Hello, I should mention that I still don't read Go Language Specification (https://go.dev/ref/spec), due to my decision to first study Unicode and UTF-8, before reading it. It maybe strange thing to do, but I just how I need to deal with Unicode and UTF-8.
Regardless of that I quickly check few sections of it and I still baffled by what I find that compiler accepts. I write this to ask some gophers to help me find a way to think about this. I hope that you forgive me some stupid questions, I have so knowledge of Go, but still very little of "feeling" of Go. I also have almost no knowledge about compilers. I just compiler front-end user. In all code examples I use two following versions of Go. go version go1.17.7 linux/amd64 go version go1.18beta2 linux/amd64 "Type parameters proposal" (https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md) add new "[]" in new role. It allows to write > func someFunction[T Constraint](...) { ... } > type someType[T Constraint] ... where "Constraint" is constraint on allowed type parameters and "T"" is a type parameter. (I hope that I didn't mess up names.) As a byproduct of some obvious mistakes I find that > type someInt[3] int work fine in both Go 17 and 18beta2. It defines someInt as new type with underling type [3]int. This looks weird and pouting something like that in the working code is probably a sin, but this is not that big issue. I'm now trying to play with compilers with this construction. > type someDifferentInt[float64] int In Go 1.17 I get this complain > invalid array bound float64 > type float64 is not an expression while in Go 1.18beta2 I get > float64 (type) is not an expression It probably need be this way, that with using "[T Constraint]" to define (?) type parameters, compiler can't says that it is "invalid array bound float64", but new error message is still less useful. I guess we need to live with that. > type someOtherInt[float64 float64] int This is awful thing to write, but I still perplexed by what compilers say. Go 1.17: > syntax error: unexpected float64, expecting ] Go 1.18beta2: > cannot use a type parameter as constraint This example is to compare Go compilers with and without generics. > type someAnotherInt[T any] int Go 1.17: > syntax error: unexpected any, expecting ] Go 1.18beta2: it compile just fine. Can someone explain me, why compiler can't throw an error when it find unused type parameter? I like that in Go unused variable, or import, is compile time error and I would appreciate the same behavior with unused type parameters. I need to go for a while, I will go back with more questions about what you can get when using "[]" in Go. Best, Kamil -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/b085b991-e59e-4225-a4d6-36b2391e1dc2n%40googlegroups.com.
