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
::{self, RegionVid, Ty}
;
9 use rustc_middle
::ty
::{GenericArgKind, GenericArgsRef}
;
10 use rustc_span
::symbol
::{kw, sym, Ident, Symbol}
;
11 use rustc_span
::{Span, DUMMY_SP}
;
13 use crate::{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 pub(crate) struct RegionName
{
19 /// The name of the region (interned).
20 pub(crate) name
: Symbol
,
21 /// Where the region comes from.
22 pub(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 pub(crate) enum RegionNameSource
{
30 /// A bound (not free) region that was instantiated 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
, &'
static str),
38 /// The region corresponding to an argument.
39 AnonRegionFromArgument(RegionNameHighlight
),
40 /// The region corresponding to a closure upvar.
41 AnonRegionFromUpvar(Span
, Symbol
),
42 /// The region corresponding to the return type of a closure.
43 AnonRegionFromOutput(RegionNameHighlight
, &'
static str),
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
),
48 /// An anonymous region from an impl self type or trait
49 AnonRegionFromImplSignature(Span
, &'
static str),
52 /// Describes what to highlight to explain to the user that we're giving an anonymous region a
53 /// synthesized name, and how to highlight it.
54 #[derive(Debug, Clone)]
55 pub(crate) enum RegionNameHighlight
{
56 /// The anonymous region corresponds to a reference that was found by traversing the type in the HIR.
58 /// The anonymous region corresponds to a `'_` in the generics list of a struct/enum/union.
59 MatchedAdtAndSegment(Span
),
60 /// The anonymous region corresponds to a region where the type annotation is completely missing
61 /// from the code, e.g. in a closure arguments `|x| { ... }`, where `x` is a reference.
62 CannotMatchHirTy(Span
, String
),
63 /// The anonymous region corresponds to a region where the type annotation is completely missing
64 /// from the code, and *even if* we print out the full name of the type, the region name won't
65 /// be included. This currently occurs for opaque types like `impl Future`.
66 Occluded(Span
, String
),
70 pub(crate) fn was_named(&self) -> bool
{
72 RegionNameSource
::NamedEarlyBoundRegion(..)
73 | RegionNameSource
::NamedFreeRegion(..)
74 | RegionNameSource
::Static
=> true,
75 RegionNameSource
::SynthesizedFreeEnvRegion(..)
76 | RegionNameSource
::AnonRegionFromArgument(..)
77 | RegionNameSource
::AnonRegionFromUpvar(..)
78 | RegionNameSource
::AnonRegionFromOutput(..)
79 | RegionNameSource
::AnonRegionFromYieldTy(..)
80 | RegionNameSource
::AnonRegionFromAsyncFn(..)
81 | RegionNameSource
::AnonRegionFromImplSignature(..) => false,
85 pub(crate) fn span(&self) -> Option
<Span
> {
87 RegionNameSource
::Static
=> None
,
88 RegionNameSource
::NamedEarlyBoundRegion(span
)
89 | RegionNameSource
::NamedFreeRegion(span
)
90 | RegionNameSource
::SynthesizedFreeEnvRegion(span
, _
)
91 | RegionNameSource
::AnonRegionFromUpvar(span
, _
)
92 | RegionNameSource
::AnonRegionFromYieldTy(span
, _
)
93 | RegionNameSource
::AnonRegionFromAsyncFn(span
)
94 | RegionNameSource
::AnonRegionFromImplSignature(span
, _
) => Some(span
),
95 RegionNameSource
::AnonRegionFromArgument(ref highlight
)
96 | RegionNameSource
::AnonRegionFromOutput(ref highlight
, _
) => match *highlight
{
97 RegionNameHighlight
::MatchedHirTy(span
)
98 | RegionNameHighlight
::MatchedAdtAndSegment(span
)
99 | RegionNameHighlight
::CannotMatchHirTy(span
, _
)
100 | RegionNameHighlight
::Occluded(span
, _
) => Some(span
),
105 pub(crate) fn highlight_region_name(&self, diag
: &mut Diagnostic
) {
107 RegionNameSource
::NamedFreeRegion(span
)
108 | RegionNameSource
::NamedEarlyBoundRegion(span
) => {
109 diag
.span_label(*span
, format
!("lifetime `{self}` defined here"));
