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|
use std::collections::HashMap;
use proc_macro2::Span;
use quote::quote;
use syn::{
spanned::Spanned, GenericArgument, Generics, Ident, PathArguments, TraitBound, Type,
TypeParamBound, TypePath, TypeReference, TypeTraitObject, WherePredicate,
};
use crate::{
filter_map_assoc_paths, match_assoc_type,
parse_assoc_type::{BoxType, DestType},
parse_trait_sig::{MethodError, TypeTransform},
syn_utils::{iter_path, iter_type, type_arguments_mut},
};
#[derive(Default)]
pub struct TypeConverter<'a> {
pub assoc_type_conversions: HashMap<Ident, DestType<'a>>,
}
#[derive(Debug)]
pub enum TransformError {
AssocTypeWithoutDestType,
UnsupportedType,
}
impl TypeConverter<'_> {
/// Returns true for types that take one generic type parameter T
/// and implement IntoIterator<Item=T> and FromIterator<T>
fn known_as_collection_with_one_type(&self, ident: &Ident) -> bool {
// when adding a type here don't forget to document it in the README
ident == "Vec"
|| ident == "VecDeque"
|| ident == "LinkedList"
|| ident == "HashSet"
|| ident == "BinaryHeap"
|| ident == "BTreeSet"
}
/// Returns true for types that take two generic type parameter K and V
/// and implement IntoIterator<Item=(K, V)> and FromIterator<(K, V)>
fn known_as_collection_with_two_types(&self, ident: &Ident) -> bool {
// when adding a type here don't forget to document it in the README
ident == "HashMap" || ident == "BTreeMap"
}
pub fn convert_type(&self, type_: &mut Type) -> Result<TypeTransform, (Span, TransformError)> {
if !iter_type(type_).any(match_assoc_type) {
return Ok(TypeTransform::NoOp);
}
if let Type::Reference(TypeReference {
lifetime: None,
mutability: Some(_),
elem,
..
}) = type_
{
if let Type::TraitObject(TypeTraitObject {
dyn_token: Some(_),
bounds,
}) = elem.as_mut()
{
if bounds.len() == 1 {
if let TypeParamBound::Trait(bound) = &mut bounds[0] {
if bound.path.segments.len() == 1 {
let first = &mut bound.path.segments[0];
if first.ident == "Iterator" {
if let PathArguments::AngleBracketed(args) = &mut first.arguments {
if args.args.len() == 1 {
if let GenericArgument::Binding(binding) = &mut args.args[0]
{
if binding.ident == "Item"
&& iter_type(&binding.ty).any(match_assoc_type)
{
let inner = self.convert_type(&mut binding.ty)?;
let box_type = BoxType {
inner: quote! {#elem},
placeholder_lifetime: true,
};
*type_ = Type::Verbatim(quote! {#box_type});
return Ok(TypeTransform::Iterator(
box_type,
inner.into(),
));
}
}
}
}
}
}
}
}
}
}
if let Type::Path(TypePath { path, qself: None }) = type_ {
if path.segments[0].ident == "Self" {
if path.segments.len() == 2 {
let ident = &path.segments.last().unwrap().ident;
let dest_type = self
.assoc_type_conversions
.get(ident)
.ok_or_else(|| (ident.span(), TransformError::AssocTypeWithoutDestType))?;
*type_ = dest_type.get_dest();
return Ok(dest_type.type_transformation());
}
} else {
let path_len = path.segments.len();
let last_seg = path.segments.last_mut().unwrap();
if let PathArguments::AngleBracketed(args) = &mut last_seg.arguments {
let mut args: Vec<_> = type_arguments_mut(&mut args.args).collect();
if args.len() == 1 {
if iter_type(args[0]).any(match_assoc_type) {
if (last_seg.ident == "Option" && path_len == 1)
|| last_seg.ident == "Result"
{
return Ok(TypeTransform::Map(self.convert_type(args[0])?.into()));
} else if self.known_as_collection_with_one_type(&last_seg.ident)
&& path_len == 1
{
return Ok(TypeTransform::IntoIterMapCollect(vec![
self.convert_type(args[0])?
]));
}
}
} else if args.len() == 2
&& path_len == 1
&& (iter_type(args[0]).any(match_assoc_type)
|| iter_type(args[1]).any(match_assoc_type))
{
if last_seg.ident == "Result" {
return Ok(TypeTransform::Result(
self.convert_type(args[0])?.into(),
self.convert_type(args[1])?.into(),
));
} else if self.known_as_collection_with_two_types(&last_seg.ident) {
return Ok(TypeTransform::IntoIterMapCollect(vec![
self.convert_type(args[0])?,
self.convert_type(args[1])?,
]));
}
}
}
}
}
// the type contains an associated type but we
// don't know how to deal with it so we abort
Err((type_.span(), TransformError::UnsupportedType))
}
}
pub fn dynamize_function_bounds(
generics: &mut Generics,
type_converter: &TypeConverter,
) -> Result<HashMap<Ident, Vec<TypeTransform>>, (Span, MethodError)> {
let mut type_param_transforms = HashMap::new();
for type_param in generics.type_params_mut() {
for bound in &mut type_param.bounds {
if let TypeParamBound::Trait(bound) = bound {
dynamize_trait_bound(
bound,
type_converter,
&type_param.ident,
&mut type_param_transforms,
)?;
}
}
}
if let Some(where_clause) = &mut generics.where_clause {
for predicate in &mut where_clause.predicates {
if let WherePredicate::Type(predicate_type) = predicate {
if let Type::Path(path) = &mut predicate_type.bounded_ty {
if let Some(ident) = path.path.get_ident() {
for bound in &mut predicate_type.bounds {
if let TypeParamBound::Trait(bound) = bound {
dynamize_trait_bound(
bound,
type_converter,
ident,
&mut type_param_transforms,
)?;
}
}
continue;
}
}
// just to provide better error messages
if let Some(assoc_type) =
iter_type(&predicate_type.bounded_ty).find_map(filter_map_assoc_paths)
{
return Err((assoc_type.span(), MethodError::UnconvertedAssocType));
}
// just to provide better error messages
for bound in &mut predicate_type.bounds {
if let TypeParamBound::Trait(bound) = bound {
if let Some(assoc_type) =
iter_path(&bound.path).find_map(filter_map_assoc_paths)
{
return Err((assoc_type.span(), MethodError::UnconvertedAssocType));
}
}
}
}
}
}
Ok(type_param_transforms)
}
fn dynamize_trait_bound(
bound: &mut TraitBound,
type_converter: &TypeConverter,
type_ident: &Ident,
type_param_transforms: &mut HashMap<Ident, Vec<TypeTransform>>,
) -> Result<(), (Span, MethodError)> {
if bound.path.segments.len() == 1 {
let segment = &mut bound.path.segments[0];
if let PathArguments::Parenthesized(args) = &mut segment.arguments {
if segment.ident == "Fn" || segment.ident == "FnOnce" || segment.ident == "FnMut" {
let mut transforms = Vec::new();
for input_type in &mut args.inputs {
match type_converter.convert_type(input_type) {
Ok(ret_type) => {
transforms.push(ret_type);
}
Err((span, err)) => {
return Err((span, err.into()));
}
}
}
if transforms.iter().any(|t| !matches!(t, TypeTransform::NoOp)) {
type_param_transforms.insert(type_ident.clone(), transforms);
}
}
}
}
if let Some(path) = iter_path(&bound.path)
.filter_map(filter_map_assoc_paths)
.next()
{
return Err((path.span(), MethodError::UnconvertedAssocType));
}
Ok(())
}
|
