Auto merge of #123230 - matthiaskrgr:rollup-4twuzj4, r=matthiaskrgr

Rollup of 5 pull requests

Successful merges:

 - #121573 (unix_sigpipe: Add test for SIGPIPE disposition in child processes)
 - #123170 (Replace regions in const canonical vars' types with `'static` in next-solver canonicalizer)
 - #123200 (KCFI: Require -C panic=abort)
 - #123201 (Improve wording in std::any explanation)
 - #123224 (compiletest: print reason for failing to read tests)

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_middle/src/ty/region.rs

@@ -140,6 +140,10 @@ impl<'tcx> rustc_type_ir::new::Region<TyCtxt<'tcx>> for Region<'tcx> {
     fn new_anon_bound(tcx: TyCtxt<'tcx>, debruijn: ty::DebruijnIndex, var: ty::BoundVar) -> Self {
         Region::new_bound(tcx, debruijn, ty::BoundRegion { var, kind: ty::BoundRegionKind::BrAnon })
     }
+
+    fn new_static(tcx: TyCtxt<'tcx>) -> Self {
+        tcx.lifetimes.re_static
+    }
 }
 
 /// Region utilities

compiler/rustc_next_trait_solver/src/canonicalizer.rs

@@ -296,10 +296,7 @@ impl<Infcx: InferCtxtLike<Interner = I>, I: Interner> TypeFolder<I>
         Region::new_anon_bound(self.interner(), self.binder_index, var)
     }
 
-    fn fold_ty(&mut self, t: I::Ty) -> I::Ty
-    where
-        I::Ty: TypeSuperFoldable<I>,
-    {
+    fn fold_ty(&mut self, t: I::Ty) -> I::Ty {
         let kind = match t.kind() {
             ty::Infer(i) => match i {
                 ty::TyVar(vid) => {
@@ -378,47 +375,48 @@ impl<Infcx: InferCtxtLike<Interner = I>, I: Interner> TypeFolder<I>
         Ty::new_anon_bound(self.interner(), self.binder_index, var)
     }
 
-    fn fold_const(&mut self, c: I::Const) -> I::Const
-    where
-        I::Const: TypeSuperFoldable<I>,
-    {
+    fn fold_const(&mut self, c: I::Const) -> I::Const {
+        // We could canonicalize all consts with static types, but the only ones we
+        // *really* need to worry about are the ones that we end up putting into `CanonicalVarKind`
+        // since canonical vars can't reference other canonical vars.
+        let ty = c
+            .ty()
+            .fold_with(&mut RegionsToStatic { interner: self.interner(), binder: ty::INNERMOST });
         let kind = match c.kind() {
-            ty::ConstKind::Infer(i) => {
-                // FIXME: we should fold the ty too eventually
-                match i {
-                    ty::InferConst::Var(vid) => {
-                        assert_eq!(
-                            self.infcx.root_ct_var(vid),
-                            vid,
-                            "region vid should have been resolved fully before canonicalization"
-                        );
-                        assert_eq!(
-                            self.infcx.probe_ct_var(vid),
-                            None,
-                            "region vid should have been resolved fully before canonicalization"
-                        );
-                        CanonicalVarKind::Const(self.infcx.universe_of_ct(vid).unwrap(), c.ty())
-                    }
-                    ty::InferConst::EffectVar(_) => CanonicalVarKind::Effect,
-                    ty::InferConst::Fresh(_) => todo!(),
+            ty::ConstKind::Infer(i) => match i {
+                ty::InferConst::Var(vid) => {
+                    assert_eq!(
+                        self.infcx.root_ct_var(vid),
+                        vid,
+                        "region vid should have been resolved fully before canonicalization"
+                    );
+                    assert_eq!(
+                        self.infcx.probe_ct_var(vid),
+                        None,
+                        "region vid should have been resolved fully before canonicalization"
+                    );
+                    CanonicalVarKind::Const(self.infcx.universe_of_ct(vid).unwrap(), ty)
                 }
-            }
+                ty::InferConst::EffectVar(_) => CanonicalVarKind::Effect,
+                ty::InferConst::Fresh(_) => todo!(),
+            },
             ty::ConstKind::Placeholder(placeholder) => match self.canonicalize_mode {
                 CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst(
                     PlaceholderLike::new(placeholder.universe(), self.variables.len().into()),
-                    c.ty(),
+                    ty,
                 ),
                 CanonicalizeMode::Response { .. } => {
-                    CanonicalVarKind::PlaceholderConst(placeholder, c.ty())
+                    CanonicalVarKind::PlaceholderConst(placeholder, ty)
                 }
             },
             ty::ConstKind::Param(_) => match self.canonicalize_mode {
                 CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst(
                     PlaceholderLike::new(ty::UniverseIndex::ROOT, self.variables.len().into()),
-                    c.ty(),
+                    ty,
                 ),
                 CanonicalizeMode::Response { .. } => panic!("param ty in response: {c:?}"),
             },
+            // FIXME: See comment above -- we could fold the region separately or something.
             ty::ConstKind::Bound(_, _)
             | ty::ConstKind::Unevaluated(_)
             | ty::ConstKind::Value(_)
@@ -435,6 +433,35 @@ impl<Infcx: InferCtxtLike<Interner = I>, I: Interner> TypeFolder<I>
             }),
         );
 
