Elevate precedence of explicitly marked backtrace

impl/src/expand.rs

@@ -28,7 +28,8 @@ fn impl_struct(input: Struct) -> TokenStream {
         }
     });
 
-    let backtrace_method = input.backtrace_member().map(|backtrace| {
+    let backtrace_method = input.backtrace_field().map(|backtrace| {
+        let backtrace = &backtrace.member;
         let body = if let Some(source) = input.source_member() {
             let dyn_error = quote_spanned!(source.span()=> self.#source.as_dyn_error());
             quote!({
@@ -103,8 +104,9 @@ fn impl_enum(input: Enum) -> TokenStream {
     let backtrace_method = if input.has_backtrace() {
         let arms = input.variants.iter().map(|variant| {
             let ident = &variant.ident;
-            match (variant.backtrace_member(), variant.source_member()) {
-                (Some(backtrace), Some(source)) => {
+            match (variant.backtrace_field(), variant.source_member()) {
+                (Some(backtrace), Some(source)) if backtrace.attrs.backtrace.is_none() => {
+                    let backtrace = &backtrace.member;
                     let dyn_error = quote_spanned!(source.span()=> source.as_dyn_error());
                     quote! {
                         #ty::#ident {
@@ -117,9 +119,12 @@ fn impl_enum(input: Enum) -> TokenStream {
                         }),
                     }
                 }
-                (Some(backtrace), None) => quote! {
+                (Some(backtrace), _) => {
+                    let backtrace = &backtrace.member;
+                    quote! {
                         #ty::#ident {#backtrace: backtrace, ..} => std::option::Option::Some(backtrace),
-                },
+                    }
+                }
                 (None, _) => quote! {
                     #ty::#ident {..} => std::option::Option::None,
                 },

impl/src/prop.rs

@@ -6,8 +6,8 @@ impl Struct<'_> {
         source_member(&self.fields)
     }
 
-    pub(crate) fn backtrace_member(&self) -> Option<&Member> {
-        backtrace_member(&self.fields)
+    pub(crate) fn backtrace_field(&self) -> Option<&Field> {
+        backtrace_field(&self.fields)
     }
 }
 
@@ -21,7 +21,7 @@ impl Enum<'_> {
     pub(crate) fn has_backtrace(&self) -> bool {
         self.variants
             .iter()
-            .any(|variant| variant.backtrace_member().is_some())
+            .any(|variant| variant.backtrace_field().is_some())
     }
 
     pub(crate) fn has_display(&self) -> bool {
@@ -38,8 +38,8 @@ impl Variant<'_> {
         source_member(&self.fields)
     }
 
-    pub(crate) fn backtrace_member(&self) -> Option<&Member> {
-        backtrace_member(&self.fields)
+    pub(crate) fn backtrace_field(&self) -> Option<&Field> {
+        backtrace_field(&self.fields)
     }
 }
 
@@ -58,15 +58,15 @@ fn source_member<'a>(fields: &'a [Field]) -> Option<&'a Member> {
     None
 }
 
-fn backtrace_member<'a>(fields: &'a [Field]) -> Option<&'a Member> {
+fn backtrace_field<'a, 'b>(fields: &'a [Field<'b>]) -> Option<&'a Field<'b>> {
     for field in fields {
         if field.attrs.backtrace.is_some() {
-            return Some(&field.member);
+            return Some(&field);
         }
     }
     for field in fields {
         if type_is_backtrace(field.ty) {
-            return Some(&field.member);
+            return Some(&field);
         }
     }
     None