publishv0.1.0

1 files changed, 505 insertions, 0 deletions

diff --git a/src/parse_trait_sig.rs b/src/parse_trait_sig.rs
new file mode 100644
index 0000000..55a3214
--- /dev/null
+++ b/src/parse_trait_sig.rs
@@ -0,0 +1,505 @@
+use std::collections::HashMap;
+
+use proc_macro2::Span;
+use syn::{
+    spanned::Spanned, FnArg, Ident, PathArguments, PredicateType, Receiver, ReturnType, Type,
+    TypePath, WherePredicate,
+};
+use syn::{GenericParam, Signature, TypeImplTrait, TypeParamBound};
+
+use crate::syn_utils::{find_in_path, find_in_type, trait_bounds, TypeMatcher};
+use crate::{As, AssocTypeMatcher};
+
+#[derive(Debug, Clone)]
+pub enum TypeTransform {
+    NoOp,
+    Into,
+    Map(Box<TypeTransform>),
+    Result(Box<TypeTransform>, Box<TypeTransform>),
+}
+
+#[derive(Debug)]
+pub enum MethodParseError {
+    NonDispatchableMethod,
+    AssocTypeInInputs,
+    ImplTraitInInputs,
+    AssocTypeInUnsupportedReturnType,
+    UnconvertibleAssocTypeInFnInput,
+    UnconvertibleAssocTypeInTraitBound,
+    UnconvertibleAssocType,
+}
+
+struct ImplTraitMatcher;
+impl TypeMatcher<TypeImplTrait> for ImplTraitMatcher {
+    fn match_type<'a>(&self, t: &'a Type) -> Option<&'a TypeImplTrait> {
+        if let Type::ImplTrait(impltrait) = t {
+            Some(impltrait)
+        } else {
+            None
+        }
+    }
+}
+
+pub struct SignatureChanges {
+    pub return_type: TypeTransform,
+    pub inputs: Vec<Option<Vec<TypeTransform>>>,
+}
+
+pub fn parse_trait_signature(
+    signature: &mut Signature,
+    assoc_type_conversions: &HashMap<&Ident, &Type>,
+) -> Result<SignatureChanges, (Span, MethodParseError)> {
+    let assoc_type_conversions = AssocTypeConversions(assoc_type_conversions);
+
+    if is_non_dispatchable(signature) {
+        return Err((signature.span(), MethodParseError::NonDispatchableMethod));
+    }
+
+    // provide better error messages for associated types in params
+    for input in &signature.inputs {
+        if let FnArg::Typed(pattype) = input {
+            if find_in_type(&pattype.ty, &AssocTypeMatcher).is_some() {
+                return Err((pattype.ty.span(), MethodParseError::AssocTypeInInputs));
+            }
+            if let Some(impl_trait) = find_in_type(&pattype.ty, &ImplTraitMatcher) {
+                return Err((impl_trait.span(), MethodParseError::ImplTraitInInputs));
+            }
+        }
+    }
+
+    let mut type_param_transforms = HashMap::new();
+    let mut input_transforms = Vec::new();
+
+    for generic_param in &mut signature.generics.params {
+        if let GenericParam::Type(type_param) = generic_param {
+            for bound in &mut type_param.bounds {
+                if let TypeParamBound::Trait(bound) = bound {
+                    if bound.path.segments.len() == 1 {
+                        let segment = bound.path.segments.first_mut().unwrap();
+
+                        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 assoc_type_conversions.parse_type_path(input_type) {
+                                        Ok(ret_type) => {
+                                            transforms.push(ret_type);
+                                        }
+                                        Err(TransformError::UnconvertibleAssocType(span)) => {
+                                            return Err((
+                                                span,
+                                                MethodParseError::UnconvertibleAssocType,
+                                            ));
+                                        }
+                                        Err(TransformError::AssocTypeInUnsupportedType(span)) => {
+                                            return Err((
+                                                span,
+                                                MethodParseError::UnconvertibleAssocTypeInFnInput,
+                                            ));
+                                        }
+                                    }
+                                }
+                                if transforms.iter().any(|t| !matches!(t, TypeTransform::NoOp)) {
+                                    type_param_transforms.insert(&type_param.ident, transforms);
+                                }
+                            }
+                        }
+                    }
+                    if let Some(path) = find_in_path(&bound.path, &AssocTypeMatcher) {
+                        return Err((
+                            path.span(),
+                            MethodParseError::UnconvertibleAssocTypeInTraitBound,
+                        ));
+                    }
+                }
+            }
+        }
+    }
+
+    for input in &signature.inputs {
+        if let FnArg::Typed(pattype) = input {
+            if let Type::Path(path) = &*pattype.ty {
+                if let Some(ident) = path.path.get_ident() {
+                    input_transforms.push(type_param_transforms.get(ident).map(|x| (*x).clone()));
+                    continue;
+                }
+            }
+        }
+        input_transforms.push(None);
+    }
+
+    let return_type = match &mut signature.output {
+        ReturnType::Type(_, og_type) => match assoc_type_conversions.parse_type_path(og_type) {
+            Ok(ret_type) => ret_type,
