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new lint: iter_out_of_bounds
#11396
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new lint: iter_out_of_bounds
#11396
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,106 @@ | ||
| use clippy_utils::diagnostics::span_lint_and_note; | ||
| use clippy_utils::higher::VecArgs; | ||
| use clippy_utils::{expr_or_init, is_trait_method, match_def_path, paths}; | ||
| use rustc_ast::LitKind; | ||
| use rustc_hir::{Expr, ExprKind}; | ||
| use rustc_lint::LateContext; | ||
| use rustc_middle::ty::{self}; | ||
| use rustc_span::sym; | ||
|
|
||
| use super::ITER_OUT_OF_BOUNDS; | ||
|
|
||
| fn expr_as_u128(cx: &LateContext<'_>, e: &Expr<'_>) -> Option<u128> { | ||
| if let ExprKind::Lit(lit) = expr_or_init(cx, e).kind | ||
| && let LitKind::Int(n, _) = lit.node | ||
| { | ||
| Some(n) | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
|
|
||
| /// Attempts to extract the length out of an iterator expression. | ||
| fn get_iterator_length<'tcx>(cx: &LateContext<'tcx>, iter: &'tcx Expr<'tcx>) -> Option<u128> { | ||
| let ty::Adt(adt, substs) = cx.typeck_results().expr_ty(iter).kind() else { | ||
| return None; | ||
| }; | ||
| let did = adt.did(); | ||
|
|
||
| if match_def_path(cx, did, &paths::ARRAY_INTO_ITER) { | ||
| // For array::IntoIter<T, const N: usize>, the length is the second generic | ||
| // parameter. | ||
| substs | ||
| .const_at(1) | ||
| .try_eval_target_usize(cx.tcx, cx.param_env) | ||
| .map(u128::from) | ||
| } else if match_def_path(cx, did, &paths::SLICE_ITER) | ||
| && let ExprKind::MethodCall(_, recv, ..) = iter.kind | ||
| { | ||
| if let ty::Array(_, len) = cx.typeck_results().expr_ty(recv).peel_refs().kind() { | ||
| // For slice::Iter<'_, T>, the receiver might be an array literal: [1,2,3].iter().skip(..) | ||
| len.try_eval_target_usize(cx.tcx, cx.param_env).map(u128::from) | ||
| } else if let Some(args) = VecArgs::hir(cx, expr_or_init(cx, recv)) { | ||
| match args { | ||
| VecArgs::Vec(vec) => vec.len().try_into().ok(), | ||
| VecArgs::Repeat(_, len) => expr_as_u128(cx, len), | ||
| } | ||
| } else { | ||
| None | ||
| } | ||
| } else if match_def_path(cx, did, &paths::ITER_EMPTY) { | ||
| Some(0) | ||
| } else if match_def_path(cx, did, &paths::ITER_ONCE) { | ||
| Some(1) | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
|
|
||
| fn check<'tcx>( | ||
| cx: &LateContext<'tcx>, | ||
| expr: &'tcx Expr<'tcx>, | ||
| recv: &'tcx Expr<'tcx>, | ||
| arg: &'tcx Expr<'tcx>, | ||
| message: &'static str, | ||
| note: &'static str, | ||
| ) { | ||
| if is_trait_method(cx, expr, sym::Iterator) | ||
| && let Some(len) = get_iterator_length(cx, recv) | ||
| && let Some(skipped) = expr_as_u128(cx, arg) | ||
| && skipped > len | ||
| { | ||
| span_lint_and_note(cx, ITER_OUT_OF_BOUNDS, expr.span, message, None, note); | ||
| } | ||
| } | ||
|
|
||
| pub(super) fn check_skip<'tcx>( | ||
| cx: &LateContext<'tcx>, | ||
| expr: &'tcx Expr<'tcx>, | ||
| recv: &'tcx Expr<'tcx>, | ||
| arg: &'tcx Expr<'tcx>, | ||
| ) { | ||
| check( | ||
| cx, | ||
| expr, | ||
| recv, | ||
| arg, | ||
| "this `.skip()` call skips more items than the iterator will produce", | ||
| "this operation is useless and will create an empty iterator", | ||
| ); | ||
| } | ||
|
|
||
| pub(super) fn check_take<'tcx>( | ||
| cx: &LateContext<'tcx>, | ||
| expr: &'tcx Expr<'tcx>, | ||
| recv: &'tcx Expr<'tcx>, | ||
| arg: &'tcx Expr<'tcx>, | ||
| ) { | ||
| check( | ||
| cx, | ||
| expr, | ||
| recv, | ||
| arg, | ||
| "this `.take()` call takes more items than the iterator will produce", | ||
| "this operation is useless and the returned iterator will simply yield the same items", | ||
| ); | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,70 @@ | ||
