[rustc.git] / src / tools / clippy / clippy_lints / src / needless_pass_by_value.rs

use clippy_utils::diagnostics::{multispan_sugg, span_lint_and_then};
use clippy_utils::ptr::get_spans;
use clippy_utils::source::{snippet, snippet_opt};
use clippy_utils::ty::{implements_trait, is_copy, is_type_diagnostic_item};
use clippy_utils::{get_trait_def_id, is_self, paths};
use if_chain::if_chain;
use rustc_ast::ast::Attribute;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{Applicability, DiagnosticBuilder};
use rustc_hir::intravisit::FnKind;
use rustc_hir::{BindingAnnotation, Body, FnDecl, GenericArg, HirId, Impl, ItemKind, Node, PatKind, QPath, TyKind};
use rustc_hir::{HirIdMap, HirIdSet};
use rustc_infer::infer::TyCtxtInferExt;
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::mir::FakeReadCause;
use rustc_middle::ty::{self, TypeFoldable};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::symbol::kw;
use rustc_span::{sym, Span};
use rustc_target::spec::abi::Abi;
use rustc_trait_selection::traits;
use rustc_trait_selection::traits::misc::can_type_implement_copy;
use rustc_typeck::expr_use_visitor as euv;
use std::borrow::Cow;

declare_clippy_lint! {
    /// ### What it does
    /// Checks for functions taking arguments by value, but not
    /// consuming them in its
    /// body.
    ///
    /// ### Why is this bad?
    /// Taking arguments by reference is more flexible and can
    /// sometimes avoid
    /// unnecessary allocations.
    ///
    /// ### Known problems
    /// * This lint suggests taking an argument by reference,
    /// however sometimes it is better to let users decide the argument type
    /// (by using `Borrow` trait, for example), depending on how the function is used.
    ///
    /// ### Example
    /// ```rust
    /// fn foo(v: Vec<i32>) {
    ///     assert_eq!(v.len(), 42);
    /// }
    /// ```
    /// should be
    /// ```rust
    /// fn foo(v: &[i32]) {
    ///     assert_eq!(v.len(), 42);
    /// }
    /// ```
    pub NEEDLESS_PASS_BY_VALUE,
    pedantic,
    "functions taking arguments by value, but not consuming them in its body"
}

declare_lint_pass!(NeedlessPassByValue => [NEEDLESS_PASS_BY_VALUE]);

macro_rules! need {
    ($e: expr) => {
        if let Some(x) = $e {
            x
        } else {
            return;
        }
    };
}

impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
    #[allow(clippy::too_many_lines)]
    fn check_fn(
        &mut self,
        cx: &LateContext<'tcx>,
        kind: FnKind<'tcx>,
        decl: &'tcx FnDecl<'_>,
        body: &'tcx Body<'_>,
        span: Span,
        hir_id: HirId,
    ) {
        if span.from_expansion() {
            return;
        }

        match kind {
            FnKind::ItemFn(.., header, _) => {
                let attrs = cx.tcx.hir().attrs(hir_id);
                if header.abi != Abi::Rust || requires_exact_signature(attrs) {
                    return;
                }
            },
            FnKind::Method(..) => (),
            FnKind::Closure => return,
        }

        // Exclude non-inherent impls
        if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(hir_id)) {
            if matches!(
                item.kind,
                ItemKind::Impl(Impl { of_trait: Some(_), .. }) | ItemKind::Trait(..)
            ) {
                return;
            }
        }

        // Allow `Borrow` or functions to be taken by value
        let allowed_traits = [
            need!(cx.tcx.lang_items().fn_trait()),
            need!(cx.tcx.lang_items().fn_once_trait()),
            need!(cx.tcx.lang_items().fn_mut_trait()),
            need!(get_trait_def_id(cx, &paths::RANGE_ARGUMENT_TRAIT)),
        ];

        let sized_trait = need!(cx.tcx.lang_items().sized_trait());

        let fn_def_id = cx.tcx.hir().local_def_id(hir_id);

        let preds = traits::elaborate_predicates(cx.tcx, cx.param_env.caller_bounds().iter())
            .filter(|p| !p.is_global(cx.tcx))
            .filter_map(|obligation| {
                // Note that we do not want to deal with qualified predicates here.
                match obligation.predicate.kind().no_bound_vars() {
                    Some(ty::PredicateKind::Trait(pred)) if pred.def_id() != sized_trait => Some(pred),
                    _ => None,
                }
            })
            .collect::<Vec<_>>();

