1 use std
::fmt
::{self, Display}
;
4 use rustc_errors
::Diagnostic
;
6 use rustc_hir
::def
::{DefKind, Res}
;
7 use rustc_middle
::ty
::print
::RegionHighlightMode
;
8 use rustc_middle
::ty
::subst
::{GenericArgKind, SubstsRef}
;
9 use rustc_middle
::ty
::{self, RegionVid, Ty}
;
10 use rustc_span
::symbol
::{kw, sym, Ident, Symbol}
;
11 use rustc_span
::{Span, DUMMY_SP}
;
13 use crate::{nll::ToRegionVid, universal_regions::DefiningTy, MirBorrowckCtxt}
;
15 /// A name for a particular region used in emitting diagnostics. This name could be a generated
16 /// name like `'1`, a name used by the user like `'a`, or a name like `'static`.
17 #[derive(Debug, Clone)]
18 crate struct RegionName
{
19 /// The name of the region (interned).
21 /// Where the region comes from.
22 crate source
: RegionNameSource
,
25 /// Denotes the source of a region that is named by a `RegionName`. For example, a free region that
26 /// was named by the user would get `NamedFreeRegion` and `'static` lifetime would get `Static`.
27 /// This helps to print the right kinds of diagnostics.
28 #[derive(Debug, Clone)]
29 crate enum RegionNameSource
{
30 /// A bound (not free) region that was substituted at the def site (not an HRTB).
31 NamedEarlyBoundRegion(Span
),
32 /// A free region that the user has a name (`'a`) for.
33 NamedFreeRegion(Span
),
34 /// The `'static` region.
36 /// The free region corresponding to the environment of a closure.
37 SynthesizedFreeEnvRegion(Span
, String
),
38 /// The region corresponding to an argument.
39 AnonRegionFromArgument(RegionNameHighlight
),
40 /// The region corresponding to a closure upvar.
41 AnonRegionFromUpvar(Span
, String
),
42 /// The region corresponding to the return type of a closure.
43 AnonRegionFromOutput(RegionNameHighlight
, String
),
44 /// The region from a type yielded by a generator.
45 AnonRegionFromYieldTy(Span
, String
),
46 /// An anonymous region from an async fn.
47 AnonRegionFromAsyncFn(Span
),
50 /// Describes what to highlight to explain to the user that we're giving an anonymous region a
51 /// synthesized name, and how to highlight it.
52 #[derive(Debug, Clone)]
53 crate enum RegionNameHighlight
{
54 /// The anonymous region corresponds to a reference that was found by traversing the type in the HIR.
56 /// The anonymous region corresponds to a `'_` in the generics list of a struct/enum/union.
57 MatchedAdtAndSegment(Span
),
58 /// The anonymous region corresponds to a region where the type annotation is completely missing
59 /// from the code, e.g. in a closure arguments `|x| { ... }`, where `x` is a reference.
60 CannotMatchHirTy(Span
, String
),
61 /// The anonymous region corresponds to a region where the type annotation is completely missing
62 /// from the code, and *even if* we print out the full name of the type, the region name won't
63 /// be included. This currently occurs for opaque types like `impl Future`.
64 Occluded(Span
, String
),
68 crate fn was_named(&self) -> bool
{
70 RegionNameSource
::NamedEarlyBoundRegion(..)
71 | RegionNameSource
::NamedFreeRegion(..)
72 | RegionNameSource
::Static
=> true,
73 RegionNameSource
::SynthesizedFreeEnvRegion(..)
74 | RegionNameSource
::AnonRegionFromArgument(..)
75 | RegionNameSource
::AnonRegionFromUpvar(..)
76 | RegionNameSource
::AnonRegionFromOutput(..)
77 | RegionNameSource
::AnonRegionFromYieldTy(..)
