Type mismatch for tuple union types passed to tuple functions

[zeddidragon]

Steps to reproduce:

type Foo
  = Bar (String, Int)
  | Baz (Int, Int)

bar : Foo
bar = Bar ("Bar", 1)

derp : (a, Int) -> Int
derp (a, b) = b

herp = derp bar

Actual result:

-- TYPE MISMATCH ------------------------------------------------- UnionType.elm

The argument to function `derp` is causing a mismatch.

11|        derp bar
                ^^^
Function `derp` is expecting the argument to be:

    ( a, Int )

But it is:

    Foo

Expected result:
Program compiles, herp is 1

Since any instance of Foo is guaranteed to be a tuple where the second element is an Int, it should be reasonable to expect a function that only cares about the second element of the tuple to accept instances of Foo.

Version
Elm version 0.18.0 for OSX

[process-bot]

Thanks for the issue! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[process-bot]

Thanks for the issue! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[mgold]

This behaves as designed and is unlikely to be changed. I can go into more depth if you ask on the mailing list.

[mgold]

This behaves as designed and is unlikely to be changed. I can go into more depth if you ask on the mailing list.

[jvoigtlaender]

Max is right. I'm closing this issue.

[jvoigtlaender]

Max is right. I'm closing this issue.