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Rollup merge of rust-lang#88312 - jackh726:issue-87748, r=nikomatsakis
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Treat types in unnormalized function signatures as well-formed

Fixes rust-lang#87748

r? `@nikomatsakis`
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Manishearth authored Aug 27, 2021
2 parents dccd7cd + 97bf80d commit 3bf30d0
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Showing 6 changed files with 90 additions and 9 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -256,6 +256,9 @@ impl UniversalRegionRelationsBuilder<'cx, 'tcx> {
let constraint_sets: Vec<_> = unnormalized_input_output_tys
.flat_map(|ty| {
debug!("build: input_or_output={:?}", ty);
// We add implied bounds from both the unnormalized and normalized ty
// See issue #87748
let constraints_implied_1 = self.add_implied_bounds(ty);
let TypeOpOutput { output: ty, constraints: constraints1, .. } = self
.param_env
.and(type_op::normalize::Normalize::new(ty))
Expand All @@ -271,9 +274,21 @@ impl UniversalRegionRelationsBuilder<'cx, 'tcx> {
canonicalized_query: None,
}
});
let constraints2 = self.add_implied_bounds(ty);
// Note: we need this in examples like
// ```
// trait Foo {
// type Bar;
// fn foo(&self) -> &Self::Bar;
// }
// impl Foo for () {
// type Bar = ();
// fn foo(&self) ->&() {}
// }
// ```
// Both &Self::Bar and &() are WF
let constraints_implied_2 = self.add_implied_bounds(ty);
normalized_inputs_and_output.push(ty);
constraints1.into_iter().chain(constraints2)
constraints1.into_iter().chain(constraints_implied_1).chain(constraints_implied_2)
})
.collect();

Expand Down
12 changes: 11 additions & 1 deletion compiler/rustc_typeck/src/check/compare_method.rs
Original file line number Diff line number Diff line change
Expand Up @@ -250,6 +250,8 @@ fn compare_predicate_entailment<'tcx>(
// Compute placeholder form of impl and trait method tys.
let tcx = infcx.tcx;

let mut wf_tys = vec![];

let (impl_sig, _) = infcx.replace_bound_vars_with_fresh_vars(
impl_m_span,
infer::HigherRankedType,
Expand All @@ -260,10 +262,18 @@ fn compare_predicate_entailment<'tcx>(
let impl_fty = tcx.mk_fn_ptr(ty::Binder::dummy(impl_sig));
debug!("compare_impl_method: impl_fty={:?}", impl_fty);

// First liberate late bound regions and subst placeholders
let trait_sig = tcx.liberate_late_bound_regions(impl_m.def_id, tcx.fn_sig(trait_m.def_id));
let trait_sig = trait_sig.subst(tcx, trait_to_placeholder_substs);
// Next, add all inputs and output as well-formed tys. Importantly,
// we have to do this before normalization, since the normalized ty may
// not contain the input parameters. See issue #87748.
wf_tys.extend(trait_sig.inputs_and_output.iter());
let trait_sig =
inh.normalize_associated_types_in(impl_m_span, impl_m_hir_id, param_env, trait_sig);
// Also add the resulting inputs and output as well-formed.
// This probably isn't strictly necessary.
wf_tys.extend(trait_sig.inputs_and_output.iter());
let trait_fty = tcx.mk_fn_ptr(ty::Binder::dummy(trait_sig));

debug!("compare_impl_method: trait_fty={:?}", trait_fty);
Expand Down Expand Up @@ -388,7 +398,7 @@ fn compare_predicate_entailment<'tcx>(
// Finally, resolve all regions. This catches wily misuses of
// lifetime parameters.
let fcx = FnCtxt::new(&inh, param_env, impl_m_hir_id);
fcx.regionck_item(impl_m_hir_id, impl_m_span, trait_sig.inputs_and_output);
fcx.regionck_item(impl_m_hir_id, impl_m_span, &wf_tys);

Ok(())
})
Expand Down
16 changes: 12 additions & 4 deletions compiler/rustc_typeck/src/check/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -364,7 +364,7 @@ fn typeck_with_fallback<'tcx>(

let typeck_results = Inherited::build(tcx, def_id).enter(|inh| {
let param_env = tcx.param_env(def_id);
let fcx = if let Some(hir::FnSig { header, decl, .. }) = fn_sig {
let (fcx, wf_tys) = if let Some(hir::FnSig { header, decl, .. }) = fn_sig {
let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
<dyn AstConv<'_>>::ty_of_fn(
Expand All @@ -383,17 +383,25 @@ fn typeck_with_fallback<'tcx>(

check_abi(tcx, id, span, fn_sig.abi());