78 | RegionNameSource
::AnonRegionFromAsyncFn(..) => false,
82 crate fn span(&self) -> Option
<Span
> {
84 RegionNameSource
::Static
=> None
,
85 RegionNameSource
::NamedEarlyBoundRegion(span
)
86 | RegionNameSource
::NamedFreeRegion(span
)
87 | RegionNameSource
::SynthesizedFreeEnvRegion(span
, _
)
88 | RegionNameSource
::AnonRegionFromUpvar(span
, _
)
89 | RegionNameSource
::AnonRegionFromYieldTy(span
, _
)
90 | RegionNameSource
::AnonRegionFromAsyncFn(span
) => Some(span
),
91 RegionNameSource
::AnonRegionFromArgument(ref highlight
)
92 | RegionNameSource
::AnonRegionFromOutput(ref highlight
, _
) => match *highlight
{
93 RegionNameHighlight
::MatchedHirTy(span
)
94 | RegionNameHighlight
::MatchedAdtAndSegment(span
)
95 | RegionNameHighlight
::CannotMatchHirTy(span
, _
)
96 | RegionNameHighlight
::Occluded(span
, _
) => Some(span
),
101 crate fn highlight_region_name(&self, diag
: &mut Diagnostic
) {
103 RegionNameSource
::NamedFreeRegion(span
)
104 | RegionNameSource
::NamedEarlyBoundRegion(span
) => {
105 diag
.span_label(*span
, format
!("lifetime `{}` defined here", self));
107 RegionNameSource
::SynthesizedFreeEnvRegion(span
, note
) => {
110 format
!("lifetime `{}` represents this closure's body", self),
114 RegionNameSource
::AnonRegionFromArgument(RegionNameHighlight
::CannotMatchHirTy(
118 diag
.span_label(*span
, format
!("has type `{}`", type_name
));
120 RegionNameSource
::AnonRegionFromArgument(RegionNameHighlight
::MatchedHirTy(span
))
121 | RegionNameSource
::AnonRegionFromOutput(RegionNameHighlight
::MatchedHirTy(span
), _
)
122 | RegionNameSource
::AnonRegionFromAsyncFn(span
) => {
125 format
!("let's call the lifetime of this reference `{}`", self),
128 RegionNameSource
::AnonRegionFromArgument(
129 RegionNameHighlight
::MatchedAdtAndSegment(span
),
131 | RegionNameSource
::AnonRegionFromOutput(
132 RegionNameHighlight
::MatchedAdtAndSegment(span
),
135 diag
.span_label(*span
, format
!("let's call this `{}`", self));
137 RegionNameSource
::AnonRegionFromArgument(RegionNameHighlight
::Occluded(
143 format
!("lifetime `{}` appears in the type {}", self, type_name
),
146 RegionNameSource
::AnonRegionFromOutput(
147 RegionNameHighlight
::Occluded(span
, type_name
),
153 "return type{} `{}` contains a lifetime `{}`",
154 mir_description
, type_name
, self
158 RegionNameSource
::AnonRegionFromUpvar(span
, upvar_name
) => {
161 format
!("lifetime `{}` appears in the type of `{}`", self, upvar_name
),
164 RegionNameSource
::AnonRegionFromOutput(
165 RegionNameHighlight
::CannotMatchHirTy(span
, type_name
),
168 diag
.span_label(*span
, format
!("return type{} is {}", mir_description
, type_name
));
170 RegionNameSource
::AnonRegionFromYieldTy(span
, type_name
) => {
171 diag
.span_label(*span
, format
!("yield type is {}", type_name
));
173 RegionNameSource
::Static
=> {}
178 impl Display
for RegionName
{
179 fn fmt(&self, f
: &mut fmt
::Formatter
<'_
>) -> fmt
::Result
{
180 write
!(f
, "{}", self.name
)
184 impl<'tcx
> MirBorrowckCtxt
<'_
, 'tcx
> {
185 crate fn mir_def_id(&self) -> hir
::def_id
::LocalDefId
{
186 self.body
.source
.def_id().as_local().unwrap()
189 crate fn mir_hir_id(&self) -> hir
::HirId
{
190 self.infcx
.tcx
.hir().local_def_id_to_hir_id(self.mir_def_id())
193 /// Generate a synthetic region named `'N`, where `N` is the next value of the counter. Then,
194 /// increment the counter.
