use crate::ast::{Enum, Field, Input, Struct};
use crate::attr::Trait;
use crate::generics::InferredBounds;
use proc_macro2::TokenStream;
use quote::{format_ident, quote, quote_spanned, ToTokens};
use std::collections::BTreeSet as Set;
use syn::spanned::Spanned;
use syn::{
Data, DeriveInput, GenericArgument, Member, PathArguments, Result, Token, Type, Visibility,
};
pub fn derive(node: &DeriveInput) -> Result<TokenStream> {
let input = Input::from_syn(node)?;
input.validate()?;
Ok(match input {
Input::Struct(input) => impl_struct(input),
Input::Enum(input) => impl_enum(input),
})
}
#[allow(unused)]
fn impl_struct(input: Struct) -> TokenStream {
let ty = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let mut error_inferred_bounds = InferredBounds::new();
let source_body = if input.attrs.transparent.is_some() {
let only_field = &input.fields[0];
if only_field.contains_generic {
error_inferred_bounds.insert(only_field.ty, quote!(std::error::Error));
}
let member = &only_field.member;
Some(quote! {
std::error::Error::source(self.#member.as_dyn_error())
})
} else if let Some(source_field) = input.source_field() {
let source = &source_field.member;
if source_field.contains_generic {
let ty = unoptional_type(source_field.ty);
error_inferred_bounds.insert(ty, quote!(std::error::Error + 'static));
}
let asref = if type_is_option(source_field.ty) {
Some(quote_spanned!(source.span()=> .as_ref()?))
} else {
None
};
let dyn_error = quote_spanned!(source.span()=> self.#source #asref.as_dyn_error());
Some(quote! {
std::option::Option::Some(#dyn_error)
})
} else {
None
};
let source_method = source_body.map(|body| {
quote! {
fn source(&self) -> std::option::Option<&(dyn std::error::Error + 'static)> {
use thiserror_no_std::private::AsDynError;
#body
}
}
});
let backtrace_method = input.backtrace_field().map(|backtrace_field| {
let backtrace = &backtrace_field.member;
let body = if let Some(source_field) = input.source_field() {
let source = &source_field.member;
let source_backtrace = if type_is_option(source_field.ty) {
quote_spanned! {source.span()=>
self.#source.as_ref().and_then(|source| source.as_dyn_error().backtrace())
}
} else {
quote_spanned! {source.span()=>
self.#source.as_dyn_error().backtrace()
}
};
let combinator = if source == backtrace {
source_backtrace
} else if type_is_option(backtrace_field.ty) {
quote! {
#source_backtrace.or(self.#backtrace.as_ref())
}
} else {
quote! {
std::option::Option::Some(#source_backtrace.unwrap_or(&self.#backtrace))
}
};
quote! {
use thiserror_no_std::private::AsDynError;
#combinator
}
} else if type_is_option(backtrace_field.ty) {
quote! {
self.#backtrace.as_ref()
}
} else {
quote! {
std::option::Option::Some(&self.#backtrace)
}
};
quote! {
fn backtrace(&self) -> std::option::Option<&std::backtrace::Backtrace> {
#body
}
}
});
let mut display_implied_bounds = Set::new();
let display_body = if input.attrs.transparent.is_some() {
let only_field = &input.fields[0].member;
display_implied_bounds.insert((0, Trait::Display));
Some(quote! {
core::fmt::Display::fmt(&self.#only_field, __formatter)
})
} else if let Some(display) = &input.attrs.display {
display_implied_bounds = display.implied_bounds.clone();
let use_as_display = if display.has_bonus_display {
#[cfg(feature = "std")]
let t = quote! {
#[allow(unused_imports)]
use thiserror_no_std::private::{DisplayAsDisplay, PathAsDisplay};
};
#[cfg(not(feature = "std"))]
let t = quote! {
#[allow(unused_imports)]
use thiserror_no_std::private::DisplayAsDisplay;
};
Some(t)
} else {
None
};
let pat = fields_pat(&input.fields);
Some(quote! {
#use_as_display
#[allow(unused_variables, deprecated)]
let Self #pat = self;
#display
})
} else {
None
};
let display_impl = display_body.map(|body| {
let mut display_inferred_bounds = InferredBounds::new();
for (field, bound) in display_implied_bounds {
let field = &input.fields[field];
if field.contains_generic {
