[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, Diagnostic};
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);
    /// }
    /// ```
    #[clippy::version = "pre 1.29.0"]
    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())
            .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 Diagnostic| {
                        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,
                                    traits::ObligationCause::dummy_with_span(span),
                                ).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);
                            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) {
                            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;
ee023bcb	9	use rustc_errors::{Applicability, Diagnostic};
f20569fa XL	10	use rustc_hir::intravisit::FnKind;
f20569fa XL	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	/// ```
a2a8927a	54	#[clippy::version = "pre 1.29.0"]
f20569fa XL	55	pub NEEDLESS_PASS_BY_VALUE,
	56	pedantic,
	57	"functions taking arguments by value, but not consuming them in its body"
	58	}
	59
	60	declare_lint_pass!(NeedlessPassByValue => [NEEDLESS_PASS_BY_VALUE]);
	61
	62	macro_rules! need {
	63	($e: expr) => {
	64	if let Some(x) = $e {
	65	x
	66	} else {
	67	return;
	68	}
	69	};
	70	}
	71
	72	impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
	73	#[allow(clippy::too_many_lines)]
	74	fn check_fn(
	75	&mut self,
	76	cx: &LateContext<'tcx>,
	77	kind: FnKind<'tcx>,
	78	decl: &'tcx FnDecl<'_>,
	79	body: &'tcx Body<'_>,
	80	span: Span,
	81	hir_id: HirId,
	82	) {
	83	if span.from_expansion() {
	84	return;
	85	}
	86
	87	match kind {
	88	FnKind::ItemFn(.., header, _) => {
	89	let attrs = cx.tcx.hir().attrs(hir_id);
	90	if header.abi != Abi::Rust \|\| requires_exact_signature(attrs) {
	91	return;
	92	}
	93	},
	94	FnKind::Method(..) => (),
	95	FnKind::Closure => return,
	96	}
	97
	98	// Exclude non-inherent impls
	99	if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(hir_id)) {
	100	if matches!(
	101	item.kind,
	102	ItemKind::Impl(Impl { of_trait: Some(_), .. }) \| ItemKind::Trait(..)
	103	) {
	104	return;
	105	}
	106	}
	107
	108	// Allow `Borrow` or functions to be taken by value
f20569fa XL	109	let allowed_traits = [
	110	need!(cx.tcx.lang_items().fn_trait()),
	111	need!(cx.tcx.lang_items().fn_once_trait()),
	112	need!(cx.tcx.lang_items().fn_mut_trait()),
	113	need!(get_trait_def_id(cx, &paths::RANGE_ARGUMENT_TRAIT)),
	114	];
	115
	116	let sized_trait = need!(cx.tcx.lang_items().sized_trait());
	117
	118	let fn_def_id = cx.tcx.hir().local_def_id(hir_id);
	119
	120	let preds = traits::elaborate_predicates(cx.tcx, cx.param_env.caller_bounds().iter())
5099ac24	121	.filter(\|p\| !p.is_global())
f20569fa XL	122	.filter_map(\|obligation\| {
	123	// Note that we do not want to deal with qualified predicates here.
	124	match obligation.predicate.kind().no_bound_vars() {
94222f64	125	Some(ty::PredicateKind::Trait(pred)) if pred.def_id() != sized_trait => Some(pred),
f20569fa XL	126	_ => None,
	127	}
	128	})
	129	.collect::<Vec<_>>();
	130
	131	// Collect moved variables and spans which will need dereferencings from the
	132	// function body.
	133	let MovedVariablesCtxt {
	134	moved_vars,
	135	spans_need_deref,
	136	..
	137	} = {
	138	let mut ctx = MovedVariablesCtxt::default();
	139	cx.tcx.infer_ctxt().enter(\|infcx\| {
	140	euv::ExprUseVisitor::new(&mut ctx, &infcx, fn_def_id, cx.param_env, cx.typeck_results())
	141	.consume_body(body);
	142	});
	143	ctx
	144	};
	145
	146	let fn_sig = cx.tcx.fn_sig(fn_def_id);
	147	let fn_sig = cx.tcx.erase_late_bound_regions(fn_sig);
	148
	149	for (idx, ((input, &ty), arg)) in decl.inputs.iter().zip(fn_sig.inputs()).zip(body.params).enumerate() {
	150	// All spans generated from a proc-macro invocation are the same...
