2022-06-30 03:50:09 -05:00
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use clippy_utils::diagnostics::span_lint_hir;
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2020-02-18 07:28:18 -06:00
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use rustc_hir::intravisit;
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2022-06-28 13:15:30 -05:00
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use rustc_hir::{self, AssocItemKind, Body, FnDecl, HirId, HirIdSet, Impl, ItemKind, Node, Pat, PatKind};
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2022-10-20 10:51:48 -05:00
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use rustc_hir_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
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2020-02-16 20:07:26 -06:00
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use rustc_infer::infer::TyCtxtInferExt;
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2020-01-12 00:08:41 -06:00
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use rustc_lint::{LateContext, LateLintPass};
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2021-02-25 14:33:18 -06:00
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use rustc_middle::mir::FakeReadCause;
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2021-08-30 09:38:27 -05:00
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use rustc_middle::ty::layout::LayoutOf;
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2021-01-15 03:56:44 -06:00
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use rustc_middle::ty::{self, TraitRef, Ty};
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2020-01-11 05:37:08 -06:00
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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2020-01-04 04:00:00 -06:00
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use rustc_span::source_map::Span;
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2021-01-15 03:56:44 -06:00
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use rustc_span::symbol::kw;
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2020-10-09 05:45:29 -05:00
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use rustc_target::spec::abi::Abi;
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2015-12-04 04:12:53 -06:00
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2019-04-08 15:43:55 -05:00
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#[derive(Copy, Clone)]
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pub struct BoxedLocal {
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2016-07-10 08:23:50 -05:00
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pub too_large_for_stack: u64,
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}
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2015-12-04 04:12:53 -06:00
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2018-03-28 08:24:26 -05:00
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declare_clippy_lint! {
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2021-07-29 05:16:06 -05:00
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/// ### What it does
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/// Checks for usage of `Box<T>` where an unboxed `T` would
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2019-03-05 10:50:33 -06:00
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/// work fine.
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///
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2021-07-29 05:16:06 -05:00
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/// ### Why is this bad?
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/// This is an unnecessary allocation, and bad for
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2019-03-05 10:50:33 -06:00
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/// performance. It is only necessary to allocate if you wish to move the box
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/// into something.
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///
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2021-07-29 05:16:06 -05:00
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/// ### Example
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2019-03-05 10:50:33 -06:00
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/// ```rust
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2022-08-31 08:24:45 -05:00
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/// fn foo(x: Box<u32>) {}
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2022-06-04 06:34:07 -05:00
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/// ```
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2020-06-09 09:36:01 -05:00
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///
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2022-06-04 06:34:07 -05:00
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/// Use instead:
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/// ```rust
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2022-08-31 08:24:45 -05:00
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/// fn foo(x: u32) {}
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2019-03-05 10:50:33 -06:00
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/// ```
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2021-12-06 05:33:31 -06:00
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#[clippy::version = "pre 1.29.0"]
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2016-08-06 03:18:36 -05:00
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pub BOXED_LOCAL,
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2018-03-28 08:24:26 -05:00
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perf,
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2016-08-06 03:18:36 -05:00
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"using `Box<T>` where unnecessary"
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2016-02-05 17:13:29 -06:00
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}
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2015-12-04 04:12:53 -06:00
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2018-07-23 06:01:12 -05:00
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fn is_non_trait_box(ty: Ty<'_>) -> bool {
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2017-02-03 04:52:13 -06:00
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ty.is_box() && !ty.boxed_ty().is_trait()
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2015-12-28 08:12:57 -06:00
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}
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2019-06-19 13:36:23 -05:00
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struct EscapeDelegate<'a, 'tcx> {
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2020-06-25 15:41:36 -05:00
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cx: &'a LateContext<'tcx>,
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2019-03-01 06:26:06 -06:00
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set: HirIdSet,
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2021-07-17 09:43:23 -05:00
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trait_self_ty: Option<Ty<'tcx>>,
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2016-07-10 08:23:50 -05:00
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too_large_for_stack: u64,
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2015-12-04 04:12:53 -06:00
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}
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2019-04-08 15:43:55 -05:00
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impl_lint_pass!(BoxedLocal => [BOXED_LOCAL]);
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2019-01-26 13:40:55 -06:00
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2020-06-25 15:41:36 -05:00
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impl<'tcx> LateLintPass<'tcx> for BoxedLocal {
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2016-12-21 03:25:14 -06:00
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fn check_fn(
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&mut self,
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2020-06-25 15:41:36 -05:00