display_inferred_bounds.insert(field.ty, bound);
}
}
let display_where_clause = display_inferred_bounds.augment_where_clause(input.generics);
quote! {
#[allow(unused_qualifications)]
impl #impl_generics core::fmt::Display for #ty #ty_generics #display_where_clause {
#[allow(clippy::used_underscore_binding)]
fn fmt(&self, __formatter: &mut core::fmt::Formatter) -> core::fmt::Result {
#body
}
}
}
});
let from_impl = input.from_field().map(|from_field| {
let backtrace_field = input.distinct_backtrace_field();
let from = unoptional_type(from_field.ty);
let body = from_initializer(from_field, backtrace_field);
quote! {
#[allow(unused_qualifications)]
impl #impl_generics core::convert::From<#from> for #ty #ty_generics #where_clause {
#[allow(deprecated)]
fn from(source: #from) -> Self {
#ty #body
}
}
}
});
let error_trait = spanned_error_trait(input.original);
if input.generics.type_params().next().is_some() {
let self_token = <Token![Self]>::default();
error_inferred_bounds.insert(self_token, Trait::Debug);
error_inferred_bounds.insert(self_token, Trait::Display);
}
let error_where_clause = error_inferred_bounds.augment_where_clause(input.generics);
#[cfg(feature = "std")]
let error_trait = quote! {
#[allow(unused_qualifications)]
impl #impl_generics #error_trait for #ty #ty_generics #error_where_clause {
#source_method
#backtrace_method
}
};
#[cfg(not(feature = "std"))]
let error_trait = quote! {};
quote! {
#error_trait
#display_impl
#from_impl
}
}
#[allow(unused)]
fn impl_enum(input: Enum) -> TokenStream {
let ty = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let mut error_inferred_bounds = InferredBounds::new();
let source_method = if input.has_source() {
let arms = input.variants.iter().map(|variant| {
let ident = &variant.ident;
if variant.attrs.transparent.is_some() {
let only_field = &variant.fields[0];
if only_field.contains_generic {
error_inferred_bounds.insert(only_field.ty, quote!(std::error::Error));
}
let member = &only_field.member;
let source = quote!(std::error::Error::source(transparent.as_dyn_error()));
quote! {
#ty::#ident {#member: transparent} => #source,
}
} else if let Some(source_field) = variant.source_field() {
let source = &source_field.member;
if source_field.contains_generic {
let ty = unoptional_type(source_field.ty);
error_inferred_bounds.insert(ty, quote!(std::error::Error + 'static));
}
let asref = if type_is_option(source_field.ty) {
Some(quote_spanned!(source.span()=> .as_ref()?))
} else {
None
};
let varsource = quote!(source);
let dyn_error = quote_spanned!(source.span()=> #varsource #asref.as_dyn_error());
quote! {
#ty::#ident {#source: #varsource, ..} => std::option::Option::Some(#dyn_error),
}
} else {
quote! {
#ty::#ident {..} => std::option::Option::None,
}
}
});
Some(quote! {
fn source(&self) -> std::option::Option<&(dyn std::error::Error + 'static)> {
use thiserror_no_std::private::AsDynError;
#[allow(deprecated)]
match self {
#(#arms)*
}
}
})
} else {
None
};
let backtrace_method = if input.has_backtrace() {
let arms = input.variants.iter().map(|variant| {
let ident = &variant.ident;
match (variant.backtrace_field(), variant.source_field()) {
(Some(backtrace_field), Some(source_field))
if backtrace_field.attrs.backtrace.is_none() =>
{
let backtrace = &backtrace_field.member;
let source = &source_field.member;
let varsource = quote!(source);
let source_backtrace = if type_is_option(source_field.ty) {
quote_spanned! {source.span()=>
#varsource.as_ref().and_then(|source| source.as_dyn_error().backtrace())
}
} else {
quote_spanned! {source.span()=>
#varsource.as_dyn_error().backtrace()
}
};
let combinator = if type_is_option(backtrace_field.ty) {
quote! {
#source_backtrace.or(backtrace.as_ref())
}
} else {
quote! {
std::option::Option::Some(#source_backtrace.unwrap_or(backtrace))
}
};
quote! {
#ty::#ident {
#backtrace: backtrace,
#source: #varsource,
..