	151	if span == input.span {
	152	return;
	153	}
	154
	155	// Ignore `self`s.
	156	if idx == 0 {
	157	if let PatKind::Binding(.., ident, _) = arg.pat.kind {
	158	if ident.name == kw::SelfLower {
	159	continue;
	160	}
	161	}
	162	}
	163
	164	//
	165	// * Exclude a type that is specifically bounded by `Borrow`.
	166	// * Exclude a type whose reference also fulfills its bound. (e.g., `std::convert::AsRef`,
	167	// `serde::Serialize`)
	168	let (implements_borrow_trait, all_borrowable_trait) = {
	169	let preds = preds.iter().filter(\|t\| t.self_ty() == ty).collect::<Vec<_>>();
	170
	171	(
94222f64	172	preds.iter().any(\|t\| cx.tcx.is_diagnostic_item(sym::Borrow, t.def_id())),
f20569fa XL	173	!preds.is_empty() && {
	174	let ty_empty_region = cx.tcx.mk_imm_ref(cx.tcx.lifetimes.re_root_empty, ty);
	175	preds.iter().all(\|t\| {
	176	let ty_params = t.trait_ref.substs.iter().skip(1).collect::<Vec<_>>();
	177	implements_trait(cx, ty_empty_region, t.def_id(), &ty_params)
	178	})
	179	},
	180	)
	181	};
	182
	183	if_chain! {
	184	if !is_self(arg);
	185	if !ty.is_mutable_ptr();
	186	if !is_copy(cx, ty);
	187	if !allowed_traits.iter().any(\|&t\| implements_trait(cx, ty, t, &[]));
	188	if !implements_borrow_trait;
	189	if !all_borrowable_trait;
	190
	191	if let PatKind::Binding(mode, canonical_id, ..) = arg.pat.kind;
	192	if !moved_vars.contains(&canonical_id);
	193	then {
	194	if mode == BindingAnnotation::Mutable \|\| mode == BindingAnnotation::RefMut {
	195	continue;
	196	}
	197
	198	// Dereference suggestion
ee023bcb	199	let sugg = \|diag: &mut Diagnostic\| {
f20569fa	200	if let ty::Adt(def, ..) = ty.kind() {
ee023bcb FG	201	if let Some(span) = cx.tcx.hir().span_if_local(def.did()) {
	202	if can_type_implement_copy(
	203	cx.tcx,
	204	cx.param_env,
	205	ty,
	206	traits::ObligationCause::dummy_with_span(span),
	207	).is_ok() {
f20569fa XL	208	diag.span_help(span, "consider marking this type as `Copy`");
	209	}
	210	}
	211	}
	212
	213	let deref_span = spans_need_deref.get(&canonical_id);
	214	if_chain! {
c295e0f8	215	if is_type_diagnostic_item(cx, ty, sym::Vec);
f20569fa XL	216	if let Some(clone_spans) =
f20569fa XL	217	get_spans(cx, Some(body.id()), idx, &[("clone", ".to_owned()")]);
cdc7bbd5	218	if let TyKind::Path(QPath::Resolved(_, path)) = input.kind;
f20569fa XL	219	if let Some(elem_ty) = path.segments.iter()
	220	.find(\|seg\| seg.ident.name == sym::Vec)
	221	.and_then(\|ps\| ps.args.as_ref())
	222	.map(\|params\| params.args.iter().find_map(\|arg\| match arg {
	223	GenericArg::Type(ty) => Some(ty),
	224	_ => None,
	225	}).unwrap());
	226	then {
	227	let slice_ty = format!("&[{}]", snippet(cx, elem_ty.span, "_"));
	228	diag.span_suggestion(
	229	input.span,
	230	"consider changing the type to",
	231	slice_ty,
	232	Applicability::Unspecified,
	233	);
	234
	235	for (span, suggestion) in clone_spans {
	236	diag.span_suggestion(
	237	span,
	238	&snippet_opt(cx, span)
	239	.map_or(
	240	"change the call to".into(),
	241	\|x\| Cow::from(format!("change `{}` to", x)),
