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//! Methods for types and navigating lifetimes within methods.
use std::collections::BTreeSet;
use std::ops::Deref;
use super::{Attrs, Docs, Ident, IdentBuf, OutType, SelfType, Type, TypeContext};
use super::lifetimes::{Lifetime, LifetimeEnv, Lifetimes, MaybeStatic};
use borrowing_field::BorrowingFieldVisitor;
use borrowing_param::BorrowingParamVisitor;
pub mod borrowing_field;
pub mod borrowing_param;
/// A method exposed to Diplomat.
#[derive(Debug)]
#[non_exhaustive]
pub struct Method {
pub docs: Docs,
pub name: IdentBuf,
pub lifetime_env: LifetimeEnv,
pub param_self: Option<ParamSelf>,
pub params: Vec<Param>,
pub output: ReturnType,
pub attrs: Attrs,
}
/// Type that the method returns.
#[derive(Debug, Clone)]
#[non_exhaustive]
pub enum SuccessType {
Writeable,
OutType(OutType),
Unit,
}
/// Whether or not the method returns a value or a result.
#[derive(Debug)]
#[allow(clippy::exhaustive_enums)] // this only exists for fallible/infallible, breaking changes for more complex returns are ok
pub enum ReturnType {
Infallible(SuccessType),
Fallible(SuccessType, Option<OutType>),
Nullable(SuccessType),
}
/// The `self` parameter of a method.
#[derive(Debug)]
#[non_exhaustive]
pub struct ParamSelf {
pub ty: SelfType,
}
/// A parameter in a method.
#[derive(Debug)]
#[non_exhaustive]
pub struct Param {
pub name: IdentBuf,
pub ty: Type,
}
impl SuccessType {
/// Returns whether the variant is `Writeable`.
pub fn is_writeable(&self) -> bool {
matches!(self, SuccessType::Writeable)
}
/// Returns whether the variant is `Unit`.
pub fn is_unit(&self) -> bool {
matches!(self, SuccessType::Unit)
}
pub fn as_type(&self) -> Option<&OutType> {
match self {
SuccessType::OutType(ty) => Some(ty),
_ => None,
}
}
}
impl Deref for ReturnType {
type Target = SuccessType;
fn deref(&self) -> &Self::Target {
match self {
ReturnType::Infallible(ret) | ReturnType::Fallible(ret, _) | Self::Nullable(ret) => ret,
}
}
}
impl ReturnType {
/// Returns `true` if the FFI function returns `void`. Not that this is different from `is_unit`,
/// which will be true for `DiplomatResult<(), E>` and false for infallible writeable.
pub fn is_ffi_unit(&self) -> bool {
matches!(
self,
ReturnType::Infallible(SuccessType::Unit | SuccessType::Writeable)
)
}
/// The "main" return type of this function: the Ok, Some, or regular type
pub fn success_type(&self) -> &SuccessType {
match &self {
Self::Infallible(s) => s,
Self::Fallible(s, _) => s,
Self::Nullable(s) => s,
}
}
/// Get the list of method lifetimes actually used by the method return type
///
/// Most input lifetimes aren't actually used. An input lifetime is generated
/// for each borrowing parameter but is only important if we use it in the return.
pub fn used_method_lifetimes(&self) -> BTreeSet<Lifetime> {
let mut set = BTreeSet::new();
let mut add_to_set = |ty: &OutType| {
for lt in ty.lifetimes() {
if let MaybeStatic::NonStatic(lt) = lt {
set.insert(lt);
}
}
};
match self {
ReturnType::Infallible(SuccessType::OutType(ref ty))
| ReturnType::Nullable(SuccessType::OutType(ref ty)) => add_to_set(ty),
ReturnType::Fallible(ref ok, ref err) => {
if let SuccessType::OutType(ref ty) = ok {
add_to_set(ty)
}
if let Some(ref ty) = err {
add_to_set(ty)
}
}
_ => (),
}
set
}
pub fn with_contained_types(&self, mut f: impl FnMut(&OutType)) {
match self {
Self::Infallible(SuccessType::OutType(o))
| Self::Nullable(SuccessType::OutType(o))
| Self::Fallible(SuccessType::OutType(o), None) => f(o),
Self::Fallible(SuccessType::OutType(o), Some(o2)) => {
f(o);
f(o2)
}
Self::Fallible(_, Some(o)) => f(o),
_ => (),
}
}
}
impl ParamSelf {
pub(super) fn new(ty: SelfType) -> Self {
Self { ty }
}
/// Return the number of fields and leaves that will show up in the [`BorrowingFieldVisitor`].
///
/// This method is used to calculate how much space to allocate upfront.
fn field_leaf_lifetime_counts(&self, tcx: &TypeContext) -> (usize, usize) {
match self.ty {
SelfType::Opaque(_) => (1, 1),
SelfType::Struct(ref ty) => ty.resolve(tcx).fields.iter().fold((1, 0), |acc, field| {
let inner = field.ty.field_leaf_lifetime_counts(tcx);
(acc.0 + inner.0, acc.1 + inner.1)
}),
SelfType::Enum(_) => (0, 0),
}
}
}
impl Param {
pub(super) fn new(name: IdentBuf, ty: Type) -> Self {
Self { name, ty }
}
}
impl Method {
/// Returns a fresh [`Lifetimes`] corresponding to `self`.
pub fn method_lifetimes(&self) -> Lifetimes {
self.lifetime_env.lifetimes()
}
/// Returns a new [`BorrowingParamVisitor`], which can *shallowly* link output lifetimes
/// to the parameters they borrow from.
///
/// This is useful for backends which wish to have lifetime codegen for methods only handle the local
/// method lifetime, and delegate to generated code on structs for handling the internals of struct lifetimes.
pub fn borrowing_param_visitor<'tcx>(
&'tcx self,
tcx: &'tcx TypeContext,
) -> BorrowingParamVisitor<'tcx> {
BorrowingParamVisitor::new(self, tcx)
}
/// Returns a new [`BorrowingFieldVisitor`], which allocates memory to
/// efficiently represent all fields (and their paths!) of the inputs that
/// have a lifetime.
///
/// This is useful for backends which wish to "splat out" lifetime edge codegen for methods,
/// linking each borrowed input param/field (however deep it may be in a struct) to a borrowed output param/field.
///
/// ```ignore
/// # use std::collections::BTreeMap;
/// let visitor = method.borrowing_field_visitor(&tcx, "this".ck().unwrap());
/// let mut map = BTreeMap::new();
/// visitor.visit_borrowing_fields(|lifetime, field| {
/// map.entry(lifetime).or_default().push(field);
/// })
/// ```
pub fn borrowing_field_visitor<'m>(
&'m self,
tcx: &'m TypeContext,
self_name: &'m Ident,
) -> BorrowingFieldVisitor<'m> {
BorrowingFieldVisitor::new(self, tcx, self_name)
}
}