196 /// This is _not_ idempotent. Call `give_region_a_name` when possible.
197 fn synthesize_region_name(&self) -> Symbol
{
198 let c
= self.next_region_name
.replace_with(|counter
| *counter
+ 1);
199 Symbol
::intern(&format
!("'{:?}", c
))
202 /// Maps from an internal MIR region vid to something that we can
203 /// report to the user. In some cases, the region vids will map
204 /// directly to lifetimes that the user has a name for (e.g.,
205 /// `'static`). But frequently they will not, in which case we
206 /// have to find some way to identify the lifetime to the user. To
207 /// that end, this function takes a "diagnostic" so that it can
208 /// create auxiliary notes as needed.
210 /// The names are memoized, so this is both cheap to recompute and idempotent.
212 /// Example (function arguments):
214 /// Suppose we are trying to give a name to the lifetime of the
218 /// fn foo(x: &u32) { .. }
221 /// This function would create a label like this:
224 /// | fn foo(x: &u32) { .. }
225 /// ------- fully elaborated type of `x` is `&'1 u32`
228 /// and then return the name `'1` for us to use.
229 crate fn give_region_a_name(&self, fr
: RegionVid
) -> Option
<RegionName
> {
231 "give_region_a_name(fr={:?}, counter={:?})",
233 self.next_region_name
.try_borrow().unwrap()
236 assert
!(self.regioncx
.universal_regions().is_universal_region(fr
));
238 if let Some(value
) = self.region_names
.try_borrow_mut().unwrap().get(&fr
) {
239 return Some(value
.clone());
243 .give_name_from_error_region(fr
)
244 .or_else(|| self.give_name_if_anonymous_region_appears_in_arguments(fr
))
245 .or_else(|| self.give_name_if_anonymous_region_appears_in_upvars(fr
))
246 .or_else(|| self.give_name_if_anonymous_region_appears_in_output(fr
))
247 .or_else(|| self.give_name_if_anonymous_region_appears_in_yield_ty(fr
));
249 if let Some(ref value
) = value
{
250 self.region_names
.try_borrow_mut().unwrap().insert(fr
, value
.clone());
253 debug
!("give_region_a_name: gave name {:?}", value
);
257 /// Checks for the case where `fr` maps to something that the
258 /// *user* has a name for. In that case, we'll be able to map
259 /// `fr` to a `Region<'tcx>`, and that region will be one of
261 fn give_name_from_error_region(&self, fr
: RegionVid
) -> Option
<RegionName
> {
262 let error_region
= self.to_error_region(fr
)?
;
264 let tcx
= self.infcx
.tcx
;
266 debug
!("give_region_a_name: error_region = {:?}", error_region
);
267 match *error_region
{
268 ty
::ReEarlyBound(ebr
) => {
270 let span
= tcx
.hir().span_if_local(ebr
.def_id
).unwrap_or(DUMMY_SP
);
273 source
: RegionNameSource
::NamedEarlyBoundRegion(span
),
281 Some(RegionName { name: kw::StaticLifetime, source: RegionNameSource::Static }
)
284 ty
::ReFree(free_region
) => match free_region
.bound_region
{
285 ty
::BoundRegionKind
::BrNamed(region_def_id
, name
) => {
286 // Get the span to point to, even if we don't use the name.
287 let span
= tcx
.hir().span_if_local(region_def_id
).unwrap_or(DUMMY_SP
);
289 "bound region named: {:?}, is_named: {:?}",
291 free_region
.bound_region
.is_named()
294 if free_region
.bound_region
.is_named() {
295 // A named region that is actually named.
