remove mutations of params from gyb script

Author: ktoso

stdlib/public/Concurrency/TaskGroup+addTask.swift.gyb

@@ -118,18 +118,19 @@ import Swift
 % ]:
 %
 % for TYPE in TYPES:
-% OP_THROWS = "throws " if "Throwing" in TYPE else ""
-% IS_DISCARDING = "Discarding" in TYPE
-% IS_THROWING = "Throwing" in TYPE
+% IS_DISCARDING = 'Discarding' in TYPE
+% IS_THROWING = 'Throwing' in TYPE
 %
-% def replace_child_task_result(strings, is_discarding, is_throwing):
-%   if is_discarding:
-%     for i in range(len(strings)):
-%       strings[i] = strings[i].replace("-> ChildTaskResult", "-> Void")
-%   if not is_throwing:
-%     for i in range(len(strings)):
-%       strings[i] = strings[i].replace("throws", "/* non throwing task group*/")
-% replace_child_task_result(PARAMS, IS_DISCARDING, IS_THROWING)
+% def adjust_params_for_group_kind(params):
+%   res = []
+%   for p in params:
+%     np = p
+%     if IS_DISCARDING:
+%       np = np.replace("-> ChildTaskResult", "-> Void")
+%     if not IS_THROWING:
+%       np = np.replace("throws", "")
+%     res.append(np)
+%   return res
 %
 % for METHOD_NAME in ADD_TASK_METHOD_VARIANT:
 %
@@ -161,8 +162,10 @@ extension ${TYPE} {
   /// Adds a child task to the group.
   % end
   ///
+  % if IS_THROWING:
   /// This method doesn't throw an error, even if the child task does.
   /// Instead, the corresponding call to `ThrowingTaskGroup.next()` rethrows that error.
+  % end
   ///
   /// - Parameters:
   % if HAS_TASK_NAME:
@@ -190,7 +193,7 @@ extension ${TYPE} {
   ${"\n  ".join(ALL_AVAILABILITY)}
   @_alwaysEmitIntoClient
   public mutating func ${METHOD_NAME}(
-    ${",\n    ".join(PARAMS)}
+    ${",\n    ".join(adjust_params_for_group_kind(PARAMS))}
   ) ${ARROW_RETURN_TYPE}{
     % if IS_IMPL_UNAVAILABLE:
     fatalError("Unavailable in task-to-thread concurrency model")