On Flutter 1.5.4 (current stable), this is breaking with the following message:
Function-typed parameters can't specify 'const', 'final' or 'var' in place of a return type.
Try replacing the keyword with a return type.dart(function_typed_parameter_var)
On Flutter 1.5.4 (current stable), this is breaking with the following message:
Breaking changes
NONE
Fixes / Enhancements
final
keyword.