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#![allow(rustc::diagnostic_outside_of_impl)]
#![allow(rustc::untranslatable_diagnostic)]
use std::fmt::{self, Display};
use std::iter;
use rustc_data_structures::fx::IndexEntry;
use rustc_errors::Diag;
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_middle::ty::print::RegionHighlightMode;
use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, RegionVid, Ty};
use rustc_middle::{bug, span_bug};
use rustc_span::symbol::{kw, sym, Symbol};
use rustc_span::{Span, DUMMY_SP};
use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
use tracing::{debug, instrument};
use crate::universal_regions::DefiningTy;
use crate::MirBorrowckCtxt;
/// A name for a particular region used in emitting diagnostics. This name could be a generated
/// name like `'1`, a name used by the user like `'a`, or a name like `'static`.
#[derive(Debug, Clone, Copy)]
pub(crate) struct RegionName {
/// The name of the region (interned).
pub(crate) name: Symbol,
/// Where the region comes from.
pub(crate) source: RegionNameSource,
}
/// Denotes the source of a region that is named by a `RegionName`. For example, a free region that
/// was named by the user would get `NamedLateParamRegion` and `'static` lifetime would get `Static`.
/// This helps to print the right kinds of diagnostics.
#[derive(Debug, Clone, Copy)]
pub(crate) enum RegionNameSource {
/// A bound (not free) region that was instantiated at the def site (not an HRTB).
NamedEarlyParamRegion(Span),
/// A free region that the user has a name (`'a`) for.
NamedLateParamRegion(Span),
/// The `'static` region.
Static,
/// The free region corresponding to the environment of a closure.
SynthesizedFreeEnvRegion(Span, &'static str),
/// The region corresponding to an argument.
AnonRegionFromArgument(RegionNameHighlight),
/// The region corresponding to a closure upvar.
AnonRegionFromUpvar(Span, Symbol),
/// The region corresponding to the return type of a closure.
AnonRegionFromOutput(RegionNameHighlight, &'static str),
/// The region from a type yielded by a coroutine.
AnonRegionFromYieldTy(Span, Symbol),
/// An anonymous region from an async fn.
AnonRegionFromAsyncFn(Span),
/// An anonymous region from an impl self type or trait
AnonRegionFromImplSignature(Span, &'static str),
}
/// Describes what to highlight to explain to the user that we're giving an anonymous region a
/// synthesized name, and how to highlight it.
#[derive(Debug, Clone, Copy)]
pub(crate) enum RegionNameHighlight {
/// The anonymous region corresponds to a reference that was found by traversing the type in the HIR.
MatchedHirTy(Span),
/// The anonymous region corresponds to a `'_` in the generics list of a struct/enum/union.
MatchedAdtAndSegment(Span),
/// The anonymous region corresponds to a region where the type annotation is completely missing
/// from the code, e.g. in a closure arguments `|x| { ... }`, where `x` is a reference.
CannotMatchHirTy(Span, Symbol),
/// The anonymous region corresponds to a region where the type annotation is completely missing
/// from the code, and *even if* we print out the full name of the type, the region name won't
/// be included. This currently occurs for opaque types like `impl Future`.
Occluded(Span, Symbol),
}
impl RegionName {
pub(crate) fn was_named(&self) -> bool {
match self.source {
RegionNameSource::NamedEarlyParamRegion(..)
| RegionNameSource::NamedLateParamRegion(..)
| RegionNameSource::Static => true,
RegionNameSource::SynthesizedFreeEnvRegion(..)
| RegionNameSource::AnonRegionFromArgument(..)
| RegionNameSource::AnonRegionFromUpvar(..)
| RegionNameSource::AnonRegionFromOutput(..)
| RegionNameSource::AnonRegionFromYieldTy(..)
| RegionNameSource::AnonRegionFromAsyncFn(..)
