tests/cases/compiler/functionCall15.ts(1,25): error TS2300: Duplicate identifier 'b'.
tests/cases/compiler/functionCall15.ts(1,39): error TS2300: Duplicate identifier 'b'.


==== tests/cases/compiler/functionCall15.ts (2 errors) ====
    function foo(a?:string, b?:number, ...b:number[]){}
                            ~
!!! error TS2300: Duplicate identifier 'b'.
                                          ~
!!! error TS2300: Duplicate identifier 'b'.