fix type ambiguity with clonable error types

Author: ModProg

CHANGELOG.md

@@ -5,6 +5,15 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 <!-- ## [Unreleased] -->
+### Added
+- `{Function,Attribute,Derive}MacroHandler`,
+
+### Removed
+- **Breaking Change** `MacroHandler` was replaced by dedicated traits for each macro type, this probably doesn't affect any usages
+
+### Fixed
+- `syn::Result` could not be used as return type of macro handlers
+
 ## [0.10.4] - 2023-11-24
 ### Changed
 - Allow parsing of types that do not implement `ToTokens`

examples/macro/src/lib.rs

@@ -158,6 +158,12 @@ pub fn parse_quote_dummy_error(_: TokenStream) -> Result<syn::Ident> {
     bail!("error message")
 }
 
+#[manyhow(input_as_dummy)]
+#[proc_macro]
+pub fn parse_quote_dummy_error_syn_result(_: TokenStream) -> syn::Result<syn::Ident> {
+    bail!("error message")
+}
+
 #[manyhow]
 #[proc_macro_attribute]
 pub fn parse_quote_attribute(_: syn::LitStr, item: syn::DeriveInput) -> syn::DeriveInput {
@@ -176,8 +182,20 @@ pub fn parse_quote_dummy_error_attribute(_: TokenStream, _: TokenStream) -> Resu
     bail!("error message")
 }
 
+#[manyhow(item_as_dummy)]
+#[proc_macro_attribute]
+pub fn parse_quote_dummy_error_attribute_syn_result(_: TokenStream, _: TokenStream) -> syn::Result<syn::Ident> {
+    bail!("error message")
+}
+
 #[manyhow]
 #[proc_macro_derive(ParseQuote)]
 pub fn parse_quote_derive(item: syn::ItemStruct) -> syn::ItemStruct {
     item
 }
+
+#[manyhow]
+#[proc_macro_derive(ParseQuoteSynResult)]
+pub fn parse_quote_derive_syn_result(item: syn::ItemStruct) -> syn::Result<syn::ItemStruct> {
+    Ok(item)
+}

examples/no_macro/src/lib.rs

@@ -148,6 +148,15 @@ pub fn parse_quote_dummy_error(input: TokenStream) -> TokenStream {
     )
 }
 
+#[proc_macro]
+pub fn parse_quote_dummy_error_syn_result(input: TokenStream) -> TokenStream {
+    function!(
+        #[as_dummy]
+        input,
+        |_: TokenStream| -> syn::Result<syn::Ident> { bail!("error message") }
+    )
+}
+
 #[proc_macro_attribute]
 pub fn parse_quote_attribute(input: TokenStream, item: TokenStream) -> TokenStream {
     attribute!(input, item, |_: syn::LitStr, item: syn::DeriveInput| item)
@@ -173,7 +182,25 @@ pub fn parse_quote_dummy_error_attribute(input: TokenStream, item: TokenStream)
     )
 }
 
+#[proc_macro_attribute]
+pub fn parse_quote_dummy_error_attribute_syn_result(input: TokenStream, item: TokenStream) -> TokenStream {
+    attribute!(
+        input,
+        #[as_dummy]
+        item,
+        |_: TokenStream, _: TokenStream| -> syn::Result<syn::Ident> { bail!("error message") }
+    )
+}
+
 #[proc_macro_derive(ParseQuote)]
 pub fn parse_quote_derive(item: TokenStream) -> TokenStream {
     derive!(item, |item: syn::ItemStruct| item)
 }
+
+#[proc_macro_derive(ParseQuoteSynResult)]
+pub fn parse_quote_derive_syn_result(item: TokenStream) -> TokenStream {
+    derive!(
+        item,
+        |item: syn::ItemStruct| -> syn::Result<syn::ItemStruct> { Ok(item) }
+    )
+}

src/error.rs

@@ -14,7 +14,7 @@ use syn1::Error as Syn1Error;
 use syn2::Error as Syn2Error;
 
 #[cfg(doc)]
-use crate::MacroHandler;
+use crate::MacroOutput;
 use crate::{to_tokens_span_range, SpanRanged};
 
 /// An alias for [`Result`](std::result::Result) suited for use with this crate
@@ -85,8 +85,8 @@ impl<I: ToTokensError + 'static> Extend<I> for Error {
 /// Can take additional attachments like [`help`](Self::help) or
 /// [`note`](Self::note).
 ///
-/// Implements `ToTokensError` and can therefore be returned from
-/// [`MacroHandler`]s.
+/// Implements `ToTokensError` and can therefore be used with
+/// [`MacroOutput`]s.
 #[derive(Debug)]
 #[must_use]
 pub struct ErrorMessage {
@@ -275,8 +275,8 @@ impl<I: ToTokensError + 'static> Extend<I> for Emitter {
     }
 }
 
-/// Error that can be converted to a [`TokenStream`] required to be returned by
-/// a [`MacroHandler`]
+/// Error that can be converted to a [`TokenStream`] required to be used with
+/// [`MacroOutput`]
 ///
 /// This trait is equivalent to [`ToTokens`].
 pub trait ToTokensError: Debug {