| RegionNameSource::AnonRegionFromImplSignature(..) => false,
}
}
pub(crate) fn span(&self) -> Option<Span> {
match self.source {
RegionNameSource::Static => None,
RegionNameSource::NamedEarlyParamRegion(span)
| RegionNameSource::NamedLateParamRegion(span)
| RegionNameSource::SynthesizedFreeEnvRegion(span, _)
| RegionNameSource::AnonRegionFromUpvar(span, _)
| RegionNameSource::AnonRegionFromYieldTy(span, _)
| RegionNameSource::AnonRegionFromAsyncFn(span)
| RegionNameSource::AnonRegionFromImplSignature(span, _) => Some(span),
RegionNameSource::AnonRegionFromArgument(ref highlight)
| RegionNameSource::AnonRegionFromOutput(ref highlight, _) => match *highlight {
RegionNameHighlight::MatchedHirTy(span)
| RegionNameHighlight::MatchedAdtAndSegment(span)
| RegionNameHighlight::CannotMatchHirTy(span, _)
| RegionNameHighlight::Occluded(span, _) => Some(span),
},
}
}
pub(crate) fn highlight_region_name(&self, diag: &mut Diag<'_>) {
match &self.source {
RegionNameSource::NamedLateParamRegion(span)
| RegionNameSource::NamedEarlyParamRegion(span) => {
diag.span_label(*span, format!("lifetime `{self}` defined here"));
}
RegionNameSource::SynthesizedFreeEnvRegion(span, note) => {
diag.span_label(*span, format!("lifetime `{self}` represents this closure's body"));
diag.note(*note);
}
RegionNameSource::AnonRegionFromArgument(RegionNameHighlight::CannotMatchHirTy(
span,
type_name,
)) => {
diag.span_label(*span, format!("has type `{type_name}`"));
}
RegionNameSource::AnonRegionFromArgument(RegionNameHighlight::MatchedHirTy(span))
| RegionNameSource::AnonRegionFromOutput(RegionNameHighlight::MatchedHirTy(span), _)
| RegionNameSource::AnonRegionFromAsyncFn(span) => {
diag.span_label(
*span,
format!("let's call the lifetime of this reference `{self}`"),
);
}
RegionNameSource::AnonRegionFromArgument(
RegionNameHighlight::MatchedAdtAndSegment(span),
)
| RegionNameSource::AnonRegionFromOutput(
RegionNameHighlight::MatchedAdtAndSegment(span),
_,
) => {
diag.span_label(*span, format!("let's call this `{self}`"));
}
RegionNameSource::AnonRegionFromArgument(RegionNameHighlight::Occluded(
span,
type_name,
)) => {
diag.span_label(
*span,
format!("lifetime `{self}` appears in the type {type_name}"),
);
}
RegionNameSource::AnonRegionFromOutput(
RegionNameHighlight::Occluded(span, type_name),
mir_description,
) => {
diag.span_label(
*span,
format!(
"return type{mir_description} `{type_name}` contains a lifetime `{self}`"
),
);
}
RegionNameSource::AnonRegionFromUpvar(span, upvar_name) => {
diag.span_label(
*span,
format!("lifetime `{self}` appears in the type of `{upvar_name}`"),
);
}
RegionNameSource::AnonRegionFromOutput(
RegionNameHighlight::CannotMatchHirTy(span, type_name),
mir_description,
) => {
diag.span_label(*span, format!("return type{mir_description} is {type_name}"));
}
RegionNameSource::AnonRegionFromYieldTy(span, type_name) => {
diag.span_label(*span, format!("yield type is {type_name}"));
}
RegionNameSource::AnonRegionFromImplSignature(span, location) => {
diag.span_label(
*span,
format!("lifetime `{self}` appears in the `impl`'s {location}"),
);
}
RegionNameSource::Static => {}
}
}
}
impl Display for RegionName {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{}", self.name)
}
}
impl rustc_errors::IntoDiagArg for RegionName {
fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
self.to_string().into_diag_arg()
}
}
impl<'tcx> MirBorrowckCtxt<'_, '_, '_, 'tcx> {
pub(crate) fn mir_def_id(&self) -> hir::def_id::LocalDefId {
self.body.source.def_id().expect_local()
}
pub(crate) fn mir_hir_id(&self) -> hir::HirId {
self.infcx.tcx.local_def_id_to_hir_id(self.mir_def_id())
}
/// Generate a synthetic region named `'N`, where `N` is the next value of the counter. Then,
/// increment the counter.
///
/// This is _not_ idempotent. Call `give_region_a_name` when possible.
pub(crate) fn synthesize_region_name(&self) -> Symbol {
let c = self.next_region_name.replace_with(|counter| *counter + 1);
Symbol::intern(&format!("'{c:?}"))
}
/// Maps from an internal MIR region vid to something that we can
/// report to the user. In some cases, the region vids will map
/// directly to lifetimes that the user has a name for (e.g.,
/// `'static`). But frequently they will not, in which case we
/// have to find some way to identify the lifetime to the user. To
/// that end, this function takes a "diagnostic" so that it can
/// create auxiliary notes as needed.