296 Some(RegionName { name, source: RegionNameSource::NamedFreeRegion(span) }
)
298 // If we spuriously thought that the region is named, we should let the
299 // system generate a true name for error messages. Currently this can
300 // happen if we have an elided name in an async fn for example: the
301 // compiler will generate a region named `'_`, but reporting such a name is
302 // not actually useful, so we synthesize a name for it instead.
303 let name
= self.synthesize_region_name();
306 source
: RegionNameSource
::AnonRegionFromAsyncFn(span
),
311 ty
::BoundRegionKind
::BrEnv
=> {
312 let def_ty
= self.regioncx
.universal_regions().defining_ty
;
314 let DefiningTy
::Closure(_
, substs
) = def_ty
else {
315 // Can't have BrEnv in functions, constants or generators.
316 bug
!("BrEnv outside of closure.");
318 let hir
::ExprKind
::Closure(_
, _
, _
, args_span
, _
) =
319 tcx
.hir().expect_expr(self.mir_hir_id()).kind
else {
320 bug
!("Closure is not defined by a closure expr");
322 let region_name
= self.synthesize_region_name();
324 let closure_kind_ty
= substs
.as_closure().kind_ty();
325 let note
= match closure_kind_ty
.to_opt_closure_kind() {
326 Some(ty
::ClosureKind
::Fn
) => {
327 "closure implements `Fn`, so references to captured variables \
328 can't escape the closure"
330 Some(ty
::ClosureKind
::FnMut
) => {
331 "closure implements `FnMut`, so references to captured variables \
332 can't escape the closure"
334 Some(ty
::ClosureKind
::FnOnce
) => {
335 bug
!("BrEnv in a `FnOnce` closure");
337 None
=> bug
!("Closure kind not inferred in borrow check"),
342 source
: RegionNameSource
::SynthesizedFreeEnvRegion(
349 ty
::BoundRegionKind
::BrAnon(_
) => None
,
354 | ty
::RePlaceholder(..)
356 | ty
::ReErased
=> None
,
360 /// Finds an argument that contains `fr` and label it with a fully
361 /// elaborated type, returning something like `'1`. Result looks
365 /// | fn foo(x: &u32) { .. }
366 /// ------- fully elaborated type of `x` is `&'1 u32`
368 fn give_name_if_anonymous_region_appears_in_arguments(
371 ) -> Option
<RegionName
> {
372 let implicit_inputs
= self.regioncx
.universal_regions().defining_ty
.implicit_inputs();
373 let argument_index
= self.regioncx
.get_argument_index_for_region(self.infcx
.tcx
, fr
)?
;
375 let arg_ty
= self.regioncx
.universal_regions().unnormalized_input_tys
376 [implicit_inputs
+ argument_index
];
377 let (_
, span
) = self.regioncx
.get_argument_name_and_span_for_region(
384 .get_argument_hir_ty_for_highlighting(argument_index
)
385 .and_then(|arg_hir_ty
| self.highlight_if_we_can_match_hir_ty(fr
, arg_ty
, arg_hir_ty
))
387 // `highlight_if_we_cannot_match_hir_ty` needs to know the number we will give to
388 // the anonymous region. If it succeeds, the `synthesize_region_name` call below
389 // will increment the counter, "reserving" the number we just used.
390 let counter
= *self.next_region_name
.try_borrow().unwrap();
391 self.highlight_if_we_cannot_match_hir_ty(fr
, arg_ty
, span
, counter
)
395 name
: self.synthesize_region_name(),
396 source
: RegionNameSource
::AnonRegionFromArgument(highlight
),
400 fn get_argument_hir_ty_for_highlighting(
402 argument_index
: usize,
403 ) -> Option
<&hir
::Ty
<'tcx
>> {
404 let fn_decl
= self.infcx
.tcx
.hir().fn_decl_by_hir_id(self.mir_hir_id())?
;
405 let argument_hir_ty
: &hir
::Ty
<'_
> = fn_decl
.inputs
.get(argument_index
)?
;
406 match argument_hir_ty
.kind
{
407 // This indicates a variable with no type annotation, like
408 // `|x|`... in that case, we can't highlight the type but
409 // must highlight the variable.
