Adding upstream version 124.0.1.upstream/124.0.1

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

1 files changed, 294 insertions, 0 deletions

diff --git a/third_party/rust/zerofrom-derive/src/lib.rs b/third_party/rust/zerofrom-derive/src/lib.rs
new file mode 100644
index 0000000000..c6a3839fb5
--- /dev/null
+++ b/third_party/rust/zerofrom-derive/src/lib.rs
@@ -0,0 +1,294 @@
+// 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 `ZeroFrom` from the `zerofrom` crate.
+
+// https://github.com/unicode-org/icu4x/blob/main/docs/process/boilerplate.md#library-annotations
+#![cfg_attr(
+    not(test),
+    deny(
+        clippy::indexing_slicing,
+        clippy::unwrap_used,
+        clippy::expect_used,
+        clippy::panic,
+        clippy::exhaustive_structs,
+        clippy::exhaustive_enums,
+        missing_debug_implementations,
+    )
+)]
+
+use core::mem;
+use proc_macro::TokenStream;
+use proc_macro2::{Span, TokenStream as TokenStream2};
+use quote::quote;
+use std::collections::{HashMap, HashSet};
+use syn::fold::{self, Fold};
+use syn::punctuated::Punctuated;
+use syn::spanned::Spanned;
+use syn::{
+    parse_macro_input, parse_quote, DeriveInput, Ident, Lifetime, MetaList, Token, Type, TypePath,
+    WherePredicate,
+};
+use synstructure::Structure;
+mod visitor;
+
+/// Custom derive for `zerofrom::ZeroFrom`,
+///
+/// This implements `ZeroFrom<Ty> for Ty` for types
+/// without a lifetime parameter, and `ZeroFrom<Ty<'data>> for Ty<'static>`
+/// for types with a lifetime parameter.
+///
+/// Apply the `#[zerofrom(clone)]` attribute to a field if it doesn't implement
+/// Copy or ZeroFrom; this data will be cloned when the struct is zero_from'ed.
+///
+/// Apply the `#[zerofrom(maybe_borrow(T, U, V))]` attribute to the struct to indicate
+/// that certain type parameters may themselves contain borrows (by default
+/// the derives assume that type parameters perform no borrows and can be copied or cloned).
+///
+/// In rust versions where [this issue](https://github.com/rust-lang/rust/issues/114393) is fixed,
+/// `#[zerofrom(may_borrow)]` can be applied directly to type parameters.
+#[proc_macro_derive(ZeroFrom, attributes(zerofrom))]
+pub fn zf_derive(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    TokenStream::from(zf_derive_impl(&input))
+}
+
+fn has_attr(attrs: &[syn::Attribute], name: &str) -> bool {
+    attrs.iter().any(|a| {
+        if let Ok(i) = a.parse_args::<Ident>() {
+            if i == name {
+                return true;
+            }
+        }
+        false
+    })
+}
+
+// Collects all idents from #[zerofrom(may_borrow(A, B, C, D))]
+// needed since #[zerofrom(may_borrow)] doesn't work yet
+// (https://github.com/rust-lang/rust/issues/114393)
+fn get_may_borrow_attr(attrs: &[syn::Attribute]) -> Result<HashSet<Ident>, Span> {
+    let mut params = HashSet::new();
+    for attr in attrs {
+        if let Ok(list) = attr.parse_args::<MetaList>() {
+            if list.path.is_ident("may_borrow") {
+                if let Ok(list) =
+                    list.parse_args_with(Punctuated::<Ident, Token![,]>::parse_terminated)
+                {
+                    params.extend(list)
+                } else {
+                    return Err(attr.span());
+                }
+            }
+        }
+    }
+    Ok(params)
+}
+
+fn zf_derive_impl(input: &DeriveInput) -> TokenStream2 {
+    let mut 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<_>>();
+    let lts = input.generics.lifetimes().count();
+    let name = &input.ident;
+    let structure = Structure::new(input);
+
+    let may_borrow_attrs = match get_may_borrow_attr(&input.attrs) {
+        Ok(mb) => mb,
+        Err(span) => {
+            return syn::Error::new(
+            span,
+            "#[zerofrom(may_borrow)] on the struct takes in a comma separated list of type parameters, like so: `#[zerofrom(may_borrow(A, B, C, D)]`",
+        ).to_compile_error();
+        }
+    };
+
+    // This contains every generic type introduced in this code.
+    // If the gneeric type is may_borrow, this additionally contains the identifier corresponding to
+    // a newly introduced mirror type parameter that we are borrowing from, similar to C in the original trait.
+    // For convenience, we are calling these "C types"
+    let generics_env: HashMap<Ident, Option<Ident>> = tybounds
+        .iter()
+        .map(|param| {
+            // First one doesn't work yet https://github.com/rust-lang/rust/issues/114393
+            let maybe_new_param = if has_attr(&param.attrs, "may_borrow")
+                || may_borrow_attrs.contains(&param.ident)
+            {
+                Some(Ident::new(
+                    &format!("{}ZFParamC", param.ident),
+                    param.ident.span(),
+                ))
+            } else {
+                None
+            };
+            (param.ident.clone(), maybe_new_param)
+        })
+        .collect();
+
+    // Do any of the generics potentially borrow?
+    let generics_may_borrow = generics_env.values().any(|x| x.is_some());
+
+    if lts == 0 && !generics_may_borrow {
+        let has_clone = structure
+            .variants()
+            .iter()
+            .flat_map(|variant| variant.bindings().iter())
+            .any(|binding| has_attr(&binding.ast().attrs, "clone"));
+        let (clone, clone_trait) = if has_clone {
+            (quote!(this.clone()), quote!(Clone))
+        } else {
+            (quote!(*this), quote!(Copy))
+        };
+        let bounds: Vec<WherePredicate> = typarams
+            .iter()
