Fix type of Nullable.t which was not untagged in the implementation. (#235)

* Fix type of `Nullable.t` which was not untagged in the implementation.

* More fixes w.r.t. compiler master.

Unused `as` annotations are not picked up.

* Use #"best fit"

Author: cristianoc

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Next version
 
 - BREAKING: Fixes the type of `RegExp.Result.t` to be `array<option<string>>` instead of `array<string>`. https://github.com/rescript-association/rescript-core/pull/234.
+- Fix type of `Nullable.t` which was not untagged in the implementation. https://github.com/rescript-association/rescript-core/pull/235
 
 ## 1.4.0
 

src/Core__Nullable.res

@@ -1,3 +1,4 @@
+@unboxed
 type t<'a> = Js.Nullable.t<'a> =
   | Value('a)
   | @as(null) Null

src/intl/Core__Intl__Common.res

@@ -1,4 +1,4 @@
-type localeMatcher = [#lookup | @as("best fit") #bestFit]
+type localeMatcher = [#lookup | #"best fit"]
 
 type calendar = [
   | #buddhist

src/intl/Core__Intl__DateTimeFormat.res

@@ -26,7 +26,7 @@ type timeZoneName = [
 ]
 
 type hourCycle = [#h11 | #h12 | #h23 | #h24]
-type formatMatcher = [#basic | @as("best fit") #bestFit]
+type formatMatcher = [#basic | #"best fit"]
 type fractionalSecondDigits = [#0 | #1 | #2 | #3]
 
 type options = {