///
/// The names are memoized, so this is both cheap to recompute and idempotent.
///
/// Example (function arguments):
///
/// Suppose we are trying to give a name to the lifetime of the
/// reference `x`:
///
/// ```ignore (pseudo-rust)
/// fn foo(x: &u32) { .. }
/// ```
///
/// This function would create a label like this:
///
/// ```text
/// | fn foo(x: &u32) { .. }
/// ------- fully elaborated type of `x` is `&'1 u32`
/// ```
///
/// and then return the name `'1` for us to use.
pub(crate) fn give_region_a_name(&self, fr: RegionVid) -> Option<RegionName> {
debug!(
"give_region_a_name(fr={:?}, counter={:?})",
fr,
self.next_region_name.try_borrow().unwrap()
);
assert!(self.regioncx.universal_regions().is_universal_region(fr));
match self.region_names.borrow_mut().entry(fr) {
IndexEntry::Occupied(precomputed_name) => Some(*precomputed_name.get()),
IndexEntry::Vacant(slot) => {
let new_name = self
.give_name_from_error_region(fr)
.or_else(|| self.give_name_if_anonymous_region_appears_in_arguments(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_upvars(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_output(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_yield_ty(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_impl_signature(fr))
.or_else(|| {
self.give_name_if_anonymous_region_appears_in_arg_position_impl_trait(fr)
});
if let Some(new_name) = new_name {
slot.insert(new_name);
}
debug!("give_region_a_name: gave name {:?}", new_name);
new_name
}
}
}
/// Checks for the case where `fr` maps to something that the
/// *user* has a name for. In that case, we'll be able to map
/// `fr` to a `Region<'tcx>`, and that region will be one of
/// named variants.
#[instrument(level = "trace", skip(self))]
fn give_name_from_error_region(&self, fr: RegionVid) -> Option<RegionName> {
let error_region = self.to_error_region(fr)?;
let tcx = self.infcx.tcx;
debug!("give_region_a_name: error_region = {:?}", error_region);
match *error_region {
ty::ReEarlyParam(ebr) => ebr.has_name().then(|| {
let def_id = tcx.generics_of(self.mir_def_id()).region_param(ebr, tcx).def_id;
let span = tcx.hir().span_if_local(def_id).unwrap_or(DUMMY_SP);
RegionName { name: ebr.name, source: RegionNameSource::NamedEarlyParamRegion(span) }
}),
ty::ReStatic => {
Some(RegionName { name: kw::StaticLifetime, source: RegionNameSource::Static })
}
ty::ReLateParam(late_param) => match late_param.bound_region {
ty::BoundRegionKind::BrNamed(region_def_id, name) => {
// Get the span to point to, even if we don't use the name.
let span = tcx.hir().span_if_local(region_def_id).unwrap_or(DUMMY_SP);
debug!(
"bound region named: {:?}, is_named: {:?}",
name,
late_param.bound_region.is_named()
);
if late_param.bound_region.is_named() {
// A named region that is actually named.
Some(RegionName {
name,
source: RegionNameSource::NamedLateParamRegion(span),
})
} else if tcx.asyncness(self.mir_hir_id().owner).is_async() {
// If we spuriously thought that the region is named, we should let the
// system generate a true name for error messages. Currently this can
// happen if we have an elided name in an async fn for example: the
// compiler will generate a region named `'_`, but reporting such a name is
// not actually useful, so we synthesize a name for it instead.
let name = self.synthesize_region_name();
Some(RegionName {
name,
source: RegionNameSource::AnonRegionFromAsyncFn(span),
})
} else {
None
}
}
ty::BoundRegionKind::BrEnv => {
let def_ty = self.regioncx.universal_regions().defining_ty;
let closure_kind = match def_ty {
DefiningTy::Closure(_, args) => args.as_closure().kind(),
DefiningTy::CoroutineClosure(_, args) => args.as_coroutine_closure().kind(),
_ => {
// Can't have BrEnv in functions, constants or coroutines.
