Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

2 files changed, 386 insertions, 0 deletions

diff --git a/third_party/rust/yoke-derive/src/lib.rs b/third_party/rust/yoke-derive/src/lib.rs
new file mode 100644
index 0000000000..dd1ea90b8d
--- /dev/null
+++ b/third_party/rust/yoke-derive/src/lib.rs
@@ -0,0 +1,273 @@
+// This file is part of ICU4X. For terms of use, please see the file
+// called LICENSE at the top level of the ICU4X source tree
+// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
+
+//! Custom derives for `Yokeable` from the `yoke` crate.
+
+use proc_macro::TokenStream;
+use proc_macro2::{Span, TokenStream as TokenStream2};
+use quote::quote;
+use syn::spanned::Spanned;
+use syn::{parse_macro_input, parse_quote, DeriveInput, Ident, Lifetime, Type, WherePredicate};
+use synstructure::Structure;
+
+mod visitor;
+
+/// Custom derive for `yoke::Yokeable`,
+///
+/// If your struct contains `zerovec::ZeroMap`, then the compiler will not
+/// be able to guarantee the lifetime covariance due to the generic types on
+/// the `ZeroMap` itself. You must add the following attribute in order for
+/// the custom derive to work with `ZeroMap`.
+///
+/// ```rust,ignore
+/// #[derive(Yokeable)]
+/// #[yoke(prove_covariance_manually)]
+/// ```
+///
+/// Beyond this case, if the derive fails to compile due to lifetime issues, it
+/// means that the lifetime is not covariant and `Yokeable` is not safe to implement.
+#[proc_macro_derive(Yokeable, attributes(yoke))]
+pub fn yokeable_derive(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    TokenStream::from(yokeable_derive_impl(&input))
+}
+
+fn yokeable_derive_impl(input: &DeriveInput) -> TokenStream2 {
+    let tybounds = input
+        .generics
+        .type_params()
+        .map(|ty| {
+            // Strip out param defaults, we don't need them in the impl
+            let mut ty = ty.clone();
+            ty.eq_token = None;
+            ty.default = None;
+            ty
+        })
+        .collect::<Vec<_>>();
+    let typarams = tybounds
+        .iter()
+        .map(|ty| ty.ident.clone())
+        .collect::<Vec<_>>();
+    // We require all type parameters be 'static, otherwise
+    // the Yokeable impl becomes really unweildy to generate safely
+    let static_bounds: Vec<WherePredicate> = typarams
+        .iter()
+        .map(|ty| parse_quote!(#ty: 'static))
+        .collect();
+    let lts = input.generics.lifetimes().count();
+    if lts == 0 {
+        let name = &input.ident;
+        quote! {
+            // This is safe because there are no lifetime parameters.
+            unsafe impl<'a, #(#tybounds),*> yoke::Yokeable<'a> for #name<#(#typarams),*> where #(#static_bounds),* {
+                type Output = Self;
+                #[inline]
+                fn transform(&self) -> &Self::Output {
+                    self
+                }
+                #[inline]
+                fn transform_owned(self) -> Self::Output {
+                    self
+                }
+                #[inline]
+                unsafe fn make(this: Self::Output) -> Self {
+                    this
+                }
+                #[inline]
+                fn transform_mut<F>(&'a mut self, f: F)
+                where
+                    F: 'static + for<'b> FnOnce(&'b mut Self::Output) {
+                    f(self)
+                }
+            }
+        }
+    } else {
+        if lts != 1 {
+            return syn::Error::new(
+                input.generics.span(),
+                "derive(Yokeable) cannot have multiple lifetime parameters",
+            )
+            .to_compile_error();
+        }
+        let name = &input.ident;
+        let manual_covariance = input.attrs.iter().any(|a| {
+            if let Ok(i) = a.parse_args::<Ident>() {
+                if i == "prove_covariance_manually" {
+                    return true;
+                }
+            }
+            false
+        });
+        if manual_covariance {
+            let mut structure = Structure::new(input);
+            let generics_env = typarams.iter().cloned().collect();
