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modifier_definition.rs
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modifier_definition.rs
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// Copyright (c) 2012-2022 Supercolony
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the"Software"),
// to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
use proc_macro2::TokenStream;
use quote::{
quote,
quote_spanned,
ToTokens,
};
use syn::{
parse2,
spanned::Spanned,
ItemFn,
};
pub fn generate(_: TokenStream, _input: TokenStream) -> TokenStream {
let fn_item: ItemFn = parse2(_input).unwrap();
if fn_item.sig.inputs.len() < 2 {
return quote_spanned! {
fn_item.sig.inputs.span() =>
compile_error!(
"Modifier must take at least two arguments, \
where first is a reference to instance `instance: \
& Trait/Struct` and second is Fn, FnMut or FnOnce");
}
}
let instance_ty: syn::TypeReference;
let first = fn_item.sig.inputs.first().unwrap();
if let syn::FnArg::Typed(pat) = first {
if let syn::Type::Reference(refer) = pat.ty.as_ref() {
instance_ty = refer.clone();
} else {
return quote_spanned! {
pat.ty.as_ref().span() =>
compile_error!("First argument of modifier must be a reference to instance `&T` or `&mut T`");
}
}
} else {
return quote_spanned! {
first.span() =>
compile_error!("First argument of modifier can't be `self`");
}
}
let return_ty = fn_item.sig.output.clone();
let mut fn_string = format!("Fn({}) {}", instance_ty.to_token_stream(), return_ty.to_token_stream());
let mut fn_mut_string = format!(
"FnMut({}) {}",
instance_ty.to_token_stream(),
return_ty.to_token_stream()
);
let mut fn_once_string = format!(
"FnOnce({}) {}",
instance_ty.to_token_stream(),
return_ty.to_token_stream()
);
let err_message = format!(
"Second argument of modifier must be body `{}`, `{}` or `{}`",
fn_string.as_str(),
fn_mut_string.as_str(),
fn_once_string.as_str()
);
fn_string.retain(|c| !c.is_whitespace());
fn_mut_string.retain(|c| !c.is_whitespace());
fn_once_string.retain(|c| !c.is_whitespace());
let second = fn_item.sig.inputs.iter().nth(1).unwrap();
if let syn::FnArg::Typed(pat) = second {
let mut found = false;
let mut found_ty = None;
let mut found_span = None;
let mut t = pat.ty.to_token_stream().to_string();
t.retain(|c| !c.is_whitespace());
if t.contains(&fn_string) || t.contains(&fn_mut_string) || t.contains(&fn_once_string) {
found_ty = Some(t.clone());
found_span = Some(pat.ty.span());
found = true;
}
let generic = fn_item
.sig
.generics
.params
.iter()
.filter_map(|param| {
if let syn::GenericParam::Type(type_param) = ¶m {
Some(type_param)
} else {
None
}
})
.find(|type_param| type_param.ident == t);
if let Some(generic) = generic {
if let Some(generic_bound) = &generic.bounds.first() {
let mut t = generic_bound.to_token_stream().to_string();
t.retain(|c| !c.is_whitespace());
if t.contains(&fn_string) || t.contains(&fn_mut_string) || t.contains(&fn_once_string) {
found_ty = Some(t);
found_span = Some(generic_bound.span());
found = true;
}
}
}
if let Some(where_clause) = &fn_item.sig.generics.where_clause {
let predicate = where_clause
.predicates
.iter()
.filter_map(|pred| {
if let syn::WherePredicate::Type(type_pred) = &pred {
Some(type_pred)
} else {
None
}
})
.find(|type_pred| type_pred.bounded_ty.to_token_stream().to_string() == t);
if let Some(pred) = predicate {
if let Some(pred_bound) = pred.bounds.first() {
let mut t = pred_bound.to_token_stream().to_string();
t.retain(|c| !c.is_whitespace());
if t.contains(&fn_string) || t.contains(&fn_mut_string) || t.contains(&fn_once_string) {
found_ty = Some(t);
found_span = Some(pred_bound.span());
found = true;
}
}
}
}
if !found {
return quote_spanned! {
pat.ty.span() =>
compile_error!(#err_message);
}
} else {
let mut modifier_ty_str = fn_item.sig.output.to_token_stream().to_string();
modifier_ty_str.retain(|c| !c.is_whitespace());
let found_ty = found_ty.unwrap();
let found_index = found_ty.find("->").unwrap_or(found_ty.len());
let found_ty_str = &found_ty[found_index..];
if found_ty_str != modifier_ty_str {
return quote_spanned! {
found_span.unwrap().span() =>
compile_error!("Return type of body mismatched with return type of modifier");
}
}
}
} else if let syn::FnArg::Receiver(rec) = second {
return quote_spanned! {
rec.span() =>
compile_error!("Second argument of modifier can't be `self`");
}
}
for arg in fn_item.sig.inputs.iter().skip(2) {
if let syn::FnArg::Typed(arg) = arg {
if let syn::Type::Reference(refer) = arg.ty.as_ref() {
return quote_spanned! {
refer.span() =>
compile_error!("The argument is a reference. \
Modifier only accepts arguments which implement `Clone` trait and only by value.");
}
}
} else {
return quote_spanned! {
arg.span() =>
compile_error!("`self` is not allowed.");
}
}
}
quote! {
#fn_item
}
}