111 RegionNameSource
::SynthesizedFreeEnvRegion(span
, note
) => {
112 diag
.span_label(*span
, format
!("lifetime `{self}` represents this closure's body"));
115 RegionNameSource
::AnonRegionFromArgument(RegionNameHighlight
::CannotMatchHirTy(
119 diag
.span_label(*span
, format
!("has type `{type_name}`"));
121 RegionNameSource
::AnonRegionFromArgument(RegionNameHighlight
::MatchedHirTy(span
))
122 | RegionNameSource
::AnonRegionFromOutput(RegionNameHighlight
::MatchedHirTy(span
), _
)
123 | RegionNameSource
::AnonRegionFromAsyncFn(span
) => {
126 format
!("let's call the lifetime of this reference `{self}`"),
129 RegionNameSource
::AnonRegionFromArgument(
130 RegionNameHighlight
::MatchedAdtAndSegment(span
),
132 | RegionNameSource
::AnonRegionFromOutput(
133 RegionNameHighlight
::MatchedAdtAndSegment(span
),
136 diag
.span_label(*span
, format
!("let's call this `{self}`"));
138 RegionNameSource
::AnonRegionFromArgument(RegionNameHighlight
::Occluded(
144 format
!("lifetime `{self}` appears in the type {type_name}"),
147 RegionNameSource
::AnonRegionFromOutput(
148 RegionNameHighlight
::Occluded(span
, type_name
),
154 "return type{mir_description} `{type_name}` contains a lifetime `{self}`"
158 RegionNameSource
::AnonRegionFromUpvar(span
, upvar_name
) => {
161 format
!("lifetime `{self}` appears in the type of `{upvar_name}`"),
164 RegionNameSource
::AnonRegionFromOutput(
165 RegionNameHighlight
::CannotMatchHirTy(span
, type_name
),
168 diag
.span_label(*span
, format
!("return type{mir_description} is {type_name}"));
170 RegionNameSource
::AnonRegionFromYieldTy(span
, type_name
) => {
171 diag
.span_label(*span
, format
!("yield type is {type_name}"));
173 RegionNameSource
::AnonRegionFromImplSignature(span
, location
) => {
176 format
!("lifetime `{self}` appears in the `impl`'s {location}"),
179 RegionNameSource
::Static
=> {}
184 impl Display
for RegionName
{
185 fn fmt(&self, f
: &mut fmt
::Formatter
<'_
>) -> fmt
::Result
{
186 write
!(f
, "{}", self.name
)
190 impl rustc_errors
::IntoDiagnosticArg
for RegionName
{
191 fn into_diagnostic_arg(self) -> rustc_errors
::DiagnosticArgValue
<'
static> {
192 self.to_string().into_diagnostic_arg()
196 impl<'tcx
> MirBorrowckCtxt
<'_
, 'tcx
> {
197 pub(crate) fn mir_def_id(&self) -> hir
::def_id
::LocalDefId
{
198 self.body
.source
.def_id().expect_local()
201 pub(crate) fn mir_hir_id(&self) -> hir
::HirId
{
202 self.infcx
.tcx
.hir().local_def_id_to_hir_id(self.mir_def_id())
205 /// Generate a synthetic region named `'N`, where `N` is the next value of the counter. Then,
206 /// increment the counter.
208 /// This is _not_ idempotent. Call `give_region_a_name` when possible.
209 pub(crate) fn synthesize_region_name(&self) -> Symbol
{
210 let c
= self.next_region_name
.replace_with(|counter
| *counter
+ 1);
211 Symbol
::intern(&format
!("'{c:?}"))
214 /// Maps from an internal MIR region vid to something that we can
215 /// report to the user. In some cases, the region vids will map
216 /// directly to lifetimes that the user has a name for (e.g.,
217 /// `'static`). But frequently they will not, in which case we
218 /// have to find some way to identify the lifetime to the user. To
219 /// that end, this function takes a "diagnostic" so that it can
220 /// create auxiliary notes as needed.
222 /// The names are memoized, so this is both cheap to recompute and idempotent.
224 /// Example (function arguments):
226 /// Suppose we are trying to give a name to the lifetime of the
229 /// ```ignore (pseudo-rust)
230 /// fn foo(x: &u32) { .. }
233 /// This function would create a label like this:
236 /// | fn foo(x: &u32) { .. }
237 /// ------- fully elaborated type of `x` is `&'1 u32`
240 /// and then return the name `'1` for us to use.
