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typeck/type_of: let wfcheck handle generics in opaque types' substs. #70272

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merged 6 commits into from
Apr 4, 2020
Merged

typeck/type_of: let wfcheck handle generics in opaque types' substs. #70272

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6465113
typeck/type_of: simplify checking of opaque types with multipler defi…
eddyb Mar 22, 2020
a98b534
typeck/type_of: don't ignore incorrect defining uses of opaque types.
eddyb Mar 22, 2020
8e9a5d9
typeck/type_of: let wfcheck handle concrete types in opaque types' su…
eddyb Mar 22, 2020
8807b00
typeck/type_of: let wfcheck handle duplicate generics in opaque types…
eddyb Mar 22, 2020
ea7999b
tests: add tests for lifetime and const params of opaque types.
eddyb Mar 22, 2020
8ad149a
typeck/type_of: only early-bound and (free) late-bound lifetimes are …
eddyb Mar 22, 2020
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48 changes: 21 additions & 27 deletions src/librustc_middle/ty/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1077,48 +1077,42 @@ impl<'tcx> Generics {
false
}

pub fn param_at(&'tcx self, param_index: usize, tcx: TyCtxt<'tcx>) -> &'tcx GenericParamDef {
if let Some(index) = param_index.checked_sub(self.parent_count) {
&self.params[index]
} else {
tcx.generics_of(self.parent.expect("parent_count > 0 but no parent?"))
.param_at(param_index, tcx)
}
}

pub fn region_param(
&'tcx self,
param: &EarlyBoundRegion,
tcx: TyCtxt<'tcx>,
) -> &'tcx GenericParamDef {
if let Some(index) = param.index.checked_sub(self.parent_count as u32) {
let param = &self.params[index as usize];
match param.kind {
GenericParamDefKind::Lifetime => param,
_ => bug!("expected lifetime parameter, but found another generic parameter"),
}
} else {
tcx.generics_of(self.parent.expect("parent_count > 0 but no parent?"))
.region_param(param, tcx)
let param = self.param_at(param.index as usize, tcx);
match param.kind {
GenericParamDefKind::Lifetime => param,
_ => bug!("expected lifetime parameter, but found another generic parameter"),
}
}

/// Returns the `GenericParamDef` associated with this `ParamTy`.
pub fn type_param(&'tcx self, param: &ParamTy, tcx: TyCtxt<'tcx>) -> &'tcx GenericParamDef {
if let Some(index) = param.index.checked_sub(self.parent_count as u32) {
let param = &self.params[index as usize];
match param.kind {
GenericParamDefKind::Type { .. } => param,
_ => bug!("expected type parameter, but found another generic parameter"),
}
} else {
tcx.generics_of(self.parent.expect("parent_count > 0 but no parent?"))
.type_param(param, tcx)
let param = self.param_at(param.index as usize, tcx);
match param.kind {
GenericParamDefKind::Type { .. } => param,
_ => bug!("expected type parameter, but found another generic parameter"),
}
}

