[Issue 2753] Cannot declare pointer to function returning ref

Oct 25, 2022

Bolpat

Oct 25, 2022

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October 25, 2022

[Issue 2753] Cannot declare pointer to function returning ref

Posted by Bolpat

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Bolpat

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https://issues.dlang.org/show_bug.cgi?id=2753

Bolpat <qs.il.paperinik@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |qs.il.paperinik@gmail.com

--- Comment #10 from Bolpat <qs.il.paperinik@gmail.com> ---
@Walter: It is “broken” in the sense that the grammar should(!) be able to express a type without requiring type aliases.

I’d suggest minimal changes to the Type grammar to allow for it.

TL;DR: The semantics is obvious, I hope. Let’s allow the following:
```d
ref (int function()) f1();
(ref int function()) f2();

void g1(ref (int function()) fp);
void g2((ref int function()) fp);

void hImpl(DG : ref int delegate())(DG dg) { }
alias h = fImpl!(ref int delegate() @safe);
```
――― End of TL;DR ―――

Note that `f1` and `g1` are equivalent to:
```d
ref int function() f1();
void g1(ref int function() fp);
```

In the grammar, I use `?` to signify optional occurrence.

```diff
  Type:
      TypeCtors? BasicType TypeSuffixes?
+     ref TypeCtors? BasicType CallableSuffix TypeSuffixes?

    BasicType:
        FundamentalType
        . QualifiedIdentifier
        QualifiedIdentifier
        Typeof
        Typeof . QualifiedIdentifier
−       TypeCtor ( Type )
+       TypeCtor? ( Type )
        Vector
        TraitsExpression
        MixinType

    TypeSuffix:
        *
        [ ]
        [ AssignExpression ]
        [ AssignExpression .. AssignExpression ]
        [ Type ]
+       CallableSuffix
+
+   CallableSuffix:
        delegate Parameters MemberFunctionAttributes?
        function Parameters FunctionAttributes?
```
(This grammar diff does not address the special casing for `alias` that is
currently in place and superseded by this. As far as I can tell, it’ll be still
good and should not be changed.)

It is worth considering to deprecate the syntax without disambiguating parentheses, akin to comparison and bit-wise operators and `() => { }`. The deprecation only applies to cases where a non-aliased function pointer or delegate type is used on a `ref` parameter or as the return type of a `ref` returning function.

--

https://issues.dlang.org/show_bug.cgi?id=2753 Dlang Bot <dlang-bot@dlang.rocks> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |pull --- Comment #11 from Dlang Bot <dlang-bot@dlang.rocks> --- @Bolpat created dlang/dlang.org pull request #3446 "Fix Issue 2753" fixing this issue: - Fix Issue 2753 https://github.com/dlang/dlang.org/pull/3446 --

https://issues.dlang.org/show_bug.cgi?id=2753 Iain Buclaw <ibuclaw@gdcproject.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Priority|P2 |P4 --

https://issues.dlang.org/show_bug.cgi?id=2753 --- Comment #12 from Dlang Bot <dlang-bot@dlang.rocks> --- @ntrel updated dlang/dmd pull request #15243 "[new syntax] Support `function` `ref` Type Parameters for function pointer types" fixing this issue: - Fix Issue 2753 - Cannot declare pointer to function returning ref. https://github.com/dlang/dmd/pull/15243 --

https://issues.dlang.org/show_bug.cgi?id=2753 --- Comment #13 from Dlang Bot <dlang-bot@dlang.rocks> --- @Bolpat updated dlang/dmd pull request #15245 "Fix Issue 2753" fixing this issue: - Fix issue 2753 - add good case tests https://github.com/dlang/dmd/pull/15245 --

https://issues.dlang.org/show_bug.cgi?id=2753 --- Comment #14 from Dlang Bot <dlang-bot@dlang.rocks> --- @Bolpat created dlang/dlang.org pull request #3616 "Primary Type Syntax" fixing this issue: - Fix Issue 2753 https://github.com/dlang/dlang.org/pull/3616 --

https://issues.dlang.org/show_bug.cgi?id=2753 --- Comment #15 from Dlang Bot <dlang-bot@dlang.rocks> --- @Bolpat created dlang/dmd pull request #15269 "Primary Type Syntax" fixing this issue: - Fix issue 2753 - add good case tests https://github.com/dlang/dmd/pull/15269 --

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