241 pub(crate) fn give_region_a_name(&self, fr
: RegionVid
) -> Option
<RegionName
> {
243 "give_region_a_name(fr={:?}, counter={:?})",
245 self.next_region_name
.try_borrow().unwrap()
248 assert
!(self.regioncx
.universal_regions().is_universal_region(fr
));
250 if let Some(value
) = self.region_names
.try_borrow_mut().unwrap().get(&fr
) {
251 return Some(value
.clone());
255 .give_name_from_error_region(fr
)
256 .or_else(|| self.give_name_if_anonymous_region_appears_in_arguments(fr
))
257 .or_else(|| self.give_name_if_anonymous_region_appears_in_upvars(fr
))
258 .or_else(|| self.give_name_if_anonymous_region_appears_in_output(fr
))
259 .or_else(|| self.give_name_if_anonymous_region_appears_in_yield_ty(fr
))
260 .or_else(|| self.give_name_if_anonymous_region_appears_in_impl_signature(fr
))
261 .or_else(|| self.give_name_if_anonymous_region_appears_in_arg_position_impl_trait(fr
));
263 if let Some(value
) = &value
{
264 self.region_names
.try_borrow_mut().unwrap().insert(fr
, value
.clone());
267 debug
!("give_region_a_name: gave name {:?}", value
);
271 /// Checks for the case where `fr` maps to something that the
272 /// *user* has a name for. In that case, we'll be able to map
273 /// `fr` to a `Region<'tcx>`, and that region will be one of
275 #[instrument(level = "trace", skip(self))]
276 fn give_name_from_error_region(&self, fr
: RegionVid
) -> Option
<RegionName
> {
277 let error_region
= self.to_error_region(fr
)?
;
279 let tcx
= self.infcx
.tcx
;
281 debug
!("give_region_a_name: error_region = {:?}", error_region
);
282 match *error_region
{
283 ty
::ReEarlyBound(ebr
) => ebr
.has_name().then(|| {
284 let span
= tcx
.hir().span_if_local(ebr
.def_id
).unwrap_or(DUMMY_SP
);
285 RegionName { name: ebr.name, source: RegionNameSource::NamedEarlyBoundRegion(span) }
289 Some(RegionName { name: kw::StaticLifetime, source: RegionNameSource::Static }
)
292 ty
::ReFree(free_region
) => match free_region
.bound_region
{
293 ty
::BoundRegionKind
::BrNamed(region_def_id
, name
) => {
294 // Get the span to point to, even if we don't use the name.
295 let span
= tcx
.hir().span_if_local(region_def_id
).unwrap_or(DUMMY_SP
);
297 "bound region named: {:?}, is_named: {:?}",
299 free_region
.bound_region
.is_named()
302 if free_region
.bound_region
.is_named() {
303 // A named region that is actually named.
304 Some(RegionName { name, source: RegionNameSource::NamedFreeRegion(span) }
)
305 } else if tcx
.asyncness(self.mir_hir_id().owner
).is_async() {
306 // If we spuriously thought that the region is named, we should let the
307 // system generate a true name for error messages. Currently this can
308 // happen if we have an elided name in an async fn for example: the
309 // compiler will generate a region named `'_`, but reporting such a name is
310 // not actually useful, so we synthesize a name for it instead.
311 let name
= self.synthesize_region_name();
314 source
: RegionNameSource
::AnonRegionFromAsyncFn(span
),
321 ty
::BoundRegionKind
::BrEnv
=> {
322 let def_ty
= self.regioncx
.universal_regions().defining_ty
;
324 let DefiningTy
::Closure(_
, args
) = def_ty
else {
325 // Can't have BrEnv in functions, constants or generators.
