rustc_borrowck/diagnostics/mod.rs
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//! Borrow checker diagnostics.
use rustc_abi::{FieldIdx, VariantIdx};
use rustc_errors::{Applicability, Diag, MultiSpan};
use rustc_hir::def::{CtorKind, Namespace};
use rustc_hir::{self as hir, CoroutineKind, LangItem};
use rustc_index::IndexSlice;
use rustc_infer::infer::BoundRegionConversionTime;
use rustc_infer::traits::SelectionError;
use rustc_middle::bug;
use rustc_middle::mir::tcx::PlaceTy;
use rustc_middle::mir::{
AggregateKind, CallSource, ConstOperand, FakeReadCause, Local, LocalInfo, LocalKind, Location,
Operand, Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator,
TerminatorKind,
};
use rustc_middle::ty::print::Print;
use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
use rustc_middle::util::{CallDesugaringKind, call_kind};
use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult};
use rustc_span::def_id::LocalDefId;
use rustc_span::source_map::Spanned;
use rustc_span::symbol::sym;
use rustc_span::{DUMMY_SP, Span, Symbol};
use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
use rustc_trait_selection::infer::InferCtxtExt;
use rustc_trait_selection::traits::{
FulfillmentErrorCode, type_known_to_meet_bound_modulo_regions,
};
use tracing::debug;
use super::MirBorrowckCtxt;
use super::borrow_set::BorrowData;
use crate::fluent_generated as fluent;
use crate::session_diagnostics::{
CaptureArgLabel, CaptureReasonLabel, CaptureReasonNote, CaptureReasonSuggest, CaptureVarCause,
CaptureVarKind, CaptureVarPathUseCause, OnClosureNote,
};
mod find_all_local_uses;
mod find_use;
mod outlives_suggestion;
mod region_name;
mod var_name;
mod bound_region_errors;
mod conflict_errors;
mod explain_borrow;
mod move_errors;
mod mutability_errors;
mod opaque_suggestions;
mod region_errors;
pub(crate) use bound_region_errors::{ToUniverseInfo, UniverseInfo};
pub(crate) use move_errors::{IllegalMoveOriginKind, MoveError};
pub(crate) use mutability_errors::AccessKind;
pub(crate) use outlives_suggestion::OutlivesSuggestionBuilder;
pub(crate) use region_errors::{ErrorConstraintInfo, RegionErrorKind, RegionErrors};
pub(crate) use region_name::{RegionName, RegionNameSource};
pub(crate) use rustc_middle::util::CallKind;
pub(super) struct DescribePlaceOpt {
including_downcast: bool,
/// Enable/Disable tuple fields.
/// For example `x` tuple. if it's `true` `x.0`. Otherwise `x`
including_tuple_field: bool,
}
pub(super) struct IncludingTupleField(pub(super) bool);
impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
/// Adds a suggestion when a closure is invoked twice with a moved variable or when a closure
/// is moved after being invoked.
///
/// ```text
/// note: closure cannot be invoked more than once because it moves the variable `dict` out of
/// its environment
/// --> $DIR/issue-42065.rs:16:29
/// |
/// LL | for (key, value) in dict {
/// | ^^^^
/// ```
#[allow(rustc::diagnostic_outside_of_impl)] // FIXME
pub(super) fn add_moved_or_invoked_closure_note(
&self,
location: Location,
place: PlaceRef<'tcx>,
diag: &mut Diag<'infcx>,
) -> bool {
debug!("add_moved_or_invoked_closure_note: location={:?} place={:?}", location, place);
let mut target = place.local_or_deref_local();
for stmt in &self.body[location.block].statements[location.statement_index..] {
debug!("add_moved_or_invoked_closure_note: stmt={:?} target={:?}", stmt, target);
if let StatementKind::Assign(box (into, Rvalue::Use(from))) = &stmt.kind {
debug!("add_fnonce_closure_note: into={:?} from={:?}", into, from);
match from {
Operand::Copy(place) | Operand::Move(place)
if target == place.local_or_deref_local() =>
{
target = into.local_or_deref_local()
}
_ => {}
}
}
}
// Check if we are attempting to call a closure after it has been invoked.
let terminator = self.body[location.block].terminator();
debug!("add_moved_or_invoked_closure_note: terminator={:?}", terminator);
if let TerminatorKind::Call {
func: Operand::Constant(box ConstOperand { const_, .. }),
args,
..
} = &terminator.kind
{
if let ty::FnDef(id, _) = *const_.ty().kind() {
debug!("add_moved_or_invoked_closure_note: id={:?}", id);
if self.infcx.tcx.is_lang_item(self.infcx.tcx.parent(id), LangItem::FnOnce) {
let closure = match args.first() {
Some(Spanned {
node: Operand::Copy(place) | Operand::Move(place), ..