        // Collect moved variables and spans which will need dereferencings from the
        // function body.
        let MovedVariablesCtxt {
            moved_vars,
            spans_need_deref,
            ..
        } = {
            let mut ctx = MovedVariablesCtxt::default();
            cx.tcx.infer_ctxt().enter(|infcx| {
                euv::ExprUseVisitor::new(&mut ctx, &infcx, fn_def_id, cx.param_env, cx.typeck_results())
                    .consume_body(body);
            });
            ctx
        };

        let fn_sig = cx.tcx.fn_sig(fn_def_id);
        let fn_sig = cx.tcx.erase_late_bound_regions(fn_sig);

        for (idx, ((input, &ty), arg)) in decl.inputs.iter().zip(fn_sig.inputs()).zip(body.params).enumerate() {
            // All spans generated from a proc-macro invocation are the same...
            if span == input.span {
                return;
            }

            // Ignore `self`s.
            if idx == 0 {
                if let PatKind::Binding(.., ident, _) = arg.pat.kind {
                    if ident.name == kw::SelfLower {
                        continue;
                    }
                }
            }

            //
            // * Exclude a type that is specifically bounded by `Borrow`.
            // * Exclude a type whose reference also fulfills its bound. (e.g., `std::convert::AsRef`,
            //   `serde::Serialize`)
            let (implements_borrow_trait, all_borrowable_trait) = {
                let preds = preds.iter().filter(|t| t.self_ty() == ty).collect::<Vec<_>>();

                (
                    preds.iter().any(|t| cx.tcx.is_diagnostic_item(sym::Borrow, t.def_id())),
                    !preds.is_empty() && {
                        let ty_empty_region = cx.tcx.mk_imm_ref(cx.tcx.lifetimes.re_root_empty, ty);
                        preds.iter().all(|t| {
                            let ty_params = t.trait_ref.substs.iter().skip(1).collect::<Vec<_>>();
                            implements_trait(cx, ty_empty_region, t.def_id(), &ty_params)
                        })
                    },
                )
            };

            if_chain! {
                if !is_self(arg);
                if !ty.is_mutable_ptr();
                if !is_copy(cx, ty);
                if !allowed_traits.iter().any(|&t| implements_trait(cx, ty, t, &[]));
                if !implements_borrow_trait;
                if !all_borrowable_trait;

                if let PatKind::Binding(mode, canonical_id, ..) = arg.pat.kind;
                if !moved_vars.contains(&canonical_id);
                then {
                    if mode == BindingAnnotation::Mutable || mode == BindingAnnotation::RefMut {
                        continue;
                    }

                    // Dereference suggestion
                    let sugg = |diag: &mut DiagnosticBuilder<'_>| {
                        if let ty::Adt(def, ..) = ty.kind() {
                            if let Some(span) = cx.tcx.hir().span_if_local(def.did) {
                                if can_type_implement_copy(cx.tcx, cx.param_env, ty).is_ok() {
                                    diag.span_help(span, "consider marking this type as `Copy`");
                                }
                            }
                        }

                        let deref_span = spans_need_deref.get(&canonical_id);
                        if_chain! {
                            if is_type_diagnostic_item(cx, ty, sym::vec_type);
                            if let Some(clone_spans) =
                                get_spans(cx, Some(body.id()), idx, &[("clone", ".to_owned()")]);
                            if let TyKind::Path(QPath::Resolved(_, path)) = input.kind;
                            if let Some(elem_ty) = path.segments.iter()
                                .find(|seg| seg.ident.name == sym::Vec)
                                .and_then(|ps| ps.args.as_ref())
                                .map(|params| params.args.iter().find_map(|arg| match arg {
                                    GenericArg::Type(ty) => Some(ty),
                                    _ => None,
                                }).unwrap());
                            then {
                                let slice_ty = format!("&[{}]", snippet(cx, elem_ty.span, "_"));
                                diag.span_suggestion(
                                    input.span,
                                    "consider changing the type to",
                                    slice_ty,
                                    Applicability::Unspecified,
                                );

                                for (span, suggestion) in clone_spans {
                                    diag.span_suggestion(
                                        span,
                                        &snippet_opt(cx, span)
                                            .map_or(
                                                "change the call to".into(),
                                                |x| Cow::from(format!("change `{}` to", x)),
                                            ),
                                        suggestion.into(),
                                        Applicability::Unspecified,
                                    );
                                }

