f fix spurious unused var warning

Author: TheBlueMatt

lightning/src/util/ser_macros.rs

@@ -929,7 +929,14 @@ macro_rules! _decode_and_build {
 		$crate::_init_and_read_len_prefixed_tlv_fields!($stream, {
 			$(($type, $field, $fieldty)),*
 		});
+		// rustc is kinda dumb about unused variable warnings when we declare a variable via an
+		// ident in a macro and then use it in an expr also defined in the same macro call. Thus,
+		// it may generate unused variable warnings for variables that are, in fact, very much
+		// used. Instead, we just blanket ignore unused variables here as it may be useful to write
+		// field names without a _ prefix for legacy fields even if we don't care about the read
+		// value.
 		$(
+			#[allow(unused_variables)]
 			let $field = $crate::_init_tlv_based_struct_field!($field, $fieldty);
 		)*
 		::lightning_macros::drop_legacy_field_definition!($thing {