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Auto merge of #102700 - oli-obk:0xDEAD_TAIT, r=compiler-errors

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Check hidden types in dead code

fixes #99490

r? `@compiler-errors`

best reviewed commit by commit
This commit is contained in:
bors 2022-10-13 22:39:05 +00:00
commit 60bd3f9677
14 changed files with 387 additions and 319 deletions
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255
compiler/rustc_borrowck/src/region_infer/opaque_types.rs
View file

@ -2,12 +2,10 @@ use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::vec_map::VecMap; use rustc_data_structures::vec_map::VecMap;
use rustc_hir::def_id::LocalDefId; use rustc_hir::def_id::LocalDefId;
use rustc_hir::OpaqueTyOrigin; use rustc_hir::OpaqueTyOrigin;
use rustc_infer::infer::error_reporting::unexpected_hidden_region_diagnostic;
use rustc_infer::infer::TyCtxtInferExt as _; use rustc_infer::infer::TyCtxtInferExt as _;
use rustc_infer::infer::{DefiningAnchor, InferCtxt}; use rustc_infer::infer::{DefiningAnchor, InferCtxt};
use rustc_infer::traits::{Obligation, ObligationCause, TraitEngine}; use rustc_infer::traits::{Obligation, ObligationCause, TraitEngine};
use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable}; use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts};
use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts};
use rustc_middle::ty::visit::TypeVisitable; use rustc_middle::ty::visit::TypeVisitable;
use rustc_middle::ty::{ use rustc_middle::ty::{
self, OpaqueHiddenType, OpaqueTypeKey, ToPredicate, Ty, TyCtxt, TypeFoldable, self, OpaqueHiddenType, OpaqueTypeKey, ToPredicate, Ty, TyCtxt, TypeFoldable,
@ -16,8 +14,6 @@ use rustc_span::Span;
use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _; use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
use rustc_trait_selection::traits::TraitEngineExt as _; use rustc_trait_selection::traits::TraitEngineExt as _;
use crate::session_diagnostics::ConstNotUsedTraitAlias;
use super::RegionInferenceContext; use super::RegionInferenceContext;
impl<'tcx> RegionInferenceContext<'tcx> { impl<'tcx> RegionInferenceContext<'tcx> {
@ -229,31 +225,9 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
return self.tcx.ty_error(); return self.tcx.ty_error();
} }
let OpaqueTypeKey { def_id, substs } = opaque_type_key; let definition_ty = instantiated_ty
.remap_generic_params_to_declaration_params(opaque_type_key, self.tcx, false)
// Use substs to build up a reverse map from regions to their .ty;
// identity mappings. This is necessary because of `impl
// Trait` lifetimes are computed by replacing existing
// lifetimes with 'static and remapping only those used in the
// `impl Trait` return type, resulting in the parameters
// shifting.
let id_substs = InternalSubsts::identity_for_item(self.tcx, def_id.to_def_id());
debug!(?id_substs);
let map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>> =
substs.iter().enumerate().map(|(index, subst)| (subst, id_substs[index])).collect();
debug!("map = {:#?}", map);
// Convert the type from the function into a type valid outside
// the function, by replacing invalid regions with 'static,
// after producing an error for each of them.
let definition_ty = instantiated_ty.ty.fold_with(&mut ReverseMapper::new(
self.tcx,
opaque_type_key,
map,
instantiated_ty.ty,
instantiated_ty.span,
));
debug!(?definition_ty);
if !check_opaque_type_parameter_valid( if !check_opaque_type_parameter_valid(
self.tcx, self.tcx,
@ -269,6 +243,7 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