}) if target == place.local_or_deref_local() => {
place.local_or_deref_local().unwrap()
}
_ => return false,
};
debug!("add_moved_or_invoked_closure_note: closure={:?}", closure);
if let ty::Closure(did, _) = self.body.local_decls[closure].ty.kind() {
let did = did.expect_local();
if let Some((span, hir_place)) = self.infcx.tcx.closure_kind_origin(did) {
diag.subdiagnostic(OnClosureNote::InvokedTwice {
place_name: &ty::place_to_string_for_capture(
self.infcx.tcx,
hir_place,
),
span: *span,
});
return true;
}
}
}
}
}
// Check if we are just moving a closure after it has been invoked.
if let Some(target) = target {
if let ty::Closure(did, _) = self.body.local_decls[target].ty.kind() {
let did = did.expect_local();
if let Some((span, hir_place)) = self.infcx.tcx.closure_kind_origin(did) {
diag.subdiagnostic(OnClosureNote::MovedTwice {
place_name: &ty::place_to_string_for_capture(self.infcx.tcx, hir_place),
span: *span,
});
return true;
}
}
}
false
}
/// End-user visible description of `place` if one can be found.
/// If the place is a temporary for instance, `"value"` will be returned.
pub(super) fn describe_any_place(&self, place_ref: PlaceRef<'tcx>) -> String {
match self.describe_place(place_ref) {
Some(mut descr) => {
// Surround descr with `backticks`.
descr.reserve(2);
descr.insert(0, '`');
descr.push('`');
descr
}
None => "value".to_string(),
}
}
/// End-user visible description of `place` if one can be found.
/// If the place is a temporary for instance, `None` will be returned.
pub(super) fn describe_place(&self, place_ref: PlaceRef<'tcx>) -> Option<String> {
self.describe_place_with_options(place_ref, DescribePlaceOpt {
including_downcast: false,
including_tuple_field: true,
})
}
/// End-user visible description of `place` if one can be found. If the place is a temporary
/// for instance, `None` will be returned.
/// `IncludingDowncast` parameter makes the function return `None` if `ProjectionElem` is
/// `Downcast` and `IncludingDowncast` is true
pub(super) fn describe_place_with_options(
&self,
place: PlaceRef<'tcx>,
opt: DescribePlaceOpt,
) -> Option<String> {
let local = place.local;
let mut autoderef_index = None;
let mut buf = String::new();
let mut ok = self.append_local_to_string(local, &mut buf);
for (index, elem) in place.projection.into_iter().enumerate() {
match elem {
ProjectionElem::Deref => {
if index == 0 {
if self.body.local_decls[local].is_ref_for_guard() {
continue;
}
if let LocalInfo::StaticRef { def_id, .. } =
*self.body.local_decls[local].local_info()
{
buf.push_str(self.infcx.tcx.item_name(def_id).as_str());
ok = Ok(());
continue;
}
}
if let Some(field) = self.is_upvar_field_projection(PlaceRef {
local,
projection: place.projection.split_at(index + 1).0,
}) {
let var_index = field.index();
buf = self.upvars[var_index].to_string(self.infcx.tcx);
ok = Ok(());
if !self.upvars[var_index].is_by_ref() {
buf.insert(0, '*');
}
} else {
if autoderef_index.is_none() {
autoderef_index = match place.projection.iter().rposition(|elem| {
!matches!(
elem,
ProjectionElem::Deref | ProjectionElem::Downcast(..)
)
}) {
Some(index) => Some(index + 1),
None => Some(0),
};
}
if index >= autoderef_index.unwrap() {
buf.insert(0, '*');
}
}
}
ProjectionElem::Downcast(..) if opt.including_downcast => return None,
ProjectionElem::Downcast(..) => (),
ProjectionElem::OpaqueCast(..) => (),
ProjectionElem::Subtype(..) => (),
ProjectionElem::Field(field, _ty) => {
// FIXME(project-rfc_2229#36): print capture precisely here.
if let Some(field) = self.is_upvar_field_projection(PlaceRef {
local,
projection: place.projection.split_at(index + 1).0,
}) {
buf = self.upvars[field.index()].to_string(self.infcx.tcx);
ok = Ok(());
} else {
let field_name = self.describe_field(
PlaceRef { local, projection: place.projection.split_at(index).0 },
*field,
IncludingTupleField(opt.including_tuple_field),
);
if let Some(field_name_str) = field_name {
buf.push('.');
buf.push_str(&field_name_str);
}
}
}
ProjectionElem::Index(index) => {
buf.push('[');
if self.append_local_to_string(*index, &mut buf).is_err() {
buf.push('_');
}
buf.push(']');
}
ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {
// Since it isn't possible to borrow an element on a particular index and
// then use another while the borrow is held, don't output indices details
// to avoid confusing the end-user
buf.push_str("[..]");
}
}
}
ok.ok().map(|_| buf)
}
fn describe_name(&self, place: PlaceRef<'tcx>) -> Option<Symbol> {
for elem in place.projection.into_iter() {
match elem {
ProjectionElem::Downcast(Some(name), _) => {
return Some(*name);
}
_ => {}
}
}
None
}
/// Appends end-user visible description of the `local` place to `buf`. If `local` doesn't have
/// a name, or its name was generated by the compiler, then `Err` is returned
fn append_local_to_string(&self, local: Local, buf: &mut String) -> Result<(), ()> {
let decl = &self.body.local_decls[local];
match self.local_names[local] {
Some(name) if !decl.from_compiler_desugaring() => {
buf.push_str(name.as_str());
Ok(())
}
_ => Err(()),
}
}
/// End-user visible description of the `field`nth field of `base`
fn describe_field(
&self,
place: PlaceRef<'tcx>,
field: FieldIdx,
including_tuple_field: IncludingTupleField,
) -> Option<String> {
let place_ty = match place {
PlaceRef { local, projection: [] } => PlaceTy::from_ty(self.body.local_decls[local].ty),
PlaceRef { local, projection: [proj_base @ .., elem] } => match elem {
ProjectionElem::Deref
| ProjectionElem::Index(..)
