FS-1053 update :: Support instantiation of C#-defined "allows ref struct" generics with ByrefLike types#787
Merged
vzarytovskii merged 1 commit intofsharp:mainfrom Nov 5, 2024
Merged
Conversation
| * Cannot be captured by any closure construct (async methods or lambda expressions) | ||
| * Cannot be used as a generic parameter | ||
| - In F# 9 and higher, this restriction is relaxed if the generic parameter is defined in C# using the `allows ref struct` anti-constraint. F# can instantiate such generics in types and methods with byref-like types. As a few examples, this affects BCL delegate types (`Action<>`,`Func<>`), interfaces (`IEnumerable<>`,`IComparable<>`) and generic arguments with a user-provided accumulator function (`String.string Create<TState>(int length, TState state, SpanAction<char, TState> action)`) | ||
| - It is impossible to author generic code supporting byref-like types in F#. |
Contributor
There was a problem hiding this comment.
Would it be worth expanding on this here? E.g., to mention that the allows ref struct anti-constraint is not automatically propagated in the same way as normal generic constraints, with some examples.
let a : Action<'T> = …
let f (x : 'T) = a.Invoke x // Can 'T be ReadOnlySpan<int> here? Presumably not?let f (g : Action<'T>) (x : 'T) = g.Invoke x // Can 'T be ReadOnlySpan<int> here?
Contributor
Author
There was a problem hiding this comment.
It is not automatically propagated, this makes sense to expand on - thanks for checking this.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Click “Files changed” → “⋯” → “View file” for the rendered RFC.