                                // cannot be destructured, no need for `*` suggestion
                                assert!(deref_span.is_none());
                                return;
                            }
                        }

                        if is_type_diagnostic_item(cx, ty, sym::string_type) {
                            if let Some(clone_spans) =
                                get_spans(cx, Some(body.id()), idx, &[("clone", ".to_string()"), ("as_str", "")]) {
                                diag.span_suggestion(
                                    input.span,
                                    "consider changing the type to",
                                    "&str".to_string(),
                                    Applicability::Unspecified,
                                );

                                for (span, suggestion) in clone_spans {
                                    diag.span_suggestion(
                                        span,
                                        &snippet_opt(cx, span)
                                            .map_or(
                                                "change the call to".into(),
                                                |x| Cow::from(format!("change `{}` to", x))
                                            ),
                                        suggestion.into(),
                                        Applicability::Unspecified,
                                    );
                                }

                                assert!(deref_span.is_none());
                                return;
                            }
                        }

                        let mut spans = vec![(input.span, format!("&{}", snippet(cx, input.span, "_")))];

                        // Suggests adding `*` to dereference the added reference.
                        if let Some(deref_span) = deref_span {
                            spans.extend(
                                deref_span
                                    .iter()
                                    .copied()
                                    .map(|span| (span, format!("*{}", snippet(cx, span, "<expr>")))),
                            );
                            spans.sort_by_key(|&(span, _)| span);
                        }
                        multispan_sugg(diag, "consider taking a reference instead", spans);
                    };

                    span_lint_and_then(
                        cx,
                        NEEDLESS_PASS_BY_VALUE,
                        input.span,
                        "this argument is passed by value, but not consumed in the function body",
                        sugg,
                    );
                }
            }
        }
    }
}

/// Functions marked with these attributes must have the exact signature.
fn requires_exact_signature(attrs: &[Attribute]) -> bool {
    attrs.iter().any(|attr| {
        [sym::proc_macro, sym::proc_macro_attribute, sym::proc_macro_derive]
            .iter()
            .any(|&allow| attr.has_name(allow))
    })
}

#[derive(Default)]
struct MovedVariablesCtxt {
    moved_vars: HirIdSet,
    /// Spans which need to be prefixed with `*` for dereferencing the
    /// suggested additional reference.
    spans_need_deref: HirIdMap<FxHashSet<Span>>,
}

impl MovedVariablesCtxt {
    fn move_common(&mut self, cmt: &euv::PlaceWithHirId<'_>) {
        if let euv::PlaceBase::Local(vid) = cmt.place.base {
            self.moved_vars.insert(vid);
        }
    }
}

impl<'tcx> euv::Delegate<'tcx> for MovedVariablesCtxt {
    fn consume(&mut self, cmt: &euv::PlaceWithHirId<'tcx>, _: HirId) {
        self.move_common(cmt);
    }

