Detects when compiler will throw unexpected comma. Parentheses are required to solve ambiguity in nested calls Function calls with multiple arguments without parentheses cannot take as arguments functions with multiple arguments without parentheses because which functional gets which arguments is unclear as in the following example:

outer_function first_outer_argument,
               # second argument is another function call without parentheses, but with multiple arguments
               inner_function first_inner_argument,
               ambiguous_keyword_key: ambiguous_keyword_value

To fix the ambiguity if first_inner_keyword_key: first_inner_keyword_value should be associated, add parentheses around the inner function's arguments:

# keywords are for inner function
outer_function first_outer_argument
               inner_function(
                 first_inner_argument
                 ambiguous_keyword_key: ambiguous_keyword_value
               )

# keywords are for outer function
outer_function first_outer_argument
               inner_function(
                 first_inner_argument
               ),
               ambiguous_keyword_key: ambiguous_keyword_value