| //@no-rustfix | ||
|
|
||
| #![deny(clippy::iter_out_of_bounds)] | ||
| #![allow(clippy::useless_vec)] | ||
|
|
||
| fn opaque_empty_iter() -> impl Iterator<Item = ()> { | ||
| std::iter::empty() | ||
| } | ||
|
|
||
| fn main() { | ||
| for _ in [1, 2, 3].iter().skip(4) { | ||
| //~^ ERROR: this `.skip()` call skips more items than the iterator will produce | ||
| unreachable!(); | ||
| } | ||
| for (i, _) in [1, 2, 3].iter().take(4).enumerate() { | ||
| //~^ ERROR: this `.take()` call takes more items than the iterator will produce | ||
| assert!(i <= 2); | ||
| } | ||
|
|
||
| #[allow(clippy::needless_borrow)] | ||
| for _ in (&&&&&&[1, 2, 3]).iter().take(4) {} | ||
| //~^ ERROR: this `.take()` call takes more items than the iterator will produce | ||
|
|
||
| for _ in [1, 2, 3].iter().skip(4) {} | ||
| //~^ ERROR: this `.skip()` call skips more items than the iterator will produce | ||
|
|
||
| for _ in [1; 3].iter().skip(4) {} | ||
| //~^ ERROR: this `.skip()` call skips more items than the iterator will produce | ||
|
|
||
| // Should not lint | ||
| for _ in opaque_empty_iter().skip(1) {} | ||
|
|
||
| for _ in vec![1, 2, 3].iter().skip(4) {} | ||
| //~^ ERROR: this `.skip()` call skips more items than the iterator will produce | ||
|
|
||
| for _ in vec![1; 3].iter().skip(4) {} | ||
| //~^ ERROR: this `.skip()` call skips more items than the iterator will produce | ||
|
|
||
| let x = [1, 2, 3]; | ||
| for _ in x.iter().skip(4) {} | ||
| //~^ ERROR: this `.skip()` call skips more items than the iterator will produce | ||
|
|
||
| let n = 4; | ||
| for _ in x.iter().skip(n) {} | ||
| //~^ ERROR: this `.skip()` call skips more items than the iterator will produce | ||
|
|
||
| let empty = std::iter::empty::<i8>; | ||
|
|
||
| for _ in empty().skip(1) {} | ||
| //~^ ERROR: this `.skip()` call skips more items than the iterator will produce | ||
|
|
||
| for _ in empty().take(1) {} | ||
| //~^ ERROR: this `.take()` call takes more items than the iterator will produce | ||
|
|
||
| for _ in std::iter::once(1).skip(2) {} | ||
| //~^ ERROR: this `.skip()` call skips more items than the iterator will produce | ||
|
|
||
| for _ in std::iter::once(1).take(2) {} | ||
| //~^ ERROR: this `.take()` call takes more items than the iterator will produce | ||
|
|
||
| for x in [].iter().take(1) { | ||
| //~^ ERROR: this `.take()` call takes more items than the iterator will produce | ||
| let _: &i32 = x; | ||
| } | ||
|
|
||
| // ok, not out of bounds | ||
| for _ in [1].iter().take(1) {} | ||
| for _ in [1, 2, 3].iter().take(2) {} | ||
| for _ in [1, 2, 3].iter().skip(2) {} | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,119 @@ | ||
| error: this `.skip()` call skips more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:11:14 | ||
| | | ||
| LL | for _ in [1, 2, 3].iter().skip(4) { | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and will create an empty iterator | ||
| note: the lint level is defined here | ||
| --> $DIR/iter_out_of_bounds.rs:3:9 | ||
| | | ||
| LL | #![deny(clippy::iter_out_of_bounds)] | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
|
|
||
| error: this `.take()` call takes more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:15:19 | ||
| | | ||
| LL | for (i, _) in [1, 2, 3].iter().take(4).enumerate() { | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and the returned iterator will simply yield the same items | ||
|
|
||
| error: this `.take()` call takes more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:21:14 | ||
| | | ||
| LL | for _ in (&&&&&&[1, 2, 3]).iter().take(4) {} | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and the returned iterator will simply yield the same items | ||
|
|
||
| error: this `.skip()` call skips more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:24:14 | ||
