[Issue 20042] __vector CTFE crashes the compiler

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20042

--- Comment #1 from Basile-z <b2.temp at gmx.com> ---
Is this issue only about the crash or do you mind about the thing being
accepted too ?

Preventing the crash is easy an then compiler would output

Error: slice operation `cast(__vector(float[4]))[nanF, nanF, nanF, nanF] =
[1.00000F, 2.00000F, 3.00000F, 4.00000F][0..4]` cannot be evaluated at compile
time
        called from here: `Vec4(cast(__vector(float[4]))[nanF, nanF, nanF,
nanF]).this(i)`

which is accurate. The code to handle this case is not there.
Then the issue would become an ER.

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