Auto merge of rust-lang#99300 - Mark-Simulacrum:beta-next, r=Mark-Simulacrum

[beta] rollup

*  Fix sized check ICE in asm check rust-lang#99124
*  Windows: Fallback for overlapped I/O rust-lang#98950
*  promote placeholder bounds to 'static obligations rust-lang#98713
*  Create fresh lifetime parameters for bare fn trait too rust-lang#98637

r? `@Mark-Simulacrum`

Author: bors

Diff for: compiler/rustc_ast_lowering/src/lib.rs

@@ -1174,6 +1174,33 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         param_mode: ParamMode,
         itctx: ImplTraitContext,
     ) -> hir::Ty<'hir> {
+        // Check whether we should interpret this as a bare trait object.
+        // This check mirrors the one in late resolution.  We only introduce this special case in
+        // the rare occurence we need to lower `Fresh` anonymous lifetimes.
+        // The other cases when a qpath should be opportunistically made a trait object are handled
+        // by `ty_path`.
+        if qself.is_none()
+            && let Some(partial_res) = self.resolver.get_partial_res(t.id)
+            && partial_res.unresolved_segments() == 0
+            && let Res::Def(DefKind::Trait | DefKind::TraitAlias, _) = partial_res.base_res()
+        {
+            let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
+                let bound = this.lower_poly_trait_ref(
+                    &PolyTraitRef {
+                        bound_generic_params: vec![],
+                        trait_ref: TraitRef { path: path.clone(), ref_id: t.id },
+                        span: t.span
+                    },
+                    itctx,
+                );
+                let bounds = this.arena.alloc_from_iter([bound]);
+                let lifetime_bound = this.elided_dyn_bound(t.span);
+                (bounds, lifetime_bound)
+            });
+            let kind = hir::TyKind::TraitObject(bounds, lifetime_bound, TraitObjectSyntax::None);
+            return hir::Ty { kind, span: self.lower_span(t.span), hir_id: self.next_id() };
+        }
+
         let id = self.lower_node_id(t.id);
         let qpath = self.lower_qpath(t.id, qself, path, param_mode, itctx);
         self.ty_path(id, t.span, qpath)

Diff for: compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -916,6 +916,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// The idea then is to lower the `T: 'X` constraint into multiple
     /// bounds -- e.g., if `'X` is the union of two free lifetimes,
     /// `'1` and `'2`, then we would create `T: '1` and `T: '2`.
+    #[instrument(level = "debug", skip(self, infcx, propagated_outlives_requirements))]
     fn try_promote_type_test(
         &self,
         infcx: &InferCtxt<'_, 'tcx>,
@@ -933,11 +934,41 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             return false;
         };
 
+        debug!("subject = {:?}", subject);
+
+        let r_scc = self.constraint_sccs.scc(*lower_bound);
+
+        debug!(
+            "lower_bound = {:?} r_scc={:?} universe={:?}",
+            lower_bound, r_scc, self.scc_universes[r_scc]
+        );
+
+        // If the type test requires that `T: 'a` where `'a` is a
+        // placeholder from another universe, that effectively requires
+        // `T: 'static`, so we have to propagate that requirement.
+        //
+        // It doesn't matter *what* universe because the promoted `T` will
+        // always be in the root universe.
+        if let Some(p) = self.scc_values.placeholders_contained_in(r_scc).next() {
+            debug!("encountered placeholder in higher universe: {:?}, requiring 'static", p);
+            let static_r = self.universal_regions.fr_static;
+            propagated_outlives_requirements.push(ClosureOutlivesRequirement {
+                subject,
+                outlived_free_region: static_r,
+                blame_span: locations.span(body),
+                category: ConstraintCategory::Boring,
+            });
+
+            // we can return here -- the code below might push add'l constraints
+            // but they would all be weaker than this one.
+            return true;
+        }
+
         // For each region outlived by lower_bound find a non-local,
         // universal region (it may be the same region) and add it to
         // `ClosureOutlivesRequirement`.
-        let r_scc = self.constraint_sccs.scc(*lower_bound);
         for ur in self.scc_values.universal_regions_outlived_by(r_scc) {
+            debug!("universal_region_outlived_by ur={:?}", ur);
             // Check whether we can already prove that the "subject" outlives `ur`.
             // If so, we don't have to propagate this requirement to our caller.
             //
@@ -962,8 +993,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 continue;
             }
 
-            debug!("try_promote_type_test: ur={:?}", ur);
-
             let non_local_ub = self.universal_region_relations.non_local_upper_bounds(ur);
             debug!("try_promote_type_test: non_local_ub={:?}", non_local_ub);
 
@@ -1000,15 +1029,14 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// will use it's *external name*, which will be a `RegionKind`
     /// variant that can be used in query responses such as
     /// `ReEarlyBound`.
+    #[instrument(level = "debug", skip(self, infcx))]
     fn try_promote_type_test_subject(
         &self,
         infcx: &InferCtxt<'_, 'tcx>,
         ty: Ty<'tcx>,
     ) -> Option<ClosureOutlivesSubject<'tcx>> {
         let tcx = infcx.tcx;
 