-        Const::new_anon_bound(self.interner(), self.binder_index, var, c.ty())
+        Const::new_anon_bound(self.interner(), self.binder_index, var, ty)
+    }
+}
+
+struct RegionsToStatic<I> {
+    interner: I,
+    binder: ty::DebruijnIndex,
+}
+
+impl<I: Interner> TypeFolder<I> for RegionsToStatic<I> {
+    fn interner(&self) -> I {
+        self.interner
+    }
+
+    fn fold_binder<T>(&mut self, t: I::Binder<T>) -> I::Binder<T>
+    where
+        T: TypeFoldable<I>,
+        I::Binder<T>: TypeSuperFoldable<I>,
+    {
+        self.binder.shift_in(1);
+        let t = t.fold_with(self);
+        self.binder.shift_out(1);
+        t
+    }
+
+    fn fold_region(&mut self, r: I::Region) -> I::Region {
+        match r.kind() {
+            ty::ReBound(db, _) if self.binder > db => r,
+            _ => Region::new_static(self.interner()),
+        }
     }
 }

compiler/rustc_session/messages.ftl

@@ -96,6 +96,8 @@ session_sanitizer_cfi_requires_lto = `-Zsanitizer=cfi` requires `-Clto` or `-Cli
 
 session_sanitizer_cfi_requires_single_codegen_unit = `-Zsanitizer=cfi` with `-Clto` requires `-Ccodegen-units=1`
 
+session_sanitizer_kcfi_requires_panic_abort = `-Z sanitizer=kcfi` requires `-C panic=abort`
+
 session_sanitizer_not_supported = {$us} sanitizer is not supported for this target
 
 session_sanitizers_not_supported = {$us} sanitizers are not supported for this target

compiler/rustc_session/src/errors.rs

@@ -145,6 +145,10 @@ pub(crate) struct SanitizerCfiGeneralizePointersRequiresCfi;
 #[diag(session_sanitizer_cfi_normalize_integers_requires_cfi)]
 pub(crate) struct SanitizerCfiNormalizeIntegersRequiresCfi;
 
+#[derive(Diagnostic)]
+#[diag(session_sanitizer_kcfi_requires_panic_abort)]
+pub(crate) struct SanitizerKcfiRequiresPanicAbort;
+
 #[derive(Diagnostic)]
 #[diag(session_split_lto_unit_requires_lto)]
 pub(crate) struct SplitLtoUnitRequiresLto;

compiler/rustc_session/src/session.rs

@@ -1211,6 +1211,11 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
         sess.dcx().emit_err(errors::SanitizerCfiRequiresLto);
     }
 
