Use more spans for error messages

serde_derive/src/de.rs

@@ -357,7 +357,10 @@ fn deserialize_transparent(cont: &Container, params: &Parameters) -> Fragment {
 
     let path = match transparent_field.attrs.deserialize_with() {
         Some(path) => quote!(#path),
-        None => quote!(_serde::Deserialize::deserialize),
+        None => {
+            let span = transparent_field.original.span();
+            quote_spanned!(span=> _serde::Deserialize::deserialize)
+        },
     };
 
     let assign = fields.iter().map(|field| {
@@ -797,8 +800,10 @@ fn deserialize_newtype_struct(
 
     let value = match field.attrs.deserialize_with() {
         None => {
+            let span = field.original.span();
+            let func = quote_spanned!(span=> <#field_ty as _serde::Deserialize>::deserialize);
             quote! {
-                try!(<#field_ty as _serde::Deserialize>::deserialize(__e))
+                try!(#func(__e))
             }
         }
         Some(path) => {
@@ -1803,10 +1808,10 @@ fn deserialize_externally_tagged_newtype_variant(
     match field.attrs.deserialize_with() {
         None => {
             let field_ty = field.ty;
+            let span = field.original.span();
+            let func = quote_spanned!(span=> _serde::de::VariantAccess::newtype_variant::<#field_ty>);
             quote_expr! {
-                _serde::export::Result::map(
-                    _serde::de::VariantAccess::newtype_variant::<#field_ty>(__variant),
-                    #this::#variant_ident)
+                _serde::export::Result::map(#func(__variant), #this::#variant_ident)
             }
         }
         Some(path) => {
@@ -1831,10 +1836,10 @@ fn deserialize_untagged_newtype_variant(
     let field_ty = field.ty;
     match field.attrs.deserialize_with() {
         None => {
+            let span = field.original.span();
+            let func = quote_spanned!(span=> <#field_ty as _serde::Deserialize>::deserialize);
             quote_expr! {
-                _serde::export::Result::map(
-                    <#field_ty as _serde::Deserialize>::deserialize(#deserializer),
-                    #this::#variant_ident)
+                _serde::export::Result::map(#func(#deserializer), #this::#variant_ident)
             }
         }
         Some(path) => {
@@ -2441,7 +2446,10 @@ fn deserialize_map(
         .map(|&(field, ref name)| {
             let field_ty = field.ty;
             let func = match field.attrs.deserialize_with() {
-                None => quote!(_serde::de::Deserialize::deserialize),
+                None => {
+                    let span = field.original.span();
+                    quote_spanned!(span=> _serde::de::Deserialize::deserialize)
+                },
                 Some(path) => quote!(#path),
             };
             quote! {
@@ -2793,7 +2801,9 @@ fn wrap_deserialize_variant_with(
 fn expr_is_missing(field: &Field, cattrs: &attr::Container) -> Fragment {
     match *field.attrs.default() {
         attr::Default::Default => {
-            return quote_expr!(_serde::export::Default::default());
+            let span = field.original.span();
+            let func = quote_spanned!(span=> _serde::export::Default::default);
+            return quote_expr!(#func());
         }
         attr::Default::Path(ref path) => {
             return quote_expr!(#path());

serde_derive/src/lib.rs

@@ -62,6 +62,7 @@ mod internals;
 
 use proc_macro::TokenStream;
 use syn::DeriveInput;
+use syn::spanned::Spanned;
 
 #[macro_use]
 mod bound;
@@ -77,7 +78,7 @@ mod try;
 pub fn derive_serialize(input: TokenStream) -> TokenStream {
     let input = parse_macro_input!(input as DeriveInput);
     ser::expand_derive_serialize(&input)
-        .unwrap_or_else(compile_error)
+        .unwrap_or_else(|message| compile_error(input.span(), message))
         .into()
 }
 
@@ -85,12 +86,12 @@ pub fn derive_serialize(input: TokenStream) -> TokenStream {
 pub fn derive_deserialize(input: TokenStream) -> TokenStream {
     let input = parse_macro_input!(input as DeriveInput);
     de::expand_derive_deserialize(&input)
-        .unwrap_or_else(compile_error)
+        .unwrap_or_else(|message| compile_error(input.span(), message))
         .into()
 }
 
-fn compile_error(message: String) -> proc_macro2::TokenStream {
-    quote! {
+fn compile_error(span: proc_macro2::Span, message: String) -> proc_macro2::TokenStream {
+    quote_spanned! {span=>
         compile_error!(#message);
     }
 }

serde_derive/src/ser.rs

@@ -200,7 +200,10 @@ fn serialize_transparent(cont: &Container, params: &Parameters) -> Fragment {
 
     let path = match transparent_field.attrs.serialize_with() {
         Some(path) => quote!(#path),
-        None => quote!(_serde::Serialize::serialize),
+        None => {
+            let span = transparent_field.original.span();
+            quote_spanned!(span=> _serde::Serialize::serialize)
+        },
     };
 
     quote_block! {
@@ -505,8 +508,10 @@ fn serialize_externally_tagged_variant(
                 field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
             }
 
+            let span = field.original.span();
+            let func = quote_spanned!(span=> _serde::Serializer::serialize_newtype_variant);
             quote_expr! {
-                _serde::Serializer::serialize_newtype_variant(
+                #func(
                     __serializer,
                     #type_name,
                     #variant_index,
@@ -579,8 +584,10 @@ fn serialize_internally_tagged_variant(
                 field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
             }
 
+            let span = field.original.span();
+            let func = quote_spanned!(span=> _serde::private::ser::serialize_tagged_newtype);
             quote_expr! {
-                _serde::private::ser::serialize_tagged_newtype(
+                #func(
                     __serializer,
                     #enum_ident_str,
                     #variant_ident_str,
@@ -637,12 +644,14 @@ fn serialize_adjacently_tagged_variant(
                     field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
                 }
 
+                let span = field.original.span();
+                let func = quote_spanned!(span=> _serde::ser::SerializeStruct::serialize_field);
                 return quote_block! {
                     let mut __struct = try!(_serde::Serializer::serialize_struct(
                         __serializer, #type_name, 2));
                     try!(_serde::ser::SerializeStruct::serialize_field(
                         &mut __struct, #tag, #variant_name));
-                    try!(_serde::ser::SerializeStruct::serialize_field(
+                    try!(#func(
                         &mut __struct, #content, #field_expr));
                     _serde::ser::SerializeStruct::end(__struct)
                 };
@@ -738,8 +747,10 @@ fn serialize_untagged_variant(
                 field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
             }
 
+            let span = field.original.span();
+            let func = quote_spanned!(span=> _serde::Serialize::serialize);
             quote_expr! {
-                _serde::Serialize::serialize(#field_expr, __serializer)
+                #func(#field_expr, __serializer)
             }
         }
         Style::Tuple => serialize_tuple_variant(TupleVariant::Untagged, params, &variant.fields),
@@ -1079,8 +1090,9 @@ fn serialize_struct_visitor(
 
             let span = field.original.span();
             let ser = if field.attrs.flatten() {
+                let func = quote_spanned!(span=> _serde::Serialize::serialize);
                 quote! {
-                    try!(_serde::Serialize::serialize(&#field_expr, _serde::private::ser::FlatMapSerializer(&mut __serde_state)));
+                    try!(#func(&#field_expr, _serde::private::ser::FlatMapSerializer(&mut __serde_state)));
                 }
             } else {
                 let func = struct_trait.serialize_field(span);