326 bug
!("BrEnv outside of closure.");
328 let hir
::ExprKind
::Closure(&hir
::Closure { fn_decl_span, .. }
) =
329 tcx
.hir().expect_expr(self.mir_hir_id()).kind
331 bug
!("Closure is not defined by a closure expr");
333 let region_name
= self.synthesize_region_name();
335 let closure_kind_ty
= args
.as_closure().kind_ty();
336 let note
= match closure_kind_ty
.to_opt_closure_kind() {
337 Some(ty
::ClosureKind
::Fn
) => {
338 "closure implements `Fn`, so references to captured variables \
339 can't escape the closure"
341 Some(ty
::ClosureKind
::FnMut
) => {
342 "closure implements `FnMut`, so references to captured variables \
343 can't escape the closure"
345 Some(ty
::ClosureKind
::FnOnce
) => {
346 bug
!("BrEnv in a `FnOnce` closure");
348 None
=> bug
!("Closure kind not inferred in borrow check"),
353 source
: RegionNameSource
::SynthesizedFreeEnvRegion(fn_decl_span
, note
),
357 ty
::BoundRegionKind
::BrAnon
=> None
,
362 | ty
::RePlaceholder(..)
364 | ty
::ReError(_
) => None
,
368 /// Finds an argument that contains `fr` and label it with a fully
369 /// elaborated type, returning something like `'1`. Result looks
373 /// | fn foo(x: &u32) { .. }
374 /// ------- fully elaborated type of `x` is `&'1 u32`
376 #[instrument(level = "trace", skip(self))]
377 fn give_name_if_anonymous_region_appears_in_arguments(
380 ) -> Option
<RegionName
> {
381 let implicit_inputs
= self.regioncx
.universal_regions().defining_ty
.implicit_inputs();
382 let argument_index
= self.regioncx
.get_argument_index_for_region(self.infcx
.tcx
, fr
)?
;
384 let arg_ty
= self.regioncx
.universal_regions().unnormalized_input_tys
385 [implicit_inputs
+ argument_index
];
386 let (_
, span
) = self.regioncx
.get_argument_name_and_span_for_region(
393 .get_argument_hir_ty_for_highlighting(argument_index
)
394 .and_then(|arg_hir_ty
| self.highlight_if_we_can_match_hir_ty(fr
, arg_ty
, arg_hir_ty
))
396 // `highlight_if_we_cannot_match_hir_ty` needs to know the number we will give to
397 // the anonymous region. If it succeeds, the `synthesize_region_name` call below
398 // will increment the counter, "reserving" the number we just used.
399 let counter
= *self.next_region_name
.try_borrow().unwrap();
400 self.highlight_if_we_cannot_match_hir_ty(fr
, arg_ty
, span
, counter
)
404 name
: self.synthesize_region_name(),
405 source
: RegionNameSource
::AnonRegionFromArgument(highlight
),
409 fn get_argument_hir_ty_for_highlighting(
411 argument_index
: usize,
412 ) -> Option
<&hir
::Ty
<'tcx
>> {
413 let fn_decl
= self.infcx
.tcx
.hir().fn_decl_by_hir_id(self.mir_hir_id())?
;
414 let argument_hir_ty
: &hir
::Ty
<'_
> = fn_decl
.inputs
.get(argument_index
)?
;
415 match argument_hir_ty
.kind
{
416 // This indicates a variable with no type annotation, like
417 // `|x|`... in that case, we can't highlight the type but
418 // must highlight the variable.
419 // NOTE(eddyb) this is handled in/by the sole caller
420 // (`give_name_if_anonymous_region_appears_in_arguments`).
421 hir
::TyKind
::Infer
=> None
,
423 _
=> Some(argument_hir_ty
),
427 /// Attempts to highlight the specific part of a type in an argument
428 /// that has no type annotation.
429 /// For example, we might produce an annotation like this:
435 /// | | has type `&'1 u32`
436 /// | has type `&'2 u32`
438 fn highlight_if_we_cannot_match_hir_ty(
440 needle_fr
: RegionVid
,
444 ) -> RegionNameHighlight
{
445 let mut highlight
= RegionHighlightMode
::default();
446 highlight
.highlighting_region_vid(self.infcx
.tcx
, needle_fr
, counter
);
448 self.infcx
.extract_inference_diagnostics_data(ty
.into(), Some(highlight
)).name
;
451 "highlight_if_we_cannot_match_hir_ty: type_name={:?} needle_fr={:?}",
454 if type_name
.contains(&format
!("'{counter}")) {
455 // Only add a label if we can confirm that a region was labelled.
