tests/cases/compiler/invocationExpressionInFunctionParameter.ts(3,24): error TS2345: Argument of type 'number' is not assignable to parameter of type 'string'. ==== tests/cases/compiler/invocationExpressionInFunctionParameter.ts (1 errors) ==== function foo1(val: string) { } function foo3(x = foo1(123)) { //should error, 123 is not string ~~~ !!! error TS2345: Argument of type 'number' is not assignable to parameter of type 'string'. }