Adding upstream version 124.0.1.upstream/124.0.1

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

1 files changed, 828 insertions, 0 deletions

diff --git a/third_party/rust/prost-derive/src/field/scalar.rs b/third_party/rust/prost-derive/src/field/scalar.rs
new file mode 100644
index 0000000000..5a3dfb2ec3
--- /dev/null
+++ b/third_party/rust/prost-derive/src/field/scalar.rs
@@ -0,0 +1,828 @@
+use std::convert::TryFrom;
+use std::fmt;
+
+use anyhow::{anyhow, bail, Error};
+use proc_macro2::{Span, TokenStream};
+use quote::{quote, ToTokens, TokenStreamExt};
+use syn::{parse_str, Expr, ExprLit, Ident, Index, Lit, LitByteStr, Meta, MetaNameValue, Path};
+
+use crate::field::{bool_attr, set_option, tag_attr, Label};
+
+/// A scalar protobuf field.
+#[derive(Clone)]
+pub struct Field {
+    pub ty: Ty,
+    pub kind: Kind,
+    pub tag: u32,
+}
+
+impl Field {
+    pub fn new(attrs: &[Meta], inferred_tag: Option<u32>) -> Result<Option<Field>, Error> {
+        let mut ty = None;
+        let mut label = None;
+        let mut packed = None;
+        let mut default = None;
+        let mut tag = None;
+
+        let mut unknown_attrs = Vec::new();
+
+        for attr in attrs {
+            if let Some(t) = Ty::from_attr(attr)? {
+                set_option(&mut ty, t, "duplicate type attributes")?;
+            } else if let Some(p) = bool_attr("packed", attr)? {
+                set_option(&mut packed, p, "duplicate packed attributes")?;
+            } else if let Some(t) = tag_attr(attr)? {
+                set_option(&mut tag, t, "duplicate tag attributes")?;
+            } else if let Some(l) = Label::from_attr(attr) {
+                set_option(&mut label, l, "duplicate label attributes")?;
+            } else if let Some(d) = DefaultValue::from_attr(attr)? {
+                set_option(&mut default, d, "duplicate default attributes")?;
+            } else {
+                unknown_attrs.push(attr);
+            }
+        }
+
+        let ty = match ty {
+            Some(ty) => ty,
+            None => return Ok(None),
+        };
+
+        match unknown_attrs.len() {
+            0 => (),
+            1 => bail!("unknown attribute: {:?}", unknown_attrs[0]),
+            _ => bail!("unknown attributes: {:?}", unknown_attrs),
+        }
+
+        let tag = match tag.or(inferred_tag) {
+            Some(tag) => tag,
+            None => bail!("missing tag attribute"),
+        };
+
+        let has_default = default.is_some();
+        let default = default.map_or_else(
+            || Ok(DefaultValue::new(&ty)),
+            |lit| DefaultValue::from_lit(&ty, lit),
+        )?;
+
+        let kind = match (label, packed, has_default) {
+            (None, Some(true), _)
+            | (Some(Label::Optional), Some(true), _)
+            | (Some(Label::Required), Some(true), _) => {
+                bail!("packed attribute may only be applied to repeated fields");
+            }
+            (Some(Label::Repeated), Some(true), _) if !ty.is_numeric() => {
+                bail!("packed attribute may only be applied to numeric types");
+            }
+            (Some(Label::Repeated), _, true) => {
+                bail!("repeated fields may not have a default value");
+            }
+
+            (None, _, _) => Kind::Plain(default),
+            (Some(Label::Optional), _, _) => Kind::Optional(default),
+            (Some(Label::Required), _, _) => Kind::Required(default),
+            (Some(Label::Repeated), packed, false) if packed.unwrap_or_else(|| ty.is_numeric()) => {
+                Kind::Packed
+            }
+            (Some(Label::Repeated), _, false) => Kind::Repeated,
+        };
+
+        Ok(Some(Field { ty, kind, tag }))
+    }
+
+    pub fn new_oneof(attrs: &[Meta]) -> Result<Option<Field>, Error> {
+        if let Some(mut field) = Field::new(attrs, None)? {
+            match field.kind {
+                Kind::Plain(default) => {
+                    field.kind = Kind::Required(default);
+                    Ok(Some(field))
+                }
+                Kind::Optional(..) => bail!("invalid optional attribute on oneof field"),
+                Kind::Required(..) => bail!("invalid required attribute on oneof field"),