+            let static_bounds: Vec<WherePredicate> = typarams
+                .iter()
+                .map(|ty| parse_quote!(#ty: 'static))
+                .collect();
+            let mut yoke_bounds: Vec<WherePredicate> = vec![];
+            structure.bind_with(|_| synstructure::BindStyle::Move);
+            let owned_body = structure.each_variant(|vi| {
+                vi.construct(|f, i| {
+                    let binding = format!("__binding_{i}");
+                    let field = Ident::new(&binding, Span::call_site());
+                    let fty_static = replace_lifetime(&f.ty, static_lt());
+
+                    let (has_ty, has_lt) = visitor::check_type_for_parameters(&f.ty, &generics_env);
+                    if has_ty {
+                        // For types without type parameters, the compiler can figure out that the field implements
+                        // Yokeable on its own. However, if there are type parameters, there may be complex preconditions
+                        // to `FieldTy: Yokeable` that need to be satisfied. We get them to be satisfied by requiring
+                        // `FieldTy<'static>: Yokeable<FieldTy<'a>>`
+                        if has_lt {
+                            let fty_a = replace_lifetime(&f.ty, custom_lt("'a"));
+                            yoke_bounds.push(
+                                parse_quote!(#fty_static: yoke::Yokeable<'a, Output = #fty_a>),
+                            );
+                        } else {
+                            yoke_bounds.push(
+                                parse_quote!(#fty_static: yoke::Yokeable<'a, Output = #fty_static>),
+                            );
+                        }
+                    }
+                    if has_ty || has_lt {
+                        // By calling transform_owned on all fields, we manually prove
+                        // that the lifetimes are covariant, since this requirement
+                        // must already be true for the type that implements transform_owned().
+                        quote! {
+                            <#fty_static as yoke::Yokeable<'a>>::transform_owned(#field)
+                        }
+                    } else {
+                        // No nested lifetimes, so nothing to be done
+                        quote! { #field }
+                    }
+                })
+            });
+            let borrowed_body = structure.each(|binding| {
+                let f = binding.ast();
+                let field = &binding.binding;
+
+                let (has_ty, has_lt) = visitor::check_type_for_parameters(&f.ty, &generics_env);
+
+                if has_ty || has_lt {
+                    let fty_static = replace_lifetime(&f.ty, static_lt());
+                    let fty_a = replace_lifetime(&f.ty, custom_lt("'a"));
+                    // We also must assert that each individual field can `transform()` correctly
+                    //
+                    // Even though transform_owned() does such an assertion already, CoerceUnsized
+                    // can cause type transformations that allow it to succeed where this would fail.
+                    // We need to check both.
+                    //
+                    // https://github.com/unicode-org/icu4x/issues/2928
+                    quote! {
+                        let _: &#fty_a = &<#fty_static as yoke::Yokeable<'a>>::transform(#field);
+                    }
+                } else {
+                    // No nested lifetimes, so nothing to be done
+                    quote! {}
+                }
+            });
+            return quote! {
+                unsafe impl<'a, #(#tybounds),*> yoke::Yokeable<'a> for #name<'static, #(#typarams),*>
+                    where #(#static_bounds,)*
+                    #(#yoke_bounds,)* {
+                    type Output = #name<'a, #(#typarams),*>;
+                    #[inline]
+                    fn transform(&'a self) -> &'a Self::Output {
+                        // These are just type asserts, we don't need them for anything
+                        if false {
+                            match self {
