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use clippy_config::Conf;
use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::msrvs::{self, Msrv};
use clippy_utils::visitors::for_each_local_use_after_expr;
use clippy_utils::{is_from_proc_macro, path_to_local};
use itertools::Itertools;
use rustc_ast::LitKind;
use rustc_hir::{Expr, ExprKind, Node, PatKind};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::ty::{self, Ty};
use rustc_session::impl_lint_pass;
use std::iter::once;
use std::ops::ControlFlow;
declare_clippy_lint! {
/// ### What it does
/// Checks for tuple<=>array conversions that are not done with `.into()`.
///
/// ### Why is this bad?
/// It may be unnecessary complexity. `.into()` works for converting tuples<=> arrays of up to
/// 12 elements and conveys the intent more clearly, while also leaving less room for hard to
/// spot bugs!
///
/// ### Known issues
/// The suggested code may hide potential asymmetry in some cases. See
/// [#11085](https://github.com/rust-lang/rust-clippy/issues/11085) for more info.
///
/// ### 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,
nursery,
"checks for tuple<=>array conversions that are not done with `.into()`"
}
impl_lint_pass!(TupleArrayConversions => [TUPLE_ARRAY_CONVERSIONS]);
pub struct TupleArrayConversions {
msrv: Msrv,
}
impl TupleArrayConversions {
pub fn new(conf: &'static Conf) -> Self {
Self {
msrv: conf.msrv.clone(),
}
}
}
impl LateLintPass<'_> for TupleArrayConversions {
fn check_expr<'tcx>(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
if expr.span.in_external_macro(cx.sess().source_map()) || !self.msrv.meets(msrvs::TUPLE_ARRAY_CONVERSIONS) {
return;
}
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);
}
fn check_array<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, elements: &'tcx [Expr<'tcx>]) {
let (ty::Array(ty, _) | ty::Slice(ty)) = cx.typeck_results().expr_ty(expr).kind() else {
unreachable!("`expr` must be an array or slice due to `ExprKind::Array`");
};
if let [first, ..] = elements
&& let Some(locals) = (match first.kind {
ExprKind::Field(_, _) => elements
.iter()
.enumerate()
.map(|(i, f)| -> Option<&'tcx Expr<'tcx>> {
let ExprKind::Field(lhs, ident) = f.kind else {
return None;
};
(ident.name.as_str() == i.to_string()).then_some(lhs)
})
.collect::<Option<Vec<_>>>(),
ExprKind::Path(_) => Some(elements.iter().collect()),
_ => None,
})
&& all_bindings_are_for_conv(cx, &[*ty], expr, elements, &locals, ToType::Array)
&& !is_from_proc_macro(cx, expr)
{
span_lint_and_help(
cx,
TUPLE_ARRAY_CONVERSIONS,
expr.span,
"it looks like you're trying to convert a tuple to an array",
None,
"use `.into()` instead, or `<[T; N]>::from` if type annotations are needed",
);
}
}
fn check_tuple<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, elements: &'tcx [Expr<'tcx>]) {
if let ty::Tuple(tys) = cx.typeck_results().expr_ty(expr).kind()
&& let [first, ..] = elements
// Fix #11100
&& tys.iter().all_equal()
&& let Some(locals) = (match first.kind {
ExprKind::Index(..) => elements
.iter()
.enumerate()
.map(|(i, i_expr)| -> Option<&'tcx Expr<'tcx>> {
if let ExprKind::Index(lhs, index, _) = i_expr.kind
&& let ExprKind::Lit(lit) = index.kind
&& let LitKind::Int(val, _) = lit.node
{
return (val == i as u128).then_some(lhs);
}
None
})
.collect::<Option<Vec<_>>>(),
ExprKind::Path(_) => Some(elements.iter().collect()),
_ => None,
})
&& all_bindings_are_for_conv(cx, tys, expr, elements, &locals, ToType::Tuple)
&& !is_from_proc_macro(cx, expr)
{
span_lint_and_help(
cx,
TUPLE_ARRAY_CONVERSIONS,
expr.span,
"it looks like you're trying to convert an array to a tuple",
None,
"use `.into()` instead, or `<(T0, T1, ..., Tn)>::from` if type annotations are needed",
);
}
}
/// Checks that every binding in `elements` comes from the same parent `Pat` with the kind if there
/// is a parent `Pat`. Returns false in any of the following cases:
/// * `kind` does not match `pat.kind`
/// * one or more elements in `elements` is not a binding
/// * one or more bindings does not have the same parent `Pat`
/// * one or more bindings are used after `expr`
/// * the bindings do not all have the same type
#[expect(clippy::cast_possible_truncation)]
fn all_bindings_are_for_conv<'tcx>(
cx: &LateContext<'tcx>,
final_tys: &[Ty<'tcx>],
expr: &Expr<'_>,
elements: &[Expr<'_>],
locals: &[&Expr<'_>],
kind: ToType,
) -> bool {
let Some(locals) = locals.iter().map(|e| path_to_local(e)).collect::<Option<Vec<_>>>() else {
return false;
};
let local_parents = locals.iter().map(|l| cx.tcx.parent_hir_node(*l)).collect::<Vec<_>>();
local_parents
.iter()
.map(|node| match node {
Node::Pat(pat) => kind.eq(&pat.kind).then_some(pat.hir_id),
Node::LetStmt(l) => Some(l.hir_id),
_ => None,
})
.all_equal()
// Fix #11124, very convenient utils function! ❤️
&& locals
.iter()
.all(|&l| for_each_local_use_after_expr(cx, l, expr.hir_id, |_| ControlFlow::Break::<()>(())).is_continue())
&& local_parents.first().is_some_and(|node| {
let Some(ty) = match node {
Node::Pat(pat) => Some(pat.hir_id),
Node::LetStmt(l) => Some(l.hir_id),
_ => None,
}
.map(|hir_id| cx.typeck_results().node_type(hir_id)) else {
return false;
};
match (kind, ty.kind()) {
// Ensure the final type and the original type have the same length, and that there
// is no implicit `&mut`<=>`&` anywhere (#11100). Bit ugly, I know, but it works.
(ToType::Array, ty::Tuple(tys)) => {
tys.len() == elements.len() && tys.iter().chain(final_tys.iter().copied()).all_equal()
},
(ToType::Tuple, ty::Array(ty, len)) => {
let Some(len) = len.try_to_target_usize(cx.tcx) else { return false };
len as usize == elements.len() && final_tys.iter().chain(once(ty)).all_equal()
},
_ => false,
}
})
}
#[derive(Clone, Copy)]
enum ToType {
Array,
Tuple,
}
impl PartialEq<PatKind<'_>> for ToType {
fn eq(&self, other: &PatKind<'_>) -> bool {
match self {
ToType::Array => matches!(other, PatKind::Tuple(_, _)),
ToType::Tuple => matches!(other, PatKind::Slice(_, _, _)),
}
}
}
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