+    // KCFI requires panic=abort
+    if sess.is_sanitizer_kcfi_enabled() && sess.panic_strategy() != PanicStrategy::Abort {
+        sess.dcx().emit_err(errors::SanitizerKcfiRequiresPanicAbort);
+    }
+
     // LLVM CFI using rustc LTO requires a single codegen unit.
     if sess.is_sanitizer_cfi_enabled()
         && sess.lto() == config::Lto::Fat

compiler/rustc_type_ir/src/fold.rs

@@ -136,31 +136,21 @@ pub trait TypeFolder<I: Interner>: FallibleTypeFolder<I, Error = Never> {
         t.super_fold_with(self)
     }
 
-    fn fold_ty(&mut self, t: I::Ty) -> I::Ty
-    where
-        I::Ty: TypeSuperFoldable<I>,
-    {
+    fn fold_ty(&mut self, t: I::Ty) -> I::Ty {
         t.super_fold_with(self)
     }
 
     // The default region folder is a no-op because `Region` is non-recursive
-    // and has no `super_fold_with` method to call. That also explains the
-    // lack of `I::Region: TypeSuperFoldable<I>` bound on this method.
+    // and has no `super_fold_with` method to call.
     fn fold_region(&mut self, r: I::Region) -> I::Region {
         r
     }
 
-    fn fold_const(&mut self, c: I::Const) -> I::Const
-    where
-        I::Const: TypeSuperFoldable<I>,
-    {
+    fn fold_const(&mut self, c: I::Const) -> I::Const {
         c.super_fold_with(self)
     }
 
-    fn fold_predicate(&mut self, p: I::Predicate) -> I::Predicate
-    where
-        I::Predicate: TypeSuperFoldable<I>,
-    {
+    fn fold_predicate(&mut self, p: I::Predicate) -> I::Predicate {
         p.super_fold_with(self)
     }
 }
@@ -185,31 +175,21 @@ pub trait FallibleTypeFolder<I: Interner>: Sized {
         t.try_super_fold_with(self)
     }
 
-    fn try_fold_ty(&mut self, t: I::Ty) -> Result<I::Ty, Self::Error>
-    where
-        I::Ty: TypeSuperFoldable<I>,
-    {
+    fn try_fold_ty(&mut self, t: I::Ty) -> Result<I::Ty, Self::Error> {
         t.try_super_fold_with(self)
     }
 
     // The default region folder is a no-op because `Region` is non-recursive
-    // and has no `super_fold_with` method to call. That also explains the
-    // lack of `I::Region: TypeSuperFoldable<I>` bound on this method.
+    // and has no `super_fold_with` method to call.
     fn try_fold_region(&mut self, r: I::Region) -> Result<I::Region, Self::Error> {
         Ok(r)
     }
 
-    fn try_fold_const(&mut self, c: I::Const) -> Result<I::Const, Self::Error>
-    where
-        I::Const: TypeSuperFoldable<I>,
-    {
+    fn try_fold_const(&mut self, c: I::Const) -> Result<I::Const, Self::Error> {
         c.try_super_fold_with(self)
     }
 
-    fn try_fold_predicate(&mut self, p: I::Predicate) -> Result<I::Predicate, Self::Error>
-    where
-        I::Predicate: TypeSuperFoldable<I>,
-    {
+    fn try_fold_predicate(&mut self, p: I::Predicate) -> Result<I::Predicate, Self::Error> {
         p.try_super_fold_with(self)
     }
 }
@@ -234,10 +214,7 @@ where
         Ok(self.fold_binder(t))
     }
 
-    fn try_fold_ty(&mut self, t: I::Ty) -> Result<I::Ty, Never>
-    where
-        I::Ty: TypeSuperFoldable<I>,
-    {
+    fn try_fold_ty(&mut self, t: I::Ty) -> Result<I::Ty, Never> {
         Ok(self.fold_ty(t))
     }
 
@@ -245,17 +222,11 @@ where
         Ok(self.fold_region(r))
     }
 
-    fn try_fold_const(&mut self, c: I::Const) -> Result<I::Const, Never>
-    where
-        I::Const: TypeSuperFoldable<I>,
-    {
+    fn try_fold_const(&mut self, c: I::Const) -> Result<I::Const, Never> {
         Ok(self.fold_const(c))
     }
 
