tests/cases/conformance/parser/ecmascript5/MemberAccessorDeclarations/parserMemberAccessorDeclaration17.ts(2,13): error TS1051: A 'set' accessor cannot have an optional parameter.
==== tests/cases/conformance/parser/ecmascript5/MemberAccessorDeclarations/parserMemberAccessorDeclaration17.ts (1 errors) ====
class C {
set Foo(a?: number) { }
~
!!! error TS1051: A 'set' accessor cannot have an optional parameter.
}