Rollup of 6 pull requests

compiler/rustc_ast_lowering/src/path.rs

@@ -191,7 +191,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
                 }
                 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
-                    ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
+                    ParenthesizedGenericArgs::Ok => {
+                        self.lower_parenthesized_parameter_data(data, itctx)
+                    }
                     ParenthesizedGenericArgs::Err => {
                         // Suggest replacing parentheses with angle brackets `Trait(params...)` to `Trait<params...>`
                         let sub = if !data.inputs.is_empty() {
@@ -344,6 +346,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_parenthesized_parameter_data(
         &mut self,
         data: &ParenthesizedArgs,
+        itctx: &ImplTraitContext,
     ) -> (GenericArgsCtor<'hir>, bool) {
         // Switch to `PassThrough` mode for anonymous lifetimes; this
         // means that we permit things like `&Ref<T>`, where `Ref` has
@@ -355,6 +358,17 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             self.lower_ty_direct(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitParam))
         }));
         let output_ty = match output {
+            // Only allow `impl Trait` in return position. i.e.:
+            // ```rust
+            // fn f(_: impl Fn() -> impl Debug) -> impl Fn() -> impl Debug
+            // //      disallowed --^^^^^^^^^^        allowed --^^^^^^^^^^
+            // ```
+            FnRetTy::Ty(ty)
+                if matches!(itctx, ImplTraitContext::ReturnPositionOpaqueTy { .. })
+                    && self.tcx.features().impl_trait_in_fn_trait_return =>
+            {
+                self.lower_ty(&ty, itctx)
+            }
             FnRetTy::Ty(ty) => {
                 self.lower_ty(&ty, &ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitReturn))
             }

compiler/rustc_error_messages/locales/en-US/hir_analysis.ftl

@@ -93,7 +93,7 @@ hir_analysis_expected_default_return_type = expected `()` because of default ret
 hir_analysis_expected_return_type = expected `{$expected}` because of return type
 
 hir_analysis_unconstrained_opaque_type = unconstrained opaque type
-    .note = `{$name}` must be used in combination with a concrete type within the same module
+    .note = `{$name}` must be used in combination with a concrete type within the same {$what}
 
 hir_analysis_missing_type_params =
     the type {$parameterCount ->

compiler/rustc_feature/src/active.rs

@@ -412,6 +412,8 @@ declare_features! (
     (active, half_open_range_patterns_in_slices, "CURRENT_RUSTC_VERSION", Some(67264), None),
     /// Allows `if let` guard in match arms.
     (active, if_let_guard, "1.47.0", Some(51114), None),
+    /// Allows `impl Trait` as output type in `Fn` traits in return position of functions.
+    (active, impl_trait_in_fn_trait_return, "1.64.0", Some(99697), None),
     /// Allows using imported `main` function
     (active, imported_main, "1.53.0", Some(28937), None),
     /// Allows associated types in inherent impls.

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -701,6 +701,12 @@ fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: LocalDefId) -> T
         tcx.sess.emit_err(UnconstrainedOpaqueType {
             span: tcx.def_span(def_id),
             name: tcx.item_name(tcx.local_parent(def_id).to_def_id()),
+            what: match tcx.hir().get(scope) {
+                _ if scope == hir::CRATE_HIR_ID => "module",
+                Node::Item(hir::Item { kind: hir::ItemKind::Mod(_), .. }) => "module",
+                Node::Item(hir::Item { kind: hir::ItemKind::Impl(_), .. }) => "impl",
+                _ => "item",
+            },
         });
         return tcx.ty_error();
     };

compiler/rustc_hir_analysis/src/errors.rs

@@ -143,6 +143,7 @@ pub struct UnconstrainedOpaqueType {
     #[primary_span]
     pub span: Span,
     pub name: Symbol,
+    pub what: &'static str,
 }
 
 pub struct MissingTypeParams {

compiler/rustc_hir_typeck/src/upvar.rs

@@ -231,7 +231,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // We now fake capture information for all variables that are mentioned within the closure
         // We do this after handling migrations so that min_captures computes before
-        if !enable_precise_capture(self.tcx, span) {
+        if !enable_precise_capture(self.tcx, span)
+            // (ouz-a) #93242 - ICE happens because closure_min_captures is empty with
+            // 2021 edition, because it sets `enable_precise_capture` to true, which won't allow us
+            // fake capture information this check sidesteps that and avoids the ICE.
+            || (infer_kind == None && self.typeck_results.borrow().closure_min_captures.is_empty())
+        {
             let mut capture_information: InferredCaptureInformation<'tcx> = Default::default();
 
