tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList15.ts(1,10): error TS2394: Overload signature is not compatible with function implementation. tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList15.ts(1,14): error TS2371: A parameter initializer is only allowed in a function or constructor implementation. ==== tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList15.ts (2 errors) ==== function foo(a = 4); ~~~ !!! error TS2394: Overload signature is not compatible with function implementation. ~~~~~ !!! error TS2371: A parameter initializer is only allowed in a function or constructor implementation. function foo(a, b) {}