fix Issue 19447 - [REG2.066] fixed size slice assignment in ctfe lose…

[WalterBright]

…s connection with array

The difficulty was that the interpreter failed to recognize a slice of a static array as being an lvalue.

[dlang-bot]

Thanks for your pull request, @WalterBright!

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	19447	regression	[REG2.066] fixed size slice assignment in ctfe loses connection with array

⚠️⚠️⚠️ Warnings ⚠️⚠️⚠️

• Regression or critical bug fixes should always target the stable branch. Learn more about rebasing to stable or the D release process.

To target stable perform these two steps:

1. Rebase your branch to upstream/stable:

git rebase --onto upstream/stable upstream/master

2. Change the base branch of your PR to stable

Testing this PR locally

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

dub fetch digger
dub run digger -- build "master + dmd#9071"

[WalterBright]

It's a fairly serious bug, as it silently generates the wrong answer.

[thewilsonator]

Please target stable. cc @UplinkCoder

[WalterBright]

I don't think there's much point to targeting stable. This broke in version 2.066, and we're at 2.083 now.

[UplinkCoder]

I'd remark that there is a bit of code duplication,
other than that, LGTM.

[thewilsonator]

I don't think there's much point to targeting stable.

It does mean LDC get the fixes sooner.

[UplinkCoder]

Please add another test.
To ensure this fails:

int [2] mh = [1, 2];
void g19447(ref int[2] a)
{
    int[2] b=2;
    a=b;
    assert(a[0]==2);
}
g19447(mh);

[WalterBright]

@UplinkCoder why should that fail?

[jacob-carlborg]

Why is there an extra commit "Merge branch 'stable' into fix19447" ?

[UplinkCoder]

the code I posted changes an array at global scope;
And then ctfe would modify an exsiting ast node.

[WalterBright]

I'm putting this back into master, as it relies on some of the refactoring work I've done earlier.

[WalterBright]

@UplinkCoder ok, but I had to rework it a bit, as the example is incomplete.

[ibuclaw]

It does mean LDC get the fixes sooner.

Targeting stable however means GDC gets the fix later. :-)

[PetarKirov]

@ibuclaw not necessarily much later, as you can merge stable to master at any time.

[RazvanN7]

This PR has introduced a regression: https://issues.dlang.org/show_bug.cgi?id=20133