-    fn try_fold_predicate(&mut self, p: I::Predicate) -> Result<I::Predicate, Never>
-    where
-        I::Predicate: TypeSuperFoldable<I>,
-    {
+    fn try_fold_predicate(&mut self, p: I::Predicate) -> Result<I::Predicate, Never> {
         Ok(self.fold_predicate(p))
     }
 }

compiler/rustc_type_ir/src/interner.rs

@@ -2,13 +2,14 @@ use smallvec::SmallVec;
 use std::fmt::Debug;
 use std::hash::Hash;
 
+use crate::fold::TypeSuperFoldable;
 use crate::visit::{Flags, TypeSuperVisitable, TypeVisitable};
 use crate::{
     new, BoundVar, BoundVars, CanonicalVarInfo, ConstKind, DebugWithInfcx, RegionKind, TyKind,
     UniverseIndex,
 };
 
-pub trait Interner: Sized {
+pub trait Interner: Sized + Copy {
     type DefId: Copy + Debug + Hash + Eq;
     type AdtDef: Copy + Debug + Hash + Eq;
 
@@ -34,6 +35,7 @@ pub trait Interner: Sized {
         + Into<Self::GenericArg>
         + IntoKind<Kind = TyKind<Self>>
         + TypeSuperVisitable<Self>
+        + TypeSuperFoldable<Self>
         + Flags
         + new::Ty<Self>;
     type Tys: Copy + Debug + Hash + Eq + IntoIterator<Item = Self::Ty>;
@@ -57,6 +59,7 @@ pub trait Interner: Sized {
         + IntoKind<Kind = ConstKind<Self>>
         + ConstTy<Self>
         + TypeSuperVisitable<Self>
+        + TypeSuperFoldable<Self>
         + Flags
         + new::Const<Self>;
     type AliasConst: Copy + DebugWithInfcx<Self> + Hash + Eq;
@@ -82,7 +85,13 @@ pub trait Interner: Sized {
     type PlaceholderRegion: Copy + Debug + Hash + Eq + PlaceholderLike;
 
     // Predicates
-    type Predicate: Copy + Debug + Hash + Eq + TypeSuperVisitable<Self> + Flags;
+    type Predicate: Copy
+        + Debug
+        + Hash
+        + Eq
+        + TypeSuperVisitable<Self>
+        + TypeSuperFoldable<Self>
+        + Flags;
     type TraitPredicate: Copy + Debug + Hash + Eq;
     type RegionOutlivesPredicate: Copy + Debug + Hash + Eq;
     type TypeOutlivesPredicate: Copy + Debug + Hash + Eq;

compiler/rustc_type_ir/src/new.rs

@@ -6,6 +6,8 @@ pub trait Ty<I: Interner<Ty = Self>> {
 
 pub trait Region<I: Interner<Region = Self>> {
     fn new_anon_bound(interner: I, debruijn: DebruijnIndex, var: BoundVar) -> Self;
+
+    fn new_static(interner: I) -> Self;
 }
 
 pub trait Const<I: Interner<Const = Self>> {

library/core/src/any.rs

@@ -40,10 +40,10 @@
 //!
 //! ## Examples
 //!
-//! Consider a situation where we want to log out a value passed to a function.
-//! We know the value we're working on implements Debug, but we don't know its
+//! Consider a situation where we want to log a value passed to a function.
+//! We know the value we're working on implements `Debug`, but we don't know its
 //! concrete type. We want to give special treatment to certain types: in this
-//! case printing out the length of String values prior to their value.
+//! case printing out the length of `String` values prior to their value.
 //! We don't know the concrete type of our value at compile time, so we need to
 //! use runtime reflection instead.
 //!
@@ -51,7 +51,7 @@
 //! use std::fmt::Debug;
 //! use std::any::Any;
 //!
-//! // Logger function for any type that implements Debug.
+//! // Logger function for any type that implements `Debug`.
 //! fn log<T: Any + Debug>(value: &T) {
 //!     let value_any = value as &dyn Any;
 //!