410 // NOTE(eddyb) this is handled in/by the sole caller
411 // (`give_name_if_anonymous_region_appears_in_arguments`).
412 hir
::TyKind
::Infer
=> None
,
414 _
=> Some(argument_hir_ty
),
418 /// Attempts to highlight the specific part of a type in an argument
419 /// that has no type annotation.
420 /// For example, we might produce an annotation like this:
426 /// | | has type `&'1 u32`
427 /// | has type `&'2 u32`
429 fn highlight_if_we_cannot_match_hir_ty(
431 needle_fr
: RegionVid
,
435 ) -> RegionNameHighlight
{
436 let mut highlight
= RegionHighlightMode
::new(self.infcx
.tcx
);
437 highlight
.highlighting_region_vid(needle_fr
, counter
);
439 self.infcx
.extract_inference_diagnostics_data(ty
.into(), Some(highlight
)).name
;
442 "highlight_if_we_cannot_match_hir_ty: type_name={:?} needle_fr={:?}",
445 if type_name
.contains(&format
!("'{}", counter
)) {
446 // Only add a label if we can confirm that a region was labelled.
447 RegionNameHighlight
::CannotMatchHirTy(span
, type_name
)
449 RegionNameHighlight
::Occluded(span
, type_name
)
453 /// Attempts to highlight the specific part of a type annotation
454 /// that contains the anonymous reference we want to give a name
455 /// to. For example, we might produce an annotation like this:
458 /// | fn a<T>(items: &[T]) -> Box<dyn Iterator<Item = &T>> {
459 /// | - let's call the lifetime of this reference `'1`
462 /// the way this works is that we match up `ty`, which is
463 /// a `Ty<'tcx>` (the internal form of the type) with
464 /// `hir_ty`, a `hir::Ty` (the syntax of the type
465 /// annotation). We are descending through the types stepwise,
466 /// looking in to find the region `needle_fr` in the internal
467 /// type. Once we find that, we can use the span of the `hir::Ty`
468 /// to add the highlight.
470 /// This is a somewhat imperfect process, so along the way we also
471 /// keep track of the **closest** type we've found. If we fail to
472 /// find the exact `&` or `'_` to highlight, then we may fall back
473 /// to highlighting that closest type instead.
474 fn highlight_if_we_can_match_hir_ty(
476 needle_fr
: RegionVid
,
478 hir_ty
: &hir
::Ty
<'_
>,
479 ) -> Option
<RegionNameHighlight
> {
480 let search_stack
: &mut Vec
<(Ty
<'tcx
>, &hir
::Ty
<'_
>)> = &mut vec
![(ty
, hir_ty
)];
482 while let Some((ty
, hir_ty
)) = search_stack
.pop() {
483 match (ty
.kind(), &hir_ty
.kind
) {
484 // Check if the `ty` is `&'X ..` where `'X`
485 // is the region we are looking for -- if so, and we have a `&T`
486 // on the RHS, then we want to highlight the `&` like so:
489 // - let's call the lifetime of this reference `'1`
491 ty
::Ref(region
, referent_ty
, _
),
492 hir
::TyKind
::Rptr(_lifetime
, referent_hir_ty
),
494 if region
.to_region_vid() == needle_fr
{
495 // Just grab the first character, the `&`.
496 let source_map
= self.infcx
.tcx
.sess
.source_map();
497 let ampersand_span
= source_map
.start_point(hir_ty
.span
);
499 return Some(RegionNameHighlight
::MatchedHirTy(ampersand_span
));
502 // Otherwise, let's descend into the referent types.
503 search_stack
.push((*referent_ty
, &referent_hir_ty
.ty
));
506 // Match up something like `Foo<'1>`
508 ty
::Adt(_adt_def
, substs
),
509 hir
::TyKind
::Path(hir
::QPath
::Resolved(None
, path
)),
512 // Type parameters of the type alias have no reason to
513 // be the same as those of the ADT.
