1 files changed, 414 insertions, 0 deletions
diff --git a/third_party/rust/thiserror-impl/src/expand.rs b/third_party/rust/thiserror-impl/src/expand.rs
new file mode 100644
index 0000000000..d712146e85
--- /dev/null
+++ b/third_party/rust/thiserror-impl/src/expand.rs
@@ -0,0 +1,414 @@
+use crate::ast::{Enum, Field, Input, Struct};
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote, quote_spanned, ToTokens};
+use syn::spanned::Spanned;
+use syn::{Data, DeriveInput, Member, PathArguments, Result, 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),
+    })
+}
+
+fn impl_struct(input: Struct) -> TokenStream {
+    let ty = &input.ident;
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+
+    let source_body = if input.attrs.transparent.is_some() {
+        let only_field = &input.fields[0].member;
+        Some(quote! {
+            std::error::Error::source(self.#only_field.as_dyn_error())
+        })
+    } else if let Some(source_field) = input.source_field() {
+        let source = &source_field.member;
+        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::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 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::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 display_body = if input.attrs.transparent.is_some() {
+        let only_field = &input.fields[0].member;
+        Some(quote! {
+            std::fmt::Display::fmt(&self.#only_field, __formatter)
+        })
+    } else if let Some(display) = &input.attrs.display {
+        let use_as_display = if display.has_bonus_display {
+            Some(quote! {
+                #[allow(unused_imports)]
+                use thiserror::private::{DisplayAsDisplay, PathAsDisplay};
+            })
+        } 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| {
+        quote! {
+            #[allow(unused_qualifications)]
+            impl #impl_generics std::fmt::Display for #ty #ty_generics #where_clause {
+                #[allow(clippy::used_underscore_binding)]
+                fn fmt(&self, __formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+                    #body
+                }
+            }
+        }
+    });
+
+    let from_impl = input.from_field().map(|from_field| {
+        let backtrace_field = input.backtrace_field();
+        let from = from_field.ty;
+        let body = from_initializer(from_field, backtrace_field);
+        quote! {
+            #[allow(unused_qualifications)]
+            impl #impl_generics std::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);
+
+    quote! {
+        #[allow(unused_qualifications)]
+        impl #impl_generics #error_trait for #ty #ty_generics #where_clause {
+            #source_method
+            #backtrace_method
+        }
+        #display_impl
+        #from_impl
+    }
+}
+
+fn impl_enum(input: Enum) -> TokenStream {
+    let ty = &input.ident;
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+
+    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].member;
+                let source = quote!(std::error::Error::source(transparent.as_dyn_error()));
+                quote! {
+                    #ty::#ident {#only_field: transparent} => #source,
+                }
+            } else if let Some(source_field) = variant.source_field() {
+                let source = &source_field.member;
+                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()=> source #asref.as_dyn_error());
+                quote! {
+                    #ty::#ident {#source: source, ..} => 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::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 source_backtrace = if type_is_option(source_field.ty) {
+                        quote_spanned! {source.span()=>
+                            source.as_ref().and_then(|source| source.as_dyn_error().backtrace())
+                        }
+                    } else {
+                        quote_spanned! {source.span()=>
+                            source.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: source,
+                            ..
+                        } => {
+                            use thiserror::private::AsDynError;
+                            #combinator
+                        }
+                    }
+                }
+                (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 use_as_display = if input.variants.iter().any(|v| {
+            v.attrs
+                .display
+                .as_ref()
+                .map_or(false, |display| display.has_bonus_display)
+        }) {
+            Some(quote! {
+                #[allow(unused_imports)]
+                use thiserror::private::{DisplayAsDisplay, PathAsDisplay};
+            })
+        } else {
+            None
+        };
+        let void_deref = if input.variants.is_empty() {
+            Some(quote!(*))
+        } else {
+            None
+        };
+        let arms = input.variants.iter().map(|variant| {
+            let display = match &variant.attrs.display {
+                Some(display) => display.to_token_stream(),
+                None => {
+                    let only_field = match &variant.fields[0].member {
+                        Member::Named(ident) => ident.clone(),
+                        Member::Unnamed(index) => format_ident!("_{}", index),
+                    };
+                    quote!(std::fmt::Display::fmt(#only_field, __formatter))
+                }
+            };
+            let ident = &variant.ident;
+            let pat = fields_pat(&variant.fields);
+            quote! {
+                #ty::#ident #pat => #display
+            }
+        });
+        Some(quote! {
+            #[allow(unused_qualifications)]
+            impl #impl_generics std::fmt::Display for #ty #ty_generics #where_clause {
+                fn fmt(&self, __formatter: &mut std::fmt::Formatter) -> std::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.backtrace_field();
+        let variant = &variant.ident;
+        let from = from_field.ty;
+        let body = from_initializer(from_field, backtrace_field);
+        Some(quote! {
+            #[allow(unused_qualifications)]
+            impl #impl_generics std::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);
+
+    quote! {
+        #[allow(unused_qualifications)]
+        impl #impl_generics #error_trait for #ty #ty_generics #where_clause {
+            #source_method
+            #backtrace_method
+        }
+        #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 backtrace = backtrace_field.map(|backtrace_field| {
+        let backtrace_member = &backtrace_field.member;
+        if type_is_option(backtrace_field.ty) {
+            quote! {
+                #backtrace_member: std::option::Option::Some(std::backtrace::Backtrace::capture()),
+            }
+        } else {
+            quote! {
+                #backtrace_member: std::convert::From::from(std::backtrace::Backtrace::capture()),
+            }
+        }
+    });
+    quote!({
+        #from_member: source,
+        #backtrace
+    })
+}
+
+fn type_is_option(ty: &Type) -> bool {
+    let path = match ty {
+        Type::Path(ty) => &ty.path,
+        _ => return false,
+    };
+
+    let last = path.segments.last().unwrap();
+    if last.ident != "Option" {
+        return false;
+    }
+
+    match &last.arguments {
+        PathArguments::AngleBracketed(bracketed) => bracketed.args.len() == 1,
+        _ => false,
+    }
+}
+
+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)
+}