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Merged
jonathanpallant merged 1 commit into from
Jun 15, 2026
+78 −44
Merged

Use syn::Error #76

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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

### Changed

- Swapped from `proc-macro-error2` to `syn::Error`
- Renamed the API for getting the length of an inner block of registers (from
`XXX_array_len` to `len_XXX`)
- The generated wrapper struct now `#[repr(transparent)]`.
Expand Down
1 change: 0 additions & 1 deletion macro/Cargo.toml
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Expand Up @@ -14,7 +14,6 @@ version = "0.6.1"
proc-macro = true

[dependencies]
proc-macro-error2 = "2.0.1"
proc-macro2 = "1.0.93"
quote = "1.0.38"
syn = "2.0.98"
108 changes: 72 additions & 36 deletions macro/src/lib.rs
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@@ -1,18 +1,22 @@
//! The derive macro for the Mmio crate.

use proc_macro2::TokenStream;
use proc_macro_error2::{abort, abort_call_site, proc_macro_error};
use quote::{format_ident, quote, ToTokens, TokenStreamExt};
use syn::{
parse_macro_input, punctuated::Punctuated, spanned::Spanned, Data, DeriveInput, Field, Fields,
Ident, Meta, Path, Token, TypeArray, TypePath,
};

#[proc_macro_error]
#[proc_macro_derive(Mmio, attributes(mmio))]
pub fn derive_mmio(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
// validate our input
let input = parse_macro_input!(input as DeriveInput);
try_derive_mmio(input)
.unwrap_or_else(syn::Error::into_compile_error)
.into()
}

fn try_derive_mmio(input: DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
let mut is_repr_c = false;
let mut omit_ctor = false;
let mut const_ptr = false;
Expand All @@ -37,7 +41,7 @@ pub fn derive_mmio(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
"invalid content of mmio attribute, allowed values: `no_ctors`, `const_ptr`, `const_inner`"
))
}) {
abort!(e);
return Err(syn::Error::new(input.span(), e));
};
}
}
Expand All @@ -56,15 +60,24 @@ pub fn derive_mmio(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
}
}
if !is_repr_c {
abort_call_site!("`#[derive(Mmio)]` only works on repr(C) types");
return Err(syn::Error::new(
input.ident.span(),
"`#[derive(Mmio)]` only works on repr(C) types",
));
}
let ident = input.ident;
let ident = &input.ident;
let wrapper_ident = format_ident!("Mmio{}", ident);
let Data::Struct(ref s) = input.data else {
abort_call_site!("`#[derive(Mmio)]` only supports struct");
return Err(syn::Error::new(
input.span(),
"`#[derive(Mmio)]` only supports struct",
));
};
let Fields::Named(ref fields) = &s.fields else {
abort_call_site!("`#[derive(Mmio)]` only supports structs with named fields");
return Err(syn::Error::new(
input.span(),
"`#[derive(Mmio)]` only supports structs with named fields",
));
};

let config = FieldConfig {
Expand All @@ -80,7 +93,8 @@ pub fn derive_mmio(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
.filter(|(_field, field_ident)| !field_ident.to_string().starts_with("_"))
.map(|(field, field_ident)| {
field_parser.generate_access_methods(&ident, field, field_ident)
});
})
.collect::<syn::Result<Vec<_>>>()?;

let access_methods_quoted = quote! {
#(#access_methods)*
Expand Down Expand Up @@ -140,7 +154,7 @@ pub fn derive_mmio(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let vis = input.vis;

// combine the fragments into the desired output code
proc_macro::TokenStream::from(quote! {
let tokens = quote! {
#[doc = "An MMIO wrapper for ["]
#[doc = stringify!(#ident)]
#[doc = "]"]
Expand Down Expand Up @@ -199,7 +213,8 @@ pub fn derive_mmio(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
#constructors
}