456 RegionNameHighlight
::CannotMatchHirTy(span
, type_name
)
458 RegionNameHighlight
::Occluded(span
, type_name
)
462 /// Attempts to highlight the specific part of a type annotation
463 /// that contains the anonymous reference we want to give a name
464 /// to. For example, we might produce an annotation like this:
467 /// | fn a<T>(items: &[T]) -> Box<dyn Iterator<Item = &T>> {
468 /// | - let's call the lifetime of this reference `'1`
471 /// the way this works is that we match up `ty`, which is
472 /// a `Ty<'tcx>` (the internal form of the type) with
473 /// `hir_ty`, a `hir::Ty` (the syntax of the type
474 /// annotation). We are descending through the types stepwise,
475 /// looking in to find the region `needle_fr` in the internal
476 /// type. Once we find that, we can use the span of the `hir::Ty`
477 /// to add the highlight.
479 /// This is a somewhat imperfect process, so along the way we also
480 /// keep track of the **closest** type we've found. If we fail to
481 /// find the exact `&` or `'_` to highlight, then we may fall back
482 /// to highlighting that closest type instead.
483 fn highlight_if_we_can_match_hir_ty(
485 needle_fr
: RegionVid
,
487 hir_ty
: &hir
::Ty
<'_
>,
488 ) -> Option
<RegionNameHighlight
> {
489 let search_stack
: &mut Vec
<(Ty
<'tcx
>, &hir
::Ty
<'_
>)> = &mut vec
![(ty
, hir_ty
)];
491 while let Some((ty
, hir_ty
)) = search_stack
.pop() {
492 match (ty
.kind(), &hir_ty
.kind
) {
493 // Check if the `ty` is `&'X ..` where `'X`
494 // is the region we are looking for -- if so, and we have a `&T`
495 // on the RHS, then we want to highlight the `&` like so:
498 // - let's call the lifetime of this reference `'1`
499 (ty
::Ref(region
, referent_ty
, _
), hir
::TyKind
::Ref(_lifetime
, referent_hir_ty
)) => {
500 if region
.as_var() == needle_fr
{
501 // Just grab the first character, the `&`.
502 let source_map
= self.infcx
.tcx
.sess
.source_map();
503 let ampersand_span
= source_map
.start_point(hir_ty
.span
);
505 return Some(RegionNameHighlight
::MatchedHirTy(ampersand_span
));
508 // Otherwise, let's descend into the referent types.
509 search_stack
.push((*referent_ty
, &referent_hir_ty
.ty
));
512 // Match up something like `Foo<'1>`
513 (ty
::Adt(_adt_def
, args
), hir
::TyKind
::Path(hir
::QPath
::Resolved(None
, path
))) => {
515 // Type parameters of the type alias have no reason to
516 // be the same as those of the ADT.
517 // FIXME: We should be able to do something similar to
518 // match_adt_and_segment in this case.
519 Res
::Def(DefKind
::TyAlias
, _
) => (),
521 if let Some(last_segment
) = path
.segments
.last() {
522 if let Some(highlight
) = self.match_adt_and_segment(
528 return Some(highlight
);
535 // The following cases don't have lifetimes, so we
536 // just worry about trying to match up the rustc type
537 // with the HIR types:
538 (&ty
::Tuple(elem_tys
), hir
::TyKind
::Tup(elem_hir_tys
)) => {
539 search_stack
.extend(iter
::zip(elem_tys
, *elem_hir_tys
));
542 (ty
::Slice(elem_ty
), hir
::TyKind
::Slice(elem_hir_ty
))
543 | (ty
::Array(elem_ty
, _
), hir
::TyKind
::Array(elem_hir_ty
, _
)) => {
544 search_stack
.push((*elem_ty
, elem_hir_ty
));
547 (ty
::RawPtr(mut_ty
), hir
::TyKind
::Ptr(mut_hir_ty
)) => {
548 search_stack
.push((mut_ty
.ty
, &mut_hir_ty
.ty
));
552 // FIXME there are other cases that we could trace
560 /// We've found an enum/struct/union type with the generic args
561 /// `args` and -- in the HIR -- a path type with the final
562 /// segment `last_segment`. Try to find a `'_` to highlight in
563 /// the generic args (or, if not, to produce new zipped pairs of
564 /// types+hir to search through).