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Subslice { .. } => {
PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx)
}
ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx),
ProjectionElem::Subtype(ty) | ProjectionElem::OpaqueCast(ty) => {
PlaceTy::from_ty(*ty)
}
ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type),
},
};
self.describe_field_from_ty(
place_ty.ty,
field,
place_ty.variant_index,
including_tuple_field,
)
}
/// End-user visible description of the `field_index`nth field of `ty`
fn describe_field_from_ty(
&self,
ty: Ty<'_>,
field: FieldIdx,
variant_index: Option<VariantIdx>,
including_tuple_field: IncludingTupleField,
) -> Option<String> {
if let Some(boxed_ty) = ty.boxed_ty() {
// If the type is a box, the field is described from the boxed type
self.describe_field_from_ty(boxed_ty, field, variant_index, including_tuple_field)
} else {
match *ty.kind() {
ty::Adt(def, _) => {
let variant = if let Some(idx) = variant_index {
assert!(def.is_enum());
def.variant(idx)
} else {
def.non_enum_variant()
};
if !including_tuple_field.0 && variant.ctor_kind() == Some(CtorKind::Fn) {
return None;
}
Some(variant.fields[field].name.to_string())
}
ty::Tuple(_) => Some(field.index().to_string()),
ty::Ref(_, ty, _) | ty::RawPtr(ty, _) => {
self.describe_field_from_ty(ty, field, variant_index, including_tuple_field)
}
ty::Array(ty, _) | ty::Slice(ty) => {
self.describe_field_from_ty(ty, field, variant_index, including_tuple_field)
}
ty::Closure(def_id, _) | ty::Coroutine(def_id, _) => {
// We won't be borrowck'ing here if the closure came from another crate,
// so it's safe to call `expect_local`.
//
// We know the field exists so it's safe to call operator[] and `unwrap` here.
let def_id = def_id.expect_local();
let var_id =
self.infcx.tcx.closure_captures(def_id)[field.index()].get_root_variable();
Some(self.infcx.tcx.hir().name(var_id).to_string())
}
_ => {
// Might need a revision when the fields in trait RFC is implemented
// (https://github.com/rust-lang/rfcs/pull/1546)
bug!("End-user description not implemented for field access on `{:?}`", ty);
}
}
}
}
pub(super) fn borrowed_content_source(
&self,
deref_base: PlaceRef<'tcx>,
) -> BorrowedContentSource<'tcx> {
let tcx = self.infcx.tcx;
// Look up the provided place and work out the move path index for it,
// we'll use this to check whether it was originally from an overloaded
// operator.
match self.move_data.rev_lookup.find(deref_base) {
LookupResult::Exact(mpi) | LookupResult::Parent(Some(mpi)) => {
debug!("borrowed_content_source: mpi={:?}", mpi);
for i in &self.move_data.init_path_map[mpi] {
let init = &self.move_data.inits[*i];
debug!("borrowed_content_source: init={:?}", init);
// We're only interested in statements that initialized a value, not the
// initializations from arguments.
let InitLocation::Statement(loc) = init.location else { continue };
let bbd = &self.body[loc.block];
let is_terminator = bbd.statements.len() == loc.statement_index;
debug!(
"borrowed_content_source: loc={:?} is_terminator={:?}",
loc, is_terminator,
);
if !is_terminator {
continue;
} else if let Some(Terminator {
kind:
TerminatorKind::Call {
func,
call_source: CallSource::OverloadedOperator,
..
},
..
}) = &bbd.terminator
{
if let Some(source) =
BorrowedContentSource::from_call(func.ty(self.body, tcx), tcx)
{
return source;
}
}
}
}
// Base is a `static` so won't be from an overloaded operator
_ => (),
};
// If we didn't find an overloaded deref or index, then assume it's a
// built in deref and check the type of the base.
let base_ty = deref_base.ty(self.body, tcx).ty;
if base_ty.is_unsafe_ptr() {
BorrowedContentSource::DerefRawPointer
} else if base_ty.is_mutable_ptr() {
BorrowedContentSource::DerefMutableRef
} else {
BorrowedContentSource::DerefSharedRef
}
}
/// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime
/// name where required.
pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
// We need to add synthesized lifetimes where appropriate. We do
// this by hooking into the pretty printer and telling it to label the
// lifetimes without names with the value `'0`.
if let ty::Ref(region, ..) = ty.kind() {
match **region {
ty::ReBound(_, ty::BoundRegion { kind: br, .. })
| ty::RePlaceholder(ty::PlaceholderRegion {
bound: ty::BoundRegion { kind: br, .. },
..
}) => printer.region_highlight_mode.highlighting_bound_region(br, counter),
_ => {}
}
}
ty.print(&mut printer).unwrap();
printer.into_buffer()
}
/// Returns the name of the provided `Ty` (that must be a reference)'s region with a
/// synthesized lifetime name where required.
pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
let region = if let ty::Ref(region, ..) = ty.kind() {
match **region {
ty::ReBound(_, ty::BoundRegion { kind: br, .. })
| ty::RePlaceholder(ty::PlaceholderRegion {
bound: ty::BoundRegion { kind: br, .. },
..