+            Err(TransformError::UnconvertibleAssocType(span)) => {
+                return Err((span, MethodParseError::UnconvertibleAssocType));
+            }
+            Err(TransformError::AssocTypeInUnsupportedType(span)) => {
+                return Err((span, MethodParseError::AssocTypeInUnsupportedReturnType));
+            }
+        },
+        ReturnType::Default => TypeTransform::NoOp,
+    };
+    Ok(SignatureChanges {
+        return_type,
+        inputs: input_transforms,
+    })
+}
+
+struct AssocTypeConversions<'a>(&'a HashMap<&'a Ident, &'a Type>);
+
+enum TransformError {
+    UnconvertibleAssocType(Span),
+    AssocTypeInUnsupportedType(Span),
+}
+
+impl AssocTypeConversions<'_> {
+    fn parse_type_path(&self, type_: &mut Type) -> Result<TypeTransform, TransformError> {
+        let assoc_span = match find_in_type(type_, &AssocTypeMatcher) {
+            Some(path) => path.span(),
+            None => return Ok(TypeTransform::NoOp),
+        };
+
+        if let Type::Path(TypePath { path, qself: None }) = type_ {
+            let ident = &path.segments.first().unwrap().ident;
+
+            // TODO: support &mut dyn Iterator<Item = Self::A>
+            // conversion to  Box<dyn Iterator<Item = Whatever>> via .map(Into::into)
+
+            if ident == "Self" && path.segments.len() == 2 {
+                let ident = &path.segments.last().unwrap().ident;
+                *type_ = (*self
+                    .0
+                    .get(&ident)
+                    .ok_or_else(|| TransformError::UnconvertibleAssocType(ident.span()))?)
+                .clone();
+                return Ok(TypeTransform::Into);
+            } else if ident == "Option" && path.segments.len() == 1 {
+                let first_seg = path.segments.first_mut().unwrap();
+
+                if let Some(args) = first_seg.arguments.get_as_mut() {
+                    if args.args.len() == 1 {
+                        if let Some(generic_type) = args.args.first_mut().unwrap().get_as_mut() {
+                            if find_in_type(generic_type, &AssocTypeMatcher).is_some() {
+                                return Ok(TypeTransform::Map(
+                                    self.parse_type_path(generic_type)?.into(),
+                                ));
+                            }
+                        }
+                    }
+                }
+            } else if ident == "Result" && path.segments.len() == 1 {
+                let first_seg = path.segments.first_mut().unwrap();
+                if let Some(args) = first_seg.arguments.get_as_mut() {
+                    if args.args.len() == 2 {
+                        let mut args_iter = args.args.iter_mut();
+                        if let (Some(ok_type), Some(err_type)) = (
+                            args_iter.next().unwrap().get_as_mut(),
+                            args_iter.next().unwrap().get_as_mut(),
+                        ) {
+                            if find_in_type(ok_type, &AssocTypeMatcher).is_some()
+                                || find_in_type(err_type, &AssocTypeMatcher).is_some()
+                            {
+                                return Ok(TypeTransform::Result(
+                                    self.parse_type_path(ok_type)?.into(),
+                                    self.parse_type_path(err_type)?.into(),
+                                ));
+                            }
+                        }
+                    }
+                }
+            } else {
+                let last_seg = &path.segments.last().unwrap();
+                if last_seg.ident == "Result" {
+                    let last_seg = path.segments.last_mut().unwrap();
+                    if let Some(args) = last_seg.arguments.get_as_mut() {
+                        if args.args.len() == 1 {
+                            if let Some(generic_type) = args.args.first_mut().unwrap().get_as_mut()
+                            {
+                                if find_in_type(generic_type, &AssocTypeMatcher).is_some() {
+                                    return Ok(TypeTransform::Map(
+                                        self.parse_type_path(generic_type)?.into(),
+                                    ));
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        // the type contains an associated type but we
+        // don't know how to deal with it so we abort
+        Err(TransformError::AssocTypeInUnsupportedType(assoc_span))
+    }
+}
+
+fn is_non_dispatchable(signature: &Signature) -> bool {
+    // non-dispatchable: fn example(&self) where Self: Sized;
+    if let Some(where_clause) = &signature.generics.where_clause {
+        if where_clause
+            .predicates
+            .iter()
+            .any(bounds_self_and_has_bound_sized)
+        {
+            return true;
+        }
+    }
+
+    // non-dispatchable: fn example();
+    if signature.inputs.is_empty() {
+        return true;
+    }
+
+    // non-dispatchable: fn example(arg: Type);
+    if matches!(signature.inputs.first(), Some(FnArg::Typed(_))) {
+        return true;
+    }
+
+    // non-dispatchable: fn example(self);
+    if matches!(
+        signature.inputs.first(),
+        Some(FnArg::Receiver(Receiver {
+            reference: None,
+            ..