bug!("BrEnv outside of closure.");
}
};
let hir::ExprKind::Closure(&hir::Closure { fn_decl_span, .. }) =
tcx.hir().expect_expr(self.mir_hir_id()).kind
else {
bug!("Closure is not defined by a closure expr");
};
let region_name = self.synthesize_region_name();
let note = match closure_kind {
ty::ClosureKind::Fn => {
"closure implements `Fn`, so references to captured variables \
can't escape the closure"
}
ty::ClosureKind::FnMut => {
"closure implements `FnMut`, so references to captured variables \
can't escape the closure"
}
ty::ClosureKind::FnOnce => {
bug!("BrEnv in a `FnOnce` closure");
}
};
Some(RegionName {
name: region_name,
source: RegionNameSource::SynthesizedFreeEnvRegion(fn_decl_span, note),
})
}
ty::BoundRegionKind::BrAnon => None,
},
ty::ReBound(..)
| ty::ReVar(..)
| ty::RePlaceholder(..)
| ty::ReErased
| ty::ReError(_) => None,
}
}
/// Finds an argument that contains `fr` and label it with a fully
/// elaborated type, returning something like `'1`. Result looks
/// like:
///
/// ```text
/// | fn foo(x: &u32) { .. }
/// ------- fully elaborated type of `x` is `&'1 u32`
/// ```
#[instrument(level = "trace", skip(self))]
fn give_name_if_anonymous_region_appears_in_arguments(
&self,
fr: RegionVid,
) -> Option<RegionName> {
let implicit_inputs = self.regioncx.universal_regions().defining_ty.implicit_inputs();
let argument_index = self.regioncx.get_argument_index_for_region(self.infcx.tcx, fr)?;
let arg_ty = self.regioncx.universal_regions().unnormalized_input_tys
[implicit_inputs + argument_index];
let (_, span) = self.regioncx.get_argument_name_and_span_for_region(
self.body,
&self.local_names,
argument_index,
);
let highlight = self
.get_argument_hir_ty_for_highlighting(argument_index)
.and_then(|arg_hir_ty| self.highlight_if_we_can_match_hir_ty(fr, arg_ty, arg_hir_ty))
.unwrap_or_else(|| {
// `highlight_if_we_cannot_match_hir_ty` needs to know the number we will give to
// the anonymous region. If it succeeds, the `synthesize_region_name` call below
// will increment the counter, "reserving" the number we just used.
let counter = *self.next_region_name.try_borrow().unwrap();
self.highlight_if_we_cannot_match_hir_ty(fr, arg_ty, span, counter)
});
Some(RegionName {
name: self.synthesize_region_name(),
source: RegionNameSource::AnonRegionFromArgument(highlight),
})
}
fn get_argument_hir_ty_for_highlighting(
&self,
argument_index: usize,
) -> Option<&hir::Ty<'tcx>> {
let fn_decl = self.infcx.tcx.hir().fn_decl_by_hir_id(self.mir_hir_id())?;
let argument_hir_ty: &hir::Ty<'_> = fn_decl.inputs.get(argument_index)?;
match argument_hir_ty.kind {
// This indicates a variable with no type annotation, like
// `|x|`... in that case, we can't highlight the type but
// must highlight the variable.
// NOTE(eddyb) this is handled in/by the sole caller
// (`give_name_if_anonymous_region_appears_in_arguments`).
hir::TyKind::Infer => None,
_ => Some(argument_hir_ty),
}
}
/// Attempts to highlight the specific part of a type in an argument
/// that has no type annotation.
/// For example, we might produce an annotation like this:
///
/// ```text
/// | foo(|a, b| b)
/// | - -
/// | | |
/// | | has type `&'1 u32`
/// | has type `&'2 u32`
/// ```
fn highlight_if_we_cannot_match_hir_ty(
&self,
needle_fr: RegionVid,
ty: Ty<'tcx>,
span: Span,
counter: usize,
) -> RegionNameHighlight {
let mut highlight = RegionHighlightMode::default();
highlight.highlighting_region_vid(self.infcx.tcx, needle_fr, counter);
let type_name = self
.infcx
.err_ctxt()
.extract_inference_diagnostics_data(ty.into(), Some(highlight))
.name;
debug!(
"highlight_if_we_cannot_match_hir_ty: type_name={:?} needle_fr={:?}",
type_name, needle_fr
);
if type_name.contains(&format!("'{counter}")) {
// Only add a label if we can confirm that a region was labelled.