}) => printer.region_highlight_mode.highlighting_bound_region(br, counter),
_ => {}
}
region
} else {
bug!("ty for annotation of borrow region is not a reference");
};
region.print(&mut printer).unwrap();
printer.into_buffer()
}
}
/// The span(s) associated to a use of a place.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub(super) enum UseSpans<'tcx> {
/// The access is caused by capturing a variable for a closure.
ClosureUse {
/// This is true if the captured variable was from a coroutine.
closure_kind: hir::ClosureKind,
/// The span of the args of the closure, including the `move` keyword if
/// it's present.
args_span: Span,
/// The span of the use resulting in capture kind
/// Check `ty::CaptureInfo` for more details
capture_kind_span: Span,
/// The span of the use resulting in the captured path
/// Check `ty::CaptureInfo` for more details
path_span: Span,
},
/// The access is caused by using a variable as the receiver of a method
/// that takes 'self'
FnSelfUse {
/// The span of the variable being moved
var_span: Span,
/// The span of the method call on the variable
fn_call_span: Span,
/// The definition span of the method being called
fn_span: Span,
kind: CallKind<'tcx>,
},
/// This access is caused by a `match` or `if let` pattern.
PatUse(Span),
/// This access has a single span associated to it: common case.
OtherUse(Span),
}
impl UseSpans<'_> {
pub(super) fn args_or_use(self) -> Span {
match self {
UseSpans::ClosureUse { args_span: span, .. }
| UseSpans::PatUse(span)
| UseSpans::OtherUse(span) => span,
UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
fn_call_span
}
UseSpans::FnSelfUse { var_span, .. } => var_span,
}
}
/// Returns the span of `self`, in the case of a `ClosureUse` returns the `path_span`
pub(super) fn var_or_use_path_span(self) -> Span {
match self {
UseSpans::ClosureUse { path_span: span, .. }
| UseSpans::PatUse(span)
| UseSpans::OtherUse(span) => span,
UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
fn_call_span
}
UseSpans::FnSelfUse { var_span, .. } => var_span,
}
}
/// Returns the span of `self`, in the case of a `ClosureUse` returns the `capture_kind_span`
pub(super) fn var_or_use(self) -> Span {
match self {
UseSpans::ClosureUse { capture_kind_span: span, .. }
| UseSpans::PatUse(span)
| UseSpans::OtherUse(span) => span,
UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
fn_call_span
}
UseSpans::FnSelfUse { var_span, .. } => var_span,
}
}
// FIXME(coroutines): Make this just return the `ClosureKind` directly?
pub(super) fn coroutine_kind(self) -> Option<CoroutineKind> {
match self {
UseSpans::ClosureUse {
closure_kind: hir::ClosureKind::Coroutine(coroutine_kind),
..
} => Some(coroutine_kind),
_ => None,
}
}
/// Add a span label to the arguments of the closure, if it exists.
#[allow(rustc::diagnostic_outside_of_impl)]
pub(super) fn args_subdiag(self, err: &mut Diag<'_>, f: impl FnOnce(Span) -> CaptureArgLabel) {
if let UseSpans::ClosureUse { args_span, .. } = self {
err.subdiagnostic(f(args_span));
}
}
/// Add a span label to the use of the captured variable, if it exists.
/// only adds label to the `path_span`
#[allow(rustc::diagnostic_outside_of_impl)]
pub(super) fn var_path_only_subdiag(
self,
err: &mut Diag<'_>,
action: crate::InitializationRequiringAction,
) {
use CaptureVarPathUseCause::*;
use crate::InitializationRequiringAction::*;
if let UseSpans::ClosureUse { closure_kind, path_span, .. } = self {
match closure_kind {
hir::ClosureKind::Coroutine(_) => {
err.subdiagnostic(match action {
Borrow => BorrowInCoroutine { path_span },
MatchOn | Use => UseInCoroutine { path_span },
Assignment => AssignInCoroutine { path_span },
PartialAssignment => AssignPartInCoroutine { path_span },
});
}
hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
err.subdiagnostic(match action {
Borrow => BorrowInClosure { path_span },
MatchOn | Use => UseInClosure { path_span },
Assignment => AssignInClosure { path_span },
PartialAssignment => AssignPartInClosure { path_span },
});
}
}
}
}
/// Add a subdiagnostic to the use of the captured variable, if it exists.
#[allow(rustc::diagnostic_outside_of_impl)]
pub(super) fn var_subdiag(
self,
err: &mut Diag<'_>,
kind: Option<rustc_middle::mir::BorrowKind>,
f: impl FnOnce(hir::ClosureKind, Span) -> CaptureVarCause,
) {
if let UseSpans::ClosureUse { closure_kind, capture_kind_span, path_span, .. } = self {
if capture_kind_span != path_span {
err.subdiagnostic(match kind {
Some(kd) => match kd {
rustc_middle::mir::BorrowKind::Shared
| rustc_middle::mir::BorrowKind::Fake(_) => {
CaptureVarKind::Immut { kind_span: capture_kind_span }
}
rustc_middle::mir::BorrowKind::Mut { .. } => {
CaptureVarKind::Mut { kind_span: capture_kind_span }
}
},
None => CaptureVarKind::Move { kind_span: capture_kind_span },
});
};
let diag = f(closure_kind, path_span);
err.subdiagnostic(diag);
}
}
/// Returns `false` if this place is not used in a closure.
pub(super) fn for_closure(&self) -> bool {
match *self {
UseSpans::ClosureUse { closure_kind, .. } => {
matches!(closure_kind, hir::ClosureKind::Closure)
}
_ => false,
}
}
/// Returns `false` if this place is not used in a coroutine.
pub(super) fn for_coroutine(&self) -> bool {
match *self {
// FIXME(coroutines): Do we want this to apply to synthetic coroutines?