let OpaqueTyOrigin::TyAlias = origin else { let OpaqueTyOrigin::TyAlias = origin else {
return definition_ty; return definition_ty;
}; };
let def_id = opaque_type_key.def_id;
// This logic duplicates most of `check_opaque_meets_bounds`. // This logic duplicates most of `check_opaque_meets_bounds`.
// FIXME(oli-obk): Also do region checks here and then consider removing `check_opaque_meets_bounds` entirely. // FIXME(oli-obk): Also do region checks here and then consider removing `check_opaque_meets_bounds` entirely.
let param_env = self.tcx.param_env(def_id); let param_env = self.tcx.param_env(def_id);
@ -284,6 +259,8 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
.to_predicate(infcx.tcx); .to_predicate(infcx.tcx);
let mut fulfillment_cx = <dyn TraitEngine<'tcx>>::new(infcx.tcx); let mut fulfillment_cx = <dyn TraitEngine<'tcx>>::new(infcx.tcx);
let id_substs = InternalSubsts::identity_for_item(self.tcx, def_id.to_def_id());
// Require that the hidden type actually fulfills all the bounds of the opaque type, even without // Require that the hidden type actually fulfills all the bounds of the opaque type, even without
// the bounds that the function supplies. // the bounds that the function supplies.
match infcx.register_hidden_type( match infcx.register_hidden_type(
@ -424,221 +401,3 @@ fn check_opaque_type_parameter_valid(
} }
true true
} }
struct ReverseMapper<'tcx> {
tcx: TyCtxt<'tcx>,
key: ty::OpaqueTypeKey<'tcx>,
map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>>,
do_not_error: bool,
/// initially `Some`, set to `None` once error has been reported
hidden_ty: Option<Ty<'tcx>>,
/// Span of function being checked.
span: Span,
}
impl<'tcx> ReverseMapper<'tcx> {
fn new(
tcx: TyCtxt<'tcx>,
key: ty::OpaqueTypeKey<'tcx>,
map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>>,
hidden_ty: Ty<'tcx>,
span: Span,
) -> Self {
Self { tcx, key, map, do_not_error: false, hidden_ty: Some(hidden_ty), span }
}
fn fold_kind_no_missing_regions_error(&mut self, kind: GenericArg<'tcx>) -> GenericArg<'tcx> {
assert!(!self.do_not_error);
self.do_not_error = true;
let kind = kind.fold_with(self);
self.do_not_error = false;
kind
}
fn fold_kind_normally(&mut self, kind: GenericArg<'tcx>) -> GenericArg<'tcx> {
assert!(!self.do_not_error);
kind.fold_with(self)
}
}
impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.tcx
}
#[instrument(skip(self), level = "debug")]
fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
match *r {
// Ignore bound regions and `'static` regions that appear in the
// type, we only need to remap regions that reference lifetimes
// from the function declaration.
// This would ignore `'r` in a type like `for<'r> fn(&'r u32)`.
ty::ReLateBound(..) | ty::ReStatic => return r,
// If regions have been erased (by writeback), don't try to unerase
// them.
ty::ReErased => return r,
// The regions that we expect from borrow checking.
ty::ReEarlyBound(_) | ty::ReFree(_) => {}
ty::RePlaceholder(_) | ty::ReVar(_) => {
// All of the regions in the type should either have been
// erased by writeback, or mapped back to named regions by
// borrow checking.
bug!("unexpected region kind in opaque type: {:?}", r);
}
}
let generics = self.tcx().generics_of(self.key.def_id);
match self.map.get(&r.into()).map(|k| k.unpack()) {
Some(GenericArgKind::Lifetime(r1)) => r1,
Some(u) => panic!("region mapped to unexpected kind: {:?}", u),
None if self.do_not_error => self.tcx.lifetimes.re_static,
None if generics.parent.is_some() => {
if let Some(hidden_ty) = self.hidden_ty.take() {
unexpected_hidden_region_diagnostic(
