Default value fields don't type check for closed records

[quelgar]

roc nightly pre-release, built from commit e5ea6dc4617 on Mon May 13 10:47:45 UTC 2024

In certain circumstances, default value records do not work as expected:

i = Num.toI32 1

# f1 is all fine
f1 = \{ a, b ? "DEFAULT" } -> (a < i, b)

expect f1 { a: 1 } == (Bool.false, "DEFAULT")

expect f1 { a: 1, b: "foo" } == (Bool.false, "foo")

# for f2, the first expect does not compile if the second expect exists
# unless the record parameter is open
f2 : { a : I32, b ? Str } -> (Bool, Str)
f2 = \{ a, b ? "DEFAULT" } -> (a < i, b)

expect f2 { a: 1 } == (Bool.false, "DEFAULT")

expect f2 { a: 1, b: "foo" } == (Bool.false, "foo")

results in:

── TYPE MISMATCH in Test.roc ───────────────────────────────────────────────────

This 1st argument to f2 has an unexpected type:

21│  expect f2 { a: 1 } == (Bool.false, "DEFAULT")
               ^^^^^^^^

The argument is a record of type:

    { … }

But f2 needs its 1st argument to be:

    { b : Str, … }

Tip: Looks like the b field is missing.

────────────────────────────────────────────────────────────────────────────────

If the type annotation is changed to an open record, it compiles:

f2 : { a : I32, b ? Str }* -> (Bool, Str)

Zulip topic.