tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors4.ts(1,14): error TS1015: Parameter cannot have question mark and initializer. tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors4.ts(2,15): error TS1015: Parameter cannot have question mark and initializer. tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors4.ts(3,21): error TS1015: Parameter cannot have question mark and initializer. tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors4.ts(4,7): error TS1015: Parameter cannot have question mark and initializer. tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors4.ts(4,39): error TS1015: Parameter cannot have question mark and initializer. tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors4.ts(6,5): error TS2304: Cannot find name 'foo'. tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors4.ts(17,10): error TS1015: Parameter cannot have question mark and initializer. tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors4.ts(19,13): error TS1015: Parameter cannot have question mark and initializer. ==== tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors4.ts (8 errors) ==== false ? (arg?: number = 0) => 47 : null; ~~~ !!! error TS1015: Parameter cannot have question mark and initializer. false ? ((arg?: number = 0) => 57) : null; ~~~ !!! error TS1015: Parameter cannot have question mark and initializer. false ? null : (arg?: number = 0) => 67; ~~~ !!! error TS1015: Parameter cannot have question mark and initializer. ((arg?:number = 1) => 0) + '' + ((arg?:number = 2) => 106); ~~~ !!! error TS1015: Parameter cannot have question mark and initializer. ~~~ !!! error TS1015: Parameter cannot have question mark and initializer. foo( ~~~ !!! error TS2304: Cannot find name 'foo'. (a) => 110, ((a) => 111), (a) => { return 112; }, (a? ) => 113, (a, b? ) => 114, (a: number) => 115, (a: number = 0) => 116, (a = 0) => 117, (a?: number = 0) => 118, ~ !!! error TS1015: Parameter cannot have question mark and initializer. (...a: number[]) => 119, (a, b? = 0, ...c: number[]) => 120, ~ !!! error TS1015: Parameter cannot have question mark and initializer. (a) => (b) => (c) => 121, false? (a) => 0 : (b) => 122 );