self.tcx,
self.tcx.def_span(self.key.def_id),
hidden_ty,
r,
self.key,
)
.emit();
}
self.tcx.lifetimes.re_static
}
None => {
self.tcx
.sess
.struct_span_err(self.span, "non-defining opaque type use in defining scope")
.span_label(
self.span,
format!(
"lifetime `{}` is part of concrete type but not used in \
parameter list of the `impl Trait` type alias",
r
),
)
.emit();
self.tcx().lifetimes.re_static
}
}
}
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
match *ty.kind() {
ty::Closure(def_id, substs) => {
// I am a horrible monster and I pray for death. When
// we encounter a closure here, it is always a closure
// from within the function that we are currently
// type-checking -- one that is now being encapsulated
// in an opaque type. Ideally, we would
// go through the types/lifetimes that it references
// and treat them just like we would any other type,
// which means we would error out if we find any
// reference to a type/region that is not in the
// "reverse map".
//
// **However,** in the case of closures, there is a
// somewhat subtle (read: hacky) consideration. The
// problem is that our closure types currently include
// all the lifetime parameters declared on the
// enclosing function, even if they are unused by the
// closure itself. We can't readily filter them out,
// so here we replace those values with `'empty`. This
// can't really make a difference to the rest of the
// compiler; those regions are ignored for the
// outlives relation, and hence don't affect trait
// selection or auto traits, and they are erased
// during codegen.
let generics = self.tcx.generics_of(def_id);
let substs = self.tcx.mk_substs(substs.iter().enumerate().map(|(index, kind)| {
if index < generics.parent_count {
// Accommodate missing regions in the parent kinds...
self.fold_kind_no_missing_regions_error(kind)
} else {
// ...but not elsewhere.
self.fold_kind_normally(kind)
}
}));
self.tcx.mk_closure(def_id, substs)
}
ty::Generator(def_id, substs, movability) => {
let generics = self.tcx.generics_of(def_id);
let substs = self.tcx.mk_substs(substs.iter().enumerate().map(|(index, kind)| {
if index < generics.parent_count {
// Accommodate missing regions in the parent kinds...
self.fold_kind_no_missing_regions_error(kind)
} else {
// ...but not elsewhere.
self.fold_kind_normally(kind)
}
}));
self.tcx.mk_generator(def_id, substs, movability)
}
ty::Param(param) => {
// Look it up in the substitution list.
match self.map.get(&ty.into()).map(|k| k.unpack()) {
// Found it in the substitution list; replace with the parameter from the
// opaque type.
Some(GenericArgKind::Type(t1)) => t1,
Some(u) => panic!("type mapped to unexpected kind: {:?}", u),
None => {
debug!(?param, ?self.map);
self.tcx
.sess
.struct_span_err(
self.span,
&format!(
"type parameter `{}` is part of concrete type but not \
used in parameter list for the `impl Trait` type alias",
ty
),
)
.emit();
self.tcx().ty_error()
}
}
}
_ => ty.super_fold_with(self),
}
}
fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
trace!("checking const {:?}", ct);
// Find a const parameter
match ct.kind() {
ty::ConstKind::Param(..) => {
// Look it up in the substitution list.
match self.map.get(&ct.into()).map(|k| k.unpack()) {
// Found it in the substitution list, replace with the parameter from the
// opaque type.
Some(GenericArgKind::Const(c1)) => c1,
Some(u) => panic!("const mapped to unexpected kind: {:?}", u),
None => {
self.tcx.sess.emit_err(ConstNotUsedTraitAlias {
ct: ct.to_string(),
span: self.span,
});
self.tcx().const_error(ct.ty())
}
}
}
_ => ct,
}
}
}

