diff --git a/compiler/rustc_macros/src/serialize.rs b/compiler/rustc_macros/src/serialize.rs index 66e6b571beb2b..3351564299ca5 100644 --- a/compiler/rustc_macros/src/serialize.rs +++ b/compiler/rustc_macros/src/serialize.rs @@ -1,6 +1,7 @@ use proc_macro2::TokenStream; -use quote::quote; +use quote::{quote, quote_spanned}; use syn::parse_quote; +use syn::spanned::Spanned; pub fn type_decodable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream { let decoder_ty = quote! { __D }; @@ -104,6 +105,8 @@ fn decodable_body( } fn decode_field(field: &syn::Field, index: usize, is_struct: bool) -> proc_macro2::TokenStream { + let field_span = field.ident.as_ref().map_or(field.ty.span(), |ident| ident.span()); + let decode_inner_method = if let syn::Type::Reference(_) = field.ty { quote! { ::rustc_middle::ty::codec::RefDecodable::decode } } else { @@ -111,20 +114,21 @@ fn decode_field(field: &syn::Field, index: usize, is_struct: bool) -> proc_macro }; let (decode_method, opt_field_name) = if is_struct { let field_name = field.ident.as_ref().map_or_else(|| index.to_string(), |i| i.to_string()); - ( - proc_macro2::Ident::new("read_struct_field", proc_macro2::Span::call_site()), - quote! { #field_name, }, - ) + (proc_macro2::Ident::new("read_struct_field", field_span), quote! { #field_name, }) } else { - ( - proc_macro2::Ident::new("read_enum_variant_arg", proc_macro2::Span::call_site()), - quote! {}, - ) + (proc_macro2::Ident::new("read_enum_variant_arg", field_span), quote! {}) + }; + + let __decoder = quote! { __decoder }; + // Use the span of the field for the method call, so + // that backtraces will point to the field. + let decode_call = quote_spanned! {field_span=> + ::rustc_serialize::Decoder::#decode_method( + #__decoder, #opt_field_name #decode_inner_method) }; quote! { - match ::rustc_serialize::Decoder::#decode_method( - __decoder, #opt_field_name #decode_inner_method) { + match #decode_call { ::std::result::Result::Ok(__res) => __res, ::std::result::Result::Err(__err) => return ::std::result::Result::Err(__err), }