+                                #borrowed_body
+                            }
+                        }
+                        unsafe {
+                            // safety: we have asserted covariance in
+                            // transform_owned
+                            ::core::mem::transmute(self)
+                        }
+                    }
+                    #[inline]
+                    fn transform_owned(self) -> Self::Output {
+                        match self { #owned_body }
+                    }
+                    #[inline]
+                    unsafe fn make(this: Self::Output) -> Self {
+                        use core::{mem, ptr};
+                        // unfortunately Rust doesn't think `mem::transmute` is possible since it's not sure the sizes
+                        // are the same
+                        debug_assert!(mem::size_of::<Self::Output>() == mem::size_of::<Self>());
+                        let ptr: *const Self = (&this as *const Self::Output).cast();
+                        #[allow(forgetting_copy_types, clippy::forget_copy, clippy::forget_non_drop)] // This is a noop if the struct is copy, which Clippy doesn't like
+                        mem::forget(this);
+                        ptr::read(ptr)
+                    }
+                    #[inline]
+                    fn transform_mut<F>(&'a mut self, f: F)
+                    where
+                        F: 'static + for<'b> FnOnce(&'b mut Self::Output) {
+                        unsafe { f(core::mem::transmute::<&'a mut Self, &'a mut Self::Output>(self)) }
+                    }
+                }
+            };
+        }
+        quote! {
+            // This is safe because as long as `transform()` compiles,
+            // we can be sure that `'a` is a covariant lifetime on `Self`
+            //
+            // This will not work for structs involving ZeroMap since
+            // the compiler does not know that ZeroMap is covariant.
+            //
+            // This custom derive can be improved to handle this case when
+            // necessary
+            unsafe impl<'a, #(#tybounds),*> yoke::Yokeable<'a> for #name<'static, #(#typarams),*> where #(#static_bounds),* {
+                type Output = #name<'a, #(#typarams),*>;
+                #[inline]
+                fn transform(&'a self) -> &'a Self::Output {
+                    self
+                }
+                #[inline]
+                fn transform_owned(self) -> Self::Output {
+                    self
+                }
+                #[inline]
+                unsafe fn make(this: Self::Output) -> Self {
+                    use core::{mem, ptr};
+                    // unfortunately Rust doesn't think `mem::transmute` is possible since it's not sure the sizes
+                    // are the same
+                    debug_assert!(mem::size_of::<Self::Output>() == mem::size_of::<Self>());
+                    let ptr: *const Self = (&this as *const Self::Output).cast();
+                    #[allow(forgetting_copy_types, clippy::forget_copy, clippy::forget_non_drop)] // This is a noop if the struct is copy, which Clippy doesn't like
+                    mem::forget(this);
+                    ptr::read(ptr)
+                }
+                #[inline]
+                fn transform_mut<F>(&'a mut self, f: F)
+                where
+                    F: 'static + for<'b> FnOnce(&'b mut Self::Output) {
+                    unsafe { f(core::mem::transmute::<&'a mut Self, &'a mut Self::Output>(self)) }
+                }
+            }
+        }
+    }
+}
+
+fn static_lt() -> Lifetime {
+    Lifetime::new("'static", Span::call_site())
+}
+
+fn custom_lt(s: &str) -> Lifetime {
+    Lifetime::new(s, Span::call_site())
+}
+
+fn replace_lifetime(x: &Type, lt: Lifetime) -> Type {
+    use syn::fold::Fold;
+    struct ReplaceLifetime(Lifetime);
+
+    impl Fold for ReplaceLifetime {
+        fn fold_lifetime(&mut self, _: Lifetime) -> Lifetime {
+            self.0.clone()
+        }
+    }
+    ReplaceLifetime(lt).fold_type(x.clone())
+}