514 // FIXME: We should be able to do something similar to
515 // match_adt_and_segment in this case.
516 Res
::Def(DefKind
::TyAlias
, _
) => (),
518 if let Some(last_segment
) = path
.segments
.last() {
519 if let Some(highlight
) = self.match_adt_and_segment(
525 return Some(highlight
);
532 // The following cases don't have lifetimes, so we
533 // just worry about trying to match up the rustc type
534 // with the HIR types:
535 (&ty
::Tuple(elem_tys
), hir
::TyKind
::Tup(elem_hir_tys
)) => {
536 search_stack
.extend(iter
::zip(elem_tys
, *elem_hir_tys
));
539 (ty
::Slice(elem_ty
), hir
::TyKind
::Slice(elem_hir_ty
))
540 | (ty
::Array(elem_ty
, _
), hir
::TyKind
::Array(elem_hir_ty
, _
)) => {
541 search_stack
.push((*elem_ty
, elem_hir_ty
));
544 (ty
::RawPtr(mut_ty
), hir
::TyKind
::Ptr(mut_hir_ty
)) => {
545 search_stack
.push((mut_ty
.ty
, &mut_hir_ty
.ty
));
549 // FIXME there are other cases that we could trace
557 /// We've found an enum/struct/union type with the substitutions
558 /// `substs` and -- in the HIR -- a path type with the final
559 /// segment `last_segment`. Try to find a `'_` to highlight in
560 /// the generic args (or, if not, to produce new zipped pairs of
561 /// types+hir to search through).
562 fn match_adt_and_segment
<'hir
>(
564 substs
: SubstsRef
<'tcx
>,
565 needle_fr
: RegionVid
,
566 last_segment
: &'hir hir
::PathSegment
<'hir
>,
567 search_stack
: &mut Vec
<(Ty
<'tcx
>, &'hir hir
::Ty
<'hir
>)>,
568 ) -> Option
<RegionNameHighlight
> {
569 // Did the user give explicit arguments? (e.g., `Foo<..>`)
570 let args
= last_segment
.args
.as_ref()?
;
572 self.try_match_adt_and_generic_args(substs
, needle_fr
, args
, search_stack
)?
;
573 match lifetime
.name
{
574 hir
::LifetimeName
::Param(_
)
575 | hir
::LifetimeName
::Error
576 | hir
::LifetimeName
::Static
577 | hir
::LifetimeName
::Underscore
=> {
578 let lifetime_span
= lifetime
.span
;
579 Some(RegionNameHighlight
::MatchedAdtAndSegment(lifetime_span
))
582 hir
::LifetimeName
::ImplicitObjectLifetimeDefault
| hir
::LifetimeName
::Implicit(_
) => {
583 // In this case, the user left off the lifetime; so
584 // they wrote something like:
590 // where the fully elaborated form is `Foo<'_, '1,
591 // T>`. We don't consider this a match; instead we let
592 // the "fully elaborated" type fallback above handle
599 /// We've found an enum/struct/union type with the substitutions
600 /// `substs` and -- in the HIR -- a path with the generic
601 /// arguments `args`. If `needle_fr` appears in the args, return
602 /// the `hir::Lifetime` that corresponds to it. If not, push onto
603 /// `search_stack` the types+hir to search through.
604 fn try_match_adt_and_generic_args
<'hir
>(
606 substs
: SubstsRef
<'tcx
>,
607 needle_fr
: RegionVid
,
608 args
: &'hir hir
::GenericArgs
<'hir
>,
609 search_stack
: &mut Vec
<(Ty
<'tcx
>, &'hir hir
::Ty
<'hir
>)>,
610 ) -> Option
<&'hir hir
::Lifetime
> {
611 for (kind
, hir_arg
) in iter
::zip(substs
, args
.args
) {
612 match (kind
.unpack(), hir_arg
) {
613 (GenericArgKind
::Lifetime(r
), hir
::GenericArg
::Lifetime(lt
)) => {
614 if r
.to_region_vid() == needle_fr
{
619 (GenericArgKind
::Type(ty
), hir
::GenericArg
::Type(hir_ty
)) => {
620 search_stack
.push((ty
, hir_ty
));
623 (GenericArgKind
::Const(_ct
), hir
::GenericArg
::Const(_hir_ct
)) => {
624 // Lifetimes cannot be found in consts, so we don't need
625 // to search anything here.
