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Auto merge of #94081 - oli-obk:lazy_tait_take_two, r=nikomatsakis

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Lazy type-alias-impl-trait take two

### user visible change 1: RPIT inference from recursive call sites

Lazy TAIT has an insta-stable change. The following snippet now compiles, because opaque types can now have their hidden type set from wherever the opaque type is mentioned.

```rust
fn bar(b: bool) -> impl std::fmt::Debug {
    if b {
        return 42
    }
    let x: u32 = bar(false); // this errors on stable
    99
}
```

The return type of `bar` stays opaque, you can't do `bar(false) + 42`, you need to actually mention the hidden type.

### user visible change 2: divergence between RPIT and TAIT in return statements

Note that `return` statements and the trailing return expression are special with RPIT (but not TAIT). So

```rust
#![feature(type_alias_impl_trait)]
type Foo = impl std::fmt::Debug;

fn foo(b: bool) -> Foo {
    if b {
        return vec![42];
    }
    std::iter::empty().collect() //~ ERROR `Foo` cannot be built from an iterator
}

fn bar(b: bool) -> impl std::fmt::Debug {
    if b {
        return vec![42]
    }
    std::iter::empty().collect() // Works, magic (accidentally stabilized, not intended)
}
```

But when we are working with the return value of a recursive call, the behavior of RPIT and TAIT is the same:

```rust
type Foo = impl std::fmt::Debug;

fn foo(b: bool) -> Foo {
    if b {
        return vec![];
    }
    let mut x = foo(false);
    x = std::iter::empty().collect(); //~ ERROR `Foo` cannot be built from an iterator
    vec![]
}

fn bar(b: bool) -> impl std::fmt::Debug {
    if b {
        return vec![];
    }
    let mut x = bar(false);
    x = std::iter::empty().collect(); //~ ERROR `impl Debug` cannot be built from an iterator
    vec![]
}
```

### user visible change 3: TAIT does not merge types across branches

In contrast to RPIT, TAIT does not merge types across branches, so the following does not compile.

```rust
type Foo = impl std::fmt::Debug;

fn foo(b: bool) -> Foo {
    if b {
        vec![42_i32]
    } else {
        std::iter::empty().collect()
        //~^ ERROR `Foo` cannot be built from an iterator over elements of type `_`
    }
}
```

It is easy to support, but we should make an explicit decision to include the additional complexity in the implementation (it's not much, see a721052457cf513487fb4266e3ade65c29b272d2 which needs to be reverted to enable this).

### PR formalities

previous attempt: #92007

This PR also includes #92306 and #93783, as they were reverted along with #92007 in #93893

fixes #93411
fixes #88236
fixes #89312
fixes #87340
fixes #86800
fixes #86719
fixes #84073
fixes #83919
fixes #82139
fixes #77987
fixes #74282
fixes #67830
fixes #62742
fixes #54895
This commit is contained in:
bors 2022-03-30 05:04:45 +00:00
commit f132bcf3bd
419 changed files with 5208 additions and 2490 deletions
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112
compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
View file