+        }))
+    ) {
+        return true;
+    }
+    false
+}
+
+/// Returns true if the bounded type is `Self` and the bounds contain `Sized`.
+fn bounds_self_and_has_bound_sized(predicate: &WherePredicate) -> bool {
+    matches!(
+        predicate,
+        WherePredicate::Type(PredicateType {
+            bounded_ty: Type::Path(TypePath { path, .. }),
+            bounds,
+            ..
+        })
+        if path.is_ident("Self")
+        && trait_bounds(bounds).any(|b| b.path.is_ident("Sized"))
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::HashMap;
+
+    use quote::{format_ident, quote};
+    use syn::{TraitItemMethod, Type};
+
+    use crate::parse_trait_sig::{
+        parse_trait_signature, MethodParseError, SignatureChanges, TypeTransform,
+    };
+
+    #[test]
+    fn ok_void() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self);
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Ok(SignatureChanges {
+                return_type: TypeTransform::NoOp,
+                ..
+            })
+        ));
+    }
+
+    #[test]
+    fn ok_assoc_type() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self) -> Self::A;
+        })
+        .unwrap();
+
+        let mut assoc_type_map = HashMap::new();
+        let ident = format_ident!("A");
+        let dest = Type::Verbatim(quote! {Example});
+        assoc_type_map.insert(&ident, &dest);
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &assoc_type_map),
+            Ok(SignatureChanges {
+                return_type: TypeTransform::Into,
+                ..
+            })
+        ));
+    }
+
+    #[test]
+    fn err_unconvertible_assoc_type() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self) -> Self::A;
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::UnconvertibleAssocType))
+        ));
+    }
+
+    #[test]
+    fn err_non_dispatchable_assoc_function_no_args() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test();
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::NonDispatchableMethod))
+        ));
+    }
+
+    #[test]
+    fn err_non_dispatchable_assoc_function_with_args() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(arg: Type);
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::NonDispatchableMethod))
+        ));
+    }
+
+    #[test]
+    fn err_non_dispatchable_consume_self() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(self);
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::NonDispatchableMethod))
+        ));
+    }
+
+    #[test]
+    fn err_non_dispatchable_where_self_sized() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self) where Self: Sized;
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::NonDispatchableMethod))
+        ));
+    }
+
+    #[test]
+    fn err_assoc_type_in_unsupported_return() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self) -> Foo<Self::A>;
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::AssocTypeInUnsupportedReturnType))
+        ));
+    }
+
+    #[test]
+    fn err_assoc_type_in_unsupported_return_in_opt() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self) -> Option<Foo<Self::A>>;
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::AssocTypeInUnsupportedReturnType))
+        ));
+    }
+
+    #[test]
+    fn err_assoc_type_in_unsupported_return_in_ok() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self) -> Result<Foo<Self::A>, Error>;
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::AssocTypeInUnsupportedReturnType))
+        ));
+    }
+
+    #[test]
+    fn err_assoc_type_in_unsupported_return_in_err() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self) -> Result<Ok, Foo<Self::A>>;
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::AssocTypeInUnsupportedReturnType))
+        ));
+    }
+
+    #[test]
+    fn err_assoc_type_in_input() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self, x: Self::A);
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::AssocTypeInInputs))
+        ));
+    }
+
+    #[test]
+    fn err_assoc_type_in_input_opt() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self, x: Option<Self::A>);
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::AssocTypeInInputs))
+        ));
+    }
+
+    #[test]
+    fn err_impl_in_input() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test(&self, arg: Option<impl SomeTrait>);
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::ImplTraitInInputs))
+        ));
+    }
+
+    #[test]
+    fn err_assoc_type_in_generic() {
+        let mut type1: TraitItemMethod = syn::parse2(quote! {
+            fn test<F: Fn(Foo<Self::A>)>(&self, fun: F);
+        })
+        .unwrap();
+
+        assert!(matches!(
+            parse_trait_signature(&mut type1.sig, &Default::default()),
+            Err((_, MethodParseError::UnconvertibleAssocTypeInFnInput))
+        ));
+    }
+}