-        debug!("try_promote_type_test_subject(ty = {:?})", ty);
-
         let ty = tcx.fold_regions(ty, &mut false, |r, _depth| {
             let region_vid = self.to_region_vid(r);
 

Diff for: compiler/rustc_resolve/src/late.rs

@@ -611,6 +611,30 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
             TyKind::Path(ref qself, ref path) => {
                 self.diagnostic_metadata.current_type_path = Some(ty);
                 self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
+
+                // Check whether we should interpret this as a bare trait object.
+                if qself.is_none()
+                    && let Some(partial_res) = self.r.partial_res_map.get(&ty.id)
+                    && partial_res.unresolved_segments() == 0
+                    && let Res::Def(DefKind::Trait | DefKind::TraitAlias, _) = partial_res.base_res()
+                {
+                    // This path is actually a bare trait object.  In case of a bare `Fn`-trait
+                    // object with anonymous lifetimes, we need this rib to correctly place the
+                    // synthetic lifetimes.
+                    let span = ty.span.shrink_to_lo().to(path.span.shrink_to_lo());
+                    self.with_generic_param_rib(
+                        &[],
+                        NormalRibKind,
+                        LifetimeRibKind::Generics {
+                            binder: ty.id,
+                            kind: LifetimeBinderKind::PolyTrait,
+                            span,
+                        },
+                        |this| this.visit_path(&path, ty.id),
+                    );
+                    self.diagnostic_metadata.current_type_path = prev_ty;
+                    return;
+                }
             }
             TyKind::ImplicitSelf => {
                 let self_ty = Ident::with_dummy_span(kw::SelfUpper);

Diff for: compiler/rustc_typeck/src/check/intrinsicck.rs

@@ -4,7 +4,7 @@ use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_index::vec::Idx;
 use rustc_middle::ty::layout::{LayoutError, SizeSkeleton};
-use rustc_middle::ty::{self, Article, FloatTy, InferTy, IntTy, Ty, TyCtxt, TypeFoldable, UintTy};
+use rustc_middle::ty::{self, Article, FloatTy, IntTy, Ty, TyCtxt, TypeFoldable, UintTy};
 use rustc_session::lint;
 use rustc_span::{Span, Symbol, DUMMY_SP};
 use rustc_target::abi::{Pointer, VariantIdx};
@@ -99,8 +99,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         err.emit();
     }
 
+    // FIXME(compiler-errors): This could use `<$ty as Pointee>::Metadata == ()`
     fn is_thin_ptr_ty(&self, ty: Ty<'tcx>) -> bool {
-        if ty.is_sized(self.tcx.at(DUMMY_SP), self.param_env) {
+        // Type still may have region variables, but `Sized` does not depend
+        // on those, so just erase them before querying.
+        if self.tcx.erase_regions(ty).is_sized(self.tcx.at(DUMMY_SP), self.param_env) {
             return true;
         }
         if let ty::Foreign(..) = ty.kind() {
@@ -128,30 +131,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             64 => InlineAsmType::I64,
             _ => unreachable!(),
         };
+
+        // Expect types to be fully resolved, no const or type variables.
+        if ty.has_infer_types_or_consts() {
+            assert!(self.is_tainted_by_errors());
+            return None;
+        }
+
         let asm_ty = match *ty.kind() {
             // `!` is allowed for input but not for output (issue #87802)
             ty::Never if is_input => return None,
             ty::Error(_) => return None,
             ty::Int(IntTy::I8) | ty::Uint(UintTy::U8) => Some(InlineAsmType::I8),
             ty::Int(IntTy::I16) | ty::Uint(UintTy::U16) => Some(InlineAsmType::I16),
-            // Somewhat of a hack: fallback in the presence of errors does not actually
-            // fall back to i32, but to ty::Error. For integer inference variables this
-            // means that they don't get any fallback and stay as `{integer}`.
-            // Since compilation can't succeed anyway, it's fine to use this to avoid printing
-            // "cannot use value of type `{integer}`", even though that would absolutely
-            // work due due i32 fallback if the current function had no other errors.
-            ty::Infer(InferTy::IntVar(_)) => {
-                assert!(self.is_tainted_by_errors());
-                Some(InlineAsmType::I32)
-            }
             ty::Int(IntTy::I32) | ty::Uint(UintTy::U32) => Some(InlineAsmType::I32),
             ty::Int(IntTy::I64) | ty::Uint(UintTy::U64) => Some(InlineAsmType::I64),
             ty::Int(IntTy::I128) | ty::Uint(UintTy::U128) => Some(InlineAsmType::I128),
             ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => Some(asm_ty_isize),
-            ty::Infer(InferTy::FloatVar(_)) => {
-                assert!(self.is_tainted_by_errors());
-                Some(InlineAsmType::F32)
-            }
             ty::Float(FloatTy::F32) => Some(InlineAsmType::F32),
             ty::Float(FloatTy::F64) => Some(InlineAsmType::F64),
             ty::FnPtr(_) => Some(asm_ty_isize),
@@ -191,6 +187,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     _ => None,
                 }
             }
+            ty::Infer(_) => unreachable!(),
             _ => None,
         };
         let Some(asm_ty) = asm_ty else {
@@ -204,11 +201,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return None;
         };
 