565 fn match_adt_and_segment
<'hir
>(
567 args
: GenericArgsRef
<'tcx
>,
568 needle_fr
: RegionVid
,
569 last_segment
: &'hir hir
::PathSegment
<'hir
>,
570 search_stack
: &mut Vec
<(Ty
<'tcx
>, &'hir hir
::Ty
<'hir
>)>,
571 ) -> Option
<RegionNameHighlight
> {
572 // Did the user give explicit arguments? (e.g., `Foo<..>`)
573 let explicit_args
= last_segment
.args
.as_ref()?
;
575 self.try_match_adt_and_generic_args(args
, needle_fr
, explicit_args
, search_stack
)?
;
576 if lifetime
.is_anonymous() {
579 Some(RegionNameHighlight
::MatchedAdtAndSegment(lifetime
.ident
.span
))
583 /// We've found an enum/struct/union type with the generic args
584 /// `args` and -- in the HIR -- a path with the generic
585 /// arguments `hir_args`. If `needle_fr` appears in the args, return
586 /// the `hir::Lifetime` that corresponds to it. If not, push onto
587 /// `search_stack` the types+hir to search through.
588 fn try_match_adt_and_generic_args
<'hir
>(
590 args
: GenericArgsRef
<'tcx
>,
591 needle_fr
: RegionVid
,
592 hir_args
: &'hir hir
::GenericArgs
<'hir
>,
593 search_stack
: &mut Vec
<(Ty
<'tcx
>, &'hir hir
::Ty
<'hir
>)>,
594 ) -> Option
<&'hir hir
::Lifetime
> {
595 for (kind
, hir_arg
) in iter
::zip(args
, hir_args
.args
) {
596 match (kind
.unpack(), hir_arg
) {
597 (GenericArgKind
::Lifetime(r
), hir
::GenericArg
::Lifetime(lt
)) => {
598 if r
.as_var() == needle_fr
{
603 (GenericArgKind
::Type(ty
), hir
::GenericArg
::Type(hir_ty
)) => {
604 search_stack
.push((ty
, hir_ty
));
607 (GenericArgKind
::Const(_ct
), hir
::GenericArg
::Const(_hir_ct
)) => {
608 // Lifetimes cannot be found in consts, so we don't need
609 // to search anything here.
613 GenericArgKind
::Lifetime(_
)
614 | GenericArgKind
::Type(_
)
615 | GenericArgKind
::Const(_
),
618 // HIR lowering sometimes doesn't catch this in erroneous
619 // programs, so we need to use delay_span_bug here. See #82126.
620 self.infcx
.tcx
.sess
.delay_span_bug(
622 format
!("unmatched arg and hir arg: found {kind:?} vs {hir_arg:?}"),
631 /// Finds a closure upvar that contains `fr` and label it with a
632 /// fully elaborated type, returning something like `'1`. Result
636 /// | let x = Some(&22);
637 /// - fully elaborated type of `x` is `Option<&'1 u32>`
639 #[instrument(level = "trace", skip(self))]
640 fn give_name_if_anonymous_region_appears_in_upvars(&self, fr
: RegionVid
) -> Option
<RegionName
> {
641 let upvar_index
= self.regioncx
.get_upvar_index_for_region(self.infcx
.tcx
, fr
)?
;
642 let (upvar_name
, upvar_span
) = self.regioncx
.get_upvar_name_and_span_for_region(
647 let region_name
= self.synthesize_region_name();
651 source
: RegionNameSource
::AnonRegionFromUpvar(upvar_span
, upvar_name
),
655 /// Checks for arguments appearing in the (closure) return type. It
656 /// must be a closure since, in a free fn, such an argument would
657 /// have to either also appear in an argument (if using elision)
658 /// or be early bound (named, not in argument).