             if let Some(upvars) = self.tcx.upvars_mentioned(closure_def_id) {

compiler/rustc_span/src/symbol.rs

@@ -813,6 +813,7 @@ symbols! {
         impl_lint_pass,
         impl_macros,
         impl_trait_in_bindings,
+        impl_trait_in_fn_trait_return,
         implied_by,
         import,
         import_name_type,

library/core/src/ffi/c_str.rs

@@ -221,9 +221,7 @@ impl CStr {
     /// # Examples
     ///
     /// ```ignore (extern-declaration)
-    /// # fn main() {
-    /// use std::ffi::CStr;
-    /// use std::os::raw::c_char;
+    /// use std::ffi::{c_char, CStr};
     ///
     /// extern "C" {
     ///     fn my_string() -> *const c_char;
@@ -233,14 +231,26 @@ impl CStr {
     ///     let slice = CStr::from_ptr(my_string());
     ///     println!("string returned: {}", slice.to_str().unwrap());
     /// }
-    /// # }
+    /// ```
+    ///
+    /// ```
+    /// #![feature(const_cstr_methods)]
+    ///
+    /// use std::ffi::{c_char, CStr};
+    ///
+    /// const HELLO_PTR: *const c_char = {
+    ///     const BYTES: &[u8] = b"Hello, world!\0";
+    ///     BYTES.as_ptr().cast()
+    /// };
+    /// const HELLO: &CStr = unsafe { CStr::from_ptr(HELLO_PTR) };
     /// ```
     ///
     /// [valid]: core::ptr#safety
     #[inline]
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
+    #[rustc_const_unstable(feature = "const_cstr_methods", issue = "101719")]
+    pub const unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
         // SAFETY: The caller has provided a pointer that points to a valid C
         // string with a NUL terminator of size less than `isize::MAX`, whose
         // content remain valid and doesn't change for the lifetime of the
@@ -252,13 +262,29 @@ impl CStr {
         //
         // The cast from c_char to u8 is ok because a c_char is always one byte.
         unsafe {
-            extern "C" {
-                /// Provided by libc or compiler_builtins.
-                fn strlen(s: *const c_char) -> usize;
+            const fn strlen_ct(s: *const c_char) -> usize {
+                let mut len = 0;
+
+                // SAFETY: Outer caller has provided a pointer to a valid C string.
+                while unsafe { *s.add(len) } != 0 {
+                    len += 1;
+                }
+
+                len
             }
-            let len = strlen(ptr);
-            let ptr = ptr as *const u8;
-            CStr::from_bytes_with_nul_unchecked(slice::from_raw_parts(ptr, len as usize + 1))
+
+            fn strlen_rt(s: *const c_char) -> usize {
+                extern "C" {
+                    /// Provided by libc or compiler_builtins.
+                    fn strlen(s: *const c_char) -> usize;
+                }
+
+                // SAFETY: Outer caller has provided a pointer to a valid C string.
+                unsafe { strlen(s) }
+            }
+
+            let len = intrinsics::const_eval_select((ptr,), strlen_ct, strlen_rt);
+            Self::from_bytes_with_nul_unchecked(slice::from_raw_parts(ptr.cast(), len + 1))
         }
     }
 

library/panic_unwind/src/emcc.rs

@@ -47,7 +47,12 @@ static EXCEPTION_TYPE_INFO: TypeInfo = TypeInfo {
     name: b"rust_panic\0".as_ptr(),
 };
 
