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Bugfix: Warn when upcast drops nullness via FindUniqueFeasibleSupertype#18261

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abonie merged 4 commits into
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18232-nullness-issue---typenullinterface-subsumption-in-function-return-values-can-bypass-nullness
Feb 4, 2025
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Bugfix: Warn when upcast drops nullness via FindUniqueFeasibleSupertype#18261
abonie merged 4 commits into
mainfrom
18232-nullness-issue---typenullinterface-subsumption-in-function-return-values-can-bypass-nullness

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@T-Gro

@T-Gro T-Gro commented Jan 23, 2025

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Fixse #18232

Repro which does not warn, but should:

module Test

open System.IO
open System

// This is bad - input is nullable, output is not = must warn
let whatisThis (s:Stream|null) : IDisposable =
    s

@T-Gro T-Gro linked an issue Jan 23, 2025 that may be closed by this pull request
Nullness issue - ((Type|null):Interface) subsumption in function return values can bypass nullness #18232
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github-actions Bot commented Jan 23, 2025 •
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❗ Release notes required

✅ Found changes and release notes in following paths:

Change path Release notes path Description
src/Compiler docs/release-notes/.FSharp.Compiler.Service/9.0.300.md

@T-Gro T-Gro marked this pull request as ready for review February 3, 2025 13:17
@T-Gro T-Gro requested a review from a team as a code owner February 3, 2025 13:17
@T-Gro
Merge branch 'main' into 18232-nullness-issue---typenullinterface-sub…
784318c 
…sumption-in-function-return-values-can-bypass-nullness
@abonie abonie merged commit bacc160 into main Feb 4, 2025
@T-Gro T-Gro deleted the 18232-nullness-issue---typenullinterface-subsumption-in-function-return-values-can-bypass-nullness branch February 4, 2025 13:03
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Nullness issue - ((Type|null):Interface) subsumption in function return values can bypass nullness

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