9
compiler/rustc_borrowck/src/session_diagnostics.rs
View file

@ -52,15 +52,6 @@ pub(crate) struct VarNeedNotMut {
#[suggestion_short(applicability = "machine-applicable", code = "")] #[suggestion_short(applicability = "machine-applicable", code = "")]
pub span: Span, pub span: Span,
} }
#[derive(Diagnostic)]
#[diag(borrowck::const_not_used_in_type_alias)]
pub(crate) struct ConstNotUsedTraitAlias {
pub ct: String,
#[primary_span]
pub span: Span,
}
#[derive(Diagnostic)] #[derive(Diagnostic)]
#[diag(borrowck::var_cannot_escape_closure)] #[diag(borrowck::var_cannot_escape_closure)]
#[note] #[note]

51
compiler/rustc_hir_analysis/src/check/writeback.rs
View file

@ -536,33 +536,36 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
let opaque_types = let opaque_types =
self.fcx.infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types(); self.fcx.infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
for (opaque_type_key, decl) in opaque_types { for (opaque_type_key, decl) in opaque_types {
let hidden_type = match decl.origin { let hidden_type = self.resolve(decl.hidden_type, &decl.hidden_type.span);
hir::OpaqueTyOrigin::FnReturn(_) | hir::OpaqueTyOrigin::AsyncFn(_) => { let opaque_type_key = self.resolve(opaque_type_key, &decl.hidden_type.span);
let ty = self.resolve(decl.hidden_type.ty, &decl.hidden_type.span);
struct RecursionChecker { struct RecursionChecker {
def_id: LocalDefId, def_id: LocalDefId,
} }
impl<'tcx> ty::TypeVisitor<'tcx> for RecursionChecker { impl<'tcx> ty::TypeVisitor<'tcx> for RecursionChecker {
type BreakTy = (); type BreakTy = ();
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
if let ty::Opaque(def_id, _) = *t.kind() { if let ty::Opaque(def_id, _) = *t.kind() {
if def_id == self.def_id.to_def_id() { if def_id == self.def_id.to_def_id() {
return ControlFlow::Break(()); return ControlFlow::Break(());
}
}
t.super_visit_with(self)
} }
} }
if ty t.super_visit_with(self)
.visit_with(&mut RecursionChecker { def_id: opaque_type_key.def_id })
.is_break()
{
return;
}
Some(ty)
} }
hir::OpaqueTyOrigin::TyAlias => None, }
}; if hidden_type
.visit_with(&mut RecursionChecker { def_id: opaque_type_key.def_id })
.is_break()
{
continue;
}
let hidden_type = hidden_type.remap_generic_params_to_declaration_params(
opaque_type_key,
self.fcx.infcx.tcx,
true,
);
self.typeck_results.concrete_opaque_types.insert(opaque_type_key.def_id, hidden_type); self.typeck_results.concrete_opaque_types.insert(opaque_type_key.def_id, hidden_type);
} }
} }