    fn borrow(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {}

    fn mutate(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: HirId) {}

    fn fake_read(&mut self, _: rustc_typeck::expr_use_visitor::Place<'tcx>, _: FakeReadCause, _: HirId) {}
}
Commit	Line	Data
cdc7bbd5 XL	1	use clippy_utils::diagnostics::{multispan_sugg, span_lint_and_then};
	2	use clippy_utils::ptr::get_spans;
	3	use clippy_utils::source::{snippet, snippet_opt};
	4	use clippy_utils::ty::{implements_trait, is_copy, is_type_diagnostic_item};
	5	use clippy_utils::{get_trait_def_id, is_self, paths};
f20569fa XL	6	use if_chain::if_chain;
f20569fa XL	7	use rustc_ast::ast::Attribute;
cdc7bbd5	8	use rustc_data_structures::fx::FxHashSet;
f20569fa XL	9	use rustc_errors::{Applicability, DiagnosticBuilder};
	10	use rustc_hir::intravisit::FnKind;
	11	use rustc_hir::{BindingAnnotation, Body, FnDecl, GenericArg, HirId, Impl, ItemKind, Node, PatKind, QPath, TyKind};
cdc7bbd5	12	use rustc_hir::{HirIdMap, HirIdSet};
f20569fa XL	13	use rustc_infer::infer::TyCtxtInferExt;
	14	use rustc_lint::{LateContext, LateLintPass};
	15	use rustc_middle::mir::FakeReadCause;
	16	use rustc_middle::ty::{self, TypeFoldable};
	17	use rustc_session::{declare_lint_pass, declare_tool_lint};
	18	use rustc_span::symbol::kw;
	19	use rustc_span::{sym, Span};
	20	use rustc_target::spec::abi::Abi;
	21	use rustc_trait_selection::traits;
	22	use rustc_trait_selection::traits::misc::can_type_implement_copy;
	23	use rustc_typeck::expr_use_visitor as euv;
	24	use std::borrow::Cow;
	25
	26	declare_clippy_lint! {
94222f64 XL	27	/// ### What it does
94222f64 XL	28	/// Checks for functions taking arguments by value, but not
f20569fa XL	29	/// consuming them in its
	30	/// body.
	31	///
94222f64 XL	32	/// ### Why is this bad?
94222f64 XL	33	/// Taking arguments by reference is more flexible and can
f20569fa XL	34	/// sometimes avoid
	35	/// unnecessary allocations.
	36	///
94222f64	37	/// ### Known problems
f20569fa XL	38	/// * This lint suggests taking an argument by reference,
	39	/// however sometimes it is better to let users decide the argument type
	40	/// (by using `Borrow` trait, for example), depending on how the function is used.
	41	///
94222f64	42	/// ### Example
f20569fa XL	43	/// ```rust
	44	/// fn foo(v: Vec<i32>) {
	45	/// assert_eq!(v.len(), 42);
	46	/// }
	47	/// ```
	48	/// should be
	49	/// ```rust
	50	/// fn foo(v: &[i32]) {
	51	/// assert_eq!(v.len(), 42);
	52	/// }
	53	/// ```
	54	pub NEEDLESS_PASS_BY_VALUE,
	55	pedantic,
	56	"functions taking arguments by value, but not consuming them in its body"
	57	}
	58
	59	declare_lint_pass!(NeedlessPassByValue => [NEEDLESS_PASS_BY_VALUE]);
	60
	61	macro_rules! need {
	62	($e: expr) => {
	63	if let Some(x) = $e {
	64	x
	65	} else {
	66	return;
	67	}
	68	};
	69	}
	70
	71	impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
	72	#[allow(clippy::too_many_lines)]
	73	fn check_fn(
	74	&mut self,
	75	cx: &LateContext<'tcx>,
	76	kind: FnKind<'tcx>,
	77	decl: &'tcx FnDecl<'_>,
	78	body: &'tcx Body<'_>,
	79	span: Span,
	80	hir_id: HirId,
	81	) {
	82	if span.from_expansion() {
	83	return;
	84	}
	85
	86	match kind {
	87	FnKind::ItemFn(.., header, _) => {
	88	let attrs = cx.tcx.hir().attrs(hir_id);
	89	if header.abi != Abi::Rust \|\| requires_exact_signature(attrs) {
	90	return;
	91	}
	92	},
	93	FnKind::Method(..) => (),
	94	FnKind::Closure => return,
	95	}
	96
	97	// Exclude non-inherent impls
	98	if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(hir_id)) {
	99	if matches!(
	100	item.kind,
	101	ItemKind::Impl(Impl { of_trait: Some(_), .. }) \| ItemKind::Trait(..)
	102	) {
	103	return;
	104	}
	105	}
	106
107	// Allow `Borrow` or functions to be taken by value