@ -2,9 +2,13 @@ use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
use rustc_infer::infer::canonical::Canonical;
use rustc_infer::infer::error_reporting::nice_region_error::NiceRegionError;
use rustc_infer::infer::region_constraints::Constraint;
use rustc_infer::infer::region_constraints::RegionConstraintData;
use rustc_infer::infer::RegionVariableOrigin;
use rustc_infer::infer::{InferCtxt, RegionResolutionError, SubregionOrigin, TyCtxtInferExt as _};
use rustc_infer::traits::{Normalized, ObligationCause, TraitEngine, TraitEngineExt};
use rustc_middle::ty::error::TypeError;
use rustc_middle::ty::RegionVid;
use rustc_middle::ty::UniverseIndex;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
use rustc_span::Span;
use rustc_trait_selection::traits::query::type_op;
@ -76,6 +80,15 @@ crate trait ToUniverseInfo<'tcx> {
fn to_universe_info(self, base_universe: ty::UniverseIndex) -> UniverseInfo<'tcx>;
}
impl<'tcx> ToUniverseInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
fn to_universe_info(self, base_universe: ty::UniverseIndex) -> UniverseInfo<'tcx> {
UniverseInfo(UniverseInfoInner::TypeOp(Rc::new(crate::type_check::InstantiateOpaqueType {
base_universe: Some(base_universe),
..self
})))
}
}
impl<'tcx> ToUniverseInfo<'tcx>
for Canonical<'tcx, ty::ParamEnvAnd<'tcx, type_op::prove_predicate::ProvePredicate<'tcx>>>
{
@ -116,6 +129,12 @@ impl<'tcx, F, G> ToUniverseInfo<'tcx> for Canonical<'tcx, type_op::custom::Custo
}
}
impl<'tcx> ToUniverseInfo<'tcx> for ! {
fn to_universe_info(self, _base_universe: ty::UniverseIndex) -> UniverseInfo<'tcx> {
self
}
}
#[allow(unused_lifetimes)]
trait TypeOpInfo<'tcx> {
/// Returns an error to be reported if rerunning the type op fails to
@ -130,7 +149,7 @@ trait TypeOpInfo<'tcx> {
fn nice_error(
&self,
tcx: TyCtxt<'tcx>,
mbcx: &mut MirBorrowckCtxt<'_, 'tcx>,
cause: ObligationCause<'tcx>,
placeholder_region: ty::Region<'tcx>,
error_region: Option<ty::Region<'tcx>>,
@ -175,7 +194,7 @@ trait TypeOpInfo<'tcx> {
debug!(?placeholder_region);
let span = cause.span;
let nice_error = self.nice_error(tcx, cause, placeholder_region, error_region);
let nice_error = self.nice_error(mbcx, cause, placeholder_region, error_region);
if let Some(nice_error) = nice_error {
mbcx.buffer_error(nice_error);
@ -208,16 +227,16 @@ impl<'tcx> TypeOpInfo<'tcx> for PredicateQuery<'tcx> {
fn nice_error(
&self,
tcx: TyCtxt<'tcx>,
mbcx: &mut MirBorrowckCtxt<'_, 'tcx>,
cause: ObligationCause<'tcx>,
placeholder_region: ty::Region<'tcx>,
error_region: Option<ty::Region<'tcx>>,
) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
tcx.infer_ctxt().enter_with_canonical(
mbcx.infcx.tcx.infer_ctxt().enter_with_canonical(
cause.span,
&self.canonical_query,
|ref infcx, key, _| {
let mut fulfill_cx = <dyn TraitEngine<'_>>::new(tcx);
let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
type_op_prove_predicate_with_cause(infcx, &mut *fulfill_cx, key, cause);
try_extract_error_from_fulfill_cx(
fulfill_cx,
@ -255,16 +274,16 @@ where
fn nice_error(
&self,
tcx: TyCtxt<'tcx>,
mbcx: &mut MirBorrowckCtxt<'_, 'tcx>,
cause: ObligationCause<'tcx>,
placeholder_region: ty::Region<'tcx>,
error_region: Option<ty::Region<'tcx>>,
) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
tcx.infer_ctxt().enter_with_canonical(
mbcx.infcx.tcx.infer_ctxt().enter_with_canonical(
cause.span,
&self.canonical_query,
|ref infcx, key, _| {
let mut fulfill_cx = <dyn TraitEngine<'_>>::new(tcx);
let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
let mut selcx = SelectionContext::new(infcx);
@ -316,16 +335,16 @@ impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
fn nice_error(
&self,
tcx: TyCtxt<'tcx>,
mbcx: &mut MirBorrowckCtxt<'_, 'tcx>,
cause: ObligationCause<'tcx>,
placeholder_region: ty::Region<'tcx>,
error_region: Option<ty::Region<'tcx>>,
) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
tcx.infer_ctxt().enter_with_canonical(
mbcx.infcx.tcx.infer_ctxt().enter_with_canonical(
cause.span,
&self.canonical_query,
|ref infcx, key, _| {
let mut fulfill_cx = <dyn TraitEngine<'_>>::new(tcx);
let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
type_op_ascribe_user_type_with_span(infcx, &mut *fulfill_cx, key, Some(cause.span))
.ok()?;
try_extract_error_from_fulfill_cx(
@ -339,6 +358,43 @@ impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
}
}
impl<'tcx> TypeOpInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
fn fallback_error(
&self,
tcx: TyCtxt<'tcx>,
span: Span,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
// FIXME: This error message isn't great, but it doesn't show up in the existing UI tests,
// and is only the fallback when the nice error fails. Consider improving this some more.
tcx.sess.struct_span_err(span, "higher-ranked lifetime error for opaque type!")
}
fn base_universe(&self) -> ty::UniverseIndex {
self.base_universe.unwrap()
}
fn nice_error(
&self,
mbcx: &mut MirBorrowckCtxt<'_, 'tcx>,
_cause: ObligationCause<'tcx>,
placeholder_region: ty::Region<'tcx>,
error_region: Option<ty::Region<'tcx>>,
) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
try_extract_error_from_region_constraints(
mbcx.infcx,
placeholder_region,
error_region,
self.region_constraints.as_ref().unwrap(),
// We're using the original `InferCtxt` that we
// started MIR borrowchecking with, so the region
// constraints have already been taken. Use the data from
// our `mbcx` instead.
|vid| mbcx.regioncx.var_infos[vid].origin,
|vid| mbcx.regioncx.var_infos[vid].universe,
)
}
}
#[instrument(skip(fulfill_cx, infcx), level = "debug")]
fn try_extract_error_from_fulfill_cx<'tcx>(
mut fulfill_cx: Box<dyn TraitEngine<'tcx> + 'tcx>,
@ -346,15 +402,30 @@ fn try_extract_error_from_fulfill_cx<'tcx>(
placeholder_region: ty::Region<'tcx>,
error_region: Option<ty::Region<'tcx>>,
) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
let tcx = infcx.tcx;
// We generally shouldn't have errors here because the query was
// already run, but there's no point using `delay_span_bug`
// when we're going to emit an error here anyway.
let _errors = fulfill_cx.select_all_or_error(infcx);
let region_constraints = infcx.with_region_constraints(|r| r.clone());
try_extract_error_from_region_constraints(
infcx,
placeholder_region,
error_region,
&region_constraints,
|vid| infcx.region_var_origin(vid),
|vid| infcx.universe_of_region(infcx.tcx.mk_region(ty::ReVar(vid))),
)
}
let (sub_region, cause) = infcx.with_region_constraints(|region_constraints| {
debug!("{:#?}", region_constraints);
fn try_extract_error_from_region_constraints<'tcx>(
infcx: &InferCtxt<'_, 'tcx>,
placeholder_region: ty::Region<'tcx>,
error_region: Option<ty::Region<'tcx>>,
region_constraints: &RegionConstraintData<'tcx>,
mut region_var_origin: impl FnMut(RegionVid) -> RegionVariableOrigin,
mut universe_of_region: impl FnMut(RegionVid) -> UniverseIndex,
) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
let (sub_region, cause) =
region_constraints.constraints.iter().find_map(|(constraint, cause)| {
match *constraint {
Constraint::RegSubReg(sub, sup) if sup == placeholder_region && sup != sub => {
@ -362,12 +433,11 @@ fn try_extract_error_from_fulfill_cx<'tcx>(
}
// FIXME: Should this check the universe of the var?
Constraint::VarSubReg(vid, sup) if sup == placeholder_region => {
Some((tcx.mk_region(ty::ReVar(vid)), cause.clone()))
Some((infcx.tcx.mk_region(ty::ReVar(vid)), cause.clone()))
}
_ => None,
}
})
})?;
})?;
debug!(?sub_region, "cause = {:#?}", cause);
let nice_error = match (error_region, *sub_region) {
@ -375,7 +445,7 @@ fn try_extract_error_from_fulfill_cx<'tcx>(
infcx,
RegionResolutionError::SubSupConflict(
vid,
infcx.region_var_origin(vid),
region_var_origin(vid),
cause.clone(),
error_region,
cause.clone(),
@ -392,8 +462,8 @@ fn try_extract_error_from_fulfill_cx<'tcx>(
infcx,
RegionResolutionError::UpperBoundUniverseConflict(
vid,
infcx.region_var_origin(vid),
infcx.universe_of_region(sub_region),
region_var_origin(vid),
universe_of_region(vid),
cause.clone(),
placeholder_region,
),

