Do not call throwable's ctor from _d_newThrowable

[teodutu]

dlang/dmd#13494 is blocked because it attempted to lower new Exception(args) to _d_newThrowable!Exception(args) and have _d_newThrowable call Exception's ctor. This created a few errors due to how forward!args works with -dip1008.

Until -dip1008 is fixed, this PR removes the call to Exception's ctor from _d_newThrowable, leaving this task to the compiler.

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Testing this PR locally

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[RazvanN7]

So, essentially, you are just allocating the exception and leaving it up to the compiler to call the constructor? This looks good to me.

[dkorpel]

The comment still says "and call its constructor" and "It has the same interface as `rt.lifetime._d_newclass()"

[dkorpel]

How is this not breaking the test suite, doesn't current DMD before dlang/dmd#13494 depend on the constructor being called in the hook?

[RazvanN7]

How is this not breaking the test suite, doesn't current DMD before dlang/dmd#13494 depend on the constructor being called in the hook?

There's only 1 runnable test in dmd and it doesn't verify any of the fields of the exception instance. It simply checks that the reference count is correct.

[dkorpel]

There's only 1 runnable test in dmd and it doesn't verify any of the fields of the exception instance.

How about buildkite? Surely there's some code in there that expects the constructor of Exceptions being actually called?

[RazvanN7]

-dip1008 is actually pretty unusable. I wouldn't be surprised if it wasn't used that much. Anyway, the dmd PR should get in shortly, so I wouldn't stress too much about it.

[dkorpel]

-dip1008 is actually pretty unusable. I wouldn't be surprised if it wasn't used that much.

Ah, so _d_newThrowable is only used for -dip1008. Gotcha.

[RazvanN7]

@teodutu could you update the function description so that we can merge this?

[teodutu]

@RazvanN7 done

Addressed