659 #[instrument(level = "trace", skip(self))]
660 fn give_name_if_anonymous_region_appears_in_output(&self, fr
: RegionVid
) -> Option
<RegionName
> {
661 let tcx
= self.infcx
.tcx
;
664 let return_ty
= self.regioncx
.universal_regions().unnormalized_output_ty
;
665 debug
!("give_name_if_anonymous_region_appears_in_output: return_ty = {:?}", return_ty
);
666 if !tcx
.any_free_region_meets(&return_ty
, |r
| r
.as_var() == fr
) {
670 let mir_hir_id
= self.mir_hir_id();
672 let (return_span
, mir_description
, hir_ty
) = match hir
.get(mir_hir_id
) {
673 hir
::Node
::Expr(hir
::Expr
{
674 kind
: hir
::ExprKind
::Closure(&hir
::Closure { fn_decl, body, fn_decl_span, .. }
),
677 let (mut span
, mut hir_ty
) = match fn_decl
.output
{
678 hir
::FnRetTy
::DefaultReturn(_
) => {
679 (tcx
.sess
.source_map().end_point(fn_decl_span
), None
)
681 hir
::FnRetTy
::Return(hir_ty
) => (fn_decl
.output
.span(), Some(hir_ty
)),
683 let mir_description
= match hir
.body(body
).generator_kind
{
684 Some(hir
::GeneratorKind
::Async(gen
)) => match gen
{
685 hir
::AsyncGeneratorKind
::Block
=> " of async block",
686 hir
::AsyncGeneratorKind
::Closure
=> " of async closure",
687 hir
::AsyncGeneratorKind
::Fn
=> {
689 hir
.get_by_def_id(hir
.get_parent_item(mir_hir_id
).def_id
);
690 let output
= &parent_item
692 .expect("generator lowered from async fn should be in fn")
694 span
= output
.span();
695 if let hir
::FnRetTy
::Return(ret
) = output
{
696 hir_ty
= Some(self.get_future_inner_return_ty(*ret
));
701 Some(hir
::GeneratorKind
::Gen
) => " of generator",
702 None
=> " of closure",
704 (span
, mir_description
, hir_ty
)
706 node
=> match node
.fn_decl() {
708 let hir_ty
= match fn_decl
.output
{
709 hir
::FnRetTy
::DefaultReturn(_
) => None
,
710 hir
::FnRetTy
::Return(ty
) => Some(ty
),
712 (fn_decl
.output
.span(), "", hir_ty
)
714 None
=> (self.body
.span
, "", None
),
718 let highlight
= hir_ty
719 .and_then(|hir_ty
| self.highlight_if_we_can_match_hir_ty(fr
, return_ty
, hir_ty
))
721 // `highlight_if_we_cannot_match_hir_ty` needs to know the number we will give to
722 // the anonymous region. If it succeeds, the `synthesize_region_name` call below
723 // will increment the counter, "reserving" the number we just used.
724 let counter
= *self.next_region_name
.try_borrow().unwrap();
725 self.highlight_if_we_cannot_match_hir_ty(fr
, return_ty
, return_span
, counter
)
729 name
: self.synthesize_region_name(),
730 source
: RegionNameSource
::AnonRegionFromOutput(highlight
, mir_description
),
734 /// From the [`hir::Ty`] of an async function's lowered return type,
735 /// retrieve the `hir::Ty` representing the type the user originally wrote.
737 /// e.g. given the function:
740 /// async fn foo() -> i32 { 2 }
743 /// this function, given the lowered return type of `foo`, an [`OpaqueDef`] that implements `Future<Output=i32>`,
744 /// returns the `i32`.
746 /// [`OpaqueDef`]: hir::TyKind::OpaqueDef
747 fn get_future_inner_return_ty(&self, hir_ty
: &'tcx hir
::Ty
<'tcx
>) -> &'tcx hir
::Ty
<'tcx
> {
748 let hir
= self.infcx
.tcx
.hir();
750 let hir
::TyKind
::OpaqueDef(id
, _
, _
) = hir_ty
.kind
else {
753 "lowered return type of async fn is not OpaqueDef: {:?}",
757 let opaque_ty
= hir
.item(id
);
758 if let hir
::ItemKind
::OpaqueTy(hir
::OpaqueTy
{
761 hir
::GenericBound
::LangItemTrait(
762 hir
::LangItem
::Future
,
769 ident
: Ident { name: sym::Output, .. }
,
771 hir
::TypeBindingKind
::Equality { term: hir::Term::Ty(ty) }
,
786 "bounds from lowered return type of async fn did not match expected format: {opaque_ty:?}",
791 #[instrument(level = "trace", skip(self))]
792 fn give_name_if_anonymous_region_appears_in_yield_ty(
795 ) -> Option
<RegionName
> {
796 // Note: generators from `async fn` yield `()`, so we don't have to
797 // worry about them here.
798 let yield_ty
= self.regioncx
.universal_regions().yield_ty?