6
compiler/rustc_borrowck/src/lib.rs
View file

@ -7,6 +7,7 @@
#![feature(let_chains)]
#![feature(let_else)]
#![feature(min_specialization)]
#![feature(never_type)]
#![feature(stmt_expr_attributes)]
#![feature(trusted_step)]
#![feature(try_blocks)]
@ -125,8 +126,9 @@ fn mir_borrowck<'tcx>(
) -> &'tcx BorrowCheckResult<'tcx> {
let (input_body, promoted) = tcx.mir_promoted(def);
debug!("run query mir_borrowck: {}", tcx.def_path_str(def.did.to_def_id()));
let hir_owner = tcx.hir().local_def_id_to_hir_id(def.did).owner;
let opt_closure_req = tcx.infer_ctxt().with_opaque_type_inference(def.did).enter(|infcx| {
let opt_closure_req = tcx.infer_ctxt().with_opaque_type_inference(hir_owner).enter(|infcx| {
let input_body: &Body<'_> = &input_body.borrow();
let promoted: &IndexVec<_, _> = &promoted.borrow();
do_mir_borrowck(&infcx, input_body, promoted, false).0
@ -141,7 +143,7 @@ fn mir_borrowck<'tcx>(
/// If `return_body_with_facts` is true, then return the body with non-erased
/// region ids on which the borrow checking was performed together with Polonius
/// facts.
#[instrument(skip(infcx, input_body, input_promoted), level = "debug")]
#[instrument(skip(infcx, input_body, input_promoted), fields(id=?input_body.source.with_opt_param().as_local().unwrap()), level = "debug")]
fn do_mir_borrowck<'a, 'tcx>(
infcx: &InferCtxt<'a, 'tcx>,
input_body: &Body<'tcx>,

8
compiler/rustc_borrowck/src/nll.rs
View file

@ -8,7 +8,7 @@ use rustc_middle::mir::{
BasicBlock, Body, ClosureOutlivesSubject, ClosureRegionRequirements, LocalKind, Location,
Promoted,
};
use rustc_middle::ty::{self, OpaqueTypeKey, Region, RegionVid, Ty};
use rustc_middle::ty::{self, OpaqueHiddenType, OpaqueTypeKey, Region, RegionVid};
use rustc_span::symbol::sym;
use std::env;
use std::fmt::Debug;
@ -43,7 +43,7 @@ pub type PoloniusOutput = Output<RustcFacts>;
/// closure requirements to propagate, and any generated errors.
crate struct NllOutput<'tcx> {
pub regioncx: RegionInferenceContext<'tcx>,
pub opaque_type_values: VecMap<OpaqueTypeKey<'tcx>, Ty<'tcx>>,
pub opaque_type_values: VecMap<OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>>,
pub polonius_input: Option<Box<AllFacts>>,
pub polonius_output: Option<Rc<PoloniusOutput>>,
pub opt_closure_req: Option<ClosureRegionRequirements<'tcx>>,
@ -305,7 +305,7 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
infcx.set_tainted_by_errors();
}
let remapped_opaque_tys = regioncx.infer_opaque_types(&infcx, opaque_type_values, body.span);
let remapped_opaque_tys = regioncx.infer_opaque_types(&infcx, opaque_type_values);
NllOutput {
regioncx,
@ -372,7 +372,7 @@ pub(super) fn dump_annotation<'a, 'tcx>(
body: &Body<'tcx>,
regioncx: &RegionInferenceContext<'tcx>,
closure_region_requirements: &Option<ClosureRegionRequirements<'_>>,
opaque_type_values: &VecMap<OpaqueTypeKey<'tcx>, Ty<'tcx>>,
opaque_type_values: &VecMap<OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>>,
errors: &mut crate::error::BorrowckErrors<'tcx>,
) {
let tcx = infcx.tcx;

