Erroneous code example:
```compile_fail,E0118
-impl fn(u8) { // error: no nominal type found for inherent implementation
+impl<T> T { // error: no nominal type found for inherent implementation
fn get_state(&self) -> String {
// ...
}
fn get_state(&self) -> String;
}
-// and now you can implement it on fn(u8)
-impl LiveLongAndProsper for fn(u8) {
+// and now you can implement it on T
+impl<T> LiveLongAndProsper for T {
fn get_state(&self) -> String {
"He's dead, Jim!".to_owned()
}
Example:
```
-struct TypeWrapper(fn(u8));
+struct TypeWrapper<T>(T);
-impl TypeWrapper {
+impl<T> TypeWrapper<T> {
fn get_state(&self) -> String {
"Fascinating!".to_owned()
}
| ty::RawPtr(_)
| ty::Ref(..)
| ty::Never
+ | ty::FnPtr(_)
| ty::Tuple(..) => self.check_primitive_impl(item.def_id, self_ty, items, ty.span),
- ty::FnPtr(_) | ty::Projection(..) | ty::Opaque(..) | ty::Param(_) => {
+ ty::Projection(..) | ty::Opaque(..) | ty::Param(_) => {
let mut err = struct_span_err!(
self.tcx.sess,
ty.span,
/// Note that all of this is not portable to platforms where function pointers and data pointers
/// have different sizes.
///
-/// ### Traits
+/// ### Trait implementations
///
-/// Function pointers implement the following traits:
+/// In this documentation the shorthand `fn (T₁, T₂, …, Tₙ)` is used to represent non-variadic
+/// function pointers of varying length. Note that this is a convenience notation to avoid
+/// repetitive documentation, not valid Rust syntax.
+///
+/// Due to a temporary restriction in Rust's type system, these traits are only implemented on
+/// functions that take 12 arguments or less, with the `"Rust"` and `"C"` ABIs. In the future, this
+/// may change:
///
-/// * [`Clone`]
/// * [`PartialEq`]
/// * [`Eq`]
/// * [`PartialOrd`]
/// * [`Pointer`]
/// * [`Debug`]
///
+/// The following traits are implemented for function pointers with any number of arguments and
+/// any ABI. These traits have implementations that are automatically generated by the compiler,
+/// so are not limited by missing language features:
+///
+/// * [`Clone`]
+/// * [`Copy`]
+/// * [`Send`]
+/// * [`Sync`]
+/// * [`Unpin`]
+/// * [`UnwindSafe`]
+/// * [`RefUnwindSafe`]
+///
/// [`Hash`]: hash::Hash
/// [`Pointer`]: fmt::Pointer
+/// [`UnwindSafe`]: panic::UnwindSafe
+/// [`RefUnwindSafe`]: panic::RefUnwindSafe
///
-/// Due to a temporary restriction in Rust's type system, these traits are only implemented on
-/// functions that take 12 arguments or less, with the `"Rust"` and `"C"` ABIs. In the future, this
-/// may change.
-///
-/// In addition, function pointers of *any* signature, ABI, or safety are [`Copy`], and all *safe*
-/// function pointers implement [`Fn`], [`FnMut`], and [`FnOnce`]. This works because these traits
-/// are specially known to the compiler.
+/// In addition, all *safe* function pointers implement [`Fn`], [`FnMut`], and [`FnOnce`], because
+/// these traits are specially known to the compiler.
#[stable(feature = "rust1", since = "1.0.0")]
mod prim_fn {}
+
+// Required to make auto trait impls render.
+// See src/librustdoc/passes/collect_trait_impls.rs:collect_trait_impls
+#[doc(hidden)]
+#[cfg(not(bootstrap))]
+impl<Ret, T> fn(T) -> Ret {}
+
+// Fake impl that's only really used for docs.
+#[cfg(doc)]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), doc(fake_variadic))]
+/// This trait is implemented on function pointers with any number of arguments.
+impl<Ret, T> Clone for fn(T) -> Ret {
+ fn clone(&self) -> Self {
+ loop {}
+ }
+}
+
+// Fake impl that's only really used for docs.
+#[cfg(doc)]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), doc(fake_variadic))]
+/// This trait is implemented on function pointers with any number of arguments.
+impl<Ret, T> Copy for fn(T) -> Ret {
+ // empty
+}
hashee.hash(into);
}
+// If this is a unary fn pointer, it adds a doc comment.
+// Otherwise, it hides the docs entirely.
+macro_rules! maybe_fnptr_doc {
+ (@ #[$meta:meta] $item:item) => {
+ #[doc(hidden)]
+ #[$meta]
+ $item
+ };
+ ($a:ident @ #[$meta:meta] $item:item) => {
+ #[cfg_attr(not(bootstrap), doc(fake_variadic))]
+ #[doc = "This trait is implemented for function pointers with up to twelve arguments."]
+ #[$meta]
+ $item
+ };
+ ($a:ident $($rest_a:ident)+ @ #[$meta:meta] $item:item) => {
+ #[doc(hidden)]
+ #[$meta]
+ $item
+ };
+}
+
// FIXME(strict_provenance_magic): function pointers have buggy codegen that
// necessitates casting to a usize to get the backend to do the right thing.
