Fix Issue 22617 - CTFE rejects modification of copied static array

[RazvanN7]

int countWins(const uint[2] arr)
{
	uint[2] copy = arr;
        copy[0] = 0;
	return 0;
}

enum force = countWins([4, 8]);

When passing [4, 8] to countWins the interpreter thinks that if
the parameter is constant, then there is no need to create a copy
for CTFE, however, this is true only if the variable never gets modified.
In this case, the arr is correctly assigned to a mutable static array, but
since the interpreter thinks that the original array literal will never get
modifier it simply initializes copy to a slice of it. Hence the error.

This patch fixes the issue by copying the initial array literal on the ctfe stack.
The copy is elided only if the array element type contains indirections.

[RazvanN7]

Hmm bot seems to be down, cc @CyberShadow .

[CyberShadow]

Jan 27 15:26:55 [main(VpEu) WRN] GET https://api.github.com/repos/dlang/dmd/issues/13575/comments failed;  Not Found 404.

Race condition in GitHub API.

[dlang-bot]

Thanks for your pull request and interest in making D better, @RazvanN7! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22617	regression	CTFE rejects modification of copied static array

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "stable + dmd#13575"

[MoonlightSentinel]

That doesn't seem right. The following example still fails with this patch:

int countWins(const uint*[2] arr)
{
	const(uint)*[2] copy = arr;
	copy[0] = null;
	return 0;
}

enum force = countWins([null, null]);

[ibuclaw]

@RazvanN7 coming back to this soon?