UseSpans::ClosureUse { closure_kind, .. } => {
matches!(closure_kind, hir::ClosureKind::Coroutine(..))
}
_ => false,
}
}
pub(super) fn or_else<F>(self, if_other: F) -> Self
where
F: FnOnce() -> Self,
{
match self {
closure @ UseSpans::ClosureUse { .. } => closure,
UseSpans::PatUse(_) | UseSpans::OtherUse(_) => if_other(),
fn_self @ UseSpans::FnSelfUse { .. } => fn_self,
}
}
}
pub(super) enum BorrowedContentSource<'tcx> {
DerefRawPointer,
DerefMutableRef,
DerefSharedRef,
OverloadedDeref(Ty<'tcx>),
OverloadedIndex(Ty<'tcx>),
}
impl<'tcx> BorrowedContentSource<'tcx> {
pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String {
match *self {
BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(),
BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(),
BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(),
BorrowedContentSource::OverloadedDeref(ty) => ty
.ty_adt_def()
.and_then(|adt| match tcx.get_diagnostic_name(adt.did())? {
name @ (sym::Rc | sym::Arc) => Some(format!("an `{name}`")),
_ => None,
})
.unwrap_or_else(|| format!("dereference of `{ty}`")),
BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{ty}`"),
}
}
pub(super) fn describe_for_named_place(&self) -> Option<&'static str> {
match *self {
BorrowedContentSource::DerefRawPointer => Some("raw pointer"),
BorrowedContentSource::DerefSharedRef => Some("shared reference"),
BorrowedContentSource::DerefMutableRef => Some("mutable reference"),
// Overloaded deref and index operators should be evaluated into a
// temporary. So we don't need a description here.
BorrowedContentSource::OverloadedDeref(_)
| BorrowedContentSource::OverloadedIndex(_) => None,
}
}
pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String {
match *self {
BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(),
BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(),
BorrowedContentSource::DerefMutableRef => {
bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")
}
BorrowedContentSource::OverloadedDeref(ty) => ty
.ty_adt_def()
.and_then(|adt| match tcx.get_diagnostic_name(adt.did())? {
name @ (sym::Rc | sym::Arc) => Some(format!("an `{name}`")),
_ => None,
})
.unwrap_or_else(|| format!("dereference of `{ty}`")),
BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{ty}`"),
}
}
fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self> {
match *func.kind() {
ty::FnDef(def_id, args) => {
let trait_id = tcx.trait_of_item(def_id)?;
if tcx.is_lang_item(trait_id, LangItem::Deref)
|| tcx.is_lang_item(trait_id, LangItem::DerefMut)
{
Some(BorrowedContentSource::OverloadedDeref(args.type_at(0)))
} else if tcx.is_lang_item(trait_id, LangItem::Index)
|| tcx.is_lang_item(trait_id, LangItem::IndexMut)
{
Some(BorrowedContentSource::OverloadedIndex(args.type_at(0)))
} else {
None
}
}
_ => None,
}
}
}
/// Helper struct for `explain_captures`.
struct CapturedMessageOpt {
is_partial_move: bool,
is_loop_message: bool,
is_move_msg: bool,
is_loop_move: bool,
has_suggest_reborrow: bool,
maybe_reinitialized_locations_is_empty: bool,
}
impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
/// Finds the spans associated to a move or copy of move_place at location.
pub(super) fn move_spans(
&self,
moved_place: PlaceRef<'tcx>, // Could also be an upvar.
location: Location,
) -> UseSpans<'tcx> {
use self::UseSpans::*;
let Some(stmt) = self.body[location.block].statements.get(location.statement_index) else {
return OtherUse(self.body.source_info(location).span);
};
debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt);
if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind
&& let AggregateKind::Closure(def_id, _) | AggregateKind::Coroutine(def_id, _) = **kind
{
debug!("move_spans: def_id={:?} places={:?}", def_id, places);
let def_id = def_id.expect_local();
if let Some((args_span, closure_kind, capture_kind_span, path_span)) =
self.closure_span(def_id, moved_place, places)
{
return ClosureUse { closure_kind, args_span, capture_kind_span, path_span };
}
}
// StatementKind::FakeRead only contains a def_id if they are introduced as a result
// of pattern matching within a closure.
if let StatementKind::FakeRead(box (cause, place)) = stmt.kind {
match cause {
FakeReadCause::ForMatchedPlace(Some(closure_def_id))
| FakeReadCause::ForLet(Some(closure_def_id)) => {
debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
let places = &[Operand::Move(place)];
if let Some((args_span, closure_kind, capture_kind_span, path_span)) =
self.closure_span(closure_def_id, moved_place, IndexSlice::from_raw(places))
{
return ClosureUse {
closure_kind,
args_span,
capture_kind_span,
path_span,
};
}
}
_ => {}
}
}
let normal_ret =
if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) {
PatUse(stmt.source_info.span)
} else {
OtherUse(stmt.source_info.span)
};
// We are trying to find MIR of the form:
// ```
// _temp = _moved_val;
// ...
