Hacker News Reader

> panic is Go's term for an exception

No. An exception is a datatype. Not completely unlike an error type in concept, but intended for erroneous conditions that could have theoretically been caught at compile time (i.e. the programmer screwed up), as opposed to conditions that are not decidable at compile time (i.e. something happened in the outside world).

In Go, panic creates an exception, which may be the source of your confusion. The exception contains any metadata you passed to panic along with other data, like a stack trace. This is not panic in and of itself, though.

> but when writing idiomatic Go one would prefer error types over using panic

Not really. Idiomatic Go says that errors are in no way special and is faulty to think of them as being special. They are just values like any other. Go exceptions allow attaching any value as metadata.

The official line is that panic stack traversal should not cross package boundaries, but internal use is perfectly acceptable. Even the Go standard library does it.

View on HN

func outer() { defer catch() { if r := recover(); r != nil { fmt.Println("Recovered:", r) } }() // ... doSomething() // Can panic doSomethingElse() // Can also panic }

func outer() { r, err := doSomething() if err != nil { fmt.Println("Recovered:", r) } r, err := doSomethingElse() if err != nil { fmt.Println("Recovered else:", r) } }

func outer() { func() { defer catch() { if r := recover(); r != nil { fmt.Println("Recovered from doSomething:", r) } }() doSomething() // Can panic }() func() { defer catch() { if r := recover(); r != nil { fmt.Println("Recovered from doSomethingElse:", r) } }() doSomethingElse() // Can also panic }() }

func try(fn func(), catch func(any)) { defer func() { if r := recover(); r != nil { catch(r) } }() fn() } func outer() { try(func() { doSomething() }, func(r any) { fmt.Println(r) }) try(func() { doSomethingElse() }, func(r any) { fmt.Println(r) }) }

try { doSomething() } catch(error) { if (error instanceof FooError) { console.log('foo') } else if (error instanceof BarError) { console.log('bar') } else if (error instanceof BazError) { console.log('baz') } else { console.log('unknown') } }

err := doSomething() switch { case errors.Is(err, ErrFoo): fmt.Println("foo") case errors.Is(err, ErrBar): fmt.Println("bar") case errors.Is(err, ErrBaz): fmt.Println("baz") default: fmt.Println("unknown") }