67
compiler/rustc_hir_analysis/src/collect/type_of.rs
View file

@ -565,6 +565,11 @@ fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: LocalDefId) -> T
/// checked against it (we also carry the span of that first /// checked against it (we also carry the span of that first
/// type). /// type).
found: Option<ty::OpaqueHiddenType<'tcx>>, found: Option<ty::OpaqueHiddenType<'tcx>>,
/// In the presence of dead code, typeck may figure out a hidden type
/// while borrowck will now. We collect these cases here and check at
/// the end that we actually found a type that matches (modulo regions).
typeck_types: Vec<ty::OpaqueHiddenType<'tcx>>,
} }
impl ConstraintLocator<'_> { impl ConstraintLocator<'_> {
@ -591,18 +596,23 @@ fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: LocalDefId) -> T
self.found = Some(ty::OpaqueHiddenType { span: DUMMY_SP, ty: self.tcx.ty_error() }); self.found = Some(ty::OpaqueHiddenType { span: DUMMY_SP, ty: self.tcx.ty_error() });
return; return;
} }
if !tables.concrete_opaque_types.contains_key(&self.def_id) { let Some(&typeck_hidden_ty) = tables.concrete_opaque_types.get(&self.def_id) else {
debug!("no constraints in typeck results"); debug!("no constraints in typeck results");
return; return;
};
if self.typeck_types.iter().all(|prev| prev.ty != typeck_hidden_ty.ty) {
self.typeck_types.push(typeck_hidden_ty);
} }
// Use borrowck to get the type with unerased regions. // Use borrowck to get the type with unerased regions.
let concrete_opaque_types = &self.tcx.mir_borrowck(item_def_id).concrete_opaque_types; let concrete_opaque_types = &self.tcx.mir_borrowck(item_def_id).concrete_opaque_types;
debug!(?concrete_opaque_types); debug!(?concrete_opaque_types);
if let Some(&concrete_type) = concrete_opaque_types.get(&self.def_id) { if let Some(&concrete_type) = concrete_opaque_types.get(&self.def_id) {
debug!(?concrete_type, "found constraint"); debug!(?concrete_type, "found constraint");
if let Some(prev) = self.found { if let Some(prev) = &mut self.found {
if concrete_type.ty != prev.ty && !(concrete_type, prev).references_error() { if concrete_type.ty != prev.ty && !(concrete_type, prev.ty).references_error() {
prev.report_mismatch(&concrete_type, self.tcx); prev.report_mismatch(&concrete_type, self.tcx);
prev.ty = self.tcx.ty_error();
} }
} else { } else {
self.found = Some(concrete_type); self.found = Some(concrete_type);
@ -649,7 +659,7 @@ fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: LocalDefId) -> T
let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
let scope = tcx.hir().get_defining_scope(hir_id); let scope = tcx.hir().get_defining_scope(hir_id);
let mut locator = ConstraintLocator { def_id: def_id, tcx, found: None }; let mut locator = ConstraintLocator { def_id: def_id, tcx, found: None, typeck_types: vec![] };
debug!(?scope); debug!(?scope);
@ -679,16 +689,26 @@ fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: LocalDefId) -> T
} }
} }
match locator.found { let Some(hidden) = locator.found else {
Some(hidden) => hidden.ty, tcx.sess.emit_err(UnconstrainedOpaqueType {
None => { span: tcx.def_span(def_id),
tcx.sess.emit_err(UnconstrainedOpaqueType { name: tcx.item_name(tcx.local_parent(def_id).to_def_id()),
span: tcx.def_span(def_id), });
name: tcx.item_name(tcx.local_parent(def_id).to_def_id()), return tcx.ty_error();
}); };
tcx.ty_error()
// Only check against typeck if we didn't already error
if !hidden.ty.references_error() {
for concrete_type in locator.typeck_types {
if tcx.erase_regions(concrete_type.ty) != tcx.erase_regions(hidden.ty)
&& !(concrete_type, hidden).references_error()
{
hidden.report_mismatch(&concrete_type, tcx);
}
} }
} }
hidden.ty
} }
fn find_opaque_ty_constraints_for_rpit( fn find_opaque_ty_constraints_for_rpit(
@ -789,20 +809,15 @@ fn find_opaque_ty_constraints_for_rpit(
// the `concrete_opaque_types` table. // the `concrete_opaque_types` table.
tcx.ty_error() tcx.ty_error()
} else { } else {
table table.concrete_opaque_types.get(&def_id).map(|ty| ty.ty).unwrap_or_else(|| {
.concrete_opaque_types // We failed to resolve the opaque type or it
.get(&def_id) // resolves to itself. We interpret this as the
.copied() // no values of the hidden type ever being constructed,
.unwrap_or_else(|| { // so we can just make the hidden type be `!`.
// We failed to resolve the opaque type or it // For backwards compatibility reasons, we fall back to
// resolves to itself. We interpret this as the // `()` until we the diverging default is changed.
// no values of the hidden type ever being constructed, tcx.mk_diverging_default()
// so we can just make the hidden type be `!`. })
// For backwards compatibility reasons, we fall back to
// `()` until we the diverging default is changed.
Some(tcx.mk_diverging_default())
})
.expect("RPIT always have a hidden type from typeck")
} }
}) })
} }

8
compiler/rustc_middle/src/ty/context.rs
View file

@ -539,12 +539,10 @@ pub struct TypeckResults<'tcx> {
pub tainted_by_errors: Option<ErrorGuaranteed>, pub tainted_by_errors: Option<ErrorGuaranteed>,
/// All the opaque types that have hidden types set /// All the opaque types that have hidden types set
/// by this function. For return-position-impl-trait we also store the /// by this function. We also store the
/// type here, so that mir-borrowck can figure out hidden types, /// type here, so that mir-borrowck can use it as a hint for figuring out hidden types,
/// even if they are only set in dead code (which doesn't show up in MIR). /// even if they are only set in dead code (which doesn't show up in MIR).
/// For type-alias-impl-trait, this map is only used to prevent query cycles, pub concrete_opaque_types: VecMap<LocalDefId, ty::OpaqueHiddenType<'tcx>>,
/// so the hidden types are all `None`.
pub concrete_opaque_types: VecMap<LocalDefId, Option<Ty<'tcx>>>,
/// Tracks the minimum captures required for a closure; /// Tracks the minimum captures required for a closure;
/// see `MinCaptureInformationMap` for more details. /// see `MinCaptureInformationMap` for more details.