/// Returns the `ConstParameterDef` associated with this `ParamConst`.
pub fn const_param(&'tcx self, param: &ParamConst, tcx: TyCtxt<'tcx>) -> &GenericParamDef {
if let Some(index) = param.index.checked_sub(self.parent_count as u32) {
let param = &self.params[index as usize];
match param.kind {
GenericParamDefKind::Const => param,
_ => bug!("expected const parameter, but found another generic parameter"),
}
} else {
tcx.generics_of(self.parent.expect("parent_count>0 but no parent?"))
.const_param(param, tcx)
let param = self.param_at(param.index as usize, tcx);
match param.kind {
GenericParamDefKind::Const => param,
_ => bug!("expected const parameter, but found another generic parameter"),
}
}
}
Expand Down
108 changes: 49 additions & 59 deletions src/librustc_typeck/check/wfcheck.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ use rustc_hir::def_id::DefId;
use rustc_hir::itemlikevisit::ParItemLikeVisitor;
use rustc_hir::lang_items;
use rustc_hir::ItemKind;
use rustc_middle::ty::subst::{InternalSubsts, Subst};
use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts, Subst};
use rustc_middle::ty::trait_def::TraitSpecializationKind;
use rustc_middle::ty::{
self, AdtKind, GenericParamDefKind, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness,
Expand Down Expand Up @@ -864,87 +864,77 @@ fn check_opaque_types<'fcx, 'tcx>(
trace!("check_opaque_types: opaque_ty, {:?}, {:?}", def_id, substs);
let generics = tcx.generics_of(def_id);
// Only check named `impl Trait` types defined in this crate.
// FIXME(eddyb) is `generics.parent.is_none()` correct? It seems
// potentially risky wrt associated types in `impl`s.
if generics.parent.is_none() && def_id.is_local() {
let opaque_hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
if may_define_opaque_type(tcx, fn_def_id, opaque_hir_id) {
trace!("check_opaque_types: may define, generics={:#?}", generics);
let mut seen: FxHashMap<_, Vec<_>> = FxHashMap::default();
for (subst, param) in substs.iter().zip(&generics.params) {
match subst.unpack() {
ty::subst::GenericArgKind::Type(ty) => match ty.kind {
ty::Param(..) => {}
// Prevent `fn foo() -> Foo<u32>` from being defining.
_ => {
tcx.sess
.struct_span_err(
span,
"non-defining opaque type use \
in defining scope",
)
.span_note(
tcx.def_span(param.def_id),
&format!(
"used non-generic type {} for \
generic parameter",
ty,
),
)
.emit();
}
},
let mut seen_params: FxHashMap<_, Vec<_>> = FxHashMap::default();
for (i, &arg) in substs.iter().enumerate() {
let arg_is_param = match arg.unpack() {
GenericArgKind::Type(ty) => matches!(ty.kind, ty::Param(_)),

ty::subst::GenericArgKind::Lifetime(region) => {
let param_span = tcx.def_span(param.def_id);
GenericArgKind::Lifetime(region) => {
if let ty::ReStatic = region {
tcx.sess
.struct_span_err(
span,
"non-defining opaque type use \
in defining scope",
"non-defining opaque type use in defining scope",
)
.span_label(
param_span,
tcx.def_span(generics.param_at(i, tcx).def_id),
"cannot use static lifetime; use a bound lifetime \
instead or remove the lifetime parameter from the \
opaque type",
)
.emit();
} else {
seen.entry(region).or_default().push(param_span);
continue;
}

true
}

ty::subst::GenericArgKind::Const(ct) => match ct.val {
ty::ConstKind::Param(_) => {}
_ => {
tcx.sess
.struct_span_err(
span,
"non-defining opaque type use \
in defining scope",
)
.span_note(
tcx.def_span(param.def_id),
&format!(
"used non-generic const {} for \
generic parameter",
ty,
),
)
.emit();
}
},
} // match subst
} // for (subst, param)
for (_, spans) in seen {
if spans.len() > 1 {
GenericArgKind::Const(ct) => {
matches!(ct.val, ty::ConstKind::Param(_))
}
};

if arg_is_param {
seen_params.entry(arg).or_default().push(i);
} else {
// Prevent `fn foo() -> Foo<u32>` from being defining.
let opaque_param = generics.param_at(i, tcx);
tcx.sess
.struct_span_err(
span,
"non-defining opaque type use in defining scope",
)
.span_note(
tcx.def_span(opaque_param.def_id),
&format!(
"used non-generic {} `{}` for generic parameter",
opaque_param.kind.descr(),
arg,
),
)
.emit();
}
} // for (arg, param)

for (_, indices) in seen_params {
if indices.len() > 1 {
let descr = generics.param_at(indices[0], tcx).kind.descr();
let spans: Vec<_> = indices
.into_iter()
.map(|i| tcx.def_span(generics.param_at(i, tcx).def_id))
.collect();
tcx.sess
.struct_span_err(
span,
"non-defining opaque type use \
in defining scope",
"non-defining opaque type use in defining scope",
)
.span_note(spans, "lifetime used multiple times")
.span_note(spans, &format!("{} used multiple times", descr))
.emit();
}
}
Expand Down
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