4
compiler/rustc_borrowck/src/region_infer/mod.rs
View file

@ -45,6 +45,7 @@ mod reverse_sccs;
pub mod values;
pub struct RegionInferenceContext<'tcx> {
pub var_infos: VarInfos,
/// Contains the definition for every region variable. Region
/// variables are identified by their index (`RegionVid`). The
/// definition contains information about where the region came
@ -267,7 +268,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
) -> Self {
// Create a RegionDefinition for each inference variable.
let definitions: IndexVec<_, _> = var_infos
.into_iter()
.iter()
.map(|info| RegionDefinition::new(info.universe, info.origin))
.collect();
@ -292,6 +293,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
Rc::new(member_constraints_in.into_mapped(|r| constraint_sccs.scc(r)));
let mut result = Self {
var_infos,
definitions,
liveness_constraints,
constraints,

66
compiler/rustc_borrowck/src/region_infer/opaque_types.rs
View file

@ -1,10 +1,9 @@
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::vec_map::VecMap;
use rustc_hir::OpaqueTyOrigin;
use rustc_infer::infer::opaque_types::OpaqueTypeDecl;
use rustc_infer::infer::InferCtxt;
use rustc_middle::ty::subst::GenericArgKind;
use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable};
use rustc_middle::ty::{self, OpaqueHiddenType, OpaqueTypeKey, TyCtxt, TypeFoldable};
use rustc_span::Span;
use rustc_trait_selection::opaque_types::InferCtxtExt;
@ -54,27 +53,41 @@ impl<'tcx> RegionInferenceContext<'tcx> {
pub(crate) fn infer_opaque_types(
&self,
infcx: &InferCtxt<'_, 'tcx>,
opaque_ty_decls: VecMap<OpaqueTypeKey<'tcx>, OpaqueTypeDecl<'tcx>>,
span: Span,
) -> VecMap<OpaqueTypeKey<'tcx>, Ty<'tcx>> {
opaque_ty_decls: VecMap<OpaqueTypeKey<'tcx>, (OpaqueHiddenType<'tcx>, OpaqueTyOrigin)>,
) -> VecMap<OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>> {
opaque_ty_decls
.into_iter()
.filter_map(|(opaque_type_key, decl)| {
.map(|(opaque_type_key, (concrete_type, origin))| {
let substs = opaque_type_key.substs;
let concrete_type = decl.concrete_ty;
debug!(?concrete_type, ?substs);
let mut subst_regions = vec![self.universal_regions.fr_static];
let universal_substs = infcx.tcx.fold_regions(substs, &mut false, |region, _| {
let vid = self.universal_regions.to_region_vid(region);
subst_regions.push(vid);
self.definitions[vid].external_name.unwrap_or_else(|| {
infcx
.tcx
.sess
.delay_span_bug(span, "opaque type with non-universal region substs");
infcx.tcx.lifetimes.re_static
})
if let ty::RePlaceholder(..) = region.kind() {
// Higher kinded regions don't need remapping, they don't refer to anything outside of this the substs.
return region;
}
let vid = self.to_region_vid(region);
trace!(?vid);
let scc = self.constraint_sccs.scc(vid);
trace!(?scc);
match self.scc_values.universal_regions_outlived_by(scc).find_map(|lb| {
self.eval_equal(vid, lb).then_some(self.definitions[lb].external_name?)
}) {
Some(region) => {
let vid = self.universal_regions.to_region_vid(region);
subst_regions.push(vid);
region
}
None => {
subst_regions.push(vid);
infcx.tcx.sess.delay_span_bug(
concrete_type.span,
"opaque type with non-universal region substs",
);
infcx.tcx.lifetimes.re_static
}
}
});
subst_regions.sort();
@ -97,15 +110,18 @@ impl<'tcx> RegionInferenceContext<'tcx> {
let remapped_type = infcx.infer_opaque_definition_from_instantiation(
opaque_type_key,
universal_concrete_type,
span,
);
check_opaque_type_parameter_valid(
let ty = if check_opaque_type_parameter_valid(
infcx.tcx,
opaque_type_key,
OpaqueTypeDecl { concrete_ty: remapped_type, ..decl },
)
.then_some((opaque_type_key, remapped_type))
origin,
concrete_type.span,
) {
remapped_type
} else {
infcx.tcx.ty_error()
};
(opaque_type_key, OpaqueHiddenType { ty, span: concrete_type.span })
})
.collect()
}
@ -149,9 +165,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
fn check_opaque_type_parameter_valid(
tcx: TyCtxt<'_>,
opaque_type_key: OpaqueTypeKey<'_>,
decl: OpaqueTypeDecl<'_>,
origin: OpaqueTyOrigin,
span: Span,
) -> bool {
match decl.origin {
match origin {
// No need to check return position impl trait (RPIT)
// because for type and const parameters they are correct
// by construction: we convert
@ -177,7 +194,6 @@ fn check_opaque_type_parameter_valid(
// Check these
OpaqueTyOrigin::TyAlias => {}
}
let span = decl.definition_span;
let opaque_generics = tcx.generics_of(opaque_type_key.def_id);
let mut seen_params: FxHashMap<_, Vec<_>> = FxHashMap::default();
for (i, arg) in opaque_type_key.substs.iter().enumerate() {

