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use super::FieldAttribute;
use virtue::generate::{FnSelfArg, Generator, StreamBuilder};
use virtue::parse::{EnumVariant, Fields};
use virtue::prelude::*;
const TUPLE_FIELD_PREFIX: &str = "field_";
pub struct DeriveEnum {
pub variants: Vec<EnumVariant>,
}
impl DeriveEnum {
fn iter_fields(&self) -> EnumVariantIterator {
EnumVariantIterator {
idx: 0,
last_val: None,
variants: &self.variants,
}
}
pub fn generate_encode(self, generator: &mut Generator) -> Result<()> {
generator
.impl_for("bincode::enc::Encode")?
.modify_generic_constraints(|generics, where_constraints| {
for g in generics.iter_generics() {
where_constraints.push_constraint(g, "bincode::enc::Encode").unwrap();
}
})
.generate_fn("encode")
.with_generic("E", ["bincode::enc::Encoder"])
.with_self_arg(FnSelfArg::RefSelf)
.with_arg("mut encoder", "E")
.with_return_type("core::result::Result<(), bincode::error::EncodeError>")
.body(|fn_body| {
fn_body.ident_str("match");
fn_body.ident_str("self");
fn_body.group(Delimiter::Brace, |match_body| {
for (variant_index, variant) in self.iter_fields() {
// Self::Variant
match_body.ident_str("Self");
match_body.puncts("::");
match_body.ident(variant.name.clone());
// if we have any fields, declare them here
// Self::Variant { a, b, c }
if let Some(delimiter) = variant.fields.delimiter() {
match_body.group(delimiter, |field_body| {
for (idx, field_name) in
variant.fields.names().into_iter().enumerate()
{
if idx != 0 {
field_body.punct(',');
}
field_body.push(
field_name.to_token_tree_with_prefix(TUPLE_FIELD_PREFIX),
);
}
Ok(())
})?;
}
// Arrow
// Self::Variant { a, b, c } =>
match_body.puncts("=>");
// Body of this variant
// Note that the fields are available as locals because of the match destructuring above
// {
// encoder.encode_u32(n)?;
// bincode::enc::Encode::encode(a, &mut encoder)?;
// bincode::enc::Encode::encode(b, &mut encoder)?;
// bincode::enc::Encode::encode(c, &mut encoder)?;
// }
match_body.group(Delimiter::Brace, |body| {
// variant index
body.push_parsed("<u32 as bincode::enc::Encode>::encode")?;
body.group(Delimiter::Parenthesis, |args| {
args.punct('&');
args.group(Delimiter::Parenthesis, |num| {
num.extend(variant_index);
Ok(())
})?;
args.punct(',');
args.push_parsed("&mut encoder")?;
Ok(())
})?;
body.punct('?');
body.punct(';');
// If we have any fields, encode them all one by one
for field_name in variant.fields.names() {
if field_name.has_attribute(FieldAttribute::WithSerde)? {
body.push_parsed(format!(
"bincode::enc::Encode::encode(&bincode::serde::Compat({}), &mut encoder)?;",
field_name.to_string_with_prefix(TUPLE_FIELD_PREFIX),
))?;
} else {
body.push_parsed(format!(
"bincode::enc::Encode::encode({}, &mut encoder)?;",
field_name.to_string_with_prefix(TUPLE_FIELD_PREFIX),
))
?;
}
}
Ok(())
})?;
match_body.punct(',');
}
Ok(())
})?;
fn_body.push_parsed("Ok(())")?;
Ok(())
})?;
Ok(())
}
/// Build the catch-all case for an int-to-enum decode implementation
fn invalid_variant_case(&self, enum_name: &str, result: &mut StreamBuilder) -> Result {
// we'll be generating:
// variant => Err(
// bincode::error::DecodeError::UnexpectedVariant {
// found: variant,
// type_name: <enum_name>
// allowed: ...,
// }
// )
//
// Where allowed is either:
// - bincode::error::AllowedEnumVariants::Range { min: 0, max: <max> }
// if we have no fixed value variants
// - bincode::error::AllowedEnumVariants::Allowed(&[<variant1>, <variant2>, ...])