8
compiler/rustc_middle/src/ty/diagnostics.rs
View file

@ -511,3 +511,11 @@ impl<'tcx> TypeVisitor<'tcx> for IsSuggestableVisitor<'tcx> {
c.super_visit_with(self) c.super_visit_with(self)
} }
} }
#[derive(Diagnostic)]
#[diag(borrowck::const_not_used_in_type_alias)]
pub(super) struct ConstNotUsedTraitAlias {
pub ct: String,
#[primary_span]
pub span: Span,
}

29
compiler/rustc_middle/src/ty/mod.rs
View file

@ -131,6 +131,7 @@ mod generics;
mod impls_ty; mod impls_ty;
mod instance; mod instance;
mod list; mod list;
mod opaque_types;
mod parameterized; mod parameterized;
mod rvalue_scopes; mod rvalue_scopes;
mod structural_impls; mod structural_impls;
@ -1300,6 +1301,34 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
sub: sub_diag, sub: sub_diag,
}); });
} }
#[instrument(level = "debug", skip(tcx), ret)]
pub fn remap_generic_params_to_declaration_params(
self,
opaque_type_key: OpaqueTypeKey<'tcx>,
tcx: TyCtxt<'tcx>,
// typeck errors have subpar spans for opaque types, so delay error reporting until borrowck.
ignore_errors: bool,
) -> Self {
let OpaqueTypeKey { def_id, substs } = opaque_type_key;
// Use substs to build up a reverse map from regions to their
// identity mappings. This is necessary because of `impl
// Trait` lifetimes are computed by replacing existing
// lifetimes with 'static and remapping only those used in the
// `impl Trait` return type, resulting in the parameters
// shifting.
let id_substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
debug!(?id_substs);
let map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>> =
substs.iter().enumerate().map(|(index, subst)| (subst, id_substs[index])).collect();
debug!("map = {:#?}", map);
// Convert the type from the function into a type valid outside
// the function, by replacing invalid regions with 'static,
// after producing an error for each of them.
self.fold_with(&mut opaque_types::ReverseMapper::new(tcx, map, self.span, ignore_errors))
}
} }
/// The "placeholder index" fully defines a placeholder region, type, or const. Placeholders are /// The "placeholder index" fully defines a placeholder region, type, or const. Placeholders are