9
compiler/rustc_borrowck/src/type_check/canonical.rs
View file

@ -33,12 +33,11 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
) -> Fallible<R>
where
Op: type_op::TypeOp<'tcx, Output = R>,
Canonical<'tcx, Op>: ToUniverseInfo<'tcx>,
Op::ErrorInfo: ToUniverseInfo<'tcx>,
{
let old_universe = self.infcx.universe();
let TypeOpOutput { output, constraints, canonicalized_query } =
op.fully_perform(self.infcx)?;
let TypeOpOutput { output, constraints, error_info } = op.fully_perform(self.infcx)?;
if let Some(data) = &constraints {
self.push_region_constraints(locations, category, data);
@ -47,8 +46,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
let universe = self.infcx.universe();
if old_universe != universe {
let universe_info = match canonicalized_query {
Some(canonicalized_query) => canonicalized_query.to_universe_info(old_universe),
let universe_info = match error_info {
Some(error_info) => error_info.to_universe_info(old_universe),
None => UniverseInfo::other(),
};
for u in old_universe..universe {

2
compiler/rustc_borrowck/src/type_check/free_region_relations.rs
View file

@ -267,7 +267,7 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
TypeOpOutput {
output: self.infcx.tcx.ty_error(),
constraints: None,
canonicalized_query: None,
error_info: None,
}
});
// Note: we need this in examples like

8
compiler/rustc_borrowck/src/type_check/input_output.rs
View file

@ -147,9 +147,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
// Return types are a bit more complex. They may contain opaque `impl Trait` types.
let mir_output_ty = body.local_decls[RETURN_PLACE].ty;
let output_span = body.local_decls[RETURN_PLACE].source_info.span;
if let Err(terr) = self.eq_opaque_type_and_type(
mir_output_ty,
if let Err(terr) = self.eq_types(
normalized_output_ty,
mir_output_ty,
Locations::All(output_span),
ConstraintCategory::BoringNoLocation,
) {
@ -169,9 +169,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
let user_provided_output_ty = user_provided_sig.output();
let user_provided_output_ty =
self.normalize(user_provided_output_ty, Locations::All(output_span));
if let Err(err) = self.eq_opaque_type_and_type(
mir_output_ty,
if let Err(err) = self.eq_types(
user_provided_output_ty,
mir_output_ty,
Locations::All(output_span),
ConstraintCategory::BoringNoLocation,
) {