;
799 debug
!("give_name_if_anonymous_region_appears_in_yield_ty: yield_ty = {:?}", yield_ty
);
801 let tcx
= self.infcx
.tcx
;
803 if !tcx
.any_free_region_meets(&yield_ty
, |r
| r
.as_var() == fr
) {
807 let mut highlight
= RegionHighlightMode
::default();
808 highlight
.highlighting_region_vid(tcx
, fr
, *self.next_region_name
.try_borrow().unwrap());
810 self.infcx
.extract_inference_diagnostics_data(yield_ty
.into(), Some(highlight
)).name
;
812 let yield_span
= match tcx
.hir().get(self.mir_hir_id()) {
813 hir
::Node
::Expr(hir
::Expr
{
814 kind
: hir
::ExprKind
::Closure(&hir
::Closure { fn_decl_span, .. }
),
816 }) => tcx
.sess
.source_map().end_point(fn_decl_span
),
821 "give_name_if_anonymous_region_appears_in_yield_ty: \
822 type_name = {:?}, yield_span = {:?}",
823 yield_span
, type_name
,
827 name
: self.synthesize_region_name(),
828 source
: RegionNameSource
::AnonRegionFromYieldTy(yield_span
, type_name
),
832 fn give_name_if_anonymous_region_appears_in_impl_signature(
835 ) -> Option
<RegionName
> {
836 let ty
::ReEarlyBound(region
) = *self.to_error_region(fr
)?
else {
839 if region
.has_name() {
843 let tcx
= self.infcx
.tcx
;
844 let region_parent
= tcx
.parent(region
.def_id
);
845 let DefKind
::Impl { .. }
= tcx
.def_kind(region_parent
) else {
850 .any_free_region_meets(&tcx
.type_of(region_parent
).instantiate_identity(), |r
| {
851 *r
== ty
::ReEarlyBound(region
)
855 name
: self.synthesize_region_name(),
856 source
: RegionNameSource
::AnonRegionFromImplSignature(
857 tcx
.def_span(region
.def_id
),
858 // FIXME(compiler-errors): Does this ever actually show up
859 // anywhere other than the self type? I couldn't create an
860 // example of a `'_` in the impl's trait being referenceable.
861 if found { "self type" }
else { "header" }
,
866 fn give_name_if_anonymous_region_appears_in_arg_position_impl_trait(
869 ) -> Option
<RegionName
> {
870 let ty
::ReEarlyBound(region
) = *self.to_error_region(fr
)?
else {
873 if region
.has_name() {
877 let predicates
= self
880 .predicates_of(self.body
.source
.def_id())
881 .instantiate_identity(self.infcx
.tcx
)
884 if let Some(upvar_index
) = self
890 .position(|ty
| self.any_param_predicate_mentions(&predicates
, ty
, region
))
892 let (upvar_name
, upvar_span
) = self.regioncx
.get_upvar_name_and_span_for_region(
897 let region_name
= self.synthesize_region_name();
901 source
: RegionNameSource
::AnonRegionFromUpvar(upvar_span
, upvar_name
),
903 } else if let Some(arg_index
) = self
906 .unnormalized_input_tys
908 .position(|ty
| self.any_param_predicate_mentions(&predicates
, *ty
, region
))
910 let (arg_name
, arg_span
) = self.regioncx
.get_argument_name_and_span_for_region(
915 let region_name
= self.synthesize_region_name();
919 source
: RegionNameSource
::AnonRegionFromArgument(
920 RegionNameHighlight
::CannotMatchHirTy(arg_span
, arg_name?
.to_string()),
928 fn any_param_predicate_mentions(
930 clauses
: &[ty
::Clause
<'tcx
>],
932 region
: ty
::EarlyBoundRegion
,
934 let tcx
= self.infcx
.tcx
;
935 ty
.walk().any(|arg
| {
936 if let ty
::GenericArgKind
::Type(ty
) = arg
.unpack()
937 && let ty
::Param(_
) = ty
.kind()
939 clauses
.iter().any(|pred
| {
940 match pred
.kind().skip_binder() {
941 ty
::ClauseKind
::Trait(data
) if data
.self_ty() == ty
=> {}
942 ty
::ClauseKind
::Projection(data
) if data
.projection_ty
.self_ty() == ty
=> {}
945 tcx
.any_free_region_meets(pred
, |r
| {
946 *r
== ty
::ReEarlyBound(region
)