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Point at correct argument when async fn output type lifetime disagrees with signature #92183

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merged 3 commits into from
Jan 20, 2022
Merged

Point at correct argument when async fn output type lifetime disagrees with signature #92183

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6487845
Properly account for binders in get_impl_future_output_ty
tmandry Dec 21, 2021
5c15ad7
NiceRegionError: Use written return type for async fn
tmandry Nov 20, 2021
698631e
Simplify error reporting code, remove await point wording
tmandry Dec 10, 2021
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15 changes: 14 additions & 1 deletion compiler/rustc_hir/src/hir.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2726,6 +2726,10 @@ pub struct FnHeader {
}

impl FnHeader {
pub fn is_async(&self) -> bool {
matches!(&self.asyncness, IsAsync::Async)
}

pub fn is_const(&self) -> bool {
matches!(&self.constness, Constness::Const)
}
Expand Down Expand Up @@ -3169,7 +3173,7 @@ impl<'hir> Node<'hir> {
}
}

pub fn fn_decl(&self) -> Option<&FnDecl<'hir>> {
pub fn fn_decl(&self) -> Option<&'hir FnDecl<'hir>> {
match self {
Node::TraitItem(TraitItem { kind: TraitItemKind::Fn(fn_sig, _), .. })
| Node::ImplItem(ImplItem { kind: ImplItemKind::Fn(fn_sig, _), .. })
Expand All @@ -3181,6 +3185,15 @@ impl<'hir> Node<'hir> {
}
}

pub fn fn_sig(&self) -> Option<&'hir FnSig<'hir>> {
match self {
Node::TraitItem(TraitItem { kind: TraitItemKind::Fn(fn_sig, _), .. })
| Node::ImplItem(ImplItem { kind: ImplItemKind::Fn(fn_sig, _), .. })
| Node::Item(Item { kind: ItemKind::Fn(fn_sig, _, _), .. }) => Some(fn_sig),
_ => None,
}
}

pub fn body_id(&self) -> Option<BodyId> {
match self {
Node::TraitItem(TraitItem {
Expand Down
31 changes: 19 additions & 12 deletions compiler/rustc_infer/src/infer/error_reporting/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -65,11 +65,11 @@ use rustc_hir::def_id::DefId;
use rustc_hir::lang_items::LangItem;
use rustc_hir::{Item, ItemKind, Node};
use rustc_middle::dep_graph::DepContext;
use rustc_middle::ty::error::TypeError;
use rustc_middle::ty::{
self,
error::TypeError,
subst::{GenericArgKind, Subst, SubstsRef},
Region, Ty, TyCtxt, TypeFoldable,
Binder, Region, Ty, TyCtxt, TypeFoldable,
};
use rustc_span::{sym, BytePos, DesugaringKind, MultiSpan, Pos, Span};
use rustc_target::spec::abi;
Expand Down Expand Up @@ -1765,7 +1765,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
self.note_error_origin(diag, cause, exp_found, terr);
}

pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Binder<'tcx, Ty<'tcx>>> {
if let ty::Opaque(def_id, substs) = ty.kind() {
let future_trait = self.tcx.require_lang_item(LangItem::Future, None);
// Future::Output
Expand All @@ -1775,13 +1775,20 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {

for (predicate, _) in bounds {
let predicate = predicate.subst(self.tcx, substs);
if let ty::PredicateKind::Projection(projection_predicate) =
predicate.kind().skip_binder()
{
if projection_predicate.projection_ty.item_def_id == item_def_id {
// We don't account for multiple `Future::Output = Ty` contraints.
return projection_predicate.term.ty();
}
let output = predicate
.kind()
.map_bound(|kind| match kind {
ty::PredicateKind::Projection(projection_predicate)
if projection_predicate.projection_ty.item_def_id == item_def_id =>
{
projection_predicate.term.ty()
}
_ => None,
})
.transpose();
if output.is_some() {
// We don't account for multiple `Future::Output = Ty` contraints.
return output;
}
}
}
Expand Down Expand Up @@ -1823,8 +1830,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}

match (
self.get_impl_future_output_ty(exp_found.expected),
self.get_impl_future_output_ty(exp_found.found),
self.get_impl_future_output_ty(exp_found.expected).map(Binder::skip_binder),
self.get_impl_future_output_ty(exp_found.found).map(Binder::skip_binder),
) {
(Some(exp), Some(found)) if same_type_modulo_infer(exp, found) => match cause.code() {
ObligationCauseCode::IfExpression(box IfExpressionCause { then, .. }) => {
Expand Down
109 changes: 33 additions & 76 deletions compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -106,90 +106,47 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
None => String::new(),
};