273
compiler/rustc_borrowck/src/type_check/mod.rs
View file

@ -5,6 +5,7 @@ use std::{fmt, iter, mem};
use either::Either;
use hir::OpaqueTyOrigin;
use rustc_data_structures::frozen::Frozen;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::vec_map::VecMap;
@ -15,8 +16,8 @@ use rustc_hir::def_id::LocalDefId;
use rustc_hir::lang_items::LangItem;
use rustc_index::vec::{Idx, IndexVec};
use rustc_infer::infer::canonical::QueryRegionConstraints;
use rustc_infer::infer::opaque_types::OpaqueTypeDecl;
use rustc_infer::infer::outlives::env::RegionBoundPairs;
use rustc_infer::infer::region_constraints::RegionConstraintData;
use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use rustc_infer::infer::{
InferCtxt, InferOk, LateBoundRegionConversionTime, NllRegionVariableOrigin,
@ -30,8 +31,8 @@ use rustc_middle::ty::cast::CastTy;
use rustc_middle::ty::fold::TypeFoldable;
use rustc_middle::ty::subst::{GenericArgKind, SubstsRef, UserSubsts};
use rustc_middle::ty::{
self, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, OpaqueTypeKey, RegionVid,
ToPredicate, Ty, TyCtxt, UserType, UserTypeAnnotationIndex,
self, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, OpaqueHiddenType,
OpaqueTypeKey, RegionVid, ToPredicate, Ty, TyCtxt, UserType, UserTypeAnnotationIndex,
};
use rustc_span::def_id::CRATE_DEF_ID;
use rustc_span::{Span, DUMMY_SP};
@ -39,9 +40,11 @@ use rustc_target::abi::VariantIdx;
use rustc_trait_selection::infer::InferCtxtExt as _;
use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
use rustc_trait_selection::traits::query::type_op;
use rustc_trait_selection::traits::query::type_op::custom::scrape_region_constraints;
use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput};
use rustc_trait_selection::traits::query::Fallible;
use rustc_trait_selection::traits::{self, ObligationCause, PredicateObligations};
use rustc_trait_selection::traits::{self, ObligationCause, PredicateObligation};
use rustc_const_eval::transform::{
check_consts::ConstCx, promote_consts::is_const_fn_in_array_repeat_expression,
@ -75,7 +78,7 @@ macro_rules! span_mirbug {
$context.last_span,
&format!(
"broken MIR in {:?} ({:?}): {}",
$context.body.source.def_id(),
$context.body().source.def_id(),
$elem,
format_args!($($message)*),
),
@ -199,59 +202,44 @@ pub(crate) fn type_check<'mir, 'tcx>(
);
translate_outlives_facts(&mut cx);
let opaque_type_values = mem::take(&mut infcx.inner.borrow_mut().opaque_types);
let opaque_type_values =
infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
opaque_type_values
.into_iter()
.filter_map(|(opaque_type_key, mut decl)| {
decl.concrete_ty = infcx.resolve_vars_if_possible(decl.concrete_ty);
.map(|(opaque_type_key, decl)| {
cx.fully_perform_op(
Locations::All(body.span),
ConstraintCategory::OpaqueType,
CustomTypeOp::new(
|infcx| {
infcx.register_member_constraints(
param_env,
opaque_type_key,
decl.hidden_type.ty,
decl.hidden_type.span,
);
Ok(InferOk { value: (), obligations: vec![] })
},
|| "opaque_type_map".to_string(),
),
)
.unwrap();
let mut hidden_type = infcx.resolve_vars_if_possible(decl.hidden_type);
trace!(
"finalized opaque type {:?} to {:#?}",
opaque_type_key,
decl.concrete_ty.kind()
hidden_type.ty.kind()
);
if decl.concrete_ty.has_infer_types_or_consts() {
if hidden_type.has_infer_types_or_consts() {
infcx.tcx.sess.delay_span_bug(
body.span,
&format!("could not resolve {:#?}", decl.concrete_ty.kind()),
decl.hidden_type.span,
&format!("could not resolve {:#?}", hidden_type.ty.kind()),
);
decl.concrete_ty = infcx.tcx.ty_error();
hidden_type.ty = infcx.tcx.ty_error();
}
let concrete_is_opaque = if let ty::Opaque(def_id, _) = decl.concrete_ty.kind()
{
*def_id == opaque_type_key.def_id
} else {
false
};
if concrete_is_opaque {
// We're using an opaque `impl Trait` type without
// 'revealing' it. For example, code like this:
//
// type Foo = impl Debug;
// fn foo1() -> Foo { ... }
// fn foo2() -> Foo { foo1() }
//
// In `foo2`, we're not revealing the type of `Foo` - we're
// just treating it as the opaque type.
//
// When this occurs, we do *not* want to try to equate
// the concrete type with the underlying defining type
// of the opaque type - this will always fail, since
// the defining type of an opaque type is always
// some other type (e.g. not itself)
// Essentially, none of the normal obligations apply here -
// we're just passing around some unknown opaque type,
// without actually looking at the underlying type it
// gets 'revealed' into
debug!(
"eq_opaque_type_and_type: non-defining use of {:?}",
opaque_type_key.def_id,
);
None
} else {
Some((opaque_type_key, decl))
}
(opaque_type_key, (hidden_type, decl.origin))
})
.collect()
},
@ -283,7 +271,7 @@ fn type_check_internal<'a, 'tcx, R>(
borrowck_context,
);
let errors_reported = {
let mut verifier = TypeVerifier::new(&mut checker, body, promoted);
let mut verifier = TypeVerifier::new(&mut checker, promoted);
verifier.visit_body(&body);
verifier.errors_reported
};
@ -340,7 +328,6 @@ enum FieldAccessError {
/// is a problem.
struct TypeVerifier<'a, 'b, 'tcx> {
cx: &'a mut TypeChecker<'b, 'tcx>,
body: &'b Body<'tcx>,
promoted: &'b IndexVec<Promoted, Body<'tcx>>,
last_span: Span,
errors_reported: bool,
@ -476,7 +463,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
self.super_rvalue(rvalue, location);
let rval_ty = rvalue.ty(self.body, self.tcx());
let rval_ty = rvalue.ty(self.body(), self.tcx());
self.sanitize_type(rvalue, rval_ty);
}
@ -535,10 +522,13 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
fn new(
cx: &'a mut TypeChecker<'b, 'tcx>,
body: &'b Body<'tcx>,
promoted: &'b IndexVec<Promoted, Body<'tcx>>,
) -> Self {
TypeVerifier { body, promoted, cx, last_span: body.span, errors_reported: false }
TypeVerifier { promoted, last_span: cx.body.span, cx, errors_reported: false }
}
fn body(&self) -> &Body<'tcx> {
self.cx.body
}
fn tcx(&self) -> TyCtxt<'tcx> {
@ -563,7 +553,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
) -> PlaceTy<'tcx> {
debug!("sanitize_place: {:?}", place);
let mut place_ty = PlaceTy::from_ty(self.body.local_decls[place.local].ty);
let mut place_ty = PlaceTy::from_ty(self.body().local_decls[place.local].ty);
for elem in place.projection.iter() {
if place_ty.variant_index.is_none() {
@ -608,7 +598,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
// checker on the promoted MIR, then transfer the constraints back to
// the main MIR, changing the locations to the provided location.
let parent_body = mem::replace(&mut self.body, promoted_body);
let parent_body = mem::replace(&mut self.cx.body, promoted_body);
// Use new sets of constraints and closure bounds so that we can
// modify their locations.
@ -644,7 +634,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
self.cx.typeck_mir(promoted_body);
}
self.body = parent_body;
self.cx.body = parent_body;
// Merge the outlives constraints back in, at the given location.