// FnSelfCall(_temp, ...)
// ```
//
// where `_moved_val` is the place we generated the move error for,
// `_temp` is some other local, and `FnSelfCall` is a function
// that has a `self` parameter.
let target_temp = match stmt.kind {
StatementKind::Assign(box (temp, _)) if temp.as_local().is_some() => {
temp.as_local().unwrap()
}
_ => return normal_ret,
};
debug!("move_spans: target_temp = {:?}", target_temp);
if let Some(Terminator {
kind: TerminatorKind::Call { fn_span, call_source, .. }, ..
}) = &self.body[location.block].terminator
{
let Some((method_did, method_args)) = rustc_middle::util::find_self_call(
self.infcx.tcx,
self.body,
target_temp,
location.block,
) else {
return normal_ret;
};
let kind = call_kind(
self.infcx.tcx,
self.param_env,
method_did,
method_args,
*fn_span,
call_source.from_hir_call(),
Some(self.infcx.tcx.fn_arg_names(method_did)[0]),
);
return FnSelfUse {
var_span: stmt.source_info.span,
fn_call_span: *fn_span,
fn_span: self.infcx.tcx.def_span(method_did),
kind,
};
}
normal_ret
}
/// Finds the span of arguments of a closure (within `maybe_closure_span`)
/// and its usage of the local assigned at `location`.
/// This is done by searching in statements succeeding `location`
/// and originating from `maybe_closure_span`.
pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx> {
use self::UseSpans::*;
debug!("borrow_spans: use_span={:?} location={:?}", use_span, location);
let target = match self.body[location.block].statements.get(location.statement_index) {
Some(Statement { kind: StatementKind::Assign(box (place, _)), .. }) => {
if let Some(local) = place.as_local() {
local
} else {
return OtherUse(use_span);
}
}
_ => return OtherUse(use_span),
};
if self.body.local_kind(target) != LocalKind::Temp {
// operands are always temporaries.
return OtherUse(use_span);
}
// drop and replace might have moved the assignment to the next block
let maybe_additional_statement =
if let TerminatorKind::Drop { target: drop_target, .. } =
self.body[location.block].terminator().kind
{
self.body[drop_target].statements.first()
} else {
None
};
let statements =
self.body[location.block].statements[location.statement_index + 1..].iter();
for stmt in statements.chain(maybe_additional_statement) {
if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind {
let (&def_id, is_coroutine) = match kind {
box AggregateKind::Closure(def_id, _) => (def_id, false),
box AggregateKind::Coroutine(def_id, _) => (def_id, true),
_ => continue,
};
let def_id = def_id.expect_local();
debug!(
"borrow_spans: def_id={:?} is_coroutine={:?} places={:?}",
def_id, is_coroutine, places
);
if let Some((args_span, closure_kind, capture_kind_span, path_span)) =
self.closure_span(def_id, Place::from(target).as_ref(), places)
{
return ClosureUse { closure_kind, args_span, capture_kind_span, path_span };
} else {
return OtherUse(use_span);
}
}
if use_span != stmt.source_info.span {
break;
}
}
OtherUse(use_span)
}
/// Finds the spans of a captured place within a closure or coroutine.
/// The first span is the location of the use resulting in the capture kind of the capture
/// The second span is the location the use resulting in the captured path of the capture
fn closure_span(
&self,
def_id: LocalDefId,
target_place: PlaceRef<'tcx>,
places: &IndexSlice<FieldIdx, Operand<'tcx>>,
) -> Option<(Span, hir::ClosureKind, Span, Span)> {
debug!(
"closure_span: def_id={:?} target_place={:?} places={:?}",
def_id, target_place, places
);
let hir_id = self.infcx.tcx.local_def_id_to_hir_id(def_id);
let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind;
debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr);
if let hir::ExprKind::Closure(&hir::Closure { kind, fn_decl_span, .. }) = expr {
for (captured_place, place) in
self.infcx.tcx.closure_captures(def_id).iter().zip(places)
{
match place {
Operand::Copy(place) | Operand::Move(place)
if target_place == place.as_ref() =>
{
debug!("closure_span: found captured local {:?}", place);
return Some((
fn_decl_span,
kind,
captured_place.get_capture_kind_span(self.infcx.tcx),
captured_place.get_path_span(self.infcx.tcx),
));
}
_ => {}
}
}
}
None
}
/// Helper to retrieve span(s) of given borrow from the current MIR
/// representation
pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx> {
let span = self.body.source_info(borrow.reserve_location).span;
self.borrow_spans(span, borrow.reserve_location)
}
#[allow(rustc::diagnostic_outside_of_impl)]
#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
fn explain_captures(
&mut self,
err: &mut Diag<'infcx>,
span: Span,
move_span: Span,
move_spans: UseSpans<'tcx>,
moved_place: Place<'tcx>,
msg_opt: CapturedMessageOpt,
) {
let CapturedMessageOpt {
is_partial_move: is_partial,
is_loop_message,
is_move_msg,
is_loop_move,
has_suggest_reborrow,
maybe_reinitialized_locations_is_empty,
} = msg_opt;