let (span_1, span_2, main_label, span_label, future_return_type) =
match (sup_is_ret_type, sub_is_ret_type) {
(None, None) => {
let (main_label_1, span_label_1) = if ty_sup.hir_id == ty_sub.hir_id {
(
"this type is declared with multiple lifetimes...".to_owned(),
"...but data with one lifetime flows into the other here".to_owned(),
)
} else {
(
"these two types are declared with different lifetimes...".to_owned(),
format!("...but data{} flows{} here", span_label_var1, span_label_var2),
)
};
(ty_sup.span, ty_sub.span, main_label_1, span_label_1, None)
}
debug!(
"try_report_anon_anon_conflict: sub_is_ret_type={:?} sup_is_ret_type={:?}",
sub_is_ret_type, sup_is_ret_type
);

(Some(ret_span), _) => {
let sup_future = self.future_return_type(scope_def_id_sup);
let (return_type, action) = if sup_future.is_some() {
("returned future", "held across an await point")
} else {
("return type", "returned")
};
let mut err = struct_span_err!(self.tcx().sess, span, E0623, "lifetime mismatch");

(
ty_sub.span,
ret_span,
format!(
"this parameter and the {} are declared with different lifetimes...",
return_type
),
format!("...but data{} is {} here", span_label_var1, action),
sup_future,
)
}
(_, Some(ret_span)) => {
let sub_future = self.future_return_type(scope_def_id_sub);
let (return_type, action) = if sub_future.is_some() {
("returned future", "held across an await point")
} else {
("return type", "returned")
};
match (sup_is_ret_type, sub_is_ret_type) {
(ret_capture @ Some(ret_span), _) | (_, ret_capture @ Some(ret_span)) => {
let param_span =
if sup_is_ret_type == ret_capture { ty_sub.span } else { ty_sup.span };

err.span_label(
param_span,
"this parameter and the return type are declared with different lifetimes...",
);
err.span_label(ret_span, "");
err.span_label(span, format!("...but data{} is returned here", span_label_var1));
}

(
(None, None) => {
if ty_sup.hir_id == ty_sub.hir_id {
err.span_label(ty_sup.span, "this type is declared with multiple lifetimes...");
err.span_label(ty_sub.span, "");
err.span_label(span, "...but data with one lifetime flows into the other here");
} else {
err.span_label(
ty_sup.span,
ret_span,
format!(
"this parameter and the {} are declared with different lifetimes...",
return_type
),
format!("...but data{} is {} here", span_label_var1, action),
sub_future,
)
"these two types are declared with different lifetimes...",
);
err.span_label(ty_sub.span, "");
err.span_label(
span,
format!("...but data{} flows{} here", span_label_var1, span_label_var2),
);
}
};

let mut err = struct_span_err!(self.tcx().sess, span, E0623, "lifetime mismatch");

err.span_label(span_1, main_label);
err.span_label(span_2, String::new());
err.span_label(span, span_label);
}
}

self.suggest_adding_lifetime_params(sub, ty_sup, ty_sub, &mut err);

if let Some(t) = future_return_type {
let snip = self
.tcx()
.sess
.source_map()
.span_to_snippet(t.span)
.ok()
.and_then(|s| match (&t.kind, s.as_str()) {
(rustc_hir::TyKind::Tup(&[]), "") => Some("()".to_string()),
(_, "") => None,
_ => Some(s),
})
.unwrap_or_else(|| "{unnamed_type}".to_string());

err.span_label(
t.span,
&format!("this `async fn` implicitly returns an `impl Future<Output = {}>`", snip),
);
}
err.emit();
Some(ErrorReported)
}
Expand Down
19 changes: 6 additions & 13 deletions compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,5 @@
use rustc_hir as hir;
use rustc_hir::intravisit::{self, Visitor};
use rustc_hir::Node;
use rustc_middle::hir::map::Map;
use rustc_middle::hir::nested_filter;
use rustc_middle::middle::resolve_lifetime as rl;
Expand All @@ -25,25 +24,19 @@ pub(crate) fn find_anon_type<'tcx>(
tcx: TyCtxt<'tcx>,
region: Region<'tcx>,
br: &ty::BoundRegionKind,
) -> Option<(&'tcx hir::Ty<'tcx>, &'tcx hir::FnDecl<'tcx>)> {
) -> Option<(&'tcx hir::Ty<'tcx>, &'tcx hir::FnSig<'tcx>)> {
if let Some(anon_reg) = tcx.is_suitable_region(region) {
let hir_id = tcx.hir().local_def_id_to_hir_id(anon_reg.def_id);
let fndecl = match tcx.hir().get(hir_id) {
Node::Item(&hir::Item { kind: hir::ItemKind::Fn(ref m, ..), .. })
| Node::TraitItem(&hir::TraitItem {
kind: hir::TraitItemKind::Fn(ref m, ..), ..
})
| Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(ref m, ..), .. }) => {
&m.decl
}
_ => return None,
let Some(fn_sig) = tcx.hir().get(hir_id).fn_sig() else {
return None
};

