=== tests/cases/compiler/untypedArgumentInLambdaExpression.ts ===
declare function f(fn: (a: string) => string);
>f : (fn: (a: string) => string) => any
>fn : (a: string) => string
>a : string
 
f((input): string => {
>f((input): string => {    return "." + input;}) : any
>f : (fn: (a: string) => string) => any
>(input): string => {    return "." + input;} : (input: string) => string
>input : string

    return "." + input;
>"." + input : string
>"." : string
>input : string

});