=== tests/cases/compiler/functionOverloads23.ts ===
function foo(bar:(b:string)=>void);
>foo : Symbol(foo, Decl(functionOverloads23.ts, 0, 0), Decl(functionOverloads23.ts, 0, 35), Decl(functionOverloads23.ts, 1, 35))
>bar : Symbol(bar, Decl(functionOverloads23.ts, 0, 13))
>b : Symbol(b, Decl(functionOverloads23.ts, 0, 18))

function foo(bar:(a:number)=>void);
>foo : Symbol(foo, Decl(functionOverloads23.ts, 0, 0), Decl(functionOverloads23.ts, 0, 35), Decl(functionOverloads23.ts, 1, 35))
>bar : Symbol(bar, Decl(functionOverloads23.ts, 1, 13))
>a : Symbol(a, Decl(functionOverloads23.ts, 1, 18))

function foo(bar:(a?)=>void) { return 0 }
>foo : Symbol(foo, Decl(functionOverloads23.ts, 0, 0), Decl(functionOverloads23.ts, 0, 35), Decl(functionOverloads23.ts, 1, 35))
>bar : Symbol(bar, Decl(functionOverloads23.ts, 2, 13))
>a : Symbol(a, Decl(functionOverloads23.ts, 2, 18))