From 5271e32c463e92f1afa6c54aa9dbb6a9d8454e0d Mon Sep 17 00:00:00 2001 From: Michael Howell Date: Thu, 16 Jun 2022 14:14:38 -0700 Subject: [PATCH] Improve the function pointer docs * Reduce duplicate impls; show only the `fn (T)` and include a sentence saying that there exists up to twelve of them. * Show `Copy` and `Clone`. * Show auto traits like `Send` and `Sync`, and blanket impls like `Any`. --- .../src/error_codes/E0118.md | 10 +- .../src/coherence/inherent_impls.rs | 3 +- library/core/src/primitive_docs.rs | 60 +++++++++-- library/core/src/ptr/mod.rs | 100 +++++++++++++----- library/std/src/primitive_docs.rs | 60 +++++++++-- src/librustdoc/clean/types.rs | 2 +- src/librustdoc/html/format.rs | 32 ++++-- src/test/ui/error-codes/E0118.rs | 2 +- src/test/ui/error-codes/E0118.stderr | 6 +- src/test/ui/error-codes/E0390.rs | 2 + src/test/ui/error-codes/E0390.stderr | 10 +- src/test/ui/issues/issue-59488.stderr | 4 +- 12 files changed, 222 insertions(+), 69 deletions(-) diff --git a/compiler/rustc_error_codes/src/error_codes/E0118.md b/compiler/rustc_error_codes/src/error_codes/E0118.md index 8033aa8384c..cfabae1a634 100644 --- a/compiler/rustc_error_codes/src/error_codes/E0118.md +++ b/compiler/rustc_error_codes/src/error_codes/E0118.md @@ -4,7 +4,7 @@ enum, union, or trait object. Erroneous code example: ```compile_fail,E0118 -impl fn(u8) { // error: no nominal type found for inherent implementation +impl T { // error: no nominal type found for inherent implementation fn get_state(&self) -> String { // ... } @@ -20,8 +20,8 @@ trait LiveLongAndProsper { 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 LiveLongAndProsper for T { fn get_state(&self) -> String { "He's dead, Jim!".to_owned() } @@ -33,9 +33,9 @@ For example, `NewType` is a newtype over `Foo` in `struct NewType(Foo)`. Example: ``` -struct TypeWrapper(fn(u8)); +struct TypeWrapper(T); -impl TypeWrapper { +impl TypeWrapper { fn get_state(&self) -> String { "Fascinating!".to_owned() } diff --git a/compiler/rustc_typeck/src/coherence/inherent_impls.rs b/compiler/rustc_typeck/src/coherence/inherent_impls.rs index 7a9b874b5e4..52aad636fd8 100644 --- a/compiler/rustc_typeck/src/coherence/inherent_impls.rs +++ b/compiler/rustc_typeck/src/coherence/inherent_impls.rs @@ -219,8 +219,9 @@ impl<'tcx> InherentCollect<'tcx> { | 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, diff --git a/library/core/src/primitive_docs.rs b/library/core/src/primitive_docs.rs index 4f08b562685..b8e5461640c 100644 --- a/library/core/src/primitive_docs.rs +++ b/library/core/src/primitive_docs.rs @@ -1441,11 +1441,16 @@ mod prim_ref {} /// 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`] @@ -1454,15 +1459,50 @@ mod prim_ref {} /// * [`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 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 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 Copy for fn(T) -> Ret { + // empty +} diff --git a/library/core/src/ptr/mod.rs b/library/core/src/ptr/mod.rs index 509854225c4..caa279f0de5 100644 --- a/library/core/src/ptr/mod.rs +++ b/library/core/src/ptr/mod.rs @@ -1819,6 +1819,27 @@ pub fn hash(hashee: *const T, into: &mut S) { 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] + $item + }; +} + // FIXME(strict_provenance_magic): function pointers have buggy codegen that // necessitates casting to a usize to get the backend to do the right thing. // for now I will break AVR to silence *a billion* lints. We should probably @@ -1827,51 +1848,72 @@ pub fn hash(hashee: *const T, into: &mut S) { // Impls for function pointers macro_rules! fnptr_impls_safety_abi { ($FnTy: ty, $($Arg: ident),*) => { - #[stable(feature = "fnptr_impls", since = "1.4.0")] - impl 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 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 Eq for $FnTy {} + maybe_fnptr_doc! { + $($Arg)* @ + #[stable(feature = "fnptr_impls", since = "1.4.0")] + impl Eq for $FnTy {} + } - #[stable(feature = "fnptr_impls", since = "1.4.0")] - impl PartialOrd for $FnTy { - #[inline] - fn partial_cmp(&self, other: &Self) -> Option { - (*self as usize).partial_cmp(&(*other as usize)) + maybe_fnptr_doc! { + $($Arg)* @ + #[stable(feature = "fnptr_impls", since = "1.4.0")] + impl PartialOrd for $FnTy { + #[inline] + fn partial_cmp(&self, other: &Self) -> Option { + (*self as usize).partial_cmp(&(*other as usize)) + } } } - #[stable(feature = "fnptr_impls", since = "1.4.0")] - impl 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 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 hash::Hash for $FnTy { - fn hash(&self, state: &mut HH) { - state.write_usize(*self as usize) + maybe_fnptr_doc! { + $($Arg)* @ + #[stable(feature = "fnptr_impls", since = "1.4.0")] + impl hash::Hash for $FnTy { + fn hash(&self, state: &mut HH) { + state.write_usize(*self as usize) + } } } - #[stable(feature = "fnptr_impls", since = "1.4.0")] - impl 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 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 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 fmt::Debug for $FnTy { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt::pointer_fmt_inner(*self as usize, f) + } } } } diff --git a/library/std/src/primitive_docs.rs b/library/std/src/primitive_docs.rs index 4f08b562685..b8e5461640c 100644 --- a/library/std/src/primitive_docs.rs +++ b/library/std/src/primitive_docs.rs @@ -1441,11 +1441,16 @@ mod prim_ref {} /// 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`] @@ -1454,15 +1459,50 @@ mod prim_ref {} /// * [`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 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 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 Copy for fn(T) -> Ret { + // empty +} diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs index 5ddf7ea8a85..8c08f776679 100644 --- a/src/librustdoc/clean/types.rs +++ b/src/librustdoc/clean/types.rs @@ -1841,7 +1841,7 @@ impl PrimitiveType { 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), } }) diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs index 291e6bc2fe4..36a47b05cb9 100644 --- a/src/librustdoc/html/format.rs +++ b/src/librustdoc/html/format.rs @@ -1165,18 +1165,38 @@ impl clean::Impl { 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, " -> ")?; diff --git a/src/test/ui/error-codes/E0118.rs b/src/test/ui/error-codes/E0118.rs index aaef8113b8a..a61ba7bbf32 100644 --- a/src/test/ui/error-codes/E0118.rs +++ b/src/test/ui/error-codes/E0118.rs @@ -1,4 +1,4 @@ -impl fn(u8) { //~ ERROR E0118 +impl T { //~ ERROR E0118 fn get_state(&self) -> String { String::new() } diff --git a/src/test/ui/error-codes/E0118.stderr b/src/test/ui/error-codes/E0118.stderr index 296fb5d664a..8c6fa7947a8 100644 --- a/src/test/ui/error-codes/E0118.stderr +++ b/src/test/ui/error-codes/E0118.stderr @@ -1,8 +1,8 @@ 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 { + | ^ impl requires a nominal type | = note: either implement a trait on it or create a newtype to wrap it instead diff --git a/src/test/ui/error-codes/E0390.rs b/src/test/ui/error-codes/E0390.rs index 4eb59a053b4..507483dec2e 100644 --- a/src/test/ui/error-codes/E0390.rs +++ b/src/test/ui/error-codes/E0390.rs @@ -4,5 +4,7 @@ struct Foo { impl *mut Foo {} //~ ERROR E0390 +impl fn(Foo) {} //~ ERROR E0390 + fn main() { } diff --git a/src/test/ui/error-codes/E0390.stderr b/src/test/ui/error-codes/E0390.stderr index e635d4ec196..0e5a9ca762b 100644 --- a/src/test/ui/error-codes/E0390.stderr +++ b/src/test/ui/error-codes/E0390.stderr @@ -6,6 +6,14 @@ LL | impl *mut Foo {} | = 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`. diff --git a/src/test/ui/issues/issue-59488.stderr b/src/test/ui/issues/issue-59488.stderr index 76a47c49bba..7ce3dedaa88 100644 --- a/src/test/ui/issues/issue-59488.stderr +++ b/src/test/ui/issues/issue-59488.stderr @@ -96,13 +96,13 @@ LL | assert_eq!(Foo::Bar, i); = 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)