src/tools/compiletest/src/lib.rs

@@ -571,7 +571,9 @@ pub fn make_tests(
         &modified_tests,
         &mut poisoned,
     )
-    .unwrap_or_else(|_| panic!("Could not read tests from {}", config.src_base.display()));
+    .unwrap_or_else(|reason| {
+        panic!("Could not read tests from {}: {reason}", config.src_base.display())
+    });
 
     if poisoned {
         eprintln!();

tests/ui/attributes/unix_sigpipe/auxiliary/assert-sigpipe-disposition.rs

@@ -0,0 +1,34 @@
+// It is UB to unwind out of `fn start()` according to
+// https://doc.rust-lang.org/beta/unstable-book/language-features/start.html so
+// panic with abort to avoid UB:
+//@ compile-flags: -Cpanic=abort
+//@ no-prefer-dynamic so panic=abort works
+
+#![feature(start, rustc_private)]
+
+extern crate libc;
+
+// Use #[start] so we don't have a runtime that messes with SIGPIPE.
+#[start]
+fn start(argc: isize, argv: *const *const u8) -> isize {
+    assert_eq!(argc, 2, "Must pass SIG_IGN or SIG_DFL as first arg");
+    let arg1 = unsafe { std::ffi::CStr::from_ptr(*argv.offset(1) as *const libc::c_char) }
+        .to_str()
+        .unwrap();
+
+    let expected = match arg1 {
+        "SIG_IGN" => libc::SIG_IGN,
+        "SIG_DFL" => libc::SIG_DFL,
+        arg => panic!("Must pass SIG_IGN or SIG_DFL as first arg. Got: {}", arg),
+    };
+
+    let actual = unsafe {
+        let mut actual: libc::sigaction = std::mem::zeroed();
+        libc::sigaction(libc::SIGPIPE, std::ptr::null(), &mut actual);
+        actual.sa_sigaction
+    };
+
+    assert_eq!(actual, expected, "actual and expected SIGPIPE disposition in child differs");
+
+    0
+}

tests/ui/attributes/unix_sigpipe/unix_sigpipe-and-child-processes.rs

@@ -0,0 +1,56 @@
+//@ revisions: default sig_dfl sig_ign inherit
+//@ ignore-cross-compile because aux-bin does not yet support it
+//@ only-unix because SIGPIPE is a unix thing
+//@ run-pass
+//@ aux-bin:assert-sigpipe-disposition.rs
+//@ aux-crate:sigpipe_utils=sigpipe-utils.rs
+
+// Checks the signal disposition of `SIGPIPE` in child processes, and in our own
+// process for robustness. Without any `unix_sigpipe` attribute, `SIG_IGN` is
+// the default. But there is a difference in how `SIGPIPE` is treated in child
+// processes with and without the attribute. Search for
+// `unix_sigpipe_attr_specified()` in the code base to learn more.
+
+#![feature(rustc_private)]
+#![cfg_attr(any(sig_dfl, sig_ign, inherit), feature(unix_sigpipe))]
+
+extern crate libc;
+extern crate sigpipe_utils;
+
+use sigpipe_utils::*;
+
+#[cfg_attr(sig_dfl, unix_sigpipe = "sig_dfl")]
+#[cfg_attr(sig_ign, unix_sigpipe = "sig_ign")]
+#[cfg_attr(inherit, unix_sigpipe = "inherit")]
+fn main() {
+    // By default we get SIG_IGN but the child gets SIG_DFL through an explicit
+    // reset before exec:
+    // https://github.com/rust-lang/rust/blob/bf4de3a874753bbee3323081c8b0c133444fed2d/library/std/src/sys/pal/unix/process/process_unix.rs#L363-L384
+    #[cfg(default)]
+    let (we_expect, child_expects) = (SignalHandler::Ignore, "SIG_DFL");
+
+    // With #[unix_sigpipe = "sig_dfl"] we get SIG_DFL and the child does too
+    // without any special code running before exec.
+    #[cfg(sig_dfl)]
+    let (we_expect, child_expects) = (SignalHandler::Default, "SIG_DFL");
+
+    // With #[unix_sigpipe = "sig_ign"] we get SIG_IGN and the child does too
+    // without any special code running before exec.
+    #[cfg(sig_ign)]
+    let (we_expect, child_expects) = (SignalHandler::Ignore, "SIG_IGN");
+
+    // With #[unix_sigpipe = "inherit"] we get SIG_DFL and the child does too
+    // without any special code running before exec.
+    #[cfg(inherit)]
+    let (we_expect, child_expects) = (SignalHandler::Default, "SIG_DFL");
+
+    assert_sigpipe_handler(we_expect);
+
+    assert!(
+        std::process::Command::new("./auxiliary/bin/assert-sigpipe-disposition")
+            .arg(child_expects)
+            .status()
+            .unwrap()
+            .success()
+    );
+}