// for now I will break AVR to silence *a billion* lints. We should probably
// Impls for function pointers
macro_rules! fnptr_impls_safety_abi {
($FnTy: ty, $($Arg: ident),*) => {
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> PartialEq for $FnTy {
- #[inline]
- fn eq(&self, other: &Self) -> bool {
- *self as usize == *other as usize
+ maybe_fnptr_doc! {
+ $($Arg)* @
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> PartialEq for $FnTy {
+ #[inline]
+ fn eq(&self, other: &Self) -> bool {
+ *self as usize == *other as usize
+ }
}
}
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> Eq for $FnTy {}
+ maybe_fnptr_doc! {
+ $($Arg)* @
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> Eq for $FnTy {}
+ }
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> PartialOrd for $FnTy {
- #[inline]
- fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
- (*self as usize).partial_cmp(&(*other as usize))
+ maybe_fnptr_doc! {
+ $($Arg)* @
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> PartialOrd for $FnTy {
+ #[inline]
+ fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+ (*self as usize).partial_cmp(&(*other as usize))
+ }
}
}
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> Ord for $FnTy {
- #[inline]
- fn cmp(&self, other: &Self) -> Ordering {
- (*self as usize).cmp(&(*other as usize))
+ maybe_fnptr_doc! {
+ $($Arg)* @
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> Ord for $FnTy {
+ #[inline]
+ fn cmp(&self, other: &Self) -> Ordering {
+ (*self as usize).cmp(&(*other as usize))
+ }
}
}
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> hash::Hash for $FnTy {
- fn hash<HH: hash::Hasher>(&self, state: &mut HH) {
- state.write_usize(*self as usize)
+ maybe_fnptr_doc! {
+ $($Arg)* @
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> hash::Hash for $FnTy {
+ fn hash<HH: hash::Hasher>(&self, state: &mut HH) {
+ state.write_usize(*self as usize)
+ }
}
}
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> fmt::Pointer for $FnTy {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::pointer_fmt_inner(*self as usize, f)
+ maybe_fnptr_doc! {
+ $($Arg)* @
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> fmt::Pointer for $FnTy {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::pointer_fmt_inner(*self as usize, f)
+ }
}
}
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> fmt::Debug for $FnTy {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::pointer_fmt_inner(*self as usize, f)
+ maybe_fnptr_doc! {
+ $($Arg)* @
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> fmt::Debug for $FnTy {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::pointer_fmt_inner(*self as usize, f)
+ }
}
}
}
/// Note that all of this is not portable to platforms where function pointers and data pointers
/// have different sizes.
///
-/// ### Traits
+/// ### Trait implementations
///
-/// Function pointers implement the following traits:
+/// In this documentation the shorthand `fn (T₁, T₂, …, Tₙ)` is used to represent non-variadic
+/// function pointers of varying length. Note that this is a convenience notation to avoid
+/// repetitive documentation, not valid Rust syntax.
+///
+/// Due to a temporary restriction in Rust's type system, these traits are only implemented on
+/// functions that take 12 arguments or less, with the `"Rust"` and `"C"` ABIs. In the future, this
+/// may change:
///
-/// * [`Clone`]
/// * [`PartialEq`]
/// * [`Eq`]
/// * [`PartialOrd`]
/// * [`Pointer`]
/// * [`Debug`]
///
+/// The following traits are implemented for function pointers with any number of arguments and
+/// any ABI. These traits have implementations that are automatically generated by the compiler,
+/// so are not limited by missing language features:
+///
+/// * [`Clone`]
+/// * [`Copy`]
+/// * [`Send`]
+/// * [`Sync`]
+/// * [`Unpin`]
+/// * [`UnwindSafe`]
+/// * [`RefUnwindSafe`]
+///
/// [`Hash`]: hash::Hash
/// [`Pointer`]: fmt::Pointer
+/// [`UnwindSafe`]: panic::UnwindSafe
+/// [`RefUnwindSafe`]: panic::RefUnwindSafe
///
-/// Due to a temporary restriction in Rust's type system, these traits are only implemented on
-/// functions that take 12 arguments or less, with the `"Rust"` and `"C"` ABIs. In the future, this
-/// may change.
-///
-/// In addition, function pointers of *any* signature, ABI, or safety are [`Copy`], and all *safe*
-/// function pointers implement [`Fn`], [`FnMut`], and [`FnOnce`]. This works because these traits
-/// are specially known to the compiler.
+/// In addition, all *safe* function pointers implement [`Fn`], [`FnMut`], and [`FnOnce`], because
+/// these traits are specially known to the compiler.
#[stable(feature = "rust1", since = "1.0.0")]
mod prim_fn {}
+
+// Required to make auto trait impls render.
+// See src/librustdoc/passes/collect_trait_impls.rs:collect_trait_impls
+#[doc(hidden)]
+#[cfg(not(bootstrap))]
+impl<Ret, T> fn(T) -> Ret {}
+
+// Fake impl that's only really used for docs.
