWER).rev().filter(|x| x % 2 == 0).take(10).collect::<Vec<_>>(); + | ^^^^^^^^^^^^^^^^^^ + +error: this range is empty so it will yield no values + --> $DIR/reversed_empty_ranges_fixable.rs:10:14 + | +LL | for _ in -21..=-42 {} + | ^^^^^^^^^ + | +help: consider using the following if you are attempting to iterate over this range in reverse + | +LL | for _ in (-42..=-21).rev() {} + | ^^^^^^^^^^^^^^^^^ + +error: this range is empty so it will yield no values + --> $DIR/reversed_empty_ranges_fixable.rs:11:14 + | +LL | for _ in 42u32..21u32 {} + | ^^^^^^^^^^^^ + | +help: consider using the following if you are attempting to iterate over this range in reverse + | +LL | for _ in (21u32..42u32).rev() {} + | ^^^^^^^^^^^^^^^^^^^^ + +error: aborting due to 4 previous errors + diff --git a/tests/ui/reversed_empty_ranges_unfixable.rs b/tests/ui/reversed_empty_ranges_unfixable.rs new file mode 100644 index 00000000000..c9ca4c47668 --- /dev/null +++ b/tests/ui/reversed_empty_ranges_unfixable.rs @@ -0,0 +1,15 @@ +#![warn(clippy::reversed_empty_ranges)] + +const ANSWER: i32 = 42; +const SOME_NUM: usize = 3; + +fn main() { + let _ = (42 + 10..42 + 10).map(|x| x / 2).find(|&x| x == 21); + + let arr = [1, 2, 3, 4, 5]; + let _ = &arr[3usize..=1usize]; + let _ = &arr[SOME_NUM..1]; + let _ = &arr[3..3]; + + for _ in ANSWER..ANSWER {} +} diff --git a/tests/ui/reversed_empty_ranges_unfixable.stderr b/tests/ui/reversed_empty_ranges_unfixable.stderr new file mode 100644 index 00000000000..12e5483ecdf --- /dev/null +++ b/tests/ui/reversed_empty_ranges_unfixable.stderr @@ -0,0 +1,34 @@ +error: this range is empty so it will yield no values + --> $DIR/reversed_empty_ranges_unfixable.rs:7:13 + | +LL | let _ = (42 + 10..42 + 10).map(|x| x / 2).find(|&x| x == 21); + | ^^^^^^^^^^^^^^^^^^ + | + = note: `-D clippy::reversed-empty-ranges` implied by `-D warnings` + +error: this range is reversed and using it to index a slice will panic at run-time + --> $DIR/reversed_empty_ranges_unfixable.rs:10:18 + | +LL | let _ = &arr[3usize..=1usize]; + | ^^^^^^^^^^^^^^^ + +error: this range is reversed and using it to index a slice will panic at run-time + --> $DIR/reversed_empty_ranges_unfixable.rs:11:18 + | +LL | let _ = &arr[SOME_NUM..1]; + | ^^^^^^^^^^^ + +error: this range is empty and using it to index a slice will always yield an empty slice + --> $DIR/reversed_empty_ranges_unfixable.rs:12:18 + | +LL | let _ = &arr[3..3]; + | ^^^^ + +error: this range is empty so it will yield no values + --> $DIR/reversed_empty_ranges_unfixable.rs:14:14 + | +LL | for _ in ANSWER..ANSWER {} + | ^^^^^^^^^^^^^^ + +error: aborting due to 5 previous errors + |