RegionNameHighlight::CannotMatchHirTy(span, Symbol::intern(&type_name))
} else {
RegionNameHighlight::Occluded(span, Symbol::intern(&type_name))
}
}
/// Attempts to highlight the specific part of a type annotation
/// that contains the anonymous reference we want to give a name
/// to. For example, we might produce an annotation like this:
///
/// ```text
/// | fn a<T>(items: &[T]) -> Box<dyn Iterator<Item = &T>> {
/// | - let's call the lifetime of this reference `'1`
/// ```
///
/// the way this works is that we match up `ty`, which is
/// a `Ty<'tcx>` (the internal form of the type) with
/// `hir_ty`, a `hir::Ty` (the syntax of the type
/// annotation). We are descending through the types stepwise,
/// looking in to find the region `needle_fr` in the internal
/// type. Once we find that, we can use the span of the `hir::Ty`
/// to add the highlight.
///
/// This is a somewhat imperfect process, so along the way we also
/// keep track of the **closest** type we've found. If we fail to
/// find the exact `&` or `'_` to highlight, then we may fall back
/// to highlighting that closest type instead.
fn highlight_if_we_can_match_hir_ty(
&self,
needle_fr: RegionVid,
ty: Ty<'tcx>,
hir_ty: &hir::Ty<'_>,
) -> Option<RegionNameHighlight> {
let search_stack: &mut Vec<(Ty<'tcx>, &hir::Ty<'_>)> = &mut vec![(ty, hir_ty)];
while let Some((ty, hir_ty)) = search_stack.pop() {
match (ty.kind(), &hir_ty.kind) {
// Check if the `ty` is `&'X ..` where `'X`
// is the region we are looking for -- if so, and we have a `&T`
// on the RHS, then we want to highlight the `&` like so:
//
// &
// - let's call the lifetime of this reference `'1`
(ty::Ref(region, referent_ty, _), hir::TyKind::Ref(_lifetime, referent_hir_ty)) => {
if region.as_var() == needle_fr {
// Just grab the first character, the `&`.
let source_map = self.infcx.tcx.sess.source_map();
let ampersand_span = source_map.start_point(hir_ty.span);
return Some(RegionNameHighlight::MatchedHirTy(ampersand_span));
}
// Otherwise, let's descend into the referent types.
search_stack.push((*referent_ty, referent_hir_ty.ty));
}
// Match up something like `Foo<'1>`
(ty::Adt(_adt_def, args), hir::TyKind::Path(hir::QPath::Resolved(None, path))) => {
match path.res {
// Type parameters of the type alias have no reason to
// be the same as those of the ADT.
// FIXME: We should be able to do something similar to
// match_adt_and_segment in this case.
Res::Def(DefKind::TyAlias, _) => (),
_ => {
if let Some(last_segment) = path.segments.last() {
if let Some(highlight) = self.match_adt_and_segment(
args,
needle_fr,
last_segment,
search_stack,
) {
return Some(highlight);
}
}
}
}
}
// The following cases don't have lifetimes, so we
// just worry about trying to match up the rustc type
// with the HIR types:
(&ty::Tuple(elem_tys), hir::TyKind::Tup(elem_hir_tys)) => {
search_stack.extend(iter::zip(elem_tys, *elem_hir_tys));
}
(ty::Slice(elem_ty), hir::TyKind::Slice(elem_hir_ty))
| (ty::Array(elem_ty, _), hir::TyKind::Array(elem_hir_ty, _)) => {
search_stack.push((*elem_ty, elem_hir_ty));
}
(ty::RawPtr(mut_ty, _), hir::TyKind::Ptr(mut_hir_ty)) => {
search_stack.push((*mut_ty, mut_hir_ty.ty));
}
_ => {
// FIXME there are other cases that we could trace
}
}
}
None
}
/// We've found an enum/struct/union type with the generic args
/// `args` and -- in the HIR -- a path type with the final
/// segment `last_segment`. Try to find a `'_` to highlight in
/// the generic args (or, if not, to produce new zipped pairs of
/// types+hir to search through).
fn match_adt_and_segment<'hir>(
&self,
args: GenericArgsRef<'tcx>,
needle_fr: RegionVid,
last_segment: &'hir hir::PathSegment<'hir>,
search_stack: &mut Vec<(Ty<'tcx>, &'hir hir::Ty<'hir>)>,
) -> Option<RegionNameHighlight> {
// Did the user give explicit arguments? (e.g., `Foo<..>`)
let explicit_args = last_segment.args.as_ref()?;
let lifetime =
self.try_match_adt_and_generic_args(args, needle_fr, explicit_args, search_stack)?;
if lifetime.is_anonymous() {
None
} else {
Some(RegionNameHighlight::MatchedAdtAndSegment(lifetime.ident.span))
}
}
/// We've found an enum/struct/union type with the generic args
/// `args` and -- in the HIR -- a path with the generic
/// arguments `hir_args`. If `needle_fr` appears in the args, return
/// the `hir::Lifetime` that corresponds to it. If not, push onto
/// `search_stack` the types+hir to search through.
