[Issue 24256] New: `-preview=in` should allow array literals and delegate literals in a `@nogc` context

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24256

          Issue ID: 24256
           Summary: `-preview=in` should allow array literals and delegate
                    literals in a `@nogc` context
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: ogion.art at gmail.com

DMD allows passing array literals and delegate literals to `scope` parameters
in @nogc functions:
void foo(const scope int[]) @nogc {}
void bar(scope void delegate()) @nogc {}
void main() @nogc {
    foo([1, 2, 3]);
    int x;
    bar(() { x++; });
}

I expect this to work with `in` parameters as well, since “input parameters
behave as if they have the `const scope` storage classes” according to spec.
But as of DMD v2.105.3 this fails to compile (`-preview=in` enabled):
void foo(in int[]) @nogc {}
void bar(in void delegate()) @nogc {}
void main() @nogc {
    foo([1, 2, 3]);
    int x;
    bar(() { x++; });
}
app.d(4): Error: array literal in `@nogc` function `D main` may cause a GC
allocation
app.d(3): Error: function `D main` is `@nogc` yet allocates closure for
`main()` with the GC
app.d(6):        `app.main.__lambda2` closes over variable `x` at app.d(5)

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