+            .map(|ty| parse_quote!(#ty: #clone_trait + 'static))
+            .collect();
+        quote! {
+            impl<'zf, #(#tybounds),*> zerofrom::ZeroFrom<'zf, #name<#(#typarams),*>> for #name<#(#typarams),*> where #(#bounds),* {
+                fn zero_from(this: &'zf Self) -> Self {
+                    #clone
+                }
+            }
+        }
+    } else {
+        if lts > 1 {
+            return syn::Error::new(
+                input.generics.span(),
+                "derive(ZeroFrom) cannot have multiple lifetime parameters",
+            )
+            .to_compile_error();
+        }
+
+        let mut zf_bounds: Vec<WherePredicate> = vec![];
+        let body = structure.each_variant(|vi| {
+            vi.construct(|f, i| {
+                let binding = format!("__binding_{i}");
+                let field = Ident::new(&binding, Span::call_site());
+
+                if has_attr(&f.attrs, "clone") {
+                    quote! {
+                        #field.clone()
+                    }
+                } else {
+                    // the field type
+                    let fty = replace_lifetime(&f.ty, custom_lt("'zf"));
+                    // the corresponding lifetimey type we are borrowing from (effectively, the C type)
+                    let lifetime_ty =
+                        replace_lifetime_and_type(&f.ty, custom_lt("'zf_inner"), &generics_env);
+
+                    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
+                        // ZeroFrom on its own. However, if there are type parameters, there may be complex preconditions
+                        // to `FieldTy: ZeroFrom` that need to be satisfied. We get them to be satisfied by requiring
+                        // `FieldTy<'zf>: ZeroFrom<'zf, FieldTy<'zf_inner>>`
+                        if has_lt {
+                            zf_bounds
+                                .push(parse_quote!(#fty: zerofrom::ZeroFrom<'zf, #lifetime_ty>));
+                        } else {
+                            zf_bounds.push(parse_quote!(#fty: zerofrom::ZeroFrom<'zf, #fty>));
+                        }
+                    }
+                    if has_ty || has_lt {
+                        // By doing this we essentially require ZF to be implemented
+                        // on all fields
+                        quote! {
+                            <#fty as zerofrom::ZeroFrom<'zf, #lifetime_ty>>::zero_from(#field)
+                        }
+                    } else {
+                        // No lifetimes, so we can just copy
+                        quote! { *#field }
+                    }
+                }
+            })
+        });
+        // Due to the possibility of generics_may_borrow, we might reach here with no lifetimes on self,
+        // don't accidentally feed them to self later
+        let (maybe_zf_lifetime, maybe_zf_inner_lifetime) = if lts == 0 {
+            (quote!(), quote!())
+        } else {
+            (quote!('zf,), quote!('zf_inner,))
+        };
+
+        // Array of C types. Only different if generics are allowed to borrow
+        let mut typarams_c = typarams.clone();
+
+        if generics_may_borrow {
+            for typaram_c in &mut typarams_c {
+                if let Some(Some(replacement)) = generics_env.get(typaram_c) {
+                    // we use mem::replace here so we can be really clear about the C vs the T type
+                    let typaram_t = mem::replace(typaram_c, replacement.clone());
+                    zf_bounds
+                        .push(parse_quote!(#typaram_c: zerofrom::ZeroFrom<'zf_inner, #typaram_t>));
+                    tybounds.push(parse_quote!(#typaram_c));
+                }
+            }
+        }
+
+        quote! {
+            impl<'zf, 'zf_inner, #(#tybounds),*> zerofrom::ZeroFrom<'zf, #name<#maybe_zf_inner_lifetime #(#typarams_c),*>> for #name<#maybe_zf_lifetime #(#typarams),*>
+                where
+                #(#zf_bounds,)* {
+                fn zero_from(this: &'zf #name<#maybe_zf_inner_lifetime #(#typarams_c),*>) -> Self {
+                    match *this { #body }
+                }
+            }
+        }
+    }
+}
+
+fn custom_lt(s: &str) -> Lifetime {
+    Lifetime::new(s, Span::call_site())
+}
+
+/// Replace all lifetimes in a type with a specified one
+fn replace_lifetime(x: &Type, lt: Lifetime) -> Type {
+    struct ReplaceLifetime(Lifetime);
+
+    impl Fold for ReplaceLifetime {
+        fn fold_lifetime(&mut self, _: Lifetime) -> Lifetime {
+            self.0.clone()
+        }
+    }
+    ReplaceLifetime(lt).fold_type(x.clone())
+}
+
+/// Replace all lifetimes in a type with a specified one, AND replace all types that have a corresponding C type
+/// with the C type
+fn replace_lifetime_and_type(
+    x: &Type,
+    lt: Lifetime,
+    generics_env: &HashMap<Ident, Option<Ident>>,
+) -> Type {
+    struct ReplaceLifetimeAndTy<'a>(Lifetime, &'a HashMap<Ident, Option<Ident>>);
+
+    impl Fold for ReplaceLifetimeAndTy<'_> {
+        fn fold_lifetime(&mut self, _: Lifetime) -> Lifetime {
+            self.0.clone()
+        }
+        fn fold_type_path(&mut self, i: TypePath) -> TypePath {
+            if i.qself.is_none() {
+                if let Some(ident) = i.path.get_ident() {
+                    if let Some(Some(replacement)) = self.1.get(ident) {
+                        return parse_quote!(#replacement);
+                    }
+                }
+            }
+            fold::fold_type_path(self, i)
+        }
+    }
+    ReplaceLifetimeAndTy(lt, generics_env).fold_type(x.clone())
+}