rescript-lang / rescript-lang/rescript

Proposal: make instatiation of a private record/variant raise a warning instead of an error

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#8,458 2 comments 2 reactions 1 assignee View on GitHub

@tsnobip is already working on this.

Since May 31, 2026.

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Description

Today, when you try to create a private record or variant, it errors:

module Foo = {
  type t = private {foo: int}
}

let bar = {Foo.foo: 9} // Error: Cannot create values of the private type Foo.t

Though, there are cases where you'd want to force the instantiation for example for testing, moving this from an error to a warning would allow this. We could use the same warning when casting to a private record/variant (cf #8457)

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