+                Kind::Packed | Kind::Repeated => bail!("invalid repeated attribute on oneof field"),
+            }
+        } else {
+            Ok(None)
+        }
+    }
+
+    pub fn encode(&self, ident: TokenStream) -> TokenStream {
+        let module = self.ty.module();
+        let encode_fn = match self.kind {
+            Kind::Plain(..) | Kind::Optional(..) | Kind::Required(..) => quote!(encode),
+            Kind::Repeated => quote!(encode_repeated),
+            Kind::Packed => quote!(encode_packed),
+        };
+        let encode_fn = quote!(::prost::encoding::#module::#encode_fn);
+        let tag = self.tag;
+
+        match self.kind {
+            Kind::Plain(ref default) => {
+                let default = default.typed();
+                quote! {
+                    if #ident != #default {
+                        #encode_fn(#tag, &#ident, buf);
+                    }
+                }
+            }
+            Kind::Optional(..) => quote! {
+                if let ::core::option::Option::Some(ref value) = #ident {
+                    #encode_fn(#tag, value, buf);
+                }
+            },
+            Kind::Required(..) | Kind::Repeated | Kind::Packed => quote! {
+                #encode_fn(#tag, &#ident, buf);
+            },
+        }
+    }
+
+    /// Returns an expression which evaluates to the result of merging a decoded
+    /// scalar value into the field.
+    pub fn merge(&self, ident: TokenStream) -> TokenStream {
+        let module = self.ty.module();
+        let merge_fn = match self.kind {
+            Kind::Plain(..) | Kind::Optional(..) | Kind::Required(..) => quote!(merge),
+            Kind::Repeated | Kind::Packed => quote!(merge_repeated),
+        };
+        let merge_fn = quote!(::prost::encoding::#module::#merge_fn);
+
+        match self.kind {
+            Kind::Plain(..) | Kind::Required(..) | Kind::Repeated | Kind::Packed => quote! {
+                #merge_fn(wire_type, #ident, buf, ctx)
+            },
+            Kind::Optional(..) => quote! {
+                #merge_fn(wire_type,
+                          #ident.get_or_insert_with(::core::default::Default::default),
+                          buf,
+                          ctx)
+            },
+        }
+    }
+
+    /// Returns an expression which evaluates to the encoded length of the field.
+    pub fn encoded_len(&self, ident: TokenStream) -> TokenStream {
+        let module = self.ty.module();
+        let encoded_len_fn = match self.kind {
+            Kind::Plain(..) | Kind::Optional(..) | Kind::Required(..) => quote!(encoded_len),
+            Kind::Repeated => quote!(encoded_len_repeated),
+            Kind::Packed => quote!(encoded_len_packed),
+        };
+        let encoded_len_fn = quote!(::prost::encoding::#module::#encoded_len_fn);
+        let tag = self.tag;
+
+        match self.kind {
+            Kind::Plain(ref default) => {
+                let default = default.typed();
+                quote! {
+                    if #ident != #default {
+                        #encoded_len_fn(#tag, &#ident)
+                    } else {
+                        0
+                    }
+                }
+            }
+            Kind::Optional(..) => quote! {
+                #ident.as_ref().map_or(0, |value| #encoded_len_fn(#tag, value))
+            },
+            Kind::Required(..) | Kind::Repeated | Kind::Packed => quote! {
+                #encoded_len_fn(#tag, &#ident)
+            },
+        }
+    }
+
+    pub fn clear(&self, ident: TokenStream) -> TokenStream {
+        match self.kind {
+            Kind::Plain(ref default) | Kind::Required(ref default) => {
+                let default = default.typed();
+                match self.ty {
+                    Ty::String | Ty::Bytes(..) => quote!(#ident.clear()),
+                    _ => quote!(#ident = #default),
+                }
+            }
+            Kind::Optional(_) => quote!(#ident = ::core::option::Option::None),
+            Kind::Repeated | Kind::Packed => quote!(#ident.clear()),
+        }
+    }
+
+    /// Returns an expression which evaluates to the default value of the field.