218
compiler/rustc_middle/src/ty/opaque_types.rs Normal file
View file

@ -0,0 +1,218 @@
use rustc_data_structures::fx::FxHashMap;
use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
use rustc_middle::ty::subst::{GenericArg, GenericArgKind};
use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
use rustc_span::Span;
/// Converts generic params of a TypeFoldable from one
/// item's generics to another. Usually from a function's generics
/// list to the opaque type's own generics.
pub(super) struct ReverseMapper<'tcx> {
tcx: TyCtxt<'tcx>,
map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>>,
/// see call sites to fold_kind_no_missing_regions_error
/// for an explanation of this field.
do_not_error: bool,
/// We do not want to emit any errors in typeck because
/// the spans in typeck are subpar at the moment.
/// Borrowck will do the same work again (this time with
/// lifetime information) and thus report better errors.
ignore_errors: bool,
/// Span of function being checked.
span: Span,
}
impl<'tcx> ReverseMapper<'tcx> {
pub(super) fn new(
tcx: TyCtxt<'tcx>,
map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>>,
span: Span,
ignore_errors: bool,
) -> Self {
Self { tcx, map, do_not_error: false, ignore_errors, span }
}
fn fold_kind_no_missing_regions_error(&mut self, kind: GenericArg<'tcx>) -> GenericArg<'tcx> {
assert!(!self.do_not_error);
self.do_not_error = true;
let kind = kind.fold_with(self);
self.do_not_error = false;
kind
}
fn fold_kind_normally(&mut self, kind: GenericArg<'tcx>) -> GenericArg<'tcx> {
assert!(!self.do_not_error);
kind.fold_with(self)
}
}
impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.tcx
}
#[instrument(skip(self), level = "debug")]
fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
match *r {
// Ignore bound regions and `'static` regions that appear in the
// type, we only need to remap regions that reference lifetimes
// from the function declaration.
// This would ignore `'r` in a type like `for<'r> fn(&'r u32)`.
ty::ReLateBound(..) | ty::ReStatic => return r,
// If regions have been erased (by writeback), don't try to unerase
// them.
ty::ReErased => return r,
// The regions that we expect from borrow checking.
ty::ReEarlyBound(_) | ty::ReFree(_) => {}
ty::RePlaceholder(_) | ty::ReVar(_) => {
// All of the regions in the type should either have been
// erased by writeback, or mapped back to named regions by
// borrow checking.
bug!("unexpected region kind in opaque type: {:?}", r);
}
}
match self.map.get(&r.into()).map(|k| k.unpack()) {
Some(GenericArgKind::Lifetime(r1)) => r1,
Some(u) => panic!("region mapped to unexpected kind: {:?}", u),
None if self.do_not_error => self.tcx.lifetimes.re_static,
None => {
self.tcx
.sess
.struct_span_err(self.span, "non-defining opaque type use in defining scope")
.span_label(
self.span,
format!(
"lifetime `{}` is part of concrete type but not used in \
parameter list of the `impl Trait` type alias",
r
),
)
.emit();
self.tcx().lifetimes.re_static
}
}
}
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
match *ty.kind() {
ty::Closure(def_id, substs) => {
// I am a horrible monster and I pray for death. When
// we encounter a closure here, it is always a closure
// from within the function that we are currently
// type-checking -- one that is now being encapsulated
// in an opaque type. Ideally, we would
// go through the types/lifetimes that it references
// and treat them just like we would any other type,
// which means we would error out if we find any
// reference to a type/region that is not in the
// "reverse map".
//
// **However,** in the case of closures, there is a
// somewhat subtle (read: hacky) consideration. The
// problem is that our closure types currently include
// all the lifetime parameters declared on the
// enclosing function, even if they are unused by the
// closure itself. We can't readily filter them out,
// so here we replace those values with `'empty`. This
// can't really make a difference to the rest of the
// compiler; those regions are ignored for the
// outlives relation, and hence don't affect trait
// selection or auto traits, and they are erased
// during codegen.
let generics = self.tcx.generics_of(def_id);
let substs = self.tcx.mk_substs(substs.iter().enumerate().map(|(index, kind)| {
if index < generics.parent_count {
// Accommodate missing regions in the parent kinds...
self.fold_kind_no_missing_regions_error(kind)
} else {
// ...but not elsewhere.
self.fold_kind_normally(kind)
}
}));
self.tcx.mk_closure(def_id, substs)
}
ty::Generator(def_id, substs, movability) => {
let generics = self.tcx.generics_of(def_id);
let substs = self.tcx.mk_substs(substs.iter().enumerate().map(|(index, kind)| {
if index < generics.parent_count {
// Accommodate missing regions in the parent kinds...
self.fold_kind_no_missing_regions_error(kind)
} else {
// ...but not elsewhere.
self.fold_kind_normally(kind)
}
}));
self.tcx.mk_generator(def_id, substs, movability)
}
ty::Param(param) => {
// Look it up in the substitution list.
match self.map.get(&ty.into()).map(|k| k.unpack()) {
// Found it in the substitution list; replace with the parameter from the
// opaque type.
Some(GenericArgKind::Type(t1)) => t1,
Some(u) => panic!("type mapped to unexpected kind: {:?}", u),
None => {
debug!(?param, ?self.map);
if !self.ignore_errors {
self.tcx
.sess
.struct_span_err(
self.span,
&format!(
"type parameter `{}` is part of concrete type but not \
used in parameter list for the `impl Trait` type alias",
ty
),
)
.emit();
}
self.tcx().ty_error()
}
}
}
_ => ty.super_fold_with(self),
}
}
fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
trace!("checking const {:?}", ct);
// Find a const parameter
match ct.kind() {
ty::ConstKind::Param(..) => {
// Look it up in the substitution list.
match self.map.get(&ct.into()).map(|k| k.unpack()) {
// Found it in the substitution list, replace with the parameter from the
// opaque type.
Some(GenericArgKind::Const(c1)) => c1,
Some(u) => panic!("const mapped to unexpected kind: {:?}", u),
None => {
if !self.ignore_errors {
self.tcx.sess.emit_err(ty::ConstNotUsedTraitAlias {
ct: ct.to_string(),
span: self.span,
});
}
self.tcx().const_error(ct.ty())
}
}
}
_ => ct,
}
}
}

