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

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

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