})
};
Ok(tokens)
}

/// Convert a field into code that returns the field size
Expand Down Expand Up @@ -261,14 +276,17 @@ impl FieldParser {
ident: &Ident,
field: &Field,
field_ident: &Ident,
) -> TokenStream {
) -> syn::Result<TokenStream> {
let mut access = AccessModifiers::default();
for attr in field.attrs.iter() {
if attr.path().is_ident("mmio") {
let Ok(nested) =
attr.parse_args_with(Punctuated::<Meta, Token![,]>::parse_terminated)
else {
abort!(attr.span(), "`Failed to parse #[mmio(...)]`");
return Err(syn::Error::new(
attr.span(),
"`Failed to parse #[mmio(...)]`",
));
};
let unexpected_meta_printout =
"`#[mmio(...)]` only supports 'Inner', 'Read', 'PureRead', 'Write', and 'Modify' options";
Expand All @@ -282,39 +300,51 @@ impl FieldParser {
);
} else if path.is_ident("Read") {
if access.read.is_some() {
abort!(attr.span(), "`#[mmio(...)]` found second read argument");
return Err(syn::Error::new(
attr.span(),
"`#[mmio(...)]` found second read argument",
));
}
access.read = Some(ReadAccess::Normal);
} else if path.is_ident("PureRead") {
if access.read.is_some() {
abort!(attr.span(), "`#[mmio(...)]` found second read argument");
return Err(syn::Error::new(
attr.span(),
"`#[mmio(...)]` found second read argument",
));
}
access.read = Some(ReadAccess::Pure);
} else if path.is_ident("Write") {
if access.write {
abort!(attr.span(), "`#[mmio(...)]` found second write argument");
return Err(syn::Error::new(
attr.span(),
"`#[mmio(...)]` found second write argument",
));
}
access.write = true;
} else if path.is_ident("Modify") {
if access.modify {
abort!(attr.span(), "`#[mmio(...)]` found second write argument");
return Err(syn::Error::new(
attr.span(),
"`#[mmio(...)]` found second write argument",
));
}
access.modify = true;
} else {
abort!(attr.span(), unexpected_meta_printout);
return Err(syn::Error::new(attr.span(), unexpected_meta_printout));
}
} else {
abort!(attr.span(), unexpected_meta_printout);
return Err(syn::Error::new(attr.span(), unexpected_meta_printout));
}
}
}
}

if access.modify && (access.read.is_none() || !access.write) {
abort!(
return Err(syn::Error::new(
field.span(),
"Detected Modify field attribute without read and/or write access specifiers"
);
"Detected Modify field attribute without read and/or write access specifiers",
));
}
access.convert_unmodified();

Expand All @@ -341,7 +371,7 @@ impl FieldParser {
_ => (),
}

output
Ok(output)
}

/// Generate access methods for fields that are MMIO blocks.
Expand All @@ -350,33 +380,39 @@ impl FieldParser {
ident: &Ident,
field: &Field,
field_ident: &Ident,
) -> TokenStream {
) -> syn::Result<TokenStream> {
match &field.ty {
syn::Type::Path(type_path) => {
self.generate_access_method_for_single_inner_mmio(ident, field_ident, type_path)
}
syn::Type::Path(type_path) => Ok(self.generate_access_method_for_single_inner_mmio(
ident,
field_ident,
type_path,
)),
syn::Type::Array(array_type) => {
if let syn::Type::Path(element_type) = array_type.elem.as_ref() {
self.generate_access_method_for_inner_mmio_array(
Ok(self.generate_access_method_for_inner_mmio_array(
ident,
field_ident,
array_type,
element_type,
)
))
} else {
abort!(
return Err(syn::Error::new(
array_type.span(),
"inner field array {} does not have a valid array type",
field.to_token_stream()
);
format!(
"inner field array {} does not have a valid array type",
field.to_token_stream()
),
));
}
}
_ => {
abort!(
return Err(syn::Error::new(
field.span(),
"inner field {} does not have a valid path",
field.to_token_stream()
);
format!(
"inner field {} does not have a valid path",
field.to_token_stream()
),
));
}
}
}
Expand Down
4 changes: 2 additions & 2 deletions tests/no_compile/bad_outer_attr.stderr
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@@ -1,5 +1,5 @@
error: invalid content of mmio attribute, allowed values: `no_ctors`, `const_ptr`, `const_inner`
--> tests/no_compile/bad_outer_attr.rs:2:8
--> tests/no_compile/bad_outer_attr.rs:2:1
|
2 | #[mmio(no_ctors_x)]
| ^^^^^^^^^^
| ^
8 changes: 3 additions & 5 deletions tests/no_compile/repr_c_mandatory.stderr
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@@ -1,7 +1,5 @@
error: `#[derive(Mmio)]` only works on repr(C) types
--> tests/no_compile/repr_c_mandatory.rs:1:10
--> tests/no_compile/repr_c_mandatory.rs:2:8
|
1 | #[derive(derive_mmio::Mmio)]
| ^^^^^^^^^^^^^^^^^
|
= note: this error originates in the derive macro `derive_mmio::Mmio` (in Nightly builds, run with -Z macro-backtrace for more info)
2 | struct Uart {
| ^^^^
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