629 GenericArgKind
::Lifetime(_
)
630 | GenericArgKind
::Type(_
)
631 | GenericArgKind
::Const(_
),
634 // HIR lowering sometimes doesn't catch this in erroneous
635 // programs, so we need to use delay_span_bug here. See #82126.
636 self.infcx
.tcx
.sess
.delay_span_bug(
638 &format
!("unmatched subst and hir arg: found {:?} vs {:?}", kind
, hir_arg
),
647 /// Finds a closure upvar that contains `fr` and label it with a
648 /// fully elaborated type, returning something like `'1`. Result
652 /// | let x = Some(&22);
653 /// - fully elaborated type of `x` is `Option<&'1 u32>`
655 fn give_name_if_anonymous_region_appears_in_upvars(&self, fr
: RegionVid
) -> Option
<RegionName
> {
656 let upvar_index
= self.regioncx
.get_upvar_index_for_region(self.infcx
.tcx
, fr
)?
;
657 let (upvar_name
, upvar_span
) = self.regioncx
.get_upvar_name_and_span_for_region(
662 let region_name
= self.synthesize_region_name();
666 source
: RegionNameSource
::AnonRegionFromUpvar(upvar_span
, upvar_name
.to_string()),
670 /// Checks for arguments appearing in the (closure) return type. It
671 /// must be a closure since, in a free fn, such an argument would
672 /// have to either also appear in an argument (if using elision)
673 /// or be early bound (named, not in argument).
674 fn give_name_if_anonymous_region_appears_in_output(&self, fr
: RegionVid
) -> Option
<RegionName
> {
675 let tcx
= self.infcx
.tcx
;
678 let return_ty
= self.regioncx
.universal_regions().unnormalized_output_ty
;
679 debug
!("give_name_if_anonymous_region_appears_in_output: return_ty = {:?}", return_ty
);
680 if !tcx
.any_free_region_meets(&return_ty
, |r
| r
.to_region_vid() == fr
) {
684 let mir_hir_id
= self.mir_hir_id();
686 let (return_span
, mir_description
, hir_ty
) = match hir
.get(mir_hir_id
) {
687 hir
::Node
::Expr(hir
::Expr
{
688 kind
: hir
::ExprKind
::Closure(_
, return_ty
, body_id
, span
, _
),
691 let (mut span
, mut hir_ty
) = match return_ty
.output
{
692 hir
::FnRetTy
::DefaultReturn(_
) => {
693 (tcx
.sess
.source_map().end_point(*span
), None
)
695 hir
::FnRetTy
::Return(hir_ty
) => (return_ty
.output
.span(), Some(hir_ty
)),
697 let mir_description
= match hir
.body(*body_id
).generator_kind
{
698 Some(hir
::GeneratorKind
::Async(gen
)) => match gen
{
699 hir
::AsyncGeneratorKind
::Block
=> " of async block",
700 hir
::AsyncGeneratorKind
::Closure
=> " of async closure",
701 hir
::AsyncGeneratorKind
::Fn
=> {
702 let parent_item
= hir
.get_by_def_id(hir
.get_parent_item(mir_hir_id
));
703 let output
= &parent_item
705 .expect("generator lowered from async fn should be in fn")
707 span
= output
.span();
708 if let hir
::FnRetTy
::Return(ret
) = output
{
709 hir_ty
= Some(self.get_future_inner_return_ty(*ret
));
714 Some(hir
::GeneratorKind
::Gen
) => " of generator",
715 None
=> " of closure",
717 (span
, mir_description
, hir_ty
)
719 node
=> match node
.fn_decl() {
721 let hir_ty
= match fn_decl
.output
{
722 hir
::FnRetTy
::DefaultReturn(_
) => None
,
723 hir
::FnRetTy
::Return(ty
) => Some(ty
),
725 (fn_decl
.output
.span(), "", hir_ty
)
727 None
=> (self.body
.span
, "", None
),
731 let highlight
= hir_ty
732 .and_then(|hir_ty
| self.highlight_if_we_can_match_hir_ty(fr
, return_ty
, hir_ty
))
734 // `highlight_if_we_cannot_match_hir_ty` needs to know the number we will give to
735 // the anonymous region. If it succeeds, the `synthesize_region_name` call below
736 // will increment the counter, "reserving" the number we just used.