tests/ui/coherence/negative-coherence/regions-in-canonical.rs

@@ -0,0 +1,23 @@
+//@ check-pass
+
+#![feature(adt_const_params)]
+//~^ WARN the feature `adt_const_params` is incomplete
+#![feature(with_negative_coherence, negative_impls)]
+
+pub trait A<const K: &'static str> {}
+pub trait C {}
+
+
+struct W<T>(T);
+
+// Negative coherence:
+// Proving `W<!T>: !A<"">` requires proving `CONST alias-eq ""`, which requires proving
+// `CONST normalizes-to (?1c: &str)`. The type's region is uniquified, so it ends up being
+// put in to the canonical vars list with an infer region => ICE.
+impl<T> C for T where T: A<""> {}
+impl<T> C for W<T> {}
+
+impl<T> !A<CONST> for W<T> {}
+const CONST: &str = "";
+
+fn main() {}

tests/ui/coherence/negative-coherence/regions-in-canonical.stderr

@@ -0,0 +1,11 @@
+warning: the feature `adt_const_params` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/regions-in-canonical.rs:3:12
+   |
+LL | #![feature(adt_const_params)]
+   |            ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #95174 <https://github.com/rust-lang/rust/issues/95174> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+

tests/ui/compiletest-self-test/test-aux-bin.rs

@@ -1,4 +1,4 @@
-//@ ignore-cross-compile because we run the compiled code
+//@ ignore-cross-compile because aux-bin does not yet support it
 //@ aux-bin: print-it-works.rs
 //@ run-pass
 

tests/ui/sanitizer/cfg.rs

@@ -11,6 +11,7 @@
 //@[cfi]compile-flags:     -Clto -Ccodegen-units=1
 //@[kcfi]needs-llvm-components: x86
 //@[kcfi]compile-flags:    -Zsanitizer=kcfi    --cfg kcfi --target x86_64-unknown-none
+//@[kcfi]compile-flags:    -C panic=abort
 //@[leak]needs-sanitizer-leak
 //@[leak]compile-flags:    -Zsanitizer=leak    --cfg leak
 //@[memory]needs-sanitizer-memory

tests/ui/sanitizer/cfi-closure-fn-ptr-cast.rs

@@ -14,6 +14,7 @@
 //@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
 //@ [cfi] compile-flags: -Z sanitizer=cfi
 //@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ [kcfi] compile-flags: -C panic=abort -C prefer-dynamic=off
 //@ run-pass
 
 pub fn main() {

tests/ui/sanitizer/cfi-complex-receiver.rs

@@ -11,6 +11,7 @@
 //@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
 //@ [cfi] compile-flags: -Z sanitizer=cfi
 //@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ [kcfi] compile-flags: -C panic=abort -C prefer-dynamic=off
 //@ run-pass
 
 use std::sync::Arc;

tests/ui/sanitizer/cfi-self-ref.rs

@@ -9,6 +9,7 @@
 //@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
 //@ [cfi] compile-flags: -Z sanitizer=cfi
 //@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ [kcfi] compile-flags: -C panic=abort -C prefer-dynamic=off
 //@ run-pass
 
 use std::marker::PhantomData;

tests/ui/sanitizer/cfi-virtual-auto.rs

@@ -9,6 +9,7 @@
 //@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
 //@ [cfi] compile-flags: -Z sanitizer=cfi
 //@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ [kcfi] compile-flags: -C panic=abort -C prefer-dynamic=off
 //@ run-pass
 
 trait Foo {