+// NOTE(nbdd0121): The `canary` field will be part of stable ABI after `c_unwind` stabilization.
+#[repr(C)]
 struct Exception {
+    // See `gcc.rs` on why this is present. We already have a static here so just use it.
+    canary: *const TypeInfo,
+
     // This is necessary because C++ code can capture our exception with
     // std::exception_ptr and rethrow it multiple times, possibly even in
     // another thread.
@@ -70,27 +75,38 @@ pub unsafe fn cleanup(ptr: *mut u8) -> Box<dyn Any + Send> {
     let catch_data = &*(ptr as *mut CatchData);
 
     let adjusted_ptr = __cxa_begin_catch(catch_data.ptr as *mut libc::c_void) as *mut Exception;
-    let out = if catch_data.is_rust_panic {
-        let was_caught = (*adjusted_ptr).caught.swap(true, Ordering::SeqCst);
-        if was_caught {
-            // Since cleanup() isn't allowed to panic, we just abort instead.
-            intrinsics::abort();
-        }
-        (*adjusted_ptr).data.take().unwrap()
-    } else {
+    if !catch_data.is_rust_panic {
         super::__rust_foreign_exception();
-    };
+    }
+
+    let canary = ptr::addr_of!((*adjusted_ptr).canary).read();
+    if !ptr::eq(canary, &EXCEPTION_TYPE_INFO) {
+        super::__rust_foreign_exception();
+    }
+
+    let was_caught = (*adjusted_ptr).caught.swap(true, Ordering::SeqCst);
+    if was_caught {
+        // Since cleanup() isn't allowed to panic, we just abort instead.
+        intrinsics::abort();
+    }
+    let out = (*adjusted_ptr).data.take().unwrap();
     __cxa_end_catch();
     out
 }
 
 pub unsafe fn panic(data: Box<dyn Any + Send>) -> u32 {
-    let sz = mem::size_of_val(&data);
-    let exception = __cxa_allocate_exception(sz) as *mut Exception;
+    let exception = __cxa_allocate_exception(mem::size_of::<Exception>()) as *mut Exception;
     if exception.is_null() {
         return uw::_URC_FATAL_PHASE1_ERROR as u32;
     }
-    ptr::write(exception, Exception { caught: AtomicBool::new(false), data: Some(data) });
+    ptr::write(
+        exception,
+        Exception {
+            canary: &EXCEPTION_TYPE_INFO,
+            caught: AtomicBool::new(false),
+            data: Some(data),
+        },
+    );
     __cxa_throw(exception as *mut _, &EXCEPTION_TYPE_INFO, exception_cleanup);
 }
 

library/panic_unwind/src/gcc.rs

@@ -38,12 +38,23 @@
 
 use alloc::boxed::Box;
 use core::any::Any;
+use core::ptr;
 
 use unwind as uw;
 
+// In case where multiple copies of std exist in a single process,
+// we use address of this static variable to distinguish an exception raised by
+// this copy and some other copy (which needs to be treated as foreign exception).
+static CANARY: u8 = 0;
+
+// NOTE(nbdd0121)
+// Once `c_unwind` feature is stabilized, there will be ABI stability requirement
+// on this struct. The first two field must be `_Unwind_Exception` and `canary`,
+// as it may be accessed by a different version of the std with a different compiler.
 #[repr(C)]
 struct Exception {
     _uwe: uw::_Unwind_Exception,
+    canary: *const u8,
     cause: Box<dyn Any + Send>,
 }
 
@@ -54,6 +65,7 @@ pub unsafe fn panic(data: Box<dyn Any + Send>) -> u32 {
             exception_cleanup,
             private: [0; uw::unwinder_private_data_size],
         },
+        canary: &CANARY,
         cause: data,
     });
     let exception_param = Box::into_raw(exception) as *mut uw::_Unwind_Exception;
@@ -75,10 +87,22 @@ pub unsafe fn cleanup(ptr: *mut u8) -> Box<dyn Any + Send> {
     if (*exception).exception_class != rust_exception_class() {
         uw::_Unwind_DeleteException(exception);
         super::__rust_foreign_exception();
-    } else {
-        let exception = Box::from_raw(exception as *mut Exception);
-        exception.cause
     }
+
+    let exception = exception.cast::<Exception>();
+    // Just access the canary field, avoid accessing the entire `Exception` as
+    // it can be a foreign Rust exception.
+    let canary = ptr::addr_of!((*exception).canary).read();
+    if !ptr::eq(canary, &CANARY) {
+        // A foreign Rust exception, treat it slightly differently from other
+        // foreign exceptions, because call into `_Unwind_DeleteException` will
+        // call into `__rust_drop_panic` which produces a confusing
+        // "Rust panic must be rethrown" message.
+        super::__rust_foreign_exception();
+    }
+
+    let exception = Box::from_raw(exception as *mut Exception);
+    exception.cause
 }
 
