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47c269360c
At first I was considering moving it to a procedural macro
(source-level information should be sufficient),
and started by trying to reproduce the error case
by changing `htmldivelement.rs` to use `Element` instead of `HTMLElement`
as the first field.
The output was:
```rust
error[E0308]: mismatched types
--> /home/simon/servo2/target/debug/build/script-4caa244faca7d10f/out/Bindings/HTMLDivElementBinding.rs:665:31
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665 | let _: &HTMLElement = self.as_parent();
| ^^^^^^^^^^^^^^^^ expected struct `dom::htmlelement::HTMLElement`, found struct `dom::element::Element`
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= note: expected type `&dom::htmlelement::HTMLElement`
found type `&dom::element::Element`
```
This line number is inside a generated method called `__assert_parent_type`.
As far as I can tell, any case where this lint would error is already caught
by such methods. The lint is therefore redundant and can safely be removed.
61 lines
2 KiB
Rust
61 lines
2 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
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extern crate proc_macro;
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#[macro_use]
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extern crate quote;
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extern crate syn;
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use proc_macro::TokenStream;
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use syn::*;
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#[proc_macro_attribute]
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pub fn dom_struct(args: TokenStream, input: TokenStream) -> TokenStream {
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if !args.is_empty() {
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panic!("#[dom_struct] takes no arguments");
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}
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let attributes = quote! {
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#[derive(DenyPublicFields, DomObject, JSTraceable, MallocSizeOf)]
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#[must_root]
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#[repr(C)]
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};
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// Work around https://github.com/rust-lang/rust/issues/46489
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let attributes: TokenStream = attributes.to_string().parse().unwrap();
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let output: TokenStream = attributes.into_iter().chain(input.into_iter()).collect();
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let item: Item = syn::parse(output).unwrap();
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if let Item::Struct(s) = item {
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let s2 = s.clone();
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if s.generics.params.len() > 0 {
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return quote!(#s2).into();
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}
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if let Fields::Named(ref f) = s.fields {
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let f = f.named.first().expect("Must have at least one field");
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let ident = f.ident.as_ref().expect("Must have named fields");
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let name = &s.ident;
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let ty = &f.ty;
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quote! (
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#s2
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impl crate::dom::bindings::inheritance::HasParent for #name {
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type Parent = #ty;
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/// This is used in a type assertion to ensure that
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/// the source and webidls agree as to what the parent type is
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fn as_parent(&self) -> &#ty {
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&self.#ident
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}
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}
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)
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.into()
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} else {
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panic!("#[dom_struct] only applies to structs with named fields");
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}
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} else {
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panic!("#[dom_struct] only applies to structs");
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}
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}
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