+    pub fn default(&self) -> TokenStream {
+        match self.kind {
+            Kind::Plain(ref value) | Kind::Required(ref value) => value.owned(),
+            Kind::Optional(_) => quote!(::core::option::Option::None),
+            Kind::Repeated | Kind::Packed => quote!(::prost::alloc::vec::Vec::new()),
+        }
+    }
+
+    /// An inner debug wrapper, around the base type.
+    fn debug_inner(&self, wrap_name: TokenStream) -> TokenStream {
+        if let Ty::Enumeration(ref ty) = self.ty {
+            quote! {
+                struct #wrap_name<'a>(&'a i32);
+                impl<'a> ::core::fmt::Debug for #wrap_name<'a> {
+                    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                        let res: ::core::result::Result<#ty, _> = ::core::convert::TryFrom::try_from(*self.0);
+                        match res {
+                            Err(_) => ::core::fmt::Debug::fmt(&self.0, f),
+                            Ok(en) => ::core::fmt::Debug::fmt(&en, f),
+                        }
+                    }
+                }
+            }
+        } else {
+            quote! {
+                #[allow(non_snake_case)]
+                fn #wrap_name<T>(v: T) -> T { v }
+            }
+        }
+    }
+
+    /// Returns a fragment for formatting the field `ident` in `Debug`.
+    pub fn debug(&self, wrapper_name: TokenStream) -> TokenStream {
+        let wrapper = self.debug_inner(quote!(Inner));
+        let inner_ty = self.ty.rust_type();
+        match self.kind {
+            Kind::Plain(_) | Kind::Required(_) => self.debug_inner(wrapper_name),
+            Kind::Optional(_) => quote! {
+                struct #wrapper_name<'a>(&'a ::core::option::Option<#inner_ty>);
+                impl<'a> ::core::fmt::Debug for #wrapper_name<'a> {
+                    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                        #wrapper
+                        ::core::fmt::Debug::fmt(&self.0.as_ref().map(Inner), f)
+                    }
+                }
+            },
+            Kind::Repeated | Kind::Packed => {
+                quote! {
+                    struct #wrapper_name<'a>(&'a ::prost::alloc::vec::Vec<#inner_ty>);
+                    impl<'a> ::core::fmt::Debug for #wrapper_name<'a> {
+                        fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                            let mut vec_builder = f.debug_list();
+                            for v in self.0 {
+                                #wrapper
+                                vec_builder.entry(&Inner(v));
+                            }
+                            vec_builder.finish()
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    /// Returns methods to embed in the message.
+    pub fn methods(&self, ident: &TokenStream) -> Option<TokenStream> {
+        let mut ident_str = ident.to_string();
+        if ident_str.starts_with("r#") {
+            ident_str = ident_str[2..].to_owned();
+        }
+
+        // Prepend `get_` for getter methods of tuple structs.