// When normalizing the function signature, we assume all types are
// well-formed. So, we don't need to worry about the obligations
// from normalization. We could just discard these, but to align with
// compare_method and elsewhere, we just add implied bounds for
// these types.
let mut wf_tys = vec![];
// Compute the fty from point of view of inside the fn.
let fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
wf_tys.extend(fn_sig.inputs_and_output.iter());
let fn_sig = inh.normalize_associated_types_in(
body.value.span,
body_id.hir_id,
param_env,
fn_sig,
);
wf_tys.extend(fn_sig.inputs_and_output.iter());

let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None, true).0;
fcx
(fcx, wf_tys)
} else {
let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
let expected_type = body_ty
Expand Down Expand Up @@ -443,7 +451,7 @@ fn typeck_with_fallback<'tcx>(

fcx.write_ty(id, expected_type);

fcx
(fcx, vec![])
};

let fallback_has_occurred = fcx.type_inference_fallback();
Expand All @@ -467,7 +475,7 @@ fn typeck_with_fallback<'tcx>(
fcx.select_all_obligations_or_error();

if fn_sig.is_some() {
fcx.regionck_fn(id, body);
fcx.regionck_fn(id, body, span, &wf_tys);
} else {
fcx.regionck_expr(body);
}
Expand Down
11 changes: 10 additions & 1 deletion compiler/rustc_typeck/src/check/regionck.rs
Original file line number Diff line number Diff line change
Expand Up @@ -144,11 +144,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
/// rest of type check and because sometimes we need type
/// inference to have completed before we can determine which
/// constraints to add.
pub fn regionck_fn(&self, fn_id: hir::HirId, body: &'tcx hir::Body<'tcx>) {
pub(crate) fn regionck_fn(
&self,
fn_id: hir::HirId,
body: &'tcx hir::Body<'tcx>,
span: Span,
wf_tys: &[Ty<'tcx>],
) {
debug!("regionck_fn(id={})", fn_id);
let subject = self.tcx.hir().body_owner_def_id(body.id());
let hir_id = body.value.hir_id;
let mut rcx = RegionCtxt::new(self, hir_id, Subject(subject), self.param_env);
// We need to add the implied bounds from the function signature
rcx.outlives_environment.add_implied_bounds(self, wf_tys, fn_id, span);
rcx.outlives_environment.save_implied_bounds(fn_id);

if !self.errors_reported_since_creation() {
// regionck assumes typeck succeeded
Expand Down
11 changes: 10 additions & 1 deletion compiler/rustc_typeck/src/check/wfcheck.rs
Original file line number Diff line number Diff line change
Expand Up @@ -911,6 +911,7 @@ fn check_where_clauses<'tcx, 'fcx>(
}
}

#[tracing::instrument(level = "debug", skip(fcx, span, hir_decl))]
fn check_fn_or_method<'fcx, 'tcx>(
fcx: &FnCtxt<'fcx, 'tcx>,
span: Span,
Expand All @@ -921,6 +922,11 @@ fn check_fn_or_method<'fcx, 'tcx>(
) {
let sig = fcx.tcx.liberate_late_bound_regions(def_id, sig);

// Unnormalized types in signature are WF too
implied_bounds.extend(sig.inputs());
// FIXME(#27579) return types should not be implied bounds
implied_bounds.push(sig.output());

// Normalize the input and output types one at a time, using a different
// `WellFormedLoc` for each. We cannot call `normalize_associated_types`
// on the entire `FnSig`, since this would use the same `WellFormedLoc`
Expand Down Expand Up @@ -970,9 +976,11 @@ fn check_fn_or_method<'fcx, 'tcx>(
ObligationCauseCode::ReturnType,
);

// FIXME(#25759) return types should not be implied bounds
// FIXME(#27579) return types should not be implied bounds
implied_bounds.push(sig.output());

debug!(?implied_bounds);

check_where_clauses(fcx, span, def_id, Some((sig.output(), hir_decl.output.span())));
}

Expand Down Expand Up @@ -1117,6 +1125,7 @@ const HELP_FOR_SELF_TYPE: &str = "consider changing to `self`, `&self`, `&mut se
`self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one \
of the previous types except `Self`)";

#[tracing::instrument(level = "debug", skip(fcx))]
fn check_method_receiver<'fcx, 'tcx>(
fcx: &FnCtxt<'fcx, 'tcx>,
fn_sig: &hir::FnSig<'_>,
Expand Down
30 changes: 30 additions & 0 deletions src/test/ui/generic-associated-types/issue-87748.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
// Checks that we properly add implied bounds from unnormalized projections in
// inputs when typechecking functions.

// check-pass

#![feature(generic_associated_types)]

trait MyTrait {
type Assoc<'a, 'b> where 'b: 'a;
fn do_sth(arg: Self::Assoc<'_, '_>);
}

struct A;
struct B;
struct C;

impl MyTrait for A {
type Assoc<'a, 'b> where 'b: 'a = u32;
fn do_sth(_: u32) {}
}
impl MyTrait for B {
type Assoc<'a, 'b> where 'b: 'a = u32;
fn do_sth(_: Self::Assoc<'_, '_>) {}
}
impl MyTrait for C {
type Assoc<'a, 'b> where 'b: 'a = u32;
fn do_sth(_: Self::Assoc<'static, 'static>) {}
}

fn main () {}

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