diff --git a/third_party/rust/yoke-derive/src/visitor.rs b/third_party/rust/yoke-derive/src/visitor.rs
new file mode 100644
index 0000000000..daca1da13f
--- /dev/null
+++ b/third_party/rust/yoke-derive/src/visitor.rs
@@ -0,0 +1,113 @@
+// This file is part of ICU4X. For terms of use, please see the file
+// called LICENSE at the top level of the ICU4X source tree
+// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
+
+//! Visitor for determining whether a type has type and non-static lifetime parameters
+
+use std::collections::HashSet;
+use syn::visit::{visit_lifetime, visit_type, visit_type_path, Visit};
+use syn::{Ident, Lifetime, Type, TypePath};
+
+struct TypeVisitor<'a> {
+    /// The type parameters in scope
+    typarams: &'a HashSet<Ident>,
+    /// Whether we found a type parameter
+    found_typarams: bool,
+    /// Whether we found a non-'static lifetime parameter
+    found_lifetimes: bool,
+}
+
+impl<'a, 'ast> Visit<'ast> for TypeVisitor<'a> {
+    fn visit_lifetime(&mut self, lt: &'ast Lifetime) {
+        if lt.ident != "static" {
+            self.found_lifetimes = true;
+        }
+        visit_lifetime(self, lt)
+    }
+    fn visit_type_path(&mut self, ty: &'ast TypePath) {
+        // We only need to check ty.path.get_ident() and not ty.qself or any
+        // generics in ty.path because the visitor will eventually visit those
+        // types on its own
+        if let Some(ident) = ty.path.get_ident() {
+            if self.typarams.contains(ident) {
+                self.found_typarams = true;
+            }
+        }
+
+        visit_type_path(self, ty)
+    }
+}
+
+/// Checks if a type has type or lifetime parameters, given the local context of
+/// named type parameters. Returns (has_type_params, has_lifetime_params)
+pub fn check_type_for_parameters(ty: &Type, typarams: &HashSet<Ident>) -> (bool, bool) {
+    let mut visit = TypeVisitor {
+        typarams,
+        found_typarams: false,
+        found_lifetimes: false,
+    };
+    visit_type(&mut visit, ty);
+
+    (visit.found_typarams, visit.found_lifetimes)
+}
+
+#[cfg(test)]
+mod tests {
+    use proc_macro2::Span;
+    use std::collections::HashSet;
+    use syn::{parse_quote, Ident};
+
+    use super::check_type_for_parameters;
+    fn make_typarams(params: &[&str]) -> HashSet<Ident> {
+        params
+            .iter()
+            .map(|x| Ident::new(x, Span::call_site()))
+            .collect()
+    }
+
+    #[test]
+    fn test_simple_type() {
+        let environment = make_typarams(&["T", "U", "V"]);
+
+        let ty = parse_quote!(Foo<'a, T>);
+        let check = check_type_for_parameters(&ty, &environment);
+        assert_eq!(check, (true, true));
+
+        let ty = parse_quote!(Foo<T>);
+        let check = check_type_for_parameters(&ty, &environment);
+        assert_eq!(check, (true, false));
+
+        let ty = parse_quote!(Foo<'static, T>);
+        let check = check_type_for_parameters(&ty, &environment);
+        assert_eq!(check, (true, false));
+
+        let ty = parse_quote!(Foo<'a>);
+        let check = check_type_for_parameters(&ty, &environment);
+        assert_eq!(check, (false, true));
+
+        let ty = parse_quote!(Foo<'a, Bar<U>, Baz<(V, u8)>>);
+        let check = check_type_for_parameters(&ty, &environment);
+        assert_eq!(check, (true, true));
+
+        let ty = parse_quote!(Foo<'a, W>);
+        let check = check_type_for_parameters(&ty, &environment);
+        assert_eq!(check, (false, true));
+    }
+
+    #[test]
+    fn test_assoc_types() {
+        let environment = make_typarams(&["T"]);
+
+        let ty = parse_quote!(<Foo as SomeTrait<'a, T>>::Output);
+        let check = check_type_for_parameters(&ty, &environment);
+        assert_eq!(check, (true, true));
+
+        let ty = parse_quote!(<Foo as SomeTrait<'static, T>>::Output);
+        let check = check_type_for_parameters(&ty, &environment);
+        assert_eq!(check, (true, false));
+
+        let ty = parse_quote!(<T as SomeTrait<'static, Foo>>::Output);
+        let check = check_type_for_parameters(&ty, &environment);
+        assert_eq!(check, (true, false));
+    }
+}