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Emit an Error impl even in the presence of bad attributes

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David Tolnay 2023-12-15 12:14:48 -08:00
parent 0444cd5e66
commit 7e5ff62806
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GPG key ID: F9BA143B95FF6D82
22 changed files with 327 additions and 14 deletions
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28
impl/src/expand.rs
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@ -7,8 +7,18 @@ use quote::{format_ident, quote, quote_spanned, ToTokens};
use std::collections::BTreeSet as Set;
use syn::{DeriveInput, GenericArgument, Member, PathArguments, Result, Token, Type};
pub fn derive(node: &DeriveInput) -> Result<TokenStream> {
let input = Input::from_syn(node)?;
pub fn derive(input: &DeriveInput) -> TokenStream {
match try_expand(input) {
Ok(expanded) => expanded,
// If there are invalid attributes in the input, expand to an Error impl
// anyway to minimize spurious knock-on errors in other code that uses
// this type as an Error.
Err(error) => fallback(input, error),
}
}
fn try_expand(input: &DeriveInput) -> Result<TokenStream> {
let input = Input::from_syn(input)?;
input.validate()?;
Ok(match input {
Input::Struct(input) => impl_struct(input),
@ -16,6 +26,20 @@ pub fn derive(node: &DeriveInput) -> Result<TokenStream> {
})
}
fn fallback(input: &DeriveInput, error: syn::Error) -> TokenStream {
let ty = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let error = error.to_compile_error();
quote! {
#error
#[allow(unused_qualifications)]
impl #impl_generics std::error::Error for #ty #ty_generics #where_clause {}
}
}
fn impl_struct(input: Struct) -> TokenStream {
let ty = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();