	242	),
	243	suggestion.into(),
	244	Applicability::Unspecified,
	245	);
	246	}
	247
	248	// cannot be destructured, no need for `*` suggestion
	249	assert!(deref_span.is_none());
	250	return;
	251	}
	252	}
	253
c295e0f8	254	if is_type_diagnostic_item(cx, ty, sym::String) {
f20569fa XL	255	if let Some(clone_spans) =
	256	get_spans(cx, Some(body.id()), idx, &[("clone", ".to_string()"), ("as_str", "")]) {
	257	diag.span_suggestion(
	258	input.span,
	259	"consider changing the type to",
	260	"&str".to_string(),
	261	Applicability::Unspecified,
	262	);
	263
	264	for (span, suggestion) in clone_spans {
	265	diag.span_suggestion(
	266	span,
	267	&snippet_opt(cx, span)
	268	.map_or(
	269	"change the call to".into(),
	270	\|x\| Cow::from(format!("change `{}` to", x))
	271	),
	272	suggestion.into(),
	273	Applicability::Unspecified,
	274	);
	275	}
	276
	277	assert!(deref_span.is_none());
	278	return;
	279	}
	280	}
	281
	282	let mut spans = vec![(input.span, format!("&{}", snippet(cx, input.span, "_")))];
	283
	284	// Suggests adding `*` to dereference the added reference.
	285	if let Some(deref_span) = deref_span {
	286	spans.extend(
	287	deref_span
	288	.iter()
cdc7bbd5	289	.copied()
f20569fa XL	290	.map(\|span\| (span, format!("*{}", snippet(cx, span, "<expr>")))),
	291	);
	292	spans.sort_by_key(\|&(span, _)\| span);
	293	}
	294	multispan_sugg(diag, "consider taking a reference instead", spans);
	295	};
	296
	297	span_lint_and_then(
	298	cx,
	299	NEEDLESS_PASS_BY_VALUE,
	300	input.span,
	301	"this argument is passed by value, but not consumed in the function body",
	302	sugg,
	303	);
	304	}
	305	}
	306	}
	307	}
	308	}
	309
	310	/// Functions marked with these attributes must have the exact signature.
	311	fn requires_exact_signature(attrs: &[Attribute]) -> bool {
	312	attrs.iter().any(\|attr\| {
	313	[sym::proc_macro, sym::proc_macro_attribute, sym::proc_macro_derive]
	314	.iter()
	315	.any(\|&allow\| attr.has_name(allow))
	316	})
	317	}
	318
	319	#[derive(Default)]
	320	struct MovedVariablesCtxt {
cdc7bbd5	321	moved_vars: HirIdSet,
f20569fa XL	322	/// Spans which need to be prefixed with `*` for dereferencing the
f20569fa XL	323	/// suggested additional reference.
cdc7bbd5	324	spans_need_deref: HirIdMap<FxHashSet<Span>>,
f20569fa XL	325	}
	326
	327	impl MovedVariablesCtxt {
	328	fn move_common(&mut self, cmt: &euv::PlaceWithHirId<'_>) {
	329	if let euv::PlaceBase::Local(vid) = cmt.place.base {
	330	self.moved_vars.insert(vid);
	331	}
	332	}
	333	}
	334
	335	impl<'tcx> euv::Delegate<'tcx> for MovedVariablesCtxt {
136023e0 XL	336	fn consume(&mut self, cmt: &euv::PlaceWithHirId<'tcx>, _: HirId) {
136023e0 XL	337	self.move_common(cmt);
f20569fa XL	338	}
	339
	340	fn borrow(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {}
	341
	342	fn mutate(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: HirId) {}
	343
cdc7bbd5	344	fn fake_read(&mut self, _: rustc_typeck::expr_use_visitor::Place<'tcx>, _: FakeReadCause, _: HirId) {}
f20569fa	345	}