fn try_match_adt_and_generic_args<'hir>(
&self,
args: GenericArgsRef<'tcx>,
needle_fr: RegionVid,
hir_args: &'hir hir::GenericArgs<'hir>,
search_stack: &mut Vec<(Ty<'tcx>, &'hir hir::Ty<'hir>)>,
) -> Option<&'hir hir::Lifetime> {
for (kind, hir_arg) in iter::zip(args, hir_args.args) {
match (kind.unpack(), hir_arg) {
(GenericArgKind::Lifetime(r), hir::GenericArg::Lifetime(lt)) => {
if r.as_var() == needle_fr {
return Some(lt);
}
}
(GenericArgKind::Type(ty), hir::GenericArg::Type(hir_ty)) => {
search_stack.push((ty, hir_ty));
}
(GenericArgKind::Const(_ct), hir::GenericArg::Const(_hir_ct)) => {
// Lifetimes cannot be found in consts, so we don't need
// to search anything here.
}
(
GenericArgKind::Lifetime(_)
| GenericArgKind::Type(_)
| GenericArgKind::Const(_),
_,
) => {
self.dcx().span_delayed_bug(
hir_arg.span(),
format!("unmatched arg and hir arg: found {kind:?} vs {hir_arg:?}"),
);
}
}
}
None
}
/// Finds a closure upvar that contains `fr` and label it with a
/// fully elaborated type, returning something like `'1`. Result
/// looks like:
///
/// ```text
/// | let x = Some(&22);
/// - fully elaborated type of `x` is `Option<&'1 u32>`
/// ```
#[instrument(level = "trace", skip(self))]
fn give_name_if_anonymous_region_appears_in_upvars(&self, fr: RegionVid) -> Option<RegionName> {
let upvar_index = self.regioncx.get_upvar_index_for_region(self.infcx.tcx, fr)?;
let (upvar_name, upvar_span) = self.regioncx.get_upvar_name_and_span_for_region(
self.infcx.tcx,
self.upvars,
upvar_index,
);
let region_name = self.synthesize_region_name();
Some(RegionName {
name: region_name,
source: RegionNameSource::AnonRegionFromUpvar(upvar_span, upvar_name),
})
}
/// Checks for arguments appearing in the (closure) return type. It
/// must be a closure since, in a free fn, such an argument would
/// have to either also appear in an argument (if using elision)
/// or be early bound (named, not in argument).
#[instrument(level = "trace", skip(self))]
fn give_name_if_anonymous_region_appears_in_output(&self, fr: RegionVid) -> Option<RegionName> {
let tcx = self.infcx.tcx;
let hir = tcx.hir();
let return_ty = self.regioncx.universal_regions().unnormalized_output_ty;
debug!("give_name_if_anonymous_region_appears_in_output: return_ty = {:?}", return_ty);
if !tcx.any_free_region_meets(&return_ty, |r| r.as_var() == fr) {
return None;
}
let mir_hir_id = self.mir_hir_id();
let (return_span, mir_description, hir_ty) = match tcx.hir_node(mir_hir_id) {
hir::Node::Expr(hir::Expr {
kind: hir::ExprKind::Closure(&hir::Closure { fn_decl, kind, fn_decl_span, .. }),
..