if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans {
let place_name = self
.describe_place(moved_place.as_ref())
.map(|n| format!("`{n}`"))
.unwrap_or_else(|| "value".to_owned());
match kind {
CallKind::FnCall { fn_trait_id, self_ty }
if self.infcx.tcx.is_lang_item(fn_trait_id, LangItem::FnOnce) =>
{
err.subdiagnostic(CaptureReasonLabel::Call {
fn_call_span,
place_name: &place_name,
is_partial,
is_loop_message,
});
// Check if the move occurs on a value because of a call on a closure that comes
// from a type parameter `F: FnOnce()`. If so, we provide a targeted `note`:
// ```
// error[E0382]: use of moved value: `blk`
// --> $DIR/once-cant-call-twice-on-heap.rs:8:5
// |
// LL | fn foo<F:FnOnce()>(blk: F) {
// | --- move occurs because `blk` has type `F`, which does not implement the `Copy` trait
// LL | blk();
// | ----- `blk` moved due to this call
// LL | blk();
// | ^^^ value used here after move
// |
// note: `FnOnce` closures can only be called once
// --> $DIR/once-cant-call-twice-on-heap.rs:6:10
// |
// LL | fn foo<F:FnOnce()>(blk: F) {
// | ^^^^^^^^ `F` is made to be an `FnOnce` closure here
// LL | blk();
// | ----- this value implements `FnOnce`, which causes it to be moved when called
// ```
if let ty::Param(param_ty) = *self_ty.kind()
&& let generics = self.infcx.tcx.generics_of(self.mir_def_id())
&& let param = generics.type_param(param_ty, self.infcx.tcx)
&& let Some(hir_generics) = self
.infcx
.tcx
.typeck_root_def_id(self.mir_def_id().to_def_id())
.as_local()
.and_then(|def_id| self.infcx.tcx.hir().get_generics(def_id))
&& let spans = hir_generics
.predicates
.iter()
.filter_map(|pred| match pred {
hir::WherePredicate::BoundPredicate(pred) => Some(pred),
_ => None,
})
.filter(|pred| {
if let Some((id, _)) = pred.bounded_ty.as_generic_param() {
id == param.def_id
} else {
false
}
})
.flat_map(|pred| pred.bounds)
.filter_map(|bound| {
if let Some(trait_ref) = bound.trait_ref()
&& let Some(trait_def_id) = trait_ref.trait_def_id()
&& trait_def_id == fn_trait_id
{
Some(bound.span())
} else {
None
}
})
.collect::<Vec<Span>>()
&& !spans.is_empty()
{
let mut span: MultiSpan = spans.clone().into();
for sp in spans {
span.push_span_label(sp, fluent::borrowck_moved_a_fn_once_in_call_def);
}
span.push_span_label(
fn_call_span,
fluent::borrowck_moved_a_fn_once_in_call,
);
err.span_note(span, fluent::borrowck_moved_a_fn_once_in_call_call);
} else {
err.subdiagnostic(CaptureReasonNote::FnOnceMoveInCall { var_span });
}
}
CallKind::Operator { self_arg, trait_id, .. } => {
let self_arg = self_arg.unwrap();
err.subdiagnostic(CaptureReasonLabel::OperatorUse {
fn_call_span,
place_name: &place_name,
is_partial,
is_loop_message,
});
if self.fn_self_span_reported.insert(fn_span) {
let lang = self.infcx.tcx.lang_items();
err.subdiagnostic(
if [lang.not_trait(), lang.deref_trait(), lang.neg_trait()]
.contains(&Some(trait_id))
{
CaptureReasonNote::UnOpMoveByOperator { span: self_arg.span }
} else {
CaptureReasonNote::LhsMoveByOperator { span: self_arg.span }
},
);
}
}
CallKind::Normal { self_arg, desugaring, method_did, method_args } => {
let self_arg = self_arg.unwrap();
let mut has_sugg = false;
let tcx = self.infcx.tcx;
// Avoid pointing to the same function in multiple different
// error messages.
if span != DUMMY_SP && self.fn_self_span_reported.insert(self_arg.span) {
self.explain_iterator_advancement_in_for_loop_if_applicable(
err,
span,
&move_spans,
);
let func = tcx.def_path_str(method_did);
err.subdiagnostic(CaptureReasonNote::FuncTakeSelf {
func,
place_name: place_name.clone(),
span: self_arg.span,
});
}
let parent_did = tcx.parent(method_did);
let parent_self_ty =
matches!(tcx.def_kind(parent_did), rustc_hir::def::DefKind::Impl { .. })
.then_some(parent_did)
.and_then(|did| match tcx.type_of(did).instantiate_identity().kind() {
ty::Adt(def, ..) => Some(def.did()),
_ => None,
});
let is_option_or_result = parent_self_ty.is_some_and(|def_id| {
matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result))
});
if is_option_or_result && maybe_reinitialized_locations_is_empty {
err.subdiagnostic(CaptureReasonLabel::BorrowContent { var_span });
}
if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring {
let ty = moved_place.ty(self.body, tcx).ty;
let suggest = match tcx.get_diagnostic_item(sym::IntoIterator) {
Some(def_id) => type_known_to_meet_bound_modulo_regions(
self.infcx,
self.param_env,
Ty::new_imm_ref(tcx, tcx.lifetimes.re_erased, ty),
def_id,
),
_ => false,
};
if suggest {
err.subdiagnostic(CaptureReasonSuggest::IterateSlice {
ty,
span: move_span.shrink_to_lo(),
});
}
err.subdiagnostic(CaptureReasonLabel::ImplicitCall {
fn_call_span,
place_name: &place_name,
is_partial,
is_loop_message,
});
// If the moved place was a `&mut` ref, then we can
// suggest to reborrow it where it was moved, so it
// will still be valid by the time we get to the usage.
