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Does the compiler do that? That sounds extremely unlikely, especially because an interface with only one implementation can store the nil type tag or a tagged p

Does the compiler do that? That sounds extremely unlikely, especially because an interface with only one implementation can store the nil type tag or a tagged pointer to an instance of that implementation.

randomdata 2y ago
The nil interface is another implementation. I mean, unless it is being used as the sole implementation, but I think we can assume that isn't the implementation being talked about given that it isn't a practical implementation. We're talking about where there is one implementation.
- anonymoushn 2y ago
  Right. Can you cite anything that says that the go compiler does this sort of whole-program analysis to try to prove that a certain argument to a function is always non-nil, so that it can change the signature of that function and the types of variables declared in other functions?
  - randomdata 2y ago
    Uh. No. Why would I ever waste my time proving something I said? If I'm right, I'm right. If I'm wrong, you'll be sure to tell me. No reason for my involvement.
- Dylan16807 2y ago
  If a nil is another implementation then interfaces with a single implementation don't exist.
  - randomdata 2y ago
    Given the following, where is the nil implementation found? package main type FooInterface interface { Baz() } func bar(fizz FooInterface) { bizz.Baz() } type MyFoo struct{} func (*MyFoo) Baz() {} func main() { var foo FooInterface = &MyFoo{} bar(foo) }
    - Dylan16807 2y ago
      Nil is built-in. You just have to write the code to instantiate it and the compiler gives you one. The coder does not need to create an implementation, it's there for free. I would not have called it a "second implementation" myself, but that's your claim to defend, not mine.
      - randomdata 2y ago
        map is also built-in. Where do you find the hash map in the given program? By your logic some nebulous package in a random GitHub repository that happens to satisfy an interface is also another implementation, but you would have to be completely out to lunch to think that fits with the topic of discussion.
        Dylan16807 2y ago
        > map is also built-in. Where do you find the hash map in the given program? If you told me a type can be optimized because the compiler knows it can only have non-hash-map uses, but I could put that type into a hash map with a single line, I think I would be right to be skeptical. > By your logic some nebulous package in a GitHub repository that happens to satisfy an interface is also another implementation, but you would have to be completely out to lunch to think that fits with the topic of discussion. I expect the compiler to have a list of implementations somewhere. I don't know if I can expect it to track if nil is ever used with an interface. I could believe the optimization exists with the right analysis setup but you called the idea of finding a citation a "waste of time" so that's not very convincing.
        randomdata 2y ago
        > but you called the idea of finding a citation a "waste of time" so that's not very convincing. Not only a waste of time, but straight up illogical. If one wants to have a discussion with someone else, they can go to that someone else. There is no logical reason for me to be a pointless middleman even if time were infinite. Now, as fun as that tangent was, where is the nil implementation and hash map found in the given program?

randomdata 2y ago

The nil interface is another implementation. I mean, unless it is being used as the sole implementation, but I think we can assume that isn't the implementation being talked about given that it isn't a practical implementation. We're talking about where there is one implementation.

anonymoushn 2y ago
Right. Can you cite anything that says that the go compiler does this sort of whole-program analysis to try to prove that a certain argument to a function is always non-nil, so that it can change the signature of that function and the types of variables declared in other functions?
- randomdata 2y ago
  Uh. No. Why would I ever waste my time proving something I said? If I'm right, I'm right. If I'm wrong, you'll be sure to tell me. No reason for my involvement.
Dylan16807 2y ago
If a nil is another implementation then interfaces with a single implementation don't exist.
- randomdata 2y ago
  Given the following, where is the nil implementation found? package main type FooInterface interface { Baz() } func bar(fizz FooInterface) { bizz.Baz() } type MyFoo struct{} func (*MyFoo) Baz() {} func main() { var foo FooInterface = &MyFoo{} bar(foo) }
  - Dylan16807 2y ago
    Nil is built-in. You just have to write the code to instantiate it and the compiler gives you one. The coder does not need to create an implementation, it's there for free. I would not have called it a "second implementation" myself, but that's your claim to defend, not mine.
    - randomdata 2y ago
      map is also built-in. Where do you find the hash map in the given program? By your logic some nebulous package in a random GitHub repository that happens to satisfy an interface is also another implementation, but you would have to be completely out to lunch to think that fits with the topic of discussion.
      - Dylan16807 2y ago
        > map is also built-in. Where do you find the hash map in the given program? If you told me a type can be optimized because the compiler knows it can only have non-hash-map uses, but I could put that type into a hash map with a single line, I think I would be right to be skeptical. > By your logic some nebulous package in a GitHub repository that happens to satisfy an interface is also another implementation, but you would have to be completely out to lunch to think that fits with the topic of discussion. I expect the compiler to have a list of implementations somewhere. I don't know if I can expect it to track if nil is ever used with an interface. I could believe the optimization exists with the right analysis setup but you called the idea of finding a citation a "waste of time" so that's not very convincing.
        randomdata 2y ago
        > but you called the idea of finding a citation a "waste of time" so that's not very convincing. Not only a waste of time, but straight up illogical. If one wants to have a discussion with someone else, they can go to that someone else. There is no logical reason for me to be a pointless middleman even if time were infinite. Now, as fun as that tangent was, where is the nil implementation and hash map found in the given program?