swap_constraints(self);
@ -706,7 +696,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
}))
}
ProjectionElem::Index(i) => {
let index_ty = Place::from(i).ty(self.body, tcx).ty;
let index_ty = Place::from(i).ty(self.body(), tcx).ty;
if index_ty != tcx.types.usize {
PlaceTy::from_ty(span_mirbug_and_err!(self, i, "index by non-usize {:?}", i))
} else {
@ -915,7 +905,7 @@ struct BorrowCheckContext<'a, 'tcx> {
crate struct MirTypeckResults<'tcx> {
crate constraints: MirTypeckRegionConstraints<'tcx>,
crate universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
crate opaque_type_values: VecMap<OpaqueTypeKey<'tcx>, OpaqueTypeDecl<'tcx>>,
crate opaque_type_values: VecMap<OpaqueTypeKey<'tcx>, (OpaqueHiddenType<'tcx>, OpaqueTyOrigin)>,
}
/// A collection of region constraints that must be satisfied for the
@ -1065,17 +1055,19 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
checker
}
fn body(&self) -> &Body<'tcx> {
self.body
}
fn unsized_feature_enabled(&self) -> bool {
let features = self.tcx().features();
features.unsized_locals || features.unsized_fn_params
}
/// Equate the inferred type and the annotated type for user type annotations
#[instrument(skip(self), level = "debug")]
fn check_user_type_annotations(&mut self) {
debug!(
"check_user_type_annotations: user_type_annotations={:?}",
self.user_type_annotations
);
debug!(?self.user_type_annotations);
for user_annotation in self.user_type_annotations {
let CanonicalUserTypeAnnotation { span, ref user_ty, inferred_ty } = *user_annotation;
let inferred_ty = self.normalize(inferred_ty, Locations::All(span));
@ -1216,131 +1208,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
Ok(())
}
/// Equates a type `anon_ty` that may contain opaque types whose
/// values are to be inferred by the MIR.
///
/// The type `revealed_ty` contains the same type as `anon_ty`, but with the
/// hidden types for impl traits revealed.
///
/// # Example
///
/// Consider a piece of code like
///
/// ```rust
/// type Foo<U> = impl Debug;
///
/// fn foo<T: Debug>(t: T) -> Box<Foo<T>> {
/// Box::new((t, 22_u32))
/// }
/// ```
///
/// Here, the function signature would be something like
/// `fn(T) -> Box<impl Debug>`. The MIR return slot would have
/// the type with the opaque type revealed, so `Box<(T, u32)>`.
///
/// In terms of our function parameters:
///
/// * `anon_ty` would be `Box<Foo<T>>` where `Foo<T>` is an opaque type
/// scoped to this function (note that it is parameterized by the
/// generics of `foo`). Note that `anon_ty` is not just the opaque type,
/// but the entire return type (which may contain opaque types within it).
/// * `revealed_ty` would be `Box<(T, u32)>`
#[instrument(skip(self), level = "debug")]
fn eq_opaque_type_and_type(
&mut self,
revealed_ty: Ty<'tcx>,
anon_ty: Ty<'tcx>,
locations: Locations,
category: ConstraintCategory,
) -> Fallible<()> {
// Fast path for the common case.
if !anon_ty.has_opaque_types() {
if let Err(terr) = self.eq_types(anon_ty, revealed_ty, locations, category) {
span_mirbug!(
self,
locations,
"eq_opaque_type_and_type: `{:?}=={:?}` failed with `{:?}`",
revealed_ty,
anon_ty,
terr
);
}
return Ok(());
}
let param_env = self.param_env;
let body = self.body;
let mir_def_id = body.source.def_id().expect_local();
debug!(?mir_def_id);
self.fully_perform_op(
locations,
category,
CustomTypeOp::new(
|infcx| {
let mut obligations = ObligationAccumulator::default();
let dummy_body_id = hir::CRATE_HIR_ID;
// Replace the opaque types defined by this function with
// inference variables, creating a map. In our example above,
// this would transform the type `Box<Foo<T>>` (where `Foo` is an opaque type)
// to `Box<?T>`, returning an `opaque_type_map` mapping `{Foo<T> -> ?T}`.
// (Note that the key of the map is both the def-id of `Foo` along with
// any generic parameters.)
let output_ty = obligations.add(infcx.instantiate_opaque_types(
dummy_body_id,
param_env,
anon_ty,
locations.span(body),
));
debug!(?output_ty, ?revealed_ty);
// Make sure that the inferred types are well-formed. I'm
// not entirely sure this is needed (the HIR type check
// didn't do this) but it seems sensible to prevent opaque
// types hiding ill-formed types.
obligations.obligations.push(traits::Obligation::new(
ObligationCause::dummy(),
param_env,
ty::Binder::dummy(ty::PredicateKind::WellFormed(revealed_ty.into()))
.to_predicate(infcx.tcx),
));
obligations.add(
infcx
.at(&ObligationCause::dummy(), param_env)
.eq(output_ty, revealed_ty)?,
);
debug!("equated");
Ok(InferOk { value: (), obligations: obligations.into_vec() })
},
|| "input_output".to_string(),
),
)?;
// Finally, if we instantiated the anon types successfully, we
// have to solve any bounds (e.g., `-> impl Iterator` needs to
// prove that `T: Iterator` where `T` is the type we
// instantiated it with).
let opaque_type_map = self.infcx.inner.borrow().opaque_types.clone();
for (opaque_type_key, opaque_decl) in opaque_type_map {
self.fully_perform_op(
locations,
ConstraintCategory::OpaqueType,
CustomTypeOp::new(
|infcx| {
infcx.constrain_opaque_type(opaque_type_key, &opaque_decl);
Ok(InferOk { value: (), obligations: vec![] })
},
|| "opaque_type_map".to_string(),
),
)?;
}
Ok(())
}
fn tcx(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
@ -2772,19 +2639,31 @@ impl NormalizeLocation for Location {
}
}
#[derive(Debug, Default)]
struct ObligationAccumulator<'tcx> {
obligations: PredicateObligations<'tcx>,
/// Runs `infcx.instantiate_opaque_types`. Unlike other `TypeOp`s,
/// this is not canonicalized - it directly affects the main `InferCtxt`
/// that we use during MIR borrowchecking.
#[derive(Debug)]
pub(super) struct InstantiateOpaqueType<'tcx> {
pub base_universe: Option<ty::UniverseIndex>,
pub region_constraints: Option<RegionConstraintData<'tcx>>,
pub obligations: Vec<PredicateObligation<'tcx>>,
}
impl<'tcx> ObligationAccumulator<'tcx> {
fn add<T>(&mut self, value: InferOk<'tcx, T>) -> T {
let InferOk { value, obligations } = value;
self.obligations.extend(obligations);
value
}
impl<'tcx> TypeOp<'tcx> for InstantiateOpaqueType<'tcx> {
type Output = ();
/// We use this type itself to store the information used
/// when reporting errors. Since this is not a query, we don't
/// re-run anything during error reporting - we just use the information
/// we saved to help extract an error from the already-existing region
/// constraints in our `InferCtxt`
type ErrorInfo = InstantiateOpaqueType<'tcx>;
fn into_vec(self) -> PredicateObligations<'tcx> {
self.obligations
fn fully_perform(mut self, infcx: &InferCtxt<'_, 'tcx>) -> Fallible<TypeOpOutput<'tcx, Self>> {
let (mut output, region_constraints) = scrape_region_constraints(infcx, || {
Ok(InferOk { value: (), obligations: self.obligations.clone() })
})?;
self.region_constraints = Some(region_constraints);
output.error_info = Some(self);
Ok(output)
}
}