if let ty::Ref(_, _, hir::Mutability::Mut) =
moved_place.ty(self.body, self.infcx.tcx).ty.kind()
{
// Suggest `reborrow` in other place for following situations:
// 1. If we are in a loop this will be suggested later.
// 2. If the moved value is a mut reference, it is used in a
// generic function and the corresponding arg's type is generic param.
if !is_loop_move && !has_suggest_reborrow {
self.suggest_reborrow(
err,
move_span.shrink_to_lo(),
moved_place.as_ref(),
);
}
}
} else {
if let Some((CallDesugaringKind::Await, _)) = desugaring {
err.subdiagnostic(CaptureReasonLabel::Await {
fn_call_span,
place_name: &place_name,
is_partial,
is_loop_message,
});
} else {
err.subdiagnostic(CaptureReasonLabel::MethodCall {
fn_call_span,
place_name: &place_name,
is_partial,
is_loop_message,
});
}
// Erase and shadow everything that could be passed to the new infcx.
let ty = moved_place.ty(self.body, tcx).ty;
if let ty::Adt(def, args) = ty.peel_refs().kind()
&& tcx.is_lang_item(def.did(), LangItem::Pin)
&& let ty::Ref(_, _, hir::Mutability::Mut) = args.type_at(0).kind()
&& let self_ty = self.infcx.instantiate_binder_with_fresh_vars(
fn_call_span,
BoundRegionConversionTime::FnCall,
tcx.fn_sig(method_did).instantiate(tcx, method_args).input(0),
)
&& self.infcx.can_eq(self.param_env, ty, self_ty)
{
err.subdiagnostic(CaptureReasonSuggest::FreshReborrow {
span: move_span.shrink_to_hi(),
});
has_sugg = true;
}
if let Some(clone_trait) = tcx.lang_items().clone_trait() {
let sugg = if moved_place
.iter_projections()
.any(|(_, elem)| matches!(elem, ProjectionElem::Deref))
{
let (start, end) = if let Some(expr) = self.find_expr(move_span)
&& let Some(_) = self.clone_on_reference(expr)
&& let hir::ExprKind::MethodCall(_, rcvr, _, _) = expr.kind
{
(move_span.shrink_to_lo(), move_span.with_lo(rcvr.span.hi()))
} else {
(move_span.shrink_to_lo(), move_span.shrink_to_hi())
};
vec![
// We use the fully-qualified path because `.clone()` can
// sometimes choose `<&T as Clone>` instead of `<T as Clone>`
// when going through auto-deref, so this ensures that doesn't
// happen, causing suggestions for `.clone().clone()`.
(start, format!("<{ty} as Clone>::clone(&")),
(end, ")".to_string()),
]
} else {
vec![(move_span.shrink_to_hi(), ".clone()".to_string())]
};
if let Some(errors) = self.infcx.type_implements_trait_shallow(
clone_trait,
ty,
self.param_env,
) && !has_sugg
{
let msg = match &errors[..] {
[] => "you can `clone` the value and consume it, but this \
might not be your desired behavior"
.to_string(),
[error] => {
format!(
"you could `clone` the value and consume it, if the \
`{}` trait bound could be satisfied",
error.obligation.predicate,
)
}
[errors @ .., last] => {
format!(
"you could `clone` the value and consume it, if the \
following trait bounds could be satisfied: \
{} and `{}`",
errors
.iter()
.map(|e| format!("`{}`", e.obligation.predicate))
.collect::<Vec<_>>()
.join(", "),
last.obligation.predicate,
)
}
};
err.multipart_suggestion_verbose(
msg,
sugg,
Applicability::MaybeIncorrect,
);
for error in errors {
if let FulfillmentErrorCode::Select(
SelectionError::Unimplemented,
) = error.code
&& let ty::PredicateKind::Clause(ty::ClauseKind::Trait(
pred,
)) = error.obligation.predicate.kind().skip_binder()
{
self.infcx.err_ctxt().suggest_derive(
&error.obligation,
err,
error.obligation.predicate.kind().rebind(pred),
);
}
}
}
}
}
}
// Other desugarings takes &self, which cannot cause a move
_ => {}
}
} else {
if move_span != span || is_loop_message {
err.subdiagnostic(CaptureReasonLabel::MovedHere {
move_span,
is_partial,
is_move_msg,
is_loop_message,
});
}
// If the move error occurs due to a loop, don't show
// another message for the same span
if !is_loop_message {
move_spans.var_subdiag(err, None, |kind, var_span| match kind {
hir::ClosureKind::Coroutine(_) => {
CaptureVarCause::PartialMoveUseInCoroutine { var_span, is_partial }
}
hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
CaptureVarCause::PartialMoveUseInClosure { var_span, is_partial }
}
})
}
}
}
}