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Diffstat (limited to 'vendor/ref-cast-impl/src/lib.rs')
| -rw-r--r-- | vendor/ref-cast-impl/src/lib.rs | 540 |
1 files changed, 0 insertions, 540 deletions
diff --git a/vendor/ref-cast-impl/src/lib.rs b/vendor/ref-cast-impl/src/lib.rs deleted file mode 100644 index 96da08a0..00000000 --- a/vendor/ref-cast-impl/src/lib.rs +++ /dev/null @@ -1,540 +0,0 @@ -#![allow( - clippy::blocks_in_conditions, - clippy::needless_pass_by_value, - clippy::if_not_else -)] - -extern crate proc_macro; - -use proc_macro::TokenStream; -use proc_macro2::{Ident, Span, TokenStream as TokenStream2, TokenTree}; -use quote::{quote, quote_spanned}; -use syn::parse::{Nothing, ParseStream, Parser}; -use syn::punctuated::Punctuated; -use syn::{ - parenthesized, parse_macro_input, token, Abi, Attribute, Data, DeriveInput, Error, Expr, Field, - Generics, Path, Result, Token, Type, Visibility, -}; - -/// Derive the `RefCast` trait. -/// -/// See the [crate-level documentation](./index.html) for usage examples! -/// -/// # Attributes -/// -/// Use the `#[trivial]` attribute to mark any zero-sized fields that are *not* -/// the one that references are going to be converted from. -/// -/// ``` -/// use ref_cast::RefCast; -/// use std::marker::PhantomData; -/// -/// #[derive(RefCast)] -/// #[repr(transparent)] -/// pub struct Generic<T, U> { -/// raw: Vec<U>, -/// #[trivial] -/// aux: Variance<T, U>, -/// } -/// -/// type Variance<T, U> = PhantomData<fn(T) -> U>; -/// ``` -/// -/// Fields with a type named `PhantomData` or `PhantomPinned` are automatically -/// recognized and do not need to be marked with this attribute. -/// -/// ``` -/// use ref_cast::RefCast; -/// use std::marker::{PhantomData, PhantomPinned}; -/// -/// #[derive(RefCast)] // generates a conversion from &[u8] to &Bytes<'_> -/// #[repr(transparent)] -/// pub struct Bytes<'arena> { -/// lifetime: PhantomData<&'arena ()>, -/// pin: PhantomPinned, -/// bytes: [u8], -/// } -/// ``` -#[proc_macro_derive(RefCast, attributes(trivial))] -pub fn derive_ref_cast(input: TokenStream) -> TokenStream { - let input = parse_macro_input!(input as DeriveInput); - expand_ref_cast(&input) - .unwrap_or_else(Error::into_compile_error) - .into() -} - -/// Derive that makes the `ref_cast_custom` attribute able to generate -/// freestanding reference casting functions for a type. -/// -/// Please refer to the documentation of -/// [`#[ref_cast_custom]`][macro@ref_cast_custom] where these two macros are -/// documented together. -#[proc_macro_derive(RefCastCustom, attributes(trivial))] -pub fn derive_ref_cast_custom(input: TokenStream) -> TokenStream { - let input = parse_macro_input!(input as DeriveInput); - expand_ref_cast_custom(&input) - .unwrap_or_else(Error::into_compile_error) - .into() -} - -/// Create a function for a RefCast-style reference cast. Call site gets control -/// of the visibility, function name, argument name, `const`ness, unsafety, and -/// documentation. -/// -/// The `derive(RefCast)` macro produces a trait impl, which means the function -/// names are predefined, and public if your type is public, and not callable in -/// `const` (at least today on stable Rust). As an alternative to that, -/// `derive(RefCastCustom)` exposes greater flexibility so that instead of a -/// trait impl, the casting functions can be made associated functions or free -/// functions, can be named what you want, documented, `const` or `unsafe` if -/// you want, and have your exact choice of visibility. -/// -/// ```rust -/// use ref_cast::{ref_cast_custom, RefCastCustom}; -/// -/// #[derive(RefCastCustom)] // does not