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cx: &LateContext<'tcx>,
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fn_kind: intravisit::FnKind<'tcx>,
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_: &'tcx FnDecl<'_>,
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body: &'tcx Body<'_>,
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2016-12-21 05:14:54 -06:00
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_: Span,
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2019-02-20 04:11:11 -06:00
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hir_id: HirId,
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2016-12-21 03:25:14 -06:00
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) {
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2020-10-09 05:45:29 -05:00
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if let Some(header) = fn_kind.header() {
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if header.abi != Abi::Rust {
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return;
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}
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}
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2022-09-20 00:11:23 -05:00
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let parent_id = cx.tcx.hir().get_parent_item(hir_id).def_id;
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2021-10-21 12:41:47 -05:00
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let parent_node = cx.tcx.hir().find_by_def_id(parent_id);
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2018-10-15 13:20:50 -05:00
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2021-01-15 03:56:44 -06:00
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let mut trait_self_ty = None;
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2018-10-15 13:20:50 -05:00
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if let Some(Node::Item(item)) = parent_node {
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2021-01-15 03:56:44 -06:00
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// If the method is an impl for a trait, don't warn.
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2020-11-22 16:46:21 -06:00
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if let ItemKind::Impl(Impl { of_trait: Some(_), .. }) = item.kind {
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2018-10-15 13:20:50 -05:00
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return;
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}
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2021-01-15 03:56:44 -06:00
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// find `self` ty for this trait if relevant
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if let ItemKind::Trait(_, _, _, _, items) = item.kind {
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for trait_item in items {
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2021-01-30 13:46:50 -06:00
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if trait_item.id.hir_id() == hir_id {
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2021-01-15 03:56:44 -06:00
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// be sure we have `self` parameter in this function
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2021-10-07 04:21:30 -05:00
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if trait_item.kind == (AssocItemKind::Fn { has_self: true }) {
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2021-09-28 12:03:12 -05:00
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trait_self_ty = Some(
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2022-10-26 22:02:18 -05:00
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TraitRef::identity(cx.tcx, trait_item.id.owner_id.to_def_id())
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2021-09-28 12:03:12 -05:00
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.self_ty()
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.skip_binder(),
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);
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2021-01-15 03:56:44 -06:00
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}
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}
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}
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}
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2018-10-15 13:20:50 -05:00
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}
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2015-12-04 04:12:53 -06:00
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let mut v = EscapeDelegate {
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2018-03-15 10:07:15 -05:00
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cx,
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2019-03-01 06:26:06 -06:00
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set: HirIdSet::default(),
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2021-01-15 03:56:44 -06:00
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trait_self_ty,
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2016-07-10 08:23:50 -05:00
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too_large_for_stack: self.too_large_for_stack,
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2015-12-04 04:12:53 -06:00
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};
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2016-05-12 12:11:13 -05:00
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2019-07-05 22:52:51 -05:00
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let fn_def_id = cx.tcx.hir().local_def_id(hir_id);
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2022-09-19 22:03:59 -05:00
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let infcx = cx.tcx.infer_ctxt().build();
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ExprUseVisitor::new(&mut v, &infcx, fn_def_id, cx.param_env, cx.typeck_results()).consume_body(body);
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2016-05-12 12:11:13 -05:00
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2019-02-21 23:06:51 -06:00
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for node in v.set {
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2022-06-30 03:50:09 -05:00
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span_lint_hir(
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2017-08-09 02:30:56 -05:00
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cx,
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BOXED_LOCAL,
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2022-06-30 03:50:09 -05:00
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node,
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2019-06-18 04:15:47 -05:00
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cx.tcx.hir().span(node),
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2017-08-09 02:30:56 -05:00
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"local variable doesn't need to be boxed here",
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);
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2015-12-04 04:12:53 -06:00
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}
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}
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}
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2019-07-29 23:37:49 -05:00
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// TODO: Replace with Map::is_argument(..) when it's fixed
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2020-03-30 04:02:14 -05:00
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fn is_argument(map: rustc_middle::hir::map::Map<'_>, id: HirId) -> bool {
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2019-07-29 23:37:49 -05:00
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match map.find(id) {
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2022-06-28 13:15:30 -05:00
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Some(Node::Pat(Pat {
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kind: PatKind::Binding(..),
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..