f20569fa XL	108	let allowed_traits = [
	109	need!(cx.tcx.lang_items().fn_trait()),
	110	need!(cx.tcx.lang_items().fn_once_trait()),
	111	need!(cx.tcx.lang_items().fn_mut_trait()),
	112	need!(get_trait_def_id(cx, &paths::RANGE_ARGUMENT_TRAIT)),
	113	];
	114
	115	let sized_trait = need!(cx.tcx.lang_items().sized_trait());
	116
	117	let fn_def_id = cx.tcx.hir().local_def_id(hir_id);
	118
	119	let preds = traits::elaborate_predicates(cx.tcx, cx.param_env.caller_bounds().iter())
94222f64	120	.filter(\|p\| !p.is_global(cx.tcx))
f20569fa XL	121	.filter_map(\|obligation\| {
	122	// Note that we do not want to deal with qualified predicates here.
	123	match obligation.predicate.kind().no_bound_vars() {
94222f64	124	Some(ty::PredicateKind::Trait(pred)) if pred.def_id() != sized_trait => Some(pred),
f20569fa XL	125	_ => None,
	126	}
	127	})
	128	.collect::<Vec<_>>();
	129
	130	// Collect moved variables and spans which will need dereferencings from the
	131	// function body.
	132	let MovedVariablesCtxt {
	133	moved_vars,
	134	spans_need_deref,
	135	..
	136	} = {
	137	let mut ctx = MovedVariablesCtxt::default();
	138	cx.tcx.infer_ctxt().enter(\|infcx\| {
	139	euv::ExprUseVisitor::new(&mut ctx, &infcx, fn_def_id, cx.param_env, cx.typeck_results())
	140	.consume_body(body);
	141	});
	142	ctx
	143	};
	144
	145	let fn_sig = cx.tcx.fn_sig(fn_def_id);
	146	let fn_sig = cx.tcx.erase_late_bound_regions(fn_sig);
	147
	148	for (idx, ((input, &ty), arg)) in decl.inputs.iter().zip(fn_sig.inputs()).zip(body.params).enumerate() {
	149	// All spans generated from a proc-macro invocation are the same...
	150	if span == input.span {
	151	return;
	152	}
	153
	154	// Ignore `self`s.
	155	if idx == 0 {
	156	if let PatKind::Binding(.., ident, _) = arg.pat.kind {
	157	if ident.name == kw::SelfLower {
	158	continue;
	159	}
	160	}
	161	}
	162
	163	//
	164	// * Exclude a type that is specifically bounded by `Borrow`.
	165	// * Exclude a type whose reference also fulfills its bound. (e.g., `std::convert::AsRef`,
	166	// `serde::Serialize`)
	167	let (implements_borrow_trait, all_borrowable_trait) = {
	168	let preds = preds.iter().filter(\|t\| t.self_ty() == ty).collect::<Vec<_>>();
	169
	170	(
94222f64	171	preds.iter().any(\|t\| cx.tcx.is_diagnostic_item(sym::Borrow, t.def_id())),
f20569fa XL	172	!preds.is_empty() && {
	173	let ty_empty_region = cx.tcx.mk_imm_ref(cx.tcx.lifetimes.re_root_empty, ty);
	174	preds.iter().all(\|t\| {
	175	let ty_params = t.trait_ref.substs.iter().skip(1).collect::<Vec<_>>();
	176	implements_trait(cx, ty_empty_region, t.def_id(), &ty_params)
	177	})
	178	},
	179	)
	180	};
	181
	182	if_chain! {
	183	if !is_self(arg);
	184	if !ty.is_mutable_ptr();
	185	if !is_copy(cx, ty);
	186	if !allowed_traits.iter().any(\|&t\| implements_trait(cx, ty, t, &[]));
	187	if !implements_borrow_trait;
	188	if !all_borrowable_trait;
	189
	190	if let PatKind::Binding(mode, canonical_id, ..) = arg.pat.kind;
	191	if !moved_vars.contains(&canonical_id);
	192	then {
	193	if mode == BindingAnnotation::Mutable \|\| mode == BindingAnnotation::RefMut {
	194	continue;
	195	}
	196
	197	// Dereference suggestion
	198	let sugg = \|diag: &mut DiagnosticBuilder<'_>\| {
	199	if let ty::Adt(def, ..) = ty.kind() {
	200	if let Some(span) = cx.tcx.hir().span_if_local(def.did) {
	201	if can_type_implement_copy(cx.tcx, cx.param_env, ty).is_ok() {
	202	diag.span_help(span, "consider marking this type as `Copy`");
	203	}
	204	}
	205	}
	206
	207	let deref_span = spans_need_deref.get(&canonical_id);
	208	if_chain! {
	209	if is_type_diagnostic_item(cx, ty, sym::vec_type);
	210	if let Some(clone_spans) =
	211	get_spans(cx, Some(body.id()), idx, &[("clone", ".to_owned()")]);
cdc7bbd5	212	if let TyKind::Path(QPath::Resolved(_, path)) = input.kind;