-        if ty.has_infer_types_or_consts() {
-            assert!(self.is_tainted_by_errors());
-            return None;
-        }
-
         // Check that the type implements Copy. The only case where this can
         // possibly fail is for SIMD types which don't #[derive(Copy)].
         if !self.infcx.type_is_copy_modulo_regions(self.param_env, ty, DUMMY_SP) {

Diff for: library/std/src/sys/windows/c.rs

@@ -326,7 +326,9 @@ union IO_STATUS_BLOCK_union {
 }
 impl Default for IO_STATUS_BLOCK_union {
     fn default() -> Self {
-        Self { Pointer: ptr::null_mut() }
+        let mut this = Self { Pointer: ptr::null_mut() };
+        this.Status = STATUS_PENDING;
+        this
     }
 }
 #[repr(C)]
@@ -335,6 +337,16 @@ pub struct IO_STATUS_BLOCK {
     u: IO_STATUS_BLOCK_union,
     pub Information: usize,
 }
+impl IO_STATUS_BLOCK {
+    pub fn status(&self) -> NTSTATUS {
+        // SAFETY: If `self.u.Status` was set then this is obviously safe.
+        // If `self.u.Pointer` was set then this is the equivalent to converting
+        // the pointer to an integer, which is also safe.
+        // Currently the only safe way to construct `IO_STATUS_BLOCK` outside of
+        // this module is to call the `default` method, which sets the `Status`.
+        unsafe { self.u.Status }
+    }
+}
 
 pub type LPOVERLAPPED_COMPLETION_ROUTINE = unsafe extern "system" fn(
     dwErrorCode: DWORD,

Diff for: library/std/src/sys/windows/handle.rs

@@ -1,5 +1,8 @@
 #![unstable(issue = "none", feature = "windows_handle")]
 
+#[cfg(test)]
+mod tests;
+
 use crate::cmp;
 use crate::io::{self, ErrorKind, IoSlice, IoSliceMut, Read, ReadBuf};
 use crate::mem;
@@ -248,14 +251,18 @@ impl Handle {
             offset.map(|n| n as _).as_ref(),
             None,
         );
+
+        let status = if status == c::STATUS_PENDING {
+            c::WaitForSingleObject(self.as_raw_handle(), c::INFINITE);
+            io_status.status()
+        } else {
+            status
+        };
         match status {
             // If the operation has not completed then abort the process.
             // Doing otherwise means that the buffer and stack may be written to
             // after this function returns.
-            c::STATUS_PENDING => {
-                eprintln!("I/O error: operation failed to complete synchronously");
-                crate::process::abort();
-            }
+            c::STATUS_PENDING => rtabort!("I/O error: operation failed to complete synchronously"),
 
             // Return `Ok(0)` when there's nothing more to read.
             c::STATUS_END_OF_FILE => Ok(0),
@@ -294,13 +301,17 @@ impl Handle {
                 None,
             )
         };
+        let status = if status == c::STATUS_PENDING {
+            unsafe { c::WaitForSingleObject(self.as_raw_handle(), c::INFINITE) };
+            io_status.status()
+        } else {
+            status
+        };
         match status {
             // If the operation has not completed then abort the process.
             // Doing otherwise means that the buffer may be read and the stack
             // written to after this function returns.
-            c::STATUS_PENDING => {
-                rtabort!("I/O error: operation failed to complete synchronously");
-            }
+            c::STATUS_PENDING => rtabort!("I/O error: operation failed to complete synchronously"),
 
             // Success!
             status if c::nt_success(status) => Ok(io_status.Information),

Diff for: library/std/src/sys/windows/handle/tests.rs

@@ -0,0 +1,22 @@
+use crate::sys::pipe::{anon_pipe, Pipes};
+use crate::{thread, time};
+
+/// Test the synchronous fallback for overlapped I/O.
+#[test]
+fn overlapped_handle_fallback() {
+    // Create some pipes. `ours` will be asynchronous.
+    let Pipes { ours, theirs } = anon_pipe(true, false).unwrap();
+
+    let async_readable = ours.into_handle();
+    let sync_writeable = theirs.into_handle();
+
+    thread::scope(|_| {
+        thread::sleep(time::Duration::from_millis(100));
+        sync_writeable.write(b"hello world!").unwrap();
+    });
+
+    // The pipe buffer starts empty so reading won't complete synchronously unless
+    // our fallback path works.
+    let mut buffer = [0u8; 1024];
+    async_readable.read(&mut buffer).unwrap();
+}