=== tests/cases/compiler/functionOverloads8.ts ===
function foo();
>foo : { (): any; (foo: string): any; }, Symbol(foo, Decl(functionOverloads8.ts, 0, 0), Decl(functionOverloads8.ts, 0, 15), Decl(functionOverloads8.ts, 1, 25))

function foo(foo:string);
>foo : { (): any; (foo: string): any; }, Symbol(foo, Decl(functionOverloads8.ts, 0, 0), Decl(functionOverloads8.ts, 0, 15), Decl(functionOverloads8.ts, 1, 25))
>foo : string, Symbol(foo, Decl(functionOverloads8.ts, 1, 13))

function foo(foo?:any){ return '' }
>foo : { (): any; (foo: string): any; }, Symbol(foo, Decl(functionOverloads8.ts, 0, 0), Decl(functionOverloads8.ts, 0, 15), Decl(functionOverloads8.ts, 1, 25))
>foo : any, Symbol(foo, Decl(functionOverloads8.ts, 2, 13))
>'' : string