 // Rust's exception class identifier.  This is used by personality routines to

library/panic_unwind/src/seh.rs

@@ -49,9 +49,15 @@
 use alloc::boxed::Box;
 use core::any::Any;
 use core::mem::{self, ManuallyDrop};
+use core::ptr;
 use libc::{c_int, c_uint, c_void};
 
+// NOTE(nbdd0121): The `canary` field will be part of stable ABI after `c_unwind` stabilization.
+#[repr(C)]
 struct Exception {
+    // See `gcc.rs` on why this is present. We already have a static here so just use it.
+    canary: *const _TypeDescriptor,
+
     // This needs to be an Option because we catch the exception by reference
     // and its destructor is executed by the C++ runtime. When we take the Box
     // out of the exception, we need to leave the exception in a valid state
@@ -235,7 +241,7 @@ static mut TYPE_DESCRIPTOR: _TypeDescriptor = _TypeDescriptor {
 macro_rules! define_cleanup {
     ($abi:tt $abi2:tt) => {
         unsafe extern $abi fn exception_cleanup(e: *mut Exception) {
-            if let Exception { data: Some(b) } = e.read() {
+            if let Exception { data: Some(b), .. } = e.read() {
                 drop(b);
                 super::__rust_drop_panic();
             }
@@ -265,7 +271,7 @@ pub unsafe fn panic(data: Box<dyn Any + Send>) -> u32 {
     // The ManuallyDrop is needed here since we don't want Exception to be
     // dropped when unwinding. Instead it will be dropped by exception_cleanup
     // which is invoked by the C++ runtime.
-    let mut exception = ManuallyDrop::new(Exception { data: Some(data) });
+    let mut exception = ManuallyDrop::new(Exception { canary: &TYPE_DESCRIPTOR, data: Some(data) });
     let throw_ptr = &mut exception as *mut _ as *mut _;
 
     // This... may seems surprising, and justifiably so. On 32-bit MSVC the
@@ -321,8 +327,12 @@ pub unsafe fn cleanup(payload: *mut u8) -> Box<dyn Any + Send> {
     // __rust_try. This happens when a non-Rust foreign exception is caught.
     if payload.is_null() {
         super::__rust_foreign_exception();
-    } else {
-        let exception = &mut *(payload as *mut Exception);
-        exception.data.take().unwrap()
     }
+    let exception = payload as *mut Exception;
+    let canary = ptr::addr_of!((*exception).canary).read();
+    if !ptr::eq(canary, &TYPE_DESCRIPTOR) {
+        // A foreign Rust exception.
+        super::__rust_foreign_exception();
+    }
+    (*exception).data.take().unwrap()
 }

src/test/run-make-fulldeps/foreign-rust-exceptions/Makefile

@@ -0,0 +1,11 @@
+# ignore-i686-pc-windows-gnu
+
+# This test doesn't work on 32-bit MinGW as cdylib has its own copy of unwinder
+# so cross-DLL unwinding does not work.
+
+include ../tools.mk
+
+all:
+	$(RUSTC) bar.rs --crate-type=cdylib
+	$(RUSTC) foo.rs
+	$(call RUN,foo) 2>&1 | $(CGREP) "Rust cannot catch foreign exceptions"

src/test/run-make-fulldeps/foreign-rust-exceptions/bar.rs

@@ -0,0 +1,7 @@
+#![crate_type = "cdylib"]
+#![feature(c_unwind)]
+
+#[no_mangle]
+extern "C-unwind" fn panic() {
+    panic!();
+}

src/test/run-make-fulldeps/foreign-rust-exceptions/foo.rs

@@ -0,0 +1,13 @@
+#![feature(c_unwind)]
+
+#[cfg_attr(not(windows), link(name = "bar"))]
+#[cfg_attr(windows, link(name = "bar.dll"))]
+extern "C-unwind" {
+    fn panic();
+}
+
+fn main() {
+    let _ = std::panic::catch_unwind(|| {
+        unsafe { panic() };
+    });
+}