fndecl
fn_sig
.decl
.inputs
.iter()
.find_map(|arg| find_component_for_bound_region(tcx, arg, br))
.map(|ty| (ty, &**fndecl))
.map(|ty| (ty, fn_sig))
} else {
None
}
Expand Down
91 changes: 26 additions & 65 deletions compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
use crate::infer::error_reporting::nice_region_error::NiceRegionError;
use rustc_hir as hir;
use rustc_hir::def_id::LocalDefId;
use rustc_middle::ty::{self, DefIdTree, Region, Ty};
use rustc_middle::ty::{self, Binder, DefIdTree, Region, Ty, TypeFoldable};
use rustc_span::Span;

/// Information about the anonymous region we are searching for.
Expand Down Expand Up @@ -94,81 +94,42 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
})
}

pub(super) fn future_return_type(
&self,
local_def_id: LocalDefId,
) -> Option<&rustc_hir::Ty<'_>> {
if let Some(hir::IsAsync::Async) = self.asyncness(local_def_id) {
if let rustc_middle::ty::Opaque(def_id, _) =
self.tcx().type_of(local_def_id).fn_sig(self.tcx()).output().skip_binder().kind()
{
match self.tcx().hir().get_if_local(*def_id) {
Some(hir::Node::Item(hir::Item {
kind:
hir::ItemKind::OpaqueTy(hir::OpaqueTy {
bounds,
origin: hir::OpaqueTyOrigin::AsyncFn(..),
..
}),
..
})) => {
for b in bounds.iter() {
if let hir::GenericBound::LangItemTrait(
hir::LangItem::Future,
_span,
_hir_id,
generic_args,
) = b
{
for type_binding in generic_args.bindings.iter() {
if type_binding.ident.name == rustc_span::sym::Output {
if let hir::TypeBindingKind::Equality {
term: hir::Term::Ty(ty),
} = type_binding.kind
{
return Some(ty);
}
}
}
}
}
}
_ => {}
}
}
}
None
}

pub(super) fn asyncness(&self, local_def_id: LocalDefId) -> Option<hir::IsAsync> {
// similar to the asyncness fn in rustc_ty_utils::ty
let hir_id = self.tcx().hir().local_def_id_to_hir_id(local_def_id);
let node = self.tcx().hir().get(hir_id);
let fn_kind = node.fn_kind()?;
Some(fn_kind.asyncness())
}

// Here, we check for the case where the anonymous region
// is in the return type.
// is in the return type as written by the user.
// FIXME(#42703) - Need to handle certain cases here.
pub(super) fn is_return_type_anon(
&self,
scope_def_id: LocalDefId,
br: ty::BoundRegionKind,
decl: &hir::FnDecl<'_>,
hir_sig: &hir::FnSig<'_>,
) -> Option<Span> {
let ret_ty = self.tcx().type_of(scope_def_id);
if let ty::FnDef(_, _) = ret_ty.kind() {
let sig = ret_ty.fn_sig(self.tcx());
let late_bound_regions =
self.tcx().collect_referenced_late_bound_regions(&sig.output());
if late_bound_regions.iter().any(|r| *r == br) {
return Some(decl.output.span());
}
let fn_ty = self.tcx().type_of(scope_def_id);
if let ty::FnDef(_, _) = fn_ty.kind() {
let ret_ty = fn_ty.fn_sig(self.tcx()).output();
let span = hir_sig.decl.output.span();
let future_output = if hir_sig.header.is_async() {
ret_ty.map_bound(|ty| self.infcx.get_impl_future_output_ty(ty)).transpose()
} else {
None
};
return match future_output {
Some(output) if self.includes_region(output, br) => Some(span),
None if self.includes_region(ret_ty, br) => Some(span),
_ => None,
};
}
None
}

fn includes_region(
&self,
ty: Binder<'tcx, impl TypeFoldable<'tcx>>,
region: ty::BoundRegionKind,
) -> bool {
let late_bound_regions = self.tcx().collect_referenced_late_bound_regions(&ty);
late_bound_regions.iter().any(|r| *r == region)
}

// Here we check for the case where anonymous region
// corresponds to self and if yes, we display E0312.
// FIXME(#42700) - Need to format self properly to
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_typeck/src/check/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1909,7 +1909,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
_ => return,
};
let mut add_label = true;
if let ty::Adt(def, _) = output_ty.kind() {
if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
// no field access on enum type
if !def.is_enum() {
if def
Expand Down
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