} => {
use thiserror_no_std::private::AsDynError;
#combinator
}
}
}
(Some(backtrace_field), Some(source_field))
if backtrace_field.member == source_field.member =>
{
let backtrace = &backtrace_field.member;
let varsource = quote!(source);
let source_backtrace = if type_is_option(source_field.ty) {
quote_spanned! {backtrace.span()=>
#varsource.as_ref().and_then(|source| source.as_dyn_error().backtrace())
}
} else {
quote_spanned! {backtrace.span()=>
#varsource.as_dyn_error().backtrace()
}
};
quote! {
#ty::#ident {#backtrace: #varsource, ..} => {
use thiserror_no_std::private::AsDynError;
#source_backtrace
}
}
}
(Some(backtrace_field), _) => {
let backtrace = &backtrace_field.member;
let body = if type_is_option(backtrace_field.ty) {
quote!(backtrace.as_ref())
} else {
quote!(std::option::Option::Some(backtrace))
};
quote! {
#ty::#ident {#backtrace: backtrace, ..} => #body,
}
}
(None, _) => quote! {
#ty::#ident {..} => std::option::Option::None,
},
}
});
Some(quote! {
fn backtrace(&self) -> std::option::Option<&std::backtrace::Backtrace> {
#[allow(deprecated)]
match self {
#(#arms)*
}
}
})
} else {
None
};
let display_impl = if input.has_display() {
let mut display_inferred_bounds = InferredBounds::new();
let use_as_display = if input.variants.iter().any(|v| {
v.attrs
.display
.as_ref()
.map_or(false, |display| display.has_bonus_display)
}) {
#[cfg(feature = "std")]
let t = quote! {
#[allow(unused_imports)]
use thiserror_no_std::private::{DisplayAsDisplay, PathAsDisplay};
};
#[cfg(not(feature = "std"))]
let t = quote! {
#[allow(unused_imports)]
use thiserror_no_std::private::DisplayAsDisplay;
};
Some(t)
} else {
None
};
let void_deref = if input.variants.is_empty() {
Some(quote!(*))
} else {
None
};
let arms = input.variants.iter().map(|variant| {
let mut display_implied_bounds = Set::new();
let display = match &variant.attrs.display {
Some(display) => {
display_implied_bounds = display.implied_bounds.clone();
display.to_token_stream()
}
None => {
let only_field = match &variant.fields[0].member {
Member::Named(ident) => ident.clone(),
Member::Unnamed(index) => format_ident!("_{}", index),
};
display_implied_bounds.insert((0, Trait::Display));
quote!(core::fmt::Display::fmt(#only_field, __formatter))
}
};
for (field, bound) in display_implied_bounds {
let field = &variant.fields[field];
if field.contains_generic {
display_inferred_bounds.insert(field.ty, bound);
}
}
let ident = &variant.ident;
let pat = fields_pat(&variant.fields);
quote! {
#ty::#ident #pat => #display
}
});
let arms = arms.collect::<Vec<_>>();
let display_where_clause = display_inferred_bounds.augment_where_clause(input.generics);
Some(quote! {
#[allow(unused_qualifications)]
impl #impl_generics core::fmt::Display for #ty #ty_generics #display_where_clause {
fn fmt(&self, __formatter: &mut core::fmt::Formatter) -> core::fmt::Result {
#use_as_display
#[allow(unused_variables, deprecated, clippy::used_underscore_binding)]
match #void_deref self {
#(#arms,)*
}
}
}
})
} else {
None
};
let from_impls = input.variants.iter().filter_map(|variant| {
let from_field = variant.from_field()?;
let backtrace_field = variant.distinct_backtrace_field();
let variant = &variant.ident;
let from = unoptional_type(from_field.ty);
let body = from_initializer(from_field, backtrace_field);