+        let get = match syn::parse_str::<Index>(&ident_str) {
+            Ok(index) => {
+                let get = Ident::new(&format!("get_{}", index.index), Span::call_site());
+                quote!(#get)
+            }
+            Err(_) => quote!(#ident),
+        };
+
+        if let Ty::Enumeration(ref ty) = self.ty {
+            let set = Ident::new(&format!("set_{}", ident_str), Span::call_site());
+            let set_doc = format!("Sets `{}` to the provided enum value.", ident_str);
+            Some(match self.kind {
+                Kind::Plain(ref default) | Kind::Required(ref default) => {
+                    let get_doc = format!(
+                        "Returns the enum value of `{}`, \
+                         or the default if the field is set to an invalid enum value.",
+                        ident_str,
+                    );
+                    quote! {
+                        #[doc=#get_doc]
+                        pub fn #get(&self) -> #ty {
+                            ::core::convert::TryFrom::try_from(self.#ident).unwrap_or(#default)
+                        }
+
+                        #[doc=#set_doc]
+                        pub fn #set(&mut self, value: #ty) {
+                            self.#ident = value as i32;
+                        }
+                    }
+                }
+                Kind::Optional(ref default) => {
+                    let get_doc = format!(
+                        "Returns the enum value of `{}`, \
+                         or the default if the field is unset or set to an invalid enum value.",
+                        ident_str,
+                    );
+                    quote! {
+                        #[doc=#get_doc]
+                        pub fn #get(&self) -> #ty {
+                            self.#ident.and_then(|x| {
+                                let result: ::core::result::Result<#ty, _> = ::core::convert::TryFrom::try_from(x);
+                                result.ok()
+                            }).unwrap_or(#default)
+                        }
+
+                        #[doc=#set_doc]
+                        pub fn #set(&mut self, value: #ty) {
+                            self.#ident = ::core::option::Option::Some(value as i32);
+                        }
+                    }
+                }
+                Kind::Repeated | Kind::Packed => {
+                    let iter_doc = format!(
+                        "Returns an iterator which yields the valid enum values contained in `{}`.",
+                        ident_str,
+                    );
+                    let push = Ident::new(&format!("push_{}", ident_str), Span::call_site());
+                    let push_doc = format!("Appends the provided enum value to `{}`.", ident_str);
+                    quote! {
+                        #[doc=#iter_doc]
+                        pub fn #get(&self) -> ::core::iter::FilterMap<
+                            ::core::iter::Cloned<::core::slice::Iter<i32>>,
+                            fn(i32) -> ::core::option::Option<#ty>,
+                        > {
+                            self.#ident.iter().cloned().filter_map(|x| {
+                                let result: ::core::result::Result<#ty, _> = ::core::convert::TryFrom::try_from(x);
+                                result.ok()
+                            })
+                        }
+                        #[doc=#push_doc]
+                        pub fn #push(&mut self, value: #ty) {
+                            self.#ident.push(value as i32);
+                        }
+                    }
+                }
+            })
+        } else if let Kind::Optional(ref default) = self.kind {
+            let ty = self.ty.rust_ref_type();
+
+            let match_some = if self.ty.is_numeric() {
+                quote!(::core::option::Option::Some(val) => val,)
+            } else {
+                quote!(::core::option::Option::Some(ref val) => &val[..],)
+            };
+
+            let get_doc = format!(
+                "Returns the value of `{0}`, or the default value if `{0}` is unset.",
+                ident_str,
+            );
+
+            Some(quote! {
+                #[doc=#get_doc]
+                pub fn #get(&self) -> #ty {
+                    match self.#ident {
+                        #match_some
+                        ::core::option::Option::None => #default,
+                    }
+                }
+            })
+        } else {
+            None
+        }
+    }
+}
+
+/// A scalar protobuf field type.
+#[derive(Clone, PartialEq, Eq)]
+pub enum Ty {
+    Double,
+    Float,
+    Int32,
+    Int64,
+    Uint32,
+    Uint64,
+    Sint32,
+    Sint64,
+    Fixed32,
+    Fixed64,
+    Sfixed32,
+    Sfixed64,
+    Bool,
+    String,
+    Bytes(BytesTy),
+    Enumeration(Path),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum BytesTy {
