Weird behaviour for testing equality on Dict

[bzf]

There seems to be something weird when testing equality on the Dict type.
Depending on how you construct the Dict, the result might vary.

Consider these values:

> foo = Dict.fromList [(1,1), (2,2)]
Dict.fromList [(1,1),(2,2)] : Dict.Dict number number'
> bar = Dict.fromList [(2,2), (1,1)]
Dict.fromList [(1,1),(2,2)] : Dict.Dict number number'

Since we're comparing the Dict I would expect that these to Dicts are
equal. However when trying this in the elm-repl that does not seem to be the
case.

> foo == bar
False : Bool

If we create another value baz, built the same way as foo, they will be
considered equal.

> baz = Dict.fromList [(1,1), (2,2)]
Dict.fromList [(1,1),(2,2)] : Dict.Dict number number'
> foo == baz
True : Bool

If I look at the documentation for Dict on core/3.0.0
there is a warning that says

Dictionary equality with (==) is unreliable and should not be used.

When reading the docs for Dict on core/4.0.3 it
seems to be missing. Maybe this is by mistake?

I'm running version 0.17.0 (got it by running elm-repl --version).

Full session:

$ elm-repl
---- elm repl 0.17.0 -----------------------------------------------------------
 :help for help, :exit to exit, more at <https://github.com/elm-lang/elm-repl>
--------------------------------------------------------------------------------
> import Dict
> foo = Dict.fromList [(1,1), (2,2)]
Dict.fromList [(1,1),(2,2)] : Dict.Dict number number'
> bar = Dict.fromList [(2,2), (1,1)]
Dict.fromList [(1,1),(2,2)] : Dict.Dict number number'
> foo == bar
False : Bool
> baz = Dict.fromList [(1,1), (2,2)]
Dict.fromList [(1,1),(2,2)] : Dict.Dict number number'
> foo == baz
True : Bool

[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.

[evancz]

What version of core are you using? It was fixed in 4.0.3, but is still weird before that.

[evancz]

What version of core are you using? It was fixed in 4.0.3, but is still weird before that.

[bzf]

@evancz Checking my exact-dependencies.json it seems to be "elm-lang/core": "4.0.1". After upgrading to 4.0.3 it seems to work as expected, thanks!

[bzf]

@evancz Checking my exact-dependencies.json it seems to be "elm-lang/core": "4.0.1". After upgrading to 4.0.3 it seems to work as expected, thanks!

[evancz]

Great, glad it's working!

[evancz]

Great, glad it's working!

[jvoigtlaender]

To be on the safe side regarding the future, I've proposed addition of the above case to the test suite: https://github.com/elm-lang/core/pull/670. There wasn't such a test yet.

[jvoigtlaender]

To be on the safe side regarding the future, I've proposed addition of the above case to the test suite: https://github.com/elm-lang/core/pull/670. There wasn't such a test yet.