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Diffstat (limited to 'clippy_lints/src/tuple_array_conversions.rs')
| -rw-r--r-- | clippy_lints/src/tuple_array_conversions.rs | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/clippy_lints/src/tuple_array_conversions.rs b/clippy_lints/src/tuple_array_conversions.rs new file mode 100644 index 00000000000..bd983306508 --- /dev/null +++ b/clippy_lints/src/tuple_array_conversions.rs @@ -0,0 +1,235 @@ +use clippy_utils::{ + diagnostics::span_lint_and_help, + is_from_proc_macro, + msrvs::{self, Msrv}, + path_to_local, +}; +use rustc_ast::LitKind; +use rustc_hir::{Expr, ExprKind, HirId, Node, Pat}; +use rustc_lint::{LateContext, LateLintPass, LintContext}; +use rustc_middle::{lint::in_external_macro, ty}; +use rustc_session::{declare_tool_lint, impl_lint_pass}; +use std::iter::once; + +declare_clippy_lint! { + /// ### What it does + /// Checks for tuple<=>array conversions that are not done with `.into()`. + /// + /// ### Why is this bad? + /// It's unnecessary complexity. `.into()` works for tuples<=>arrays at or below 12 elements and + /// conveys the intent a lot better, while also leaving less room for hard to spot bugs! + /// + /// ### Example + /// ```rust,ignore + /// let t1 = &[(1, 2), (3, 4)]; + /// let v1: Vec<[u32; 2]> = t1.iter().map(|&(a, b)| [a, b]).collect(); + /// ``` + /// Use instead: + /// ```rust,ignore + /// let t1 = &[(1, 2), (3, 4)]; + /// let v1: Vec<[u32; 2]> = t1.iter().map(|&t| t.into()).collect(); + /// ``` + #[clippy::version = "1.72.0"] + pub TUPLE_ARRAY_CONVERSIONS, + complexity, + "checks for tuple<=>array conversions that are not done with `.into()`" +} +impl_lint_pass!(TupleArrayConversions => [TUPLE_ARRAY_CONVERSIONS]); + +#[derive(Clone)] +pub struct TupleArrayConversions { + pub msrv: Msrv, +} + +impl LateLintPass<'_> for TupleArrayConversions { + fn check_expr<'tcx>(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) { + if !in_external_macro(cx.sess(), expr.span) && self.msrv.meets(msrvs::TUPLE_ARRAY_CONVERSIONS) { + match expr.kind { + ExprKind::Array(elements) if (1..=12).contains(&elements.len()) => check_array(cx, expr, elements), + ExprKind::Tup(elements) if (1..=12).contains(&elements.len()) => check_tuple(cx, expr, elements), + _ => {}, + } + } + } + + extract_msrv_attr!(LateContext); +} + +#[expect( + clippy::blocks_in_if_conditions, + reason = "not a FP, but this is much easier to understand" +)] +fn check_array<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, elements: &'tcx [Expr<'tcx>]) { + if should_lint( + cx, + elements, + // This is cursed. + Some, + |(first_id, local)| { + if let Node::Pat(pat) = local + && let parent = parent_pat(cx, pat) + && parent.hir_id == first_id + { + return matches!( + cx.typeck_results().pat_ty(parent).peel_refs().kind(), + ty::Tuple(len) if len.len() == elements.len() + ); + } + + false + }, + ) || should_lint( + cx, + elements, + |(i, expr)| { + if let ExprKind::Field(path, field) = expr.kind && field.as_str() == i.to_string() { + return Some((i, path)); + }; + + None + }, + |(first_id, local)| { + if let Node::Pat(pat) = local + && let parent = parent_pat(cx, pat) + && parent.hir_id == first_id + { + return matches!( + cx.typeck_results().pat_ty(parent).peel_refs().kind(), + ty::Tuple(len) if len.len() == elements.len() + ); + } + + false + }, + ) { + emit_lint(cx, expr, ToType::Array); + } +} + +#[expect( + clippy::blocks_in_if_conditions, + reason = "not a FP, but this is much easier to understand" +)] +#[expect(clippy::cast_possible_truncation)] +fn check_tuple<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, elements: &'tcx [Expr<'tcx>]) { + if should_lint(cx, elements, Some, |(first_id, local)| { + if let Node::Pat(pat) = local + && let parent = parent_pat(cx, pat) + && parent.hir_id == first_id + { + return matches!( + cx.typeck_results().pat_ty(parent).peel_refs().kind(), + ty::Array(_, len) if len.eval_target_usize(cx.tcx, cx.param_env) as usize == elements.len() + ); + } + + false + }) || should_lint( + cx, + elements, + |(i, expr)| { + if let ExprKind::Index(path, index) = expr.kind + && let ExprKind::Lit(lit) = index.kind + && let LitKind::Int(val, _) = lit.node + && val as usize == i + { + return Some((i, path)); + }; + + None + }, + |(first_id, local)| { + if let Node::Pat(pat) = local + && let parent = parent_pat(cx, pat) + && parent.hir_id == first_id + { + return matches!( + cx.typeck_results().pat_ty(parent).peel_refs().kind(), + ty::Array(_, len) if len.eval_target_usize(cx.tcx, cx.param_env) as usize == elements.len() + ); + } + + false + }, + ) { + emit_lint(cx, expr, ToType::Tuple); + } +} + +/// Walks up the `Pat` until it's reached the final containing `Pat`. +fn parent_pat<'tcx>(cx: &LateContext<'tcx>, start: &'tcx Pat<'tcx>) -> &'tcx Pat<'tcx> { + let mut end = start; + for (_, node) in cx.tcx.hir().parent_iter(start.hir_id) { + if let Node::Pat(pat) = node { + end = pat; + } else { + break; + } + } + end +} + +#[derive(Clone, Copy)] +enum ToType { + Array, + Tuple, +} + +impl ToType { + fn msg(self) -> &'static str { + match self { + ToType::Array => "it looks like you're trying to convert a tuple to an array", + ToType::Tuple => "it looks like you're trying to convert an array to a tuple", + } + } + + fn help(self) -> &'static str { + match self { + ToType::Array => "use `.into()` instead, or `<[T; N]>::from` if type annotations are needed", + ToType::Tuple => "use `.into()` instead, or `<(T0, T1, ..., Tn)>::from` if type annotations are needed", + } + } +} + +fn emit_lint<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, to_type: ToType) -> bool { + if !is_from_proc_macro(cx, expr) { + span_lint_and_help( + cx, + TUPLE_ARRAY_CONVERSIONS, + expr.span, + to_type.msg(), + None, + to_type.help(), + ); + + return true; + } + + false +} + +fn should_lint<'tcx>( + cx: &LateContext<'tcx>, + elements: &'tcx [Expr<'tcx>], + map: impl FnMut((usize, &'tcx Expr<'tcx>)) -> Option<(usize, &Expr<'_>)>, + predicate: impl FnMut((HirId, &Node<'tcx>)) -> bool, +) -> bool { + if let Some(elements) = elements + .iter() + .enumerate() + .map(map) + .collect::<Option<Vec<_>>>() + && let Some(locals) = elements + .iter() + .map(|(_, element)| path_to_local(element).and_then(|local| cx.tcx.hir().find(local))) + .collect::<Option<Vec<_>>>() + && let [first, rest @ ..] = &*locals + && let Node::Pat(first_pat) = first + && let parent = parent_pat(cx, first_pat).hir_id + && rest.iter().chain(once(first)).map(|i| (parent, i)).all(predicate) + { + return true; + } + + false +} |