}) => {
let (mut span, mut hir_ty) = match fn_decl.output {
hir::FnRetTy::DefaultReturn(_) => {
(tcx.sess.source_map().end_point(fn_decl_span), None)
}
hir::FnRetTy::Return(hir_ty) => (fn_decl.output.span(), Some(hir_ty)),
};
let mir_description = match kind {
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Async,
hir::CoroutineSource::Block,
)) => " of async block",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Async,
hir::CoroutineSource::Closure,
))
| hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Async) => {
" of async closure"
}
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Async,
hir::CoroutineSource::Fn,
)) => {
let parent_item =
tcx.hir_node_by_def_id(hir.get_parent_item(mir_hir_id).def_id);
let output = &parent_item
.fn_decl()
.expect("coroutine lowered from async fn should be in fn")
.output;
span = output.span();
if let hir::FnRetTy::Return(ret) = output {
hir_ty = Some(self.get_future_inner_return_ty(ret));
}
" of async function"
}
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Gen,
hir::CoroutineSource::Block,
)) => " of gen block",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Gen,
hir::CoroutineSource::Closure,
))
| hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Gen) => {
" of gen closure"
}
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::Gen,
hir::CoroutineSource::Fn,
)) => {
let parent_item =
tcx.hir_node_by_def_id(hir.get_parent_item(mir_hir_id).def_id);
let output = &parent_item
.fn_decl()
.expect("coroutine lowered from gen fn should be in fn")
.output;
span = output.span();
" of gen function"
}
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::AsyncGen,
hir::CoroutineSource::Block,
)) => " of async gen block",
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::AsyncGen,
hir::CoroutineSource::Closure,
))
| hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::AsyncGen) => {
" of async gen closure"
}
hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
hir::CoroutineDesugaring::AsyncGen,
hir::CoroutineSource::Fn,
)) => {
let parent_item =
tcx.hir_node_by_def_id(hir.get_parent_item(mir_hir_id).def_id);
let output = &parent_item
.fn_decl()
.expect("coroutine lowered from async gen fn should be in fn")
.output;
span = output.span();
" of async gen function"
}
hir::ClosureKind::Coroutine(hir::CoroutineKind::Coroutine(_)) => {
" of coroutine"
}
hir::ClosureKind::Closure => " of closure",
};
(span, mir_description, hir_ty)
}
node => match node.fn_decl() {
Some(fn_decl) => {
let hir_ty = match fn_decl.output {
hir::FnRetTy::DefaultReturn(_) => None,
hir::FnRetTy::Return(ty) => Some(ty),
};
(fn_decl.output.span(), "", hir_ty)
}
None => (self.body.span, "", None),
},
};
let highlight = hir_ty
.and_then(|hir_ty| self.highlight_if_we_can_match_hir_ty(fr, return_ty, hir_ty))
.unwrap_or_else(|| {
// `highlight_if_we_cannot_match_hir_ty` needs to know the number we will give to
// the anonymous region. If it succeeds, the `synthesize_region_name` call below
// will increment the counter, "reserving" the number we just used.
let counter = *self.next_region_name.try_borrow().unwrap();
self.highlight_if_we_cannot_match_hir_ty(fr, return_ty, return_span, counter)
});
Some(RegionName {
name: self.synthesize_region_name(),
source: RegionNameSource::AnonRegionFromOutput(highlight, mir_description),
})
}
/// From the [`hir::Ty`] of an async function's lowered return type,
/// retrieve the `hir::Ty` representing the type the user originally wrote.
///
/// e.g. given the function:
///
/// ```
/// async fn foo() -> i32 { 2 }
/// ```
///
/// this function, given the lowered return type of `foo`, an [`OpaqueDef`] that implements `Future<Output=i32>`,
/// returns the `i32`.
///
/// [`OpaqueDef`]: hir::TyKind::OpaqueDef
fn get_future_inner_return_ty(&self, hir_ty: &'tcx hir::Ty<'tcx>) -> &'tcx hir::Ty<'tcx> {
let hir = self.infcx.tcx.hir();
let hir::TyKind::OpaqueDef(id, _, _) = hir_ty.kind else {
span_bug!(
hir_ty.span,
"lowered return type of async fn is not OpaqueDef: {:?}",
hir_ty
);
};
let opaque_ty = hir.item(id);
if let hir::ItemKind::OpaqueTy(hir::OpaqueTy {
bounds: [hir::GenericBound::Trait(trait_ref, _)],
..
}) = opaque_ty.kind
&& let Some(segment) = trait_ref.trait_ref.path.segments.last()
&& let Some(args) = segment.args
&& let [constraint] = args.constraints
&& constraint.ident.name == sym::Output
&& let Some(ty) = constraint.ty()
{
ty
} else {
span_bug!(
hir_ty.span,
"bounds from lowered return type of async fn did not match expected format: {opaque_ty:?}",
);
}
}
#[instrument(level = "trace", skip(self))]
fn give_name_if_anonymous_region_appears_in_yield_ty(
&self,
fr: RegionVid,
) -> Option<RegionName> {
// Note: coroutines from `async fn` yield `()`, so we don't have to
// worry about them here.
let yield_ty = self.regioncx.universal_regions().yield_ty?;
debug!("give_name_if_anonymous_region_appears_in_yield_ty: yield_ty = {:?}", yield_ty);
let tcx = self.infcx.tcx;
if !tcx.any_free_region_meets(&yield_ty, |r| r.as_var() == fr) {
return None;
}
let mut highlight = RegionHighlightMode::default();
highlight.highlighting_region_vid(tcx, fr, *self.next_region_name.try_borrow().unwrap());
let type_name = self
.infcx
.err_ctxt()
.extract_inference_diagnostics_data(yield_ty.into(), Some(highlight))
.name;
let yield_span = match tcx.hir_node(self.mir_hir_id()) {
hir::Node::Expr(hir::Expr {
kind: hir::ExprKind::Closure(&hir::Closure { fn_decl_span, .. }),
..