// if we have fixed value variants
result.ident_str("variant");
result.puncts("=>");
result.ident_str("Err");
result.group(Delimiter::Parenthesis, |err_inner| {
err_inner.push_parsed("bincode::error::DecodeError::UnexpectedVariant")?;
err_inner.group(Delimiter::Brace, |variant_inner| {
variant_inner.ident_str("found");
variant_inner.punct(':');
variant_inner.ident_str("variant");
variant_inner.punct(',');
variant_inner.ident_str("type_name");
variant_inner.punct(':');
variant_inner.lit_str(enum_name);
variant_inner.punct(',');
variant_inner.ident_str("allowed");
variant_inner.punct(':');
if self.variants.iter().any(|i| i.has_fixed_value()) {
// we have fixed values, implement AllowedEnumVariants::Allowed
variant_inner.push_parsed("bincode::error::AllowedEnumVariants::Allowed")?;
variant_inner.group(Delimiter::Parenthesis, |allowed_inner| {
allowed_inner.punct('&');
allowed_inner.group(Delimiter::Bracket, |allowed_slice| {
for (idx, (ident, _)) in self.iter_fields().enumerate() {
if idx != 0 {
allowed_slice.punct(',');
}
allowed_slice.extend(ident);
}
Ok(())
})?;
Ok(())
})?;
} else {
// no fixed values, implement a range
variant_inner.push_parsed(format!(
"bincode::error::AllowedEnumVariants::Range {{ min: 0, max: {} }}",
self.variants.len() - 1
))?;
}
Ok(())
})?;
Ok(())
})?;
Ok(())
}
pub fn generate_decode(&self, generator: &mut Generator) -> Result<()> {
// Remember to keep this mostly in sync with generate_borrow_decode
let enum_name = generator.target_name().to_string();
generator
.impl_for("bincode::Decode")?
.modify_generic_constraints(|generics, where_constraints| {
for g in generics.iter_generics() {
where_constraints.push_constraint(g, "bincode::enc::Decode").unwrap();
}
})
.generate_fn("decode")
.with_generic("D", ["bincode::de::Decoder"])
.with_arg("mut decoder", "D")
.with_return_type("core::result::Result<Self, bincode::error::DecodeError>")
.body(|fn_builder| {
fn_builder
.push_parsed(
"let variant_index = <u32 as bincode::Decode>::decode(&mut decoder)?;",
)?;
fn_builder.push_parsed("match variant_index")?;
fn_builder.group(Delimiter::Brace, |variant_case| {
for (mut variant_index, variant) in self.iter_fields() {
// idx => Ok(..)
if variant_index.len() > 1 {
variant_case.push_parsed("x if x == ")?;
variant_case.extend(variant_index);
} else {
variant_case.push(variant_index.remove(0));
}
variant_case.puncts("=>");
variant_case.ident_str("Ok");
variant_case.group(Delimiter::Parenthesis, |variant_case_body| {
// Self::Variant { }
// Self::Variant { 0: ..., 1: ... 2: ... },
// Self::Variant { a: ..., b: ... c: ... },
variant_case_body.ident_str("Self");
variant_case_body.puncts("::");
variant_case_body.ident(variant.name.clone());
variant_case_body.group(Delimiter::Brace, |variant_body| {
let is_tuple = matches!(variant.fields, Fields::Tuple(_));
for (idx, field) in variant.fields.names().into_iter().enumerate() {
if is_tuple {
variant_body.lit_usize(idx);
} else {
variant_body.ident(field.unwrap_ident().clone());
}
variant_body.punct(':');
if field.has_attribute(FieldAttribute::WithSerde)? {
variant_body
.push_parsed("<bincode::serde::Compat<_> as bincode::Decode>::decode(&mut decoder)?.0,")?;
} else {
variant_body
.push_parsed("bincode::Decode::decode(&mut decoder)?,")?;
}
}
Ok(())
})?;
Ok(())
})?;
variant_case.punct(',');
}
// invalid idx
self.invalid_variant_case(&enum_name, variant_case)
})?;
Ok(())
})?;
Ok(())
}
pub fn generate_borrow_decode(self, generator: &mut Generator) -> Result<()> {
// Remember to keep this mostly in sync with generate_decode
let enum_name = generator.target_name().to_string();
generator.impl_for_with_lifetimes("bincode::de::BorrowDecode", &["__de"])?
