Merge pull request #2555 from Mingun/field

Refactor code that generates `__Field` enums

Author: dtolnay

serde_derive/src/de.rs

@@ -965,12 +965,7 @@ fn deserialize_struct(
             )
         })
         .collect();
-    let field_visitor = Stmts(deserialize_generated_identifier(
-        &field_names_idents,
-        cattrs,
-        false,
-        None,
-    ));
+    let field_visitor = deserialize_field_identifier(&field_names_idents, cattrs);
 
     // untagged struct variants do not get a visit_seq method. The same applies to
     // structs that only have a map representation.
@@ -1128,12 +1123,7 @@ fn deserialize_struct_in_place(
         })
         .collect();
 
-    let field_visitor = Stmts(deserialize_generated_identifier(
-        &field_names_idents,
-        cattrs,
-        false,
-        None,
-    ));
+    let field_visitor = deserialize_field_identifier(&field_names_idents, cattrs);
 
     let mut_seq = if field_names_idents.is_empty() {
         quote!(_)
@@ -1247,7 +1237,12 @@ fn prepare_enum_variant_enum(
         })
         .collect();
 
-    let other_idx = deserialized_variants.position(|(_, variant)| variant.attrs.other());
+    let fallthrough = deserialized_variants
+        .position(|(_, variant)| variant.attrs.other())
+        .map(|other_idx| {
+            let ignore_variant = variant_names_idents[other_idx].1.clone();
+            quote!(_serde::__private::Ok(__Field::#ignore_variant))
+        });
 
     let variants_stmt = {
         let variant_names = variant_names_idents.iter().map(|(name, _, _)| name);
@@ -1261,7 +1256,8 @@ fn prepare_enum_variant_enum(
         &variant_names_idents,
         cattrs,
         true,
-        other_idx,
+        None,
+        fallthrough,
     ));
 
     (variants_stmt, variant_visitor)
@@ -1986,27 +1982,12 @@ fn deserialize_generated_identifier(
     fields: &[(&str, Ident, &BTreeSet<String>)],
     cattrs: &attr::Container,
     is_variant: bool,
-    other_idx: Option<usize>,
+    ignore_variant: Option<TokenStream>,
+    fallthrough: Option<TokenStream>,
 ) -> Fragment {
     let this_value = quote!(__Field);
     let field_idents: &Vec<_> = &fields.iter().map(|(_, ident, _)| ident).collect();
 
-    let (ignore_variant, fallthrough) = if !is_variant && cattrs.has_flatten() {
-        let ignore_variant = quote!(__other(_serde::__private::de::Content<'de>),);
-        let fallthrough = quote!(_serde::__private::Ok(__Field::__other(__value)));
-        (Some(ignore_variant), Some(fallthrough))
-    } else if let Some(other_idx) = other_idx {
-        let ignore_variant = fields[other_idx].1.clone();
-        let fallthrough = quote!(_serde::__private::Ok(__Field::#ignore_variant));
-        (None, Some(fallthrough))
-    } else if is_variant || cattrs.deny_unknown_fields() {
-        (None, None)
-    } else {
-        let ignore_variant = quote!(__ignore,);
-        let fallthrough = quote!(_serde::__private::Ok(__Field::__ignore));
-        (Some(ignore_variant), Some(fallthrough))
-    };
-
     let visitor_impl = Stmts(deserialize_identifier(
         &this_value,
         fields,
@@ -2052,6 +2033,33 @@ fn deserialize_generated_identifier(
     }
 }
 
+/// Generates enum and its `Deserialize` implementation that represents each
+/// non-skipped field of the struct
+fn deserialize_field_identifier(
+    fields: &[(&str, Ident, &BTreeSet<String>)],
+    cattrs: &attr::Container,
+) -> Stmts {
+    let (ignore_variant, fallthrough) = if cattrs.has_flatten() {
+        let ignore_variant = quote!(__other(_serde::__private::de::Content<'de>),);
+        let fallthrough = quote!(_serde::__private::Ok(__Field::__other(__value)));
+        (Some(ignore_variant), Some(fallthrough))
+    } else if cattrs.deny_unknown_fields() {
+        (None, None)
+    } else {
+        let ignore_variant = quote!(__ignore,);
+        let fallthrough = quote!(_serde::__private::Ok(__Field::__ignore));
+        (Some(ignore_variant), Some(fallthrough))
+    };
+
+    Stmts(deserialize_generated_identifier(
+        fields,
+        cattrs,
+        false,
+        ignore_variant,
+        fallthrough,
+    ))
+}
+
 // Generates `Deserialize::deserialize` body for an enum with
 // `serde(field_identifier)` or `serde(variant_identifier)` attribute.
 fn deserialize_custom_identifier(