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use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::{get_parent_expr, path_to_local_id, usage};
use rustc_hir::intravisit::{Visitor, walk_expr};
use rustc_hir::{BorrowKind, Expr, ExprKind, HirId, Mutability, Pat, QPath, Stmt, StmtKind};
use rustc_lint::LateContext;
use rustc_middle::hir::nested_filter;
use rustc_middle::ty::{self, Ty};
use rustc_span::Span;
use rustc_span::symbol::sym;
pub(super) fn derefs_to_slice<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'tcx>,
ty: Ty<'tcx>,
) -> Option<&'tcx Expr<'tcx>> {
fn may_slice<'a>(cx: &LateContext<'a>, ty: Ty<'a>) -> bool {
match ty.kind() {
ty::Slice(_) => true,
ty::Adt(..) if let Some(boxed) = ty.boxed_ty() => may_slice(cx, boxed),
ty::Adt(..) => is_type_diagnostic_item(cx, ty, sym::Vec),
ty::Array(_, size) => size.try_to_target_usize(cx.tcx).is_some(),
ty::Ref(_, inner, _) => may_slice(cx, *inner),
_ => false,
}
}
if let ExprKind::MethodCall(path, self_arg, ..) = &expr.kind {
if path.ident.name == sym::iter && may_slice(cx, cx.typeck_results().expr_ty(self_arg)) {
Some(self_arg)
} else {
None
}
} else {
match ty.kind() {
ty::Slice(_) => Some(expr),
_ if ty.boxed_ty().is_some_and(|boxed| may_slice(cx, boxed)) => Some(expr),
ty::Ref(_, inner, _) => {
if may_slice(cx, *inner) {
Some(expr)
} else {
None
}
},
_ => None,
}
}
}
/// The core logic of `check_for_loop_iter` in `unnecessary_iter_cloned.rs`, this function wraps a
/// use of `CloneOrCopyVisitor`.
pub(super) fn clone_or_copy_needed<'tcx>(
cx: &LateContext<'tcx>,
pat: &Pat<'tcx>,
body: &'tcx Expr<'tcx>,
) -> (bool, Vec<(Span, String)>) {
let mut visitor = CloneOrCopyVisitor {
cx,
binding_hir_ids: pat_bindings(pat),
clone_or_copy_needed: false,
references_to_binding: Vec::new(),
};
visitor.visit_expr(body);
(visitor.clone_or_copy_needed, visitor.references_to_binding)
}
/// Returns a vector of all `HirId`s bound by the pattern.
fn pat_bindings(pat: &Pat<'_>) -> Vec<HirId> {
let mut collector = usage::ParamBindingIdCollector {
binding_hir_ids: Vec::new(),
};
collector.visit_pat(pat);
collector.binding_hir_ids
}
/// `clone_or_copy_needed` will be false when `CloneOrCopyVisitor` is done visiting if the only
/// operations performed on `binding_hir_ids` are:
/// * to take non-mutable references to them
/// * to use them as non-mutable `&self` in method calls
///
/// If any of `binding_hir_ids` is used in any other way, then `clone_or_copy_needed` will be true
/// when `CloneOrCopyVisitor` is done visiting.
struct CloneOrCopyVisitor<'cx, 'tcx> {
cx: &'cx LateContext<'tcx>,
binding_hir_ids: Vec<HirId>,
clone_or_copy_needed: bool,
references_to_binding: Vec<(Span, String)>,
}
impl<'tcx> Visitor<'tcx> for CloneOrCopyVisitor<'_, 'tcx> {
type NestedFilter = nested_filter::OnlyBodies;
fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
self.cx.tcx
}
fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
walk_expr(self, expr);
if self.is_binding(expr) {
if let Some(parent) = get_parent_expr(self.cx, expr) {
match parent.kind {
ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, referent) => {
if !parent.span.from_expansion() {
self.references_to_binding
.push((parent.span.until(referent.span), String::new()));
}
return;
},
ExprKind::MethodCall(.., args, _) => {
if args.iter().all(|arg| !self.is_binding(arg))
&& let Some(method_def_id) = self.cx.typeck_results().type_dependent_def_id(parent.hir_id)
&& let method_ty = self.cx.tcx.type_of(method_def_id).instantiate_identity()
&& let self_ty = method_ty.fn_sig(self.cx.tcx).input(0).skip_binder()
&& matches!(self_ty.kind(), ty::Ref(_, _, Mutability::Not))
{
return;
}
},
_ => {},
}
}
self.clone_or_copy_needed = true;
}
}
}
impl<'tcx> CloneOrCopyVisitor<'_, 'tcx> {
fn is_binding(&self, expr: &Expr<'tcx>) -> bool {
self.binding_hir_ids
.iter()
.any(|hir_id| path_to_local_id(expr, *hir_id))
}
}
pub(super) fn get_last_chain_binding_hir_id(mut hir_id: HirId, statements: &[Stmt<'_>]) -> Option<HirId> {
for stmt in statements {
if let StmtKind::Let(local) = stmt.kind
&& let Some(init) = local.init
&& let ExprKind::Path(QPath::Resolved(_, path)) = init.kind
&& let rustc_hir::def::Res::Local(local_hir_id) = path.res
&& local_hir_id == hir_id
{
hir_id = local.pat.hir_id;
} else {
return None;
}
}
Some(hir_id)
}
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