2
src/test/incremental/hashes/function_interfaces.rs
View file

@ -323,7 +323,7 @@ pub fn change_return_impl_trait() -> impl Clone {
#[cfg(not(any(cfail1,cfail4)))] #[cfg(not(any(cfail1,cfail4)))]
#[rustc_clean(cfg = "cfail2")] #[rustc_clean(cfg = "cfail2")]
#[rustc_clean(cfg = "cfail3")] #[rustc_clean(cfg = "cfail3")]
#[rustc_clean(cfg = "cfail5")] #[rustc_clean(cfg = "cfail5", except = "typeck")]
#[rustc_clean(cfg = "cfail6")] #[rustc_clean(cfg = "cfail6")]
pub fn change_return_impl_trait() -> impl Copy { pub fn change_return_impl_trait() -> impl Copy {
0u32 0u32

15
src/test/ui/impl-trait/issues/issue-86800.stderr
View file

@ -1,3 +1,11 @@
error: unconstrained opaque type
--> $DIR/issue-86800.rs:33:34
|
LL | type TransactionFuture<'__, O> = impl '__ + Future<Output = TransactionResult<O>>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
=
stack backtrace: stack backtrace:
@ -12,8 +20,7 @@ error: internal compiler error: unexpected panic
query stack during panic: query stack during panic:
#0 [mir_borrowck] borrow-checking `execute_transaction_fut` #0 [type_of] computing type of `TransactionFuture::{opaque#0}`
#1 [type_of] computing type of `TransactionFuture::{opaque#0}` #1 [check_mod_item_types] checking item types in top-level module
#2 [check_mod_item_types] checking item types in top-level module #2 [analysis] running analysis passes on this crate
#3 [analysis] running analysis passes on this crate
end of query stack end of query stack

4
src/test/ui/type-alias-impl-trait/different_defining_uses_never_type.rs
View file

@ -1,5 +1,5 @@
#![feature(type_alias_impl_trait)] #![feature(type_alias_impl_trait)]
// check-pass
fn main() {} fn main() {}
// two definitions with different types // two definitions with different types
@ -9,7 +9,7 @@ fn foo() -> Foo {
"" ""
} }
fn bar() -> Foo { fn bar() -> Foo { //~ ERROR: concrete type differs from previous defining opaque type use
panic!() panic!()
} }

14
src/test/ui/type-alias-impl-trait/different_defining_uses_never_type.stderr Normal file
View file

@ -0,0 +1,14 @@
error: concrete type differs from previous defining opaque type use
--> $DIR/different_defining_uses_never_type.rs:12:13
|
LL | fn bar() -> Foo {
| ^^^ expected `&'static str`, got `()`
|
note: previous use here
--> $DIR/different_defining_uses_never_type.rs:9:5
|
LL | ""
| ^^
error: aborting due to previous error

12
src/test/ui/type-alias-impl-trait/different_defining_uses_never_type3.rs Normal file
View file

@ -0,0 +1,12 @@
#![feature(type_alias_impl_trait)]
type Tait = impl Sized;
struct One;
fn one() -> Tait { One }
struct Two<T>(T);
fn two() -> Tait { Two::<()>(todo!()) }
//~^ ERROR concrete type differs from previous defining opaque type use
fn main() {}

14
src/test/ui/type-alias-impl-trait/different_defining_uses_never_type3.stderr Normal file
View file

@ -0,0 +1,14 @@
error: concrete type differs from previous defining opaque type use
--> $DIR/different_defining_uses_never_type3.rs:9:13
|
LL | fn two() -> Tait { Two::<()>(todo!()) }
| ^^^^ expected `One`, got `Two<()>`
|
note: previous use here
--> $DIR/different_defining_uses_never_type3.rs:6:20
|
LL | fn one() -> Tait { One }
| ^^^
error: aborting due to previous error