+    Vec,
+    Bytes,
+}
+
+impl BytesTy {
+    fn try_from_str(s: &str) -> Result<Self, Error> {
+        match s {
+            "vec" => Ok(BytesTy::Vec),
+            "bytes" => Ok(BytesTy::Bytes),
+            _ => bail!("Invalid bytes type: {}", s),
+        }
+    }
+
+    fn rust_type(&self) -> TokenStream {
+        match self {
+            BytesTy::Vec => quote! { ::prost::alloc::vec::Vec<u8> },
+            BytesTy::Bytes => quote! { ::prost::bytes::Bytes },
+        }
+    }
+}
+
+impl Ty {
+    pub fn from_attr(attr: &Meta) -> Result<Option<Ty>, Error> {
+        let ty = match *attr {
+            Meta::Path(ref name) if name.is_ident("float") => Ty::Float,
+            Meta::Path(ref name) if name.is_ident("double") => Ty::Double,
+            Meta::Path(ref name) if name.is_ident("int32") => Ty::Int32,
+            Meta::Path(ref name) if name.is_ident("int64") => Ty::Int64,
+            Meta::Path(ref name) if name.is_ident("uint32") => Ty::Uint32,
+            Meta::Path(ref name) if name.is_ident("uint64") => Ty::Uint64,
+            Meta::Path(ref name) if name.is_ident("sint32") => Ty::Sint32,
+            Meta::Path(ref name) if name.is_ident("sint64") => Ty::Sint64,
+            Meta::Path(ref name) if name.is_ident("fixed32") => Ty::Fixed32,
+            Meta::Path(ref name) if name.is_ident("fixed64") => Ty::Fixed64,
+            Meta::Path(ref name) if name.is_ident("sfixed32") => Ty::Sfixed32,
+            Meta::Path(ref name) if name.is_ident("sfixed64") => Ty::Sfixed64,
+            Meta::Path(ref name) if name.is_ident("bool") => Ty::Bool,
+            Meta::Path(ref name) if name.is_ident("string") => Ty::String,
+            Meta::Path(ref name) if name.is_ident("bytes") => Ty::Bytes(BytesTy::Vec),
+            Meta::NameValue(MetaNameValue {
+                ref path,
+                value:
+                    Expr::Lit(ExprLit {
+                        lit: Lit::Str(ref l),
+                        ..
+                    }),
+                ..
+            }) if path.is_ident("bytes") => Ty::Bytes(BytesTy::try_from_str(&l.value())?),
+            Meta::NameValue(MetaNameValue {
+                ref path,
+                value:
+                    Expr::Lit(ExprLit {
+                        lit: Lit::Str(ref l),
+                        ..
+                    }),
+                ..
+            }) if path.is_ident("enumeration") => Ty::Enumeration(parse_str::<Path>(&l.value())?),
+            Meta::List(ref meta_list) if meta_list.path.is_ident("enumeration") => {
+                Ty::Enumeration(meta_list.parse_args::<Path>()?)
+            }
+            _ => return Ok(None),
+        };
+        Ok(Some(ty))
+    }
+
+    pub fn from_str(s: &str) -> Result<Ty, Error> {
+        let enumeration_len = "enumeration".len();
+        let error = Err(anyhow!("invalid type: {}", s));
+        let ty = match s.trim() {
+            "float" => Ty::Float,
+            "double" => Ty::Double,
+            "int32" => Ty::Int32,
+            "int64" => Ty::Int64,
+            "uint32" => Ty::Uint32,
+            "uint64" => Ty::Uint64,
+            "sint32" => Ty::Sint32,
+            "sint64" => Ty::Sint64,
+            "fixed32" => Ty::Fixed32,
+            "fixed64" => Ty::Fixed64,
+            "sfixed32" => Ty::Sfixed32,
+            "sfixed64" => Ty::Sfixed64,
+            "bool" => Ty::Bool,
+            "string" => Ty::String,
+            "bytes" => Ty::Bytes(BytesTy::Vec),
+            s if s.len() > enumeration_len && &s[..enumeration_len] == "enumeration" => {
+                let s = &s[enumeration_len..].trim();
+                match s.chars().next() {
+                    Some('<') | Some('(') => (),
+                    _ => return error,
+                }
+                match s.chars().next_back() {
+                    Some('>') | Some(')') => (),
+                    _ => return error,
+                }
+
+                Ty::Enumeration(parse_str::<Path>(s[1..s.len() - 1].trim())?)
+            }
+            _ => return error,
+        };
+        Ok(ty)
+    }
+
+    /// Returns the type as it appears in protobuf field declarations.
+    pub fn as_str(&self) -> &'static str {
+        match *self {
+            Ty::Double => "double",
+            Ty::Float => "float",
+            Ty::Int32 => "int32",
+            Ty::Int64 => "int64",
+            Ty::Uint32 => "uint32",
+            Ty::Uint64 => "uint64",
+            Ty::Sint32 => "sint32",
+            Ty::Sint64 => "sint64",
+            Ty::Fixed32 => "fixed32",
+            Ty::Fixed64 => "fixed64",
+            Ty::Sfixed32 => "sfixed32",
+            Ty::Sfixed64 => "sfixed64",
+            Ty::Bool => "bool",
+            Ty::String => "string",
+            Ty::Bytes(..) => "bytes",
+            Ty::Enumeration(..) => "enum",
+        }
+    }
+
+    // TODO: rename to 'owned_type'.
