float[2] somevalue = somefloat3value[] + cast(Unqual!float[2]) [somesharedfloatarray1[i],somesharedfloatarray2[ii]];

Older LDC/DMD releases never complained but now that i upgraded DMD, DMD-compiled builds suffer from runtime assert error core.internal.array.operations.arrayOp!(float[], float[], float[], "+", "=").arrayOp at .....\src\druntime\import\core\internal\array\operations.d(45) : Mismatched array lengths for vector operation

Explicitly specifying somefloat3value[0..2] now works, and it seems that this assert check is an addition to a recent DMD version's druntime, does it means that this was a recent change in the language+runtime or just a retroactive enforcement of language rules that didn't use to be enforced?
Big thanks.

On Wednesday, 15 September 2021 at 13:52:40 UTC, ｚ wrote:

float[2] somevalue = somefloat3value[] + cast(Unqual!float[2]) [somesharedfloatarray1[i],somesharedfloatarray2[ii]];

The history is roughly as follows:

• between dmd 2.065 and 2.076 (including), this used to fail at runtime with message "Array lengths don't match for vector operation: 2 != 3"
• dmd 2.077 included druntime PR 1891 which was a ground-up re-implementation of the way array operations are implemented and in general a very welcome improvement. Unfortunately that PR didn't include checks to ensure that all arrays have equal length (or perhaps it had insufficient checks, I didn't dig into the details).
• 2020-08-04 The issue was reported: https://issues.dlang.org/show_bug.cgi?id=21110
• 2021-08-09 A PR that fixes the issue was merged: https://github.com/dlang/druntime/pull/3267
• 2021-08-09 The fix was released in 2.097.2

In summary, the validation was always supposed to be there, but between 2.077.0 and 2.097.1 it wasn't.