42
compiler/rustc_borrowck/src/type_check/relate_tys.rs
View file

@ -1,13 +1,16 @@
use rustc_infer::infer::nll_relate::{NormalizationStrategy, TypeRelating, TypeRelatingDelegate};
use rustc_infer::infer::NllRegionVariableOrigin;
use rustc_infer::traits::ObligationCause;
use rustc_middle::mir::ConstraintCategory;
use rustc_middle::ty::error::TypeError;
use rustc_middle::ty::relate::TypeRelation;
use rustc_middle::ty::{self, Const, Ty};
use rustc_span::Span;
use rustc_trait_selection::traits::query::Fallible;
use crate::constraints::OutlivesConstraint;
use crate::diagnostics::UniverseInfo;
use crate::type_check::{Locations, TypeChecker};
use crate::type_check::{InstantiateOpaqueType, Locations, TypeChecker};
impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
/// Adds sufficient constraints to ensure that `a R b` where `R` depends on `v`:
@ -63,6 +66,10 @@ impl<'me, 'bccx, 'tcx> NllTypeRelatingDelegate<'me, 'bccx, 'tcx> {
}
impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx> {
fn span(&self) -> Span {
self.locations.span(self.type_checker.body)
}
fn param_env(&self) -> ty::ParamEnv<'tcx> {
self.type_checker.param_env
}
@ -117,6 +124,9 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx>
// We don't have to worry about the equality of consts during borrow checking
// as consts always have a static lifetime.
// FIXME(oli-obk): is this really true? We can at least have HKL and with
// inline consts we may have further lifetimes that may be unsound to treat as
// 'static.
fn const_equate(&mut self, _a: Const<'tcx>, _b: Const<'tcx>) {}
fn normalization() -> NormalizationStrategy {
@ -126,4 +136,34 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx>
fn forbid_inference_vars() -> bool {
true
}
fn register_opaque_type(
&mut self,
a: Ty<'tcx>,
b: Ty<'tcx>,
a_is_expected: bool,
) -> Result<(), TypeError<'tcx>> {
let param_env = self.param_env();
let span = self.span();
let def_id = self.type_checker.body.source.def_id().expect_local();
let body_id = self.type_checker.tcx().hir().local_def_id_to_hir_id(def_id);
let cause = ObligationCause::misc(span, body_id);
self.type_checker
.fully_perform_op(
self.locations,
self.category,
InstantiateOpaqueType {
obligations: self
.type_checker
.infcx
.handle_opaque_type(a, b, a_is_expected, &cause, param_env)?
.obligations,
// These fields are filled in during exectuion of the operation
base_universe: None,
region_constraints: None,
},
)
.unwrap();
Ok(())
}
}

14
compiler/rustc_borrowck/src/universal_regions.rs
View file

@ -725,6 +725,7 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
self.tcx.fold_regions(value, &mut false, |_region, _depth| self.next_nll_region_var(origin))
}
#[instrument(level = "debug", skip(self, indices))]
fn replace_bound_regions_with_nll_infer_vars<T>(
&self,
origin: NllRegionVariableOrigin,
@ -735,22 +736,15 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
where
T: TypeFoldable<'tcx>,
{
debug!(
"replace_bound_regions_with_nll_infer_vars(value={:?}, all_outlive_scope={:?})",
value, all_outlive_scope,
);
let (value, _map) = self.tcx.replace_late_bound_regions(value, |br| {
debug!("replace_bound_regions_with_nll_infer_vars: br={:?}", br);
debug!(?br);
let liberated_region = self.tcx.mk_region(ty::ReFree(ty::FreeRegion {
scope: all_outlive_scope.to_def_id(),
bound_region: br.kind,
}));
let region_vid = self.next_nll_region_var(origin);
indices.insert_late_bound_region(liberated_region, region_vid.to_region_vid());
debug!(
"replace_bound_regions_with_nll_infer_vars: liberated_region={:?} => {:?}",
liberated_region, region_vid
);
debug!(?liberated_region, ?region_vid);
region_vid
});
value
@ -765,6 +759,7 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
/// entries for them and store them in the indices map. This code iterates over the complete
/// set of late-bound regions and checks for any that we have not yet seen, adding them to the
/// inputs vector.
#[instrument(skip(self, indices))]
fn replace_late_bound_regions_with_nll_infer_vars(
&self,
mir_def_id: LocalDefId,
@ -776,6 +771,7 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
debug!("replace_late_bound_regions_with_nll_infer_vars: r={:?}", r);
if !indices.indices.contains_key(&r) {
let region_vid = self.next_nll_region_var(FR);
debug!(?region_vid);
indices.insert_late_bound_region(r, region_vid.to_region_vid());
}
});