| | | ||
| LL | for _ in [1, 2, 3].iter().skip(4) {} | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and will create an empty iterator | ||
|
|
||
| error: this `.skip()` call skips more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:27:14 | ||
| | | ||
| LL | for _ in [1; 3].iter().skip(4) {} | ||
| | ^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and will create an empty iterator | ||
|
|
||
| error: this `.skip()` call skips more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:33:14 | ||
| | | ||
| LL | for _ in vec![1, 2, 3].iter().skip(4) {} | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and will create an empty iterator | ||
|
|
||
| error: this `.skip()` call skips more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:36:14 | ||
| | | ||
| LL | for _ in vec![1; 3].iter().skip(4) {} | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and will create an empty iterator | ||
|
|
||
| error: this `.skip()` call skips more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:40:14 | ||
| | | ||
| LL | for _ in x.iter().skip(4) {} | ||
| | ^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and will create an empty iterator | ||
|
|
||
| error: this `.skip()` call skips more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:44:14 | ||
| | | ||
| LL | for _ in x.iter().skip(n) {} | ||
| | ^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and will create an empty iterator | ||
|
|
||
| error: this `.skip()` call skips more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:49:14 | ||
| | | ||
| LL | for _ in empty().skip(1) {} | ||
| | ^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and will create an empty iterator | ||
|
|
||
| error: this `.take()` call takes more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:52:14 | ||
| | | ||
| LL | for _ in empty().take(1) {} | ||
| | ^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and the returned iterator will simply yield the same items | ||
|
|
||
| error: this `.skip()` call skips more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:55:14 | ||
| | | ||
| LL | for _ in std::iter::once(1).skip(2) {} | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and will create an empty iterator | ||
|
|
||
| error: this `.take()` call takes more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:58:14 | ||
| | | ||
| LL | for _ in std::iter::once(1).take(2) {} | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and the returned iterator will simply yield the same items | ||
|
|
||
| error: this `.take()` call takes more items than the iterator will produce | ||
| --> $DIR/iter_out_of_bounds.rs:61:14 | ||
| | | ||
| LL | for x in [].iter().take(1) { | ||
| | ^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: this operation is useless and the returned iterator will simply yield the same items | ||
|
|
||
| error: aborting due to 14 previous errors | ||
|
|
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This really should have a
MaybeIncorrectsuggestion added to it.There was a problem hiding this comment.
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I'm not sure what the suggestion should be or if it makes sense to have one. At least for something like
[1,2,3].iter().take(4)it could probably suggest removing the.take()call as that'll still yield the same items with or without it, but I don't know what the user could have meant with[1,2,3].iter().skip(4). Should it suggest and empty iterator? 🤔There was a problem hiding this comment.
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I was only considering
takehere. Given the suggestion isn't going to have a lot of value (decent chance of being the wrong fix), I guess it's fine to not have one.