+#[cfg(doc)]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), doc(fake_variadic))]
+/// This trait is implemented on function pointers with any number of arguments.
+impl<Ret, T> Clone for fn(T) -> Ret {
+ fn clone(&self) -> Self {
+ loop {}
+ }
+}
+
+// Fake impl that's only really used for docs.
+#[cfg(doc)]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), doc(fake_variadic))]
+/// This trait is implemented on function pointers with any number of arguments.
+impl<Ret, T> Copy for fn(T) -> Ret {
+ // empty
+}
Reference => [RefSimplifiedType(Mutability::Not), RefSimplifiedType(Mutability::Mut)].into_iter().collect(),
// FIXME: This will be wrong if we ever add inherent impls
// for function pointers.
- Fn => ArrayVec::new(),
+ Fn => single(FunctionSimplifiedType(1)),
Never => single(NeverSimplifiedType),
}
})
if let clean::Type::Tuple(types) = &self.for_ &&
let [clean::Type::Generic(name)] = &types[..] &&
- (self.kind.is_fake_variadic() || self.kind.is_auto()) {
+ (self.kind.is_fake_variadic() || self.kind.is_auto())
+ {
// Hardcoded anchor library/core/src/primitive_docs.rs
// Link should match `# Trait implementations`
primitive_link_fragment(f, PrimitiveType::Tuple, &format!("({name}₁, {name}₂, …, {name}ₙ)"), "#trait-implementations-1", cx)?;
- } else if let clean::Type::BareFunction(bare_fn) = &self.for_ &&
+ } else if let clean::BareFunction(bare_fn) = &self.for_ &&
let [clean::Argument { type_: clean::Type::Generic(name), .. }] = &bare_fn.decl.inputs.values[..] &&
- (self.kind.is_fake_variadic() || self.kind.is_auto()) {
+ (self.kind.is_fake_variadic() || self.kind.is_auto())
+ {
// Hardcoded anchor library/core/src/primitive_docs.rs
// Link should match `# Trait implementations`
- primitive_link_fragment(f, PrimitiveType::Tuple, &format!("fn ({name}₁, {name}₂, …, {name}ₙ)"), "#trait-implementations-1", cx)?;
- // Not implemented.
- assert!(!bare_fn.decl.c_variadic);
+
+ let hrtb = bare_fn.print_hrtb_with_space(cx);
+ let unsafety = bare_fn.unsafety.print_with_space();
+ let abi = print_abi_with_space(bare_fn.abi);
+ if f.alternate() {
+ write!(
+ f,
+ "{hrtb:#}{unsafety}{abi:#}",
+ )?;
+ } else {
+ write!(
+ f,
+ "{hrtb}{unsafety}{abi}",
+ )?;
+ }
+ let ellipsis = if bare_fn.decl.c_variadic {
+ ", ..."
+ } else {
+ ""
+ };
+ primitive_link_fragment(f, PrimitiveType::Tuple, &format!("fn ({name}₁, {name}₂, …, {name}ₙ{ellipsis})"), "#trait-implementations-1", cx)?;
// Write output.
if let clean::FnRetTy::Return(ty) = &bare_fn.decl.output {
write!(f, " -> ")?;
-impl fn(u8) { //~ ERROR E0118
+impl<T> T { //~ ERROR E0118
fn get_state(&self) -> String {
String::new()
}
error[E0118]: no nominal type found for inherent implementation
- --> $DIR/E0118.rs:1:6
+ --> $DIR/E0118.rs:1:9
|
-LL | impl fn(u8) {
- | ^^^^^^ impl requires a nominal type
+LL | impl<T> T {
+ | ^ impl requires a nominal type
|
= note: either implement a trait on it or create a newtype to wrap it instead
impl *mut Foo {} //~ ERROR E0390
+impl fn(Foo) {} //~ ERROR E0390
+
fn main() {
}
|
= help: consider using an extension trait instead
-error: aborting due to previous error
+error[E0390]: cannot define inherent `impl` for primitive types
+ --> $DIR/E0390.rs:7:6
+ |
+LL | impl fn(Foo) {}
+ | ^^^^^^^
+ |
+ = help: consider using an extension trait instead
+
+error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0390`.
= help: the trait `Debug` is not implemented for `fn(usize) -> Foo {Foo::Bar}`
= help: the following other types implement trait `Debug`:
extern "C" fn() -> Ret
- extern "C" fn(A) -> Ret
- extern "C" fn(A, ...) -> Ret
extern "C" fn(A, B) -> Ret
extern "C" fn(A, B, ...) -> Ret
extern "C" fn(A, B, C) -> Ret
extern "C" fn(A, B, C, ...) -> Ret
extern "C" fn(A, B, C, D) -> Ret
+ extern "C" fn(A, B, C, D, ...) -> Ret
+ extern "C" fn(A, B, C, D, E) -> Ret
and 68 others
= note: this error originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
projects / rust.git / commitdiff