.modify_generic_constraints(|generics, where_constraints| {
for g in generics.iter_generics() {
where_constraints.push_constraint(g, "bincode::enc::BorrowDecode").unwrap();
}
})
.generate_fn("borrow_decode")
.with_generic("D", ["bincode::de::BorrowDecoder<'__de>"])
.with_arg("mut decoder", "D")
.with_return_type("core::result::Result<Self, bincode::error::DecodeError>")
.body(|fn_builder| {
fn_builder
.push_parsed("let variant_index = <u32 as bincode::Decode>::decode(&mut decoder)?;")?;
fn_builder.push_parsed("match variant_index")?;
fn_builder.group(Delimiter::Brace, |variant_case| {
for (mut variant_index, variant) in self.iter_fields() {
// idx => Ok(..)
if variant_index.len() > 1 {
variant_case.push_parsed("x if x == ")?;
variant_case.extend(variant_index);
} else {
variant_case.push(variant_index.remove(0));
}
variant_case.puncts("=>");
variant_case.ident_str("Ok");
variant_case.group(Delimiter::Parenthesis, |variant_case_body| {
// Self::Variant { }
// Self::Variant { 0: ..., 1: ... 2: ... },
// Self::Variant { a: ..., b: ... c: ... },
variant_case_body.ident_str("Self");
variant_case_body.puncts("::");
variant_case_body.ident(variant.name.clone());
variant_case_body.group(Delimiter::Brace, |variant_body| {
let is_tuple = matches!(variant.fields, Fields::Tuple(_));
for (idx, field) in variant.fields.names().into_iter().enumerate() {
if is_tuple {
variant_body.lit_usize(idx);
} else {
variant_body.ident(field.unwrap_ident().clone());
}
variant_body.punct(':');
if field.has_attribute(FieldAttribute::WithSerde)? {
variant_body
.push_parsed("<bincode::serde::BorrowCompat<_> as bincode::BorrowDecode>::borrow_decode(&mut decoder)?.0,")?;
} else {
variant_body.push_parsed("bincode::de::BorrowDecode::borrow_decode(&mut decoder)?,")?;
}
}
Ok(())
})?;
Ok(())
})?;
variant_case.punct(',');
}
// invalid idx
self.invalid_variant_case(&enum_name, variant_case)
})?;
Ok(())
})?;
Ok(())
}
}
struct EnumVariantIterator<'a> {
variants: &'a [EnumVariant],
idx: usize,
last_val: Option<(Literal, u32)>,
}
impl<'a> Iterator for EnumVariantIterator<'a> {
type Item = (Vec<TokenTree>, &'a EnumVariant);
fn next(&mut self) -> Option<Self::Item> {
let idx = self.idx;
let variant = self.variants.get(self.idx)?;
self.idx += 1;
let tokens = if let Fields::Integer(lit) = &variant.fields {
let tree = TokenTree::Literal(lit.clone());
self.last_val = Some((lit.clone(), 0));
vec![tree]
} else if let Some((lit, add)) = self.last_val.as_mut() {
*add += 1;
vec![
TokenTree::Literal(lit.clone()),
TokenTree::Punct(Punct::new('+', Spacing::Alone)),
TokenTree::Literal(Literal::u32_suffixed(*add)),
]
} else {
vec![TokenTree::Literal(Literal::u32_suffixed(idx as u32))]
};
Some((tokens, variant))
}
}