f20569fa XL	213	if let Some(elem_ty) = path.segments.iter()
	214	.find(\|seg\| seg.ident.name == sym::Vec)
	215	.and_then(\|ps\| ps.args.as_ref())
	216	.map(\|params\| params.args.iter().find_map(\|arg\| match arg {
	217	GenericArg::Type(ty) => Some(ty),
	218	_ => None,
	219	}).unwrap());
	220	then {
	221	let slice_ty = format!("&[{}]", snippet(cx, elem_ty.span, "_"));
	222	diag.span_suggestion(
	223	input.span,
	224	"consider changing the type to",
	225	slice_ty,
	226	Applicability::Unspecified,
	227	);
	228
	229	for (span, suggestion) in clone_spans {
	230	diag.span_suggestion(
	231	span,
	232	&snippet_opt(cx, span)
	233	.map_or(
	234	"change the call to".into(),
	235	\|x\| Cow::from(format!("change `{}` to", x)),
	236	),
	237	suggestion.into(),
	238	Applicability::Unspecified,
	239	);
	240	}
	241
	242	// cannot be destructured, no need for `*` suggestion
	243	assert!(deref_span.is_none());
	244	return;
	245	}
	246	}
	247
	248	if is_type_diagnostic_item(cx, ty, sym::string_type) {
	249	if let Some(clone_spans) =
	250	get_spans(cx, Some(body.id()), idx, &[("clone", ".to_string()"), ("as_str", "")]) {
	251	diag.span_suggestion(
	252	input.span,
	253	"consider changing the type to",
	254	"&str".to_string(),
	255	Applicability::Unspecified,
	256	);
	257
	258	for (span, suggestion) in clone_spans {
	259	diag.span_suggestion(
	260	span,
	261	&snippet_opt(cx, span)
	262	.map_or(
	263	"change the call to".into(),
	264	\|x\| Cow::from(format!("change `{}` to", x))
	265	),
	266	suggestion.into(),
	267	Applicability::Unspecified,
	268	);
	269	}
	270
	271	assert!(deref_span.is_none());
	272	return;
	273	}
	274	}
	275
	276	let mut spans = vec![(input.span, format!("&{}", snippet(cx, input.span, "_")))];
277
278	// Suggests adding `*` to dereference the added reference.
279	if let Some(deref_span) = deref_span {
280	spans.extend(
281	deref_span
282	.iter()
cdc7bbd5	283	.copied()
f20569fa XL	284	.map(\|span\| (span, format!("*{}", snippet(cx, span, "<expr>")))),
	285	);
	286	spans.sort_by_key(\|&(span, _)\| span);
	287	}
	288	multispan_sugg(diag, "consider taking a reference instead", spans);
	289	};
	290
	291	span_lint_and_then(
	292	cx,
	293	NEEDLESS_PASS_BY_VALUE,
	294	input.span,
	295	"this argument is passed by value, but not consumed in the function body",
	296	sugg,
	297	);
	298	}
	299	}
	300	}
	301	}
	302	}
	303
	304	/// Functions marked with these attributes must have the exact signature.
	305	fn requires_exact_signature(attrs: &[Attribute]) -> bool {
	306	attrs.iter().any(\|attr\| {
	307	[sym::proc_macro, sym::proc_macro_attribute, sym::proc_macro_derive]
	308	.iter()
	309	.any(\|&allow\| attr.has_name(allow))
	310	})
	311	}
	312
	313	#[derive(Default)]
	314	struct MovedVariablesCtxt {
cdc7bbd5	315	moved_vars: HirIdSet,
f20569fa XL	316	/// Spans which need to be prefixed with `*` for dereferencing the
f20569fa XL	317	/// suggested additional reference.
cdc7bbd5	318	spans_need_deref: HirIdMap<FxHashSet<Span>>,
f20569fa XL	319	}
	320
	321	impl MovedVariablesCtxt {
	322	fn move_common(&mut self, cmt: &euv::PlaceWithHirId<'_>) {
	323	if let euv::PlaceBase::Local(vid) = cmt.place.base {
	324	self.moved_vars.insert(vid);
	325	}
	326	}
	327	}
	328
	329	impl<'tcx> euv::Delegate<'tcx> for MovedVariablesCtxt {
136023e0 XL	330	fn consume(&mut self, cmt: &euv::PlaceWithHirId<'tcx>, _: HirId) {
136023e0 XL	331	self.move_common(cmt);
f20569fa XL	332	}
	333
	334	fn borrow(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {}
	335
	336	fn mutate(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: HirId) {}
	337
cdc7bbd5	338	fn fake_read(&mut self, _: rustc_typeck::expr_use_visitor::Place<'tcx>, _: FakeReadCause, _: HirId) {}
f20569fa	339	}