generate any public API by itself -/// #[repr(transparent)] -/// pub struct Frame([u8]); -/// -/// impl Frame { -/// #[ref_cast_custom] // requires derive(RefCastCustom) on the return type -/// pub(crate) const fn new(bytes: &[u8]) -> &Self; -/// -/// #[ref_cast_custom] -/// pub(crate) fn new_mut(bytes: &mut [u8]) -> &mut Self; -/// } -/// -/// // example use of the const fn -/// const FRAME: &Frame = Frame::new(b"..."); -/// ``` -/// -/// The above shows associated functions, but you might alternatively want to -/// generate free functions: -/// -/// ```rust -/// # use ref_cast::{ref_cast_custom, RefCastCustom}; -/// # -/// # #[derive(RefCastCustom)] -/// # #[repr(transparent)] -/// # pub struct Frame([u8]); -/// # -/// impl Frame { -/// pub fn new<T: AsRef<[u8]>>(bytes: &T) -> &Self { -/// #[ref_cast_custom] -/// fn ref_cast(bytes: &[u8]) -> &Frame; -/// -/// ref_cast(bytes.as_ref()) -/// } -/// } -/// ``` -#[proc_macro_attribute] -pub fn ref_cast_custom(args: TokenStream, input: TokenStream) -> TokenStream { - let input = TokenStream2::from(input); - let expanded = match (|input: ParseStream| { - let attrs = input.call(Attribute::parse_outer)?; - let vis: Visibility = input.parse()?; - let constness: Option<Token![const]> = input.parse()?; - let asyncness: Option<Token![async]> = input.parse()?; - let unsafety: Option<Token![unsafe]> = input.parse()?; - let abi: Option<Abi> = input.parse()?; - let fn_token: Token![fn] = input.parse()?; - let ident: Ident = input.parse()?; - let mut generics: Generics = input.parse()?; - - let content; - let paren_token = parenthesized!(content in input); - let arg: Ident = content.parse()?; - let colon_token: Token![:] = content.parse()?; - let from_type: Type = content.parse()?; - let _trailing_comma: Option<Token![,]> = content.parse()?; - if !content.is_empty() { - let rest: TokenStream2 = content.parse()?; - return Err(Error::new_spanned( - rest, - "ref_cast_custom function is required to have a single argument", - )); - } - - let arrow_token: Token![->] = input.parse()?; - let to_type: Type = input.parse()?; - generics.where_clause = input.parse()?; - let semi_token: Token![;] = input.parse()?; - - let _: Nothing = syn::parse::<Nothing>(args)?; - - Ok(Function { - attrs, - vis, - constness, - asyncness, - unsafety, - abi, - fn_token, - ident, - generics, - paren_token, - arg, - colon_token, - from_type, - arrow_token, - to_type, - semi_token, - }) - }) - .parse2(input.clone()) - { - Ok(function) => expand_function_body(function), - Err(parse_error) => { - let compile_error = parse_error.to_compile_error(); - quote!(#compile_error #input) - } - }; - TokenStream::from(expanded) -} - -struct Function { - attrs: Vec<Attribute>, - vis: Visibility, - constness: Option<Token![const]>, - asyncness: Option<Token![async]>, - unsafety: Option<Token![unsafe]>, - abi: Option<Abi>, - fn_token: Token![fn], - ident: Ident, - generics: Generics, - paren_token: token::Paren, - arg: Ident, - colon_token: Token![:], - from_type: Type, - arrow_token: Token![->], - to_type: Type, - semi_token: Token![;], -} - -fn expand_ref_cast(input: &DeriveInput) -> Result<TokenStream2> { - check_repr(input)?; - - let name = &input.ident; - let name_str = name.to_string(); - let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl(); - - let fields = fields(input)?; - let from = only_field_ty(fields)?; - let trivial = trivial_fields(fields)?; - - let assert_trivial_fields = if !trivial.is_empty() { - Some(quote! { - if false { - #( - ::ref_cast::__private::assert_trivial::<#trivial>(); - )* - } - }) - } else { - None - }; - - Ok(quote! { - impl #impl_generics ::ref_cast::RefCast for #name #ty_generics #where_clause { - type From = #from; - - #[inline] - fn ref_cast(_from: &Self::From) -> &Self { - #assert_trivial_fields - #[cfg(debug_assertions)] - { - #[allow(unused_imports)] - use ::ref_cast::__private::LayoutUnsized; - ::ref_cast::__private::assert_layout::<Self, Self::From>( - #name_str, - ::ref_cast::__private::Layout::<Self>::SIZE, - ::ref_cast::__private::Layout::<Self::From>::SIZE, - ::ref_cast::__private::Layout::<Self>::ALIGN, - ::ref_cast::__private::Layout::<Self::From>::ALIGN, - ); - } - unsafe { - &*(_from as *const Self::From as *const Self) - } - } - - #[inline] - fn ref_cast_mut(_from: &mut Self::From) -> &mut Self { - #[cfg(debug_assertions)] - { - #[allow(unused_imports)] - use ::ref_cast::__private::LayoutUnsized; - ::ref_cast::__private::assert_layout::<Self, Self::From>( - #name_str, - ::ref_cast::__private::Layout::<Self>::SIZE, - ::ref_cast::__private::Layout::<Self::From>::SIZE, - ::ref_cast::__private::Layout::<Self>::ALIGN, - ::ref_cast::__private::Layout::<Self::From>::ALIGN, - ); - } - unsafe { - &mut *(_from as *mut Self::From as *mut Self) - } - } - } - }) -} - -fn expand_ref_cast_custom(input: &DeriveInput) -> Result<TokenStream2> { - check_repr(input)?; - - let vis = &input.vis; - let name = &input.ident; - let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl(); - - let fields = fields(input)?; - let from = only_field_ty(fields)?; - let trivial = trivial_fields(fields)?; - - let assert_trivial_fields = if !trivial.is_empty() { - Some(quote! { - fn __static_assert() { - if false { - #( - ::ref_cast::__private::assert_trivial::<#trivial>(); - )* - } - } - }) - } else { - None - }; - - Ok(quote! { - const _: () = { - #[non_exhaustive] - #vis struct RefCastCurrentCrate {} - - unsafe impl #impl_generics ::ref_cast::__private::RefCastCustom<#from> for #name #ty_generics #where_clause { - type CurrentCrate = RefCastCurrentCrate; - #assert_trivial_fields - } - }; - }) -} - -fn expand_function_body(function: Function) -> TokenStream2 { - let Function { - attrs, - vis, - constness, - asyncness, - unsafety, - abi, - fn_token, - ident, - generics, - paren_token, - arg, - colon_token, - from_type, - arrow_token, - to_type, - semi_token, - } = function; - - let args = quote_spanned! {paren_token.span=> - (#arg #colon_token #from_type) - }; - - let allow_unused_unsafe = if unsafety.is_some() { - Some(quote!(#[allow(unused_unsafe)])) - } else { - None - }; - - let mut inline_attr = Some(quote!(#[inline])); - for attr in &attrs { - if attr.path().is_ident("inline") { - inline_attr = None; - break; - } - } - - // Apply a macro-generated span to the "unsafe" token for the unsafe block. - // This is instead of reusing the caller's function signature's #unsafety - // across both the generated function signature and generated unsafe block, - // and instead of using `semi_token.span` like for the rest of the generated - // code below, both of which would cause `forbid(unsafe_code)` located in - // the caller to reject the expanded code. - let macro_generated_unsafe = quote!(unsafe); - - quote_spanned! {semi_token.span=> - #(#attrs)* - #inline_attr - #vis #constness #asyncness #unsafety #abi - #fn_token #ident #generics #args #arrow_token #to_type { - // check lifetime - let _ = || { - ::ref_cast::__private::ref_cast_custom::<#from_type, #to_type>(#arg); - }; - - // check same crate - let _ = ::ref_cast::__private::CurrentCrate::<#from_type, #to_type> {}; - - #allow_unused_unsafe // in case they are building with deny(unsafe_op_in_unsafe_fn) - #[allow(clippy::transmute_ptr_to_ptr)] - #macro_generated_unsafe { - ::ref_cast::__private::transmute::<#from_type, #to_type>(#arg) - } - } - } -} - -fn check_repr(input: &DeriveInput) -> Result<()> { - let mut has_repr = false; - let mut errors = None; - let mut push_error = |error| match &mut errors { - Some(errors) => Error::combine(errors, error), - None => errors = Some(error), - }; - - for attr in &input.attrs { - if attr.path().is_ident("repr") { - if let Err(error) = attr.parse_args_with(|input: ParseStream| { - while !input.is_empty() { - let path = input.call(Path::parse_mod_style)?; - if path.is_ident("transparent") || path.is_ident("C") { - has_repr = true; - } else if path.is_ident("packed") { - // ignore - } else { - let meta_item_span = if input.peek(token::Paren) { - let group: TokenTree = input.parse()?; - quote!(#path #group) - } else if input.peek(Token![=]) { - let eq_token: Token![=] = input.parse()?; - let value: Expr = input.parse()?; - quote!(#path #eq_token #value) - } else { - quote!(#path) - }; - let msg = if path.is_ident("align") { - "aligned repr on struct that implements RefCast is not supported" - } else { - "unrecognized repr on struct that implements RefCast" - }; - push_error(Error::new_spanned(meta_item_span, msg)); - } - if !input.is_empty() { - input.parse::<Token![,]>()?; - } - } - Ok(()) - }) { - push_error(error); - } - } - } - - if !has_repr { - let mut requires_repr = Error::new( - Span::call_site(), - "RefCast trait requires #[repr(transparent)]", - ); - if let Some(errors) = errors { - requires_repr.combine(errors); - } - errors = Some(requires_repr); - } - - match errors { - None => Ok(()), - Some(errors) => Err(errors), - } -} - -type Fields = Punctuated<Field, Token![,]>; - -fn fields(input: &DeriveInput) -> Result<&Fields> { - use syn::Fields; - - match &input.data { - Data::Struct(data) => match &data.fields { - Fields::Named(fields) => Ok(&fields.named), - Fields::Unnamed(fields) => Ok(&fields.unnamed), - Fields::Unit => Err(Error::new( - Span::call_site(), - "RefCast does not support unit structs", - )), - }, - Data::Enum(_) => Err(Error::new( - Span::call_site(), - "RefCast does not support enums", - )), - Data::Union(_) => Err(Error::new( - Span::call_site(), - "RefCast does not support unions", - )), - } -} - -fn only_field_ty(fields: &Fields) -> Result<&Type> { - let is_trivial = decide_trivial(fields)?; - let mut only_field = None; - - for field in fields { - if !is_trivial(field)? { - if only_field.take().is_some() { - break; - } - only_field = Some(&field.ty); - } - } - - only_field.ok_or_else(|| { - Error::new( - Span::call_site(), - "RefCast requires a struct with a single field", - ) - }) -} - -fn trivial_fields(fields: &Fields) -> Result<Vec<&Type>> { - let is_trivial = decide_trivial(fields)?; - let mut trivial = Vec::new(); - - for field in fields { - if is_trivial(field)? { - trivial.push(&field.ty); - } - } - - Ok(trivial) -} - -fn decide_trivial(fields: &Fields) -> Result<fn(&Field) -> Result<bool>> { - for field in fields { - if is_explicit_trivial(field)? { - return Ok(is_explicit_trivial); - } - } - Ok(is_implicit_trivial) -} - -#[allow(clippy::unnecessary_wraps)] // match signature of is_explicit_trivial -fn is_implicit_trivial(field: &Field) -> Result<bool> { - match &field.ty { - Type::Tuple(ty) => Ok(ty.elems.is_empty()), - Type::Path(ty) => { - let ident = &ty.path.segments.last().unwrap().ident; - Ok(ident == "PhantomData" || ident == "PhantomPinned") - } - _ => Ok(false), - } -} - -fn is_explicit_trivial(field: &Field) -> Result<bool> { - for attr in &field.attrs { - if attr.path().is_ident("trivial") { - attr.meta.require_path_only()?; - return Ok(true); - } - } - Ok(false) -} |