Some(quote! {
#[allow(unused_qualifications)]
impl #impl_generics core::convert::From<#from> for #ty #ty_generics #where_clause {
#[allow(deprecated)]
fn from(source: #from) -> Self {
#ty::#variant #body
}
}
})
});
let error_trait = spanned_error_trait(input.original);
if input.generics.type_params().next().is_some() {
let self_token = <Token![Self]>::default();
error_inferred_bounds.insert(self_token, Trait::Debug);
error_inferred_bounds.insert(self_token, Trait::Display);
}
let error_where_clause = error_inferred_bounds.augment_where_clause(input.generics);
#[cfg(feature = "std")]
let error_impl = quote! {
#[allow(unused_qualifications)]
impl #impl_generics #error_trait for #ty #ty_generics #error_where_clause {
#source_method
#backtrace_method
}
};
#[cfg(not(feature = "std"))]
let error_impl = quote! {};
quote! {
#error_impl
#display_impl
#(#from_impls)*
}
}
fn fields_pat(fields: &[Field]) -> TokenStream {
let mut members = fields.iter().map(|field| &field.member).peekable();
match members.peek() {
Some(Member::Named(_)) => quote!({ #(#members),* }),
Some(Member::Unnamed(_)) => {
let vars = members.map(|member| match member {
Member::Unnamed(member) => format_ident!("_{}", member),
Member::Named(_) => unreachable!(),
});
quote!((#(#vars),*))
}
None => quote!({}),
}
}
fn from_initializer(from_field: &Field, backtrace_field: Option<&Field>) -> TokenStream {
let from_member = &from_field.member;
let some_source = if type_is_option(from_field.ty) {
quote!(core::option::Option::Some(source))
} else {
quote!(source)
};
let backtrace = backtrace_field.map(|backtrace_field| {
let backtrace_member = &backtrace_field.member;
if type_is_option(backtrace_field.ty) {
quote! {
#backtrace_member: core::option::Option::Some(std::backtrace::Backtrace::capture()),
}
} else {
quote! {
#backtrace_member: core::convert::From::from(std::backtrace::Backtrace::capture()),
}
}
});
quote!({
#from_member: #some_source,
#backtrace
})
}
fn type_is_option(ty: &Type) -> bool {
type_parameter_of_option(ty).is_some()
}
fn unoptional_type(ty: &Type) -> TokenStream {
let unoptional = type_parameter_of_option(ty).unwrap_or(ty);
quote!(#unoptional)
}
fn type_parameter_of_option(ty: &Type) -> Option<&Type> {
let path = match ty {
Type::Path(ty) => &ty.path,
_ => return None,
};
let last = path.segments.last().unwrap();
if last.ident != "Option" {
return None;
}
let bracketed = match &last.arguments {
PathArguments::AngleBracketed(bracketed) => bracketed,
_ => return None,
};
if bracketed.args.len() != 1 {
return None;
}
match &bracketed.args[0] {
GenericArgument::Type(arg) => Some(arg),
_ => None,
}
}
fn spanned_error_trait(input: &DeriveInput) -> TokenStream {
let vis_span = match &input.vis {
Visibility::Public(vis) => Some(vis.pub_token.span()),
Visibility::Crate(vis) => Some(vis.crate_token.span()),
Visibility::Restricted(vis) => Some(vis.pub_token.span()),
Visibility::Inherited => None,
};
let data_span = match &input.data {
Data::Struct(data) => data.struct_token.span(),
Data::Enum(data) => data.enum_token.span(),
Data::Union(data) => data.union_token.span(),
};
let first_span = vis_span.unwrap_or(data_span);
let last_span = input.ident.span();
let path = quote_spanned!(first_span=> std::error::);
let error = quote_spanned!(last_span=> Error);
quote!(#path #error)
}