+    pub fn rust_type(&self) -> TokenStream {
+        match self {
+            Ty::String => quote!(::prost::alloc::string::String),
+            Ty::Bytes(ty) => ty.rust_type(),
+            _ => self.rust_ref_type(),
+        }
+    }
+
+    // TODO: rename to 'ref_type'
+    pub fn rust_ref_type(&self) -> TokenStream {
+        match *self {
+            Ty::Double => quote!(f64),
+            Ty::Float => quote!(f32),
+            Ty::Int32 => quote!(i32),
+            Ty::Int64 => quote!(i64),
+            Ty::Uint32 => quote!(u32),
+            Ty::Uint64 => quote!(u64),
+            Ty::Sint32 => quote!(i32),
+            Ty::Sint64 => quote!(i64),
+            Ty::Fixed32 => quote!(u32),
+            Ty::Fixed64 => quote!(u64),
+            Ty::Sfixed32 => quote!(i32),
+            Ty::Sfixed64 => quote!(i64),
+            Ty::Bool => quote!(bool),
+            Ty::String => quote!(&str),
+            Ty::Bytes(..) => quote!(&[u8]),
+            Ty::Enumeration(..) => quote!(i32),
+        }
+    }
+
+    pub fn module(&self) -> Ident {
+        match *self {
+            Ty::Enumeration(..) => Ident::new("int32", Span::call_site()),
+            _ => Ident::new(self.as_str(), Span::call_site()),
+        }
+    }
+
+    /// Returns false if the scalar type is length delimited (i.e., `string` or `bytes`).
+    pub fn is_numeric(&self) -> bool {
+        !matches!(self, Ty::String | Ty::Bytes(..))
+    }
+}
+
+impl fmt::Debug for Ty {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+impl fmt::Display for Ty {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+/// Scalar Protobuf field types.
+#[derive(Clone)]
+pub enum Kind {
+    /// A plain proto3 scalar field.
+    Plain(DefaultValue),
+    /// An optional scalar field.
+    Optional(DefaultValue),
+    /// A required proto2 scalar field.
+    Required(DefaultValue),
+    /// A repeated scalar field.
+    Repeated,
+    /// A packed repeated scalar field.
+    Packed,
+}
+
+/// Scalar Protobuf field default value.
+#[derive(Clone, Debug)]
+pub enum DefaultValue {
+    F64(f64),
+    F32(f32),
+    I32(i32),
+    I64(i64),
+    U32(u32),
+    U64(u64),
+    Bool(bool),
+    String(String),
+    Bytes(Vec<u8>),
+    Enumeration(TokenStream),
+    Path(Path),
+}
+
+impl DefaultValue {
+    pub fn from_attr(attr: &Meta) -> Result<Option<Lit>, Error> {
+        if !attr.path().is_ident("default") {
+            Ok(None)
+        } else if let Meta::NameValue(MetaNameValue {
+            value: Expr::Lit(ExprLit { ref lit, .. }),
+            ..
+        }) = *attr
+        {
+            Ok(Some(lit.clone()))
+        } else {
+            bail!("invalid default value attribute: {:?}", attr)
+        }
+    }
+
+    pub fn from_lit(ty: &Ty, lit: Lit) -> Result<DefaultValue, Error> {
+        let is_i32 = *ty == Ty::Int32 || *ty == Ty::Sint32 || *ty == Ty::Sfixed32;
+        let is_i64 = *ty == Ty::Int64 || *ty == Ty::Sint64 || *ty == Ty::Sfixed64;
+
+        let is_u32 = *ty == Ty::Uint32 || *ty == Ty::Fixed32;
+        let is_u64 = *ty == Ty::Uint64 || *ty == Ty::Fixed64;
+
+        let empty_or_is = |expected, actual: &str| expected == actual || actual.is_empty();
+
+        let default = match lit {
+            Lit::Int(ref lit) if is_i32 && empty_or_is("i32", lit.suffix()) => {
+                DefaultValue::I32(lit.base10_parse()?)
