Take attributes_on_same_line_as_field into account

src/lists.rs

@@ -265,7 +265,7 @@ where
     // Now that we know how we will layout, we can decide for sure if there
     // will be a trailing separator.
     let mut trailing_separator = formatting.needs_trailing_separator();
-    let mut result = String::new();
+    let mut result = String::with_capacity(128);
     let cloned_items = items.clone();
     let mut iter = items.into_iter().enumerate().peekable();
     let mut item_max_width: Option<usize> = None;

src/vertical.rs

@@ -53,6 +53,8 @@ impl AlignedItem for ast::StructField {
         } else {
             mk_sp(self.attrs.last().unwrap().span.hi(), self.span.lo())
         };
+        let attrs_extendable = context.config.attributes_on_same_line_as_field() &&
+            is_attributes_extendable(&attrs_str);
         rewrite_struct_field_prefix(context, self).and_then(|field_str| {
             combine_strs_with_missing_comments(
                 context,
@@ -60,7 +62,7 @@ impl AlignedItem for ast::StructField {
                 &field_str,
                 missing_span,
                 shape,
-                is_attributes_extendable(&attrs_str),
+                attrs_extendable,
             )
         })
     }

tests/source/configs-attributes_on_same_line_as_field-false.rs

@@ -9,3 +9,9 @@ struct Lorem {
     #[ serde(rename = "Amet") ]
     amet: usize,
 }
+
+// #1943
+pub struct Bzip2 {
+    # [ serde (rename = "level") ]
+     level: i32 ,
+}

tests/target/configs-attributes_on_same_line_as_field-false.rs

@@ -9,3 +9,9 @@ struct Lorem {
     #[serde(rename = "Amet")]
     amet: usize,
 }
+
+// #1943
+pub struct Bzip2 {
+    #[serde(rename = "level")]
+    level: i32,
+}