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})) => (),
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2019-07-29 23:37:49 -05:00
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_ => return false,
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}
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2023-01-03 01:31:04 -06:00
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matches!(map.find(map.parent_id(id)), Some(Node::Param(_)))
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2019-07-29 23:37:49 -05:00
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}
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2017-06-10 21:34:47 -05:00
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impl<'a, 'tcx> Delegate<'tcx> for EscapeDelegate<'a, 'tcx> {
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2021-07-14 01:21:08 -05:00
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fn consume(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId) {
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2020-06-17 17:13:05 -05:00
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if cmt.place.projections.is_empty() {
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if let PlaceBase::Local(lid) = cmt.place.base {
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2021-07-14 01:21:08 -05:00
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self.set.remove(&lid);
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2015-12-04 04:12:53 -06:00
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}
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}
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}
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2019-10-04 07:24:47 -05:00
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2020-11-01 01:15:22 -06:00
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fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {
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2020-06-17 17:13:05 -05:00
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if cmt.place.projections.is_empty() {
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if let PlaceBase::Local(lid) = cmt.place.base {
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2019-11-29 05:57:10 -06:00
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self.set.remove(&lid);
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}
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2015-12-04 04:12:53 -06:00
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}
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}
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2019-10-04 07:24:47 -05:00
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2020-11-01 01:15:22 -06:00
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fn mutate(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId) {
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2020-06-17 17:13:05 -05:00
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if cmt.place.projections.is_empty() {
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2019-11-29 05:57:10 -06:00
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let map = &self.cx.tcx.hir();
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2020-03-15 17:41:20 -05:00
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if is_argument(*map, cmt.hir_id) {
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2019-11-29 05:57:10 -06:00
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// Skip closure arguments
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2023-01-03 01:31:04 -06:00
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let parent_id = map.parent_id(cmt.hir_id);
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if let Some(Node::Expr(..)) = map.find(map.parent_id(parent_id)) {
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2019-11-29 05:57:10 -06:00
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return;
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}
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2019-10-06 07:49:26 -05:00
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2021-01-15 03:56:44 -06:00
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// skip if there is a `self` parameter binding to a type
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// that contains `Self` (i.e.: `self: Box<Self>`), see #4804
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if let Some(trait_self_ty) = self.trait_self_ty {
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2022-08-31 08:24:45 -05:00
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if map.name(cmt.hir_id) == kw::SelfLower && cmt.place.ty().contains(trait_self_ty) {
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2021-01-15 03:56:44 -06:00
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return;
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}
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}
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2020-06-24 15:33:31 -05:00
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if is_non_trait_box(cmt.place.ty()) && !self.is_large_box(cmt.place.ty()) {
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2019-11-29 05:57:10 -06:00
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self.set.insert(cmt.hir_id);
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}
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2019-10-06 07:49:26 -05:00
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}
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}
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}
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2021-02-25 14:33:18 -06:00
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2022-11-21 13:34:47 -06:00
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fn fake_read(&mut self, _: &rustc_hir_typeck::expr_use_visitor::PlaceWithHirId<'tcx>, _: FakeReadCause, _: HirId) {}
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2015-12-04 04:12:53 -06:00
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}
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2016-07-10 08:23:50 -05:00
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2017-06-10 21:34:47 -05:00
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impl<'a, 'tcx> EscapeDelegate<'a, 'tcx> {
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2017-06-10 21:57:25 -05:00
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fn is_large_box(&self, ty: Ty<'tcx>) -> bool {
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2019-01-30 19:15:29 -06:00
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// Large types need to be boxed to avoid stack overflows.
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2017-02-03 04:52:13 -06:00
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if ty.is_box() {
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2019-11-26 08:14:28 -06:00
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self.cx.layout_of(ty.boxed_ty()).map_or(0, |l| l.size.bytes()) > self.too_large_for_stack
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2017-06-10 21:34:47 -05:00
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} else {
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false
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2016-07-10 08:23:50 -05:00
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}
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}
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}
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