+            }
+            Lit::Int(ref lit) if is_i64 && empty_or_is("i64", lit.suffix()) => {
+                DefaultValue::I64(lit.base10_parse()?)
+            }
+            Lit::Int(ref lit) if is_u32 && empty_or_is("u32", lit.suffix()) => {
+                DefaultValue::U32(lit.base10_parse()?)
+            }
+            Lit::Int(ref lit) if is_u64 && empty_or_is("u64", lit.suffix()) => {
+                DefaultValue::U64(lit.base10_parse()?)
+            }
+
+            Lit::Float(ref lit) if *ty == Ty::Float && empty_or_is("f32", lit.suffix()) => {
+                DefaultValue::F32(lit.base10_parse()?)
+            }
+            Lit::Int(ref lit) if *ty == Ty::Float => DefaultValue::F32(lit.base10_parse()?),
+
+            Lit::Float(ref lit) if *ty == Ty::Double && empty_or_is("f64", lit.suffix()) => {
+                DefaultValue::F64(lit.base10_parse()?)
+            }
+            Lit::Int(ref lit) if *ty == Ty::Double => DefaultValue::F64(lit.base10_parse()?),
+
+            Lit::Bool(ref lit) if *ty == Ty::Bool => DefaultValue::Bool(lit.value),
+            Lit::Str(ref lit) if *ty == Ty::String => DefaultValue::String(lit.value()),
+            Lit::ByteStr(ref lit)
+                if *ty == Ty::Bytes(BytesTy::Bytes) || *ty == Ty::Bytes(BytesTy::Vec) =>
+            {
+                DefaultValue::Bytes(lit.value())
+            }
+
+            Lit::Str(ref lit) => {
+                let value = lit.value();
+                let value = value.trim();
+
+                if let Ty::Enumeration(ref path) = *ty {
+                    let variant = Ident::new(value, Span::call_site());
+                    return Ok(DefaultValue::Enumeration(quote!(#path::#variant)));
+                }
+
+                // Parse special floating point values.
+                if *ty == Ty::Float {
+                    match value {
+                        "inf" => {
+                            return Ok(DefaultValue::Path(parse_str::<Path>(
+                                "::core::f32::INFINITY",
+                            )?));
+                        }
+                        "-inf" => {
+                            return Ok(DefaultValue::Path(parse_str::<Path>(
+                                "::core::f32::NEG_INFINITY",
+                            )?));
+                        }
+                        "nan" => {
+                            return Ok(DefaultValue::Path(parse_str::<Path>("::core::f32::NAN")?));
+                        }
+                        _ => (),
+                    }
+                }
+                if *ty == Ty::Double {
+                    match value {
+                        "inf" => {
+                            return Ok(DefaultValue::Path(parse_str::<Path>(
+                                "::core::f64::INFINITY",
+                            )?));
+                        }
+                        "-inf" => {
+                            return Ok(DefaultValue::Path(parse_str::<Path>(
+                                "::core::f64::NEG_INFINITY",
+                            )?));
+                        }
+                        "nan" => {
+                            return Ok(DefaultValue::Path(parse_str::<Path>("::core::f64::NAN")?));
+                        }
+                        _ => (),
+                    }
+                }
+
+                // Rust doesn't have a negative literals, so they have to be parsed specially.
+                if let Some(Ok(lit)) = value.strip_prefix('-').map(syn::parse_str::<Lit>) {
+                    match lit {
+                        Lit::Int(ref lit) if is_i32 && empty_or_is("i32", lit.suffix()) => {
+                            // Initially parse into an i64, so that i32::MIN does not overflow.
+                            let value: i64 = -lit.base10_parse()?;
+                            return Ok(i32::try_from(value).map(DefaultValue::I32)?);
+                        }
+                        Lit::Int(ref lit) if is_i64 && empty_or_is("i64", lit.suffix()) => {
+                            // Initially parse into an i128, so that i64::MIN does not overflow.
