avoid_catches_without_on_clauses

Catch clause should use 'on' to specify the type of exception being caught.

The analyzer produces this diagnostic when a catch clause lacks an on clause to specify the exception type. Catching all exceptions can mask unexpected errors and make debugging more difficult.

The following code produces this diagnostic because the catch clause has no on clause to specify the exception type:

void f() {
  try {
    int.parse('?');
  } catch (e) {
    print(e);
  }
}

Add an on clause to specify the type of exception to catch:

void f() {
  try {
    int.parse('?');
  } on FormatException catch (e) {
    print(e);
  }
}