Fix issue 'double spaces between struct field prefix and identity when using long attributes

src/formatting/items.rs

@@ -1816,7 +1816,7 @@ pub(crate) fn rewrite_struct_field(
 
     let is_prefix_empty = prefix.is_empty();
     // We must use multiline. We are going to put attributes and a field on different lines.
-    let field_str = rewrite_assign_rhs(context, prefix, &*field.ty, shape)?;
+    let field_str = rewrite_assign_rhs(context, prefix.trim_end(), &*field.ty, shape)?;
     // Remove a leading white-space from `rewrite_assign_rhs()` when rewriting a tuple struct.
     let field_str = if is_prefix_empty {
         field_str.trim_start()

tests/source/issue-4671.rs

@@ -0,0 +1,11 @@
+struct X<'a>(
+    #[X(X = "_________________________________________________________________________")]
+    pub &'a u32,
+    // ^^
+);
+
+struct X<'a>(
+    #[X(X = "_______________________________________________")]
+    pub &'a u32,
+    // ^^
+);

tests/target/issue-4671.rs

@@ -0,0 +1,10 @@
+struct X<'a>(
+    #[X(X = "_________________________________________________________________________")]
+    pub &'a u32,
+    // ^^
+);
+
+struct X<'a>(
+    #[X(X = "_______________________________________________")] pub &'a u32,
+    // ^^
+);