+                            let value: i128 = -lit.base10_parse()?;
+                            return Ok(i64::try_from(value).map(DefaultValue::I64)?);
+                        }
+                        Lit::Float(ref lit)
+                            if *ty == Ty::Float && empty_or_is("f32", lit.suffix()) =>
+                        {
+                            return Ok(DefaultValue::F32(-lit.base10_parse()?));
+                        }
+                        Lit::Float(ref lit)
+                            if *ty == Ty::Double && empty_or_is("f64", lit.suffix()) =>
+                        {
+                            return Ok(DefaultValue::F64(-lit.base10_parse()?));
+                        }
+                        Lit::Int(ref lit) if *ty == Ty::Float && lit.suffix().is_empty() => {
+                            return Ok(DefaultValue::F32(-lit.base10_parse()?));
+                        }
+                        Lit::Int(ref lit) if *ty == Ty::Double && lit.suffix().is_empty() => {
+                            return Ok(DefaultValue::F64(-lit.base10_parse()?));
+                        }
+                        _ => (),
+                    }
+                }
+                match syn::parse_str::<Lit>(value) {
+                    Ok(Lit::Str(_)) => (),
+                    Ok(lit) => return DefaultValue::from_lit(ty, lit),
+                    _ => (),
+                }
+                bail!("invalid default value: {}", quote!(#value));
+            }
+            _ => bail!("invalid default value: {}", quote!(#lit)),
+        };
+
+        Ok(default)
+    }
+
+    pub fn new(ty: &Ty) -> DefaultValue {
+        match *ty {
+            Ty::Float => DefaultValue::F32(0.0),
+            Ty::Double => DefaultValue::F64(0.0),
+            Ty::Int32 | Ty::Sint32 | Ty::Sfixed32 => DefaultValue::I32(0),
+            Ty::Int64 | Ty::Sint64 | Ty::Sfixed64 => DefaultValue::I64(0),
+            Ty::Uint32 | Ty::Fixed32 => DefaultValue::U32(0),
+            Ty::Uint64 | Ty::Fixed64 => DefaultValue::U64(0),
+
+            Ty::Bool => DefaultValue::Bool(false),
+            Ty::String => DefaultValue::String(String::new()),
+            Ty::Bytes(..) => DefaultValue::Bytes(Vec::new()),
+            Ty::Enumeration(ref path) => DefaultValue::Enumeration(quote!(#path::default())),
+        }
+    }
+
+    pub fn owned(&self) -> TokenStream {
+        match *self {
+            DefaultValue::String(ref value) if value.is_empty() => {
+                quote!(::prost::alloc::string::String::new())
+            }
+            DefaultValue::String(ref value) => quote!(#value.into()),
+            DefaultValue::Bytes(ref value) if value.is_empty() => {
+                quote!(::core::default::Default::default())
+            }
+            DefaultValue::Bytes(ref value) => {
+                let lit = LitByteStr::new(value, Span::call_site());
+                quote!(#lit.as_ref().into())
+            }
+
+            ref other => other.typed(),
+        }
+    }
+
+    pub fn typed(&self) -> TokenStream {
+        if let DefaultValue::Enumeration(_) = *self {
+            quote!(#self as i32)
+        } else {
+            quote!(#self)
+        }
+    }
+}
+
+impl ToTokens for DefaultValue {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        match *self {
+            DefaultValue::F64(value) => value.to_tokens(tokens),
+            DefaultValue::F32(value) => value.to_tokens(tokens),
+            DefaultValue::I32(value) => value.to_tokens(tokens),
+            DefaultValue::I64(value) => value.to_tokens(tokens),
+            DefaultValue::U32(value) => value.to_tokens(tokens),
+            DefaultValue::U64(value) => value.to_tokens(tokens),
+            DefaultValue::Bool(value) => value.to_tokens(tokens),
+            DefaultValue::String(ref value) => value.to_tokens(tokens),
+            DefaultValue::Bytes(ref value) => {
+                let byte_str = LitByteStr::new(value, Span::call_site());
+                tokens.append_all(quote!(#byte_str as &[u8]));
+            }
+            DefaultValue::Enumeration(ref value) => value.to_tokens(tokens),
+            DefaultValue::Path(ref value) => value.to_tokens(tokens),
+        }
+    }
+}