737 let counter
= *self.next_region_name
.try_borrow().unwrap();
738 self.highlight_if_we_cannot_match_hir_ty(fr
, return_ty
, return_span
, counter
)
742 name
: self.synthesize_region_name(),
743 source
: RegionNameSource
::AnonRegionFromOutput(highlight
, mir_description
.to_string()),
747 /// From the [`hir::Ty`] of an async function's lowered return type,
748 /// retrieve the `hir::Ty` representing the type the user originally wrote.
750 /// e.g. given the function:
753 /// async fn foo() -> i32 {}
756 /// this function, given the lowered return type of `foo`, an [`OpaqueDef`] that implements `Future<Output=i32>`,
757 /// returns the `i32`.
759 /// [`OpaqueDef`]: hir::TyKind::OpaqueDef
760 fn get_future_inner_return_ty(&self, hir_ty
: &'tcx hir
::Ty
<'tcx
>) -> &'tcx hir
::Ty
<'tcx
> {
761 let hir
= self.infcx
.tcx
.hir();
763 let hir
::TyKind
::OpaqueDef(id
, _
) = hir_ty
.kind
else {
766 "lowered return type of async fn is not OpaqueDef: {:?}",
770 let opaque_ty
= hir
.item(id
);
771 if let hir
::ItemKind
::OpaqueTy(hir
::OpaqueTy
{
774 hir
::GenericBound
::LangItemTrait(
775 hir
::LangItem
::Future
,
782 ident
: Ident { name: sym::Output, .. }
,
784 hir
::TypeBindingKind
::Equality { term: hir::Term::Ty(ty) }
,
799 "bounds from lowered return type of async fn did not match expected format: {:?}",
805 fn give_name_if_anonymous_region_appears_in_yield_ty(
808 ) -> Option
<RegionName
> {
809 // Note: generators from `async fn` yield `()`, so we don't have to
810 // worry about them here.
811 let yield_ty
= self.regioncx
.universal_regions().yield_ty?
;
812 debug
!("give_name_if_anonymous_region_appears_in_yield_ty: yield_ty = {:?}", yield_ty
,);
814 let tcx
= self.infcx
.tcx
;
816 if !tcx
.any_free_region_meets(&yield_ty
, |r
| r
.to_region_vid() == fr
) {
820 let mut highlight
= RegionHighlightMode
::new(tcx
);
821 highlight
.highlighting_region_vid(fr
, *self.next_region_name
.try_borrow().unwrap());
823 self.infcx
.extract_inference_diagnostics_data(yield_ty
.into(), Some(highlight
)).name
;
825 let yield_span
= match tcx
.hir().get(self.mir_hir_id()) {
826 hir
::Node
::Expr(hir
::Expr
{
827 kind
: hir
::ExprKind
::Closure(_
, _
, _
, span
, _
), ..
828 }) => (tcx
.sess
.source_map().end_point(*span
)),
833 "give_name_if_anonymous_region_appears_in_yield_ty: \
834 type_name = {:?}, yield_span = {:?}",
835 yield_span
, type_name
,
839 name
: self.synthesize_region_name(),
840 source
: RegionNameSource
::AnonRegionFromYieldTy(yield_span
, type_name
),