}) => tcx.sess.source_map().end_point(fn_decl_span),
_ => self.body.span,
};
debug!(
"give_name_if_anonymous_region_appears_in_yield_ty: \
type_name = {:?}, yield_span = {:?}",
yield_span, type_name,
);
Some(RegionName {
name: self.synthesize_region_name(),
source: RegionNameSource::AnonRegionFromYieldTy(yield_span, Symbol::intern(&type_name)),
})
}
fn give_name_if_anonymous_region_appears_in_impl_signature(
&self,
fr: RegionVid,
) -> Option<RegionName> {
let ty::ReEarlyParam(region) = *self.to_error_region(fr)? else {
return None;
};
if region.has_name() {
return None;
};
let tcx = self.infcx.tcx;
let region_def = tcx.generics_of(self.mir_def_id()).region_param(region, tcx).def_id;
let region_parent = tcx.parent(region_def);
let DefKind::Impl { .. } = tcx.def_kind(region_parent) else {
return None;
};
let found = tcx
.any_free_region_meets(&tcx.type_of(region_parent).instantiate_identity(), |r| {
*r == ty::ReEarlyParam(region)
});
Some(RegionName {
name: self.synthesize_region_name(),
source: RegionNameSource::AnonRegionFromImplSignature(
tcx.def_span(region_def),
// FIXME(compiler-errors): Does this ever actually show up
// anywhere other than the self type? I couldn't create an
// example of a `'_` in the impl's trait being referenceable.
if found { "self type" } else { "header" },
),
})
}
fn give_name_if_anonymous_region_appears_in_arg_position_impl_trait(
&self,
fr: RegionVid,
) -> Option<RegionName> {
let ty::ReEarlyParam(region) = *self.to_error_region(fr)? else {
return None;
};
if region.has_name() {
return None;
};
let predicates = self
.infcx
.tcx
.predicates_of(self.body.source.def_id())
.instantiate_identity(self.infcx.tcx)
.predicates;
if let Some(upvar_index) = self
.regioncx
.universal_regions()
.defining_ty
.upvar_tys()
.iter()
.position(|ty| self.any_param_predicate_mentions(&predicates, ty, region))
{
let (upvar_name, upvar_span) = self.regioncx.get_upvar_name_and_span_for_region(
self.infcx.tcx,
self.upvars,
upvar_index,
);
let region_name = self.synthesize_region_name();
Some(RegionName {
name: region_name,
source: RegionNameSource::AnonRegionFromUpvar(upvar_span, upvar_name),
})
} else if let Some(arg_index) = self
.regioncx
.universal_regions()
.unnormalized_input_tys
.iter()
.position(|ty| self.any_param_predicate_mentions(&predicates, *ty, region))
{
let (arg_name, arg_span) = self.regioncx.get_argument_name_and_span_for_region(
self.body,
&self.local_names,
arg_index,
);
let region_name = self.synthesize_region_name();
Some(RegionName {
name: region_name,
source: RegionNameSource::AnonRegionFromArgument(
RegionNameHighlight::CannotMatchHirTy(arg_span, arg_name?),
),
})
} else {
None
}
}
fn any_param_predicate_mentions(
&self,
clauses: &[ty::Clause<'tcx>],
ty: Ty<'tcx>,
region: ty::EarlyParamRegion,
) -> bool {
let tcx = self.infcx.tcx;
ty.walk().any(|arg| {
if let ty::GenericArgKind::Type(ty) = arg.unpack()
&& let ty::Param(_) = ty.kind()
{
clauses.iter().any(|pred| {
match pred.kind().skip_binder() {
ty::ClauseKind::Trait(data) if data.self_ty() == ty => {}
ty::ClauseKind::Projection(data)
if data.projection_term.self_ty() == ty => {}
_ => return false,
}
tcx.any_free_region_meets(pred, |r| *r == ty::ReEarlyParam(region))
})
} else {
false
}
})
}
}