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Diffstat (limited to 'docs/devel/rust.rst')
| -rw-r--r-- | docs/devel/rust.rst | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/docs/devel/rust.rst b/docs/devel/rust.rst index dc8c441..b673753 100644 --- a/docs/devel/rust.rst +++ b/docs/devel/rust.rst @@ -351,7 +351,7 @@ Writing procedural macros ''''''''''''''''''''''''' By conventions, procedural macros are split in two functions, one -returning ``Result<proc_macro2::TokenStream, MacroError>`` with the body of +returning ``Result<proc_macro2::TokenStream, syn::Error>`` with the body of the procedural macro, and the second returning ``proc_macro::TokenStream`` which is the actual procedural macro. The former's name is the same as the latter with the ``_or_error`` suffix. The code for the latter is more @@ -361,18 +361,19 @@ from the type after ``as`` in the invocation of ``parse_macro_input!``:: #[proc_macro_derive(Object)] pub fn derive_object(input: TokenStream) -> TokenStream { let input = parse_macro_input!(input as DeriveInput); - let expanded = derive_object_or_error(input).unwrap_or_else(Into::into); - TokenStream::from(expanded) + derive_object_or_error(input) + .unwrap_or_else(syn::Error::into_compile_error) + .into() } The ``qemu_api_macros`` crate has utility functions to examine a ``DeriveInput`` and perform common checks (e.g. looking for a struct -with named fields). These functions return ``Result<..., MacroError>`` +with named fields). These functions return ``Result<..., syn::Error>`` and can be used easily in the procedural macro function:: fn derive_object_or_error(input: DeriveInput) -> - Result<proc_macro2::TokenStream, MacroError> + Result<proc_macro2::TokenStream, Error> { is_c_repr(&input, "#[derive(Object)]")?; |