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use super::{generate_fn::FnParent, FnBuilder, Generator, Parent, StreamBuilder};
use crate::{
parse::{GenericConstraints, Generics},
prelude::{Delimiter, Result},
};
#[must_use]
/// A helper struct for implementing functions for a given struct or enum.
pub struct Impl<'a, P: Parent> {
parent: &'a mut P,
name: String,
// pub(super) group: StreamBuilder,
custom_generic_constraints: Option<GenericConstraints>,
fns: Vec<(StreamBuilder, StreamBuilder)>,
}
impl<'a, P: Parent> Impl<'a, P> {
pub(super) fn with_parent_name(parent: &'a mut P) -> Self {
Self {
name: parent.name().to_string(),
parent,
custom_generic_constraints: None,
fns: Vec::new(),
}
}
pub(super) fn new(parent: &'a mut P, name: impl Into<String>) -> Self {
Self {
parent,
name: name.into(),
custom_generic_constraints: None,
fns: Vec::new(),
}
}
/// Add a function to the trait implementation.
///
/// `generator.impl().generate_fn("bar")` results in code like:
///
/// ```ignore
/// impl <struct or enum> {
/// fn bar() {}
/// }
/// ```
///
/// See [`FnBuilder`] for more options, as well as information on how to fill the function body.
pub fn generate_fn(&mut self, name: impl Into<String>) -> FnBuilder<Self> {
FnBuilder::new(self, name)
}
}
impl<'a> Impl<'a, Generator> {
/// Modify the generic constraints of a type.
/// This can be used to add additional type constraints to your implementation.
///
/// ```ignore
/// // Your derive:
/// #[derive(YourTrait)]
/// pub struct Foo<B> {
/// ...
/// }
///
/// // With this code:
/// generator
/// .r#impl()
/// .modify_generic_constraints(|generics, constraints| {
/// for g in generics.iter_generics() {
/// constraints.push_generic(g, "YourTrait");
/// }
/// })
///
/// // will generate:
/// impl<B> Foo<B>
/// where B: YourTrait // <-
/// {
/// }
/// ```
///
/// Note that this function is only implemented when you call `.r#impl` on [`Generator`].
pub fn modify_generic_constraints<CB>(&mut self, cb: CB) -> &mut Self
where
CB: FnOnce(&Generics, &mut GenericConstraints),
{
if let Some(generics) = self.parent.generics() {
let mut constraints = self
.parent
.generic_constraints()
.cloned()
.unwrap_or_default();
cb(generics, &mut constraints);
self.custom_generic_constraints = Some(constraints)
}
self
}
}
impl<'a, P: Parent> FnParent for Impl<'a, P> {
fn append(&mut self, fn_definition: StreamBuilder, fn_body: StreamBuilder) -> Result {
self.fns.push((fn_definition, fn_body));
Ok(())
}
}
impl<'a, P: Parent> Drop for Impl<'a, P> {
fn drop(&mut self) {
if std::thread::panicking() {
return;
}
let mut builder = StreamBuilder::new();
builder.ident_str("impl");
if let Some(generics) = self.parent.generics() {
builder.append(generics.impl_generics());
}
builder.push_parsed(&self.name).unwrap();
if let Some(generics) = self.parent.generics() {
builder.append(generics.type_generics());
}
if let Some(generic_constraints) = self.custom_generic_constraints.take() {
builder.append(generic_constraints.where_clause());
} else if let Some(generic_constraints) = self.parent.generic_constraints() {
builder.append(generic_constraints.where_clause());
}
builder
.group(Delimiter::Brace, |builder| {
for (fn_def, fn_body) in std::mem::take(&mut self.fns) {
builder.append(fn_def);
builder
.group(Delimiter::Brace, |body| {
*body = fn_body;
Ok(())
})
.unwrap();
}
Ok(())
})
.unwrap();
self.parent.append(builder);
}
}