Wrong type accessibility error is not reported for a signature

[auduchinok]

B..ctor signature should report an error about a use of an internal type in a public member:

module WrongAccessibility.Library

type internal A = class end

type B =
    new: a: A -> B

A library containing such a signature is successfully built, and there's a runtime exception when trying to use the constructor of B.

The bug leads to exception when trying to use ILFieldDef:

fsharp/src/fsharp/absil/il.fsi

Line 1090 in 6b1af12

new: name: string * fieldType: ILType * attributes: FieldAttributes * data: byte[] option *

[github-actions]

🤖 This is an automated response from Repo Assist.

I tested this repro on the current compiler (F# 10.0 / SDK 10.0.104) and it now correctly fails at compile time with:

error FS0410: The type 'A' is less accessible than the value, member or type 'new: a: A -> B' it is used in.

This is the correct behavior — the library no longer compiles successfully, so the runtime exception described in the issue can no longer occur. The error is reported on the implementation file (.fs) rather than the signature file (.fsi), but the key result is that the invalid code is correctly rejected at build time.

Labeling this AI-thinks-issue-fixed. Please verify and close if correct!

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