[Issue 20383] New: [REG 2.084.z] illegal conversion from int[] to ubyte[] are accepted

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20383

          Issue ID: 20383
           Summary: [REG 2.084.z] illegal conversion from int[] to ubyte[]
                    are accepted
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: ice, wrong-code
          Severity: regression
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: b2.temp at gmx.com

This code compiles since 2.084.(1/0?) but it is illegal:

---
ubyte[1] ice(ubyte[1] data)
{
    ubyte[1] result = data[] & [42];
    return result;
}

void main()
{
    assert (ice([1]) == [0]);
} 
---

But fails at runtime with a range violation.
Previously it was rejected with the message:

---
Error: cannot implicitly convert expression `data[] & [42]` of type `int[]` to
`ubyte[]`
---

Which should still be the case, unless 42 is cast to ubyte or constructed as
ubyte(42).


The backend has a protection to detect the illegal element but it's not written
correctly. It uses the style `assert(!condition)` instead of `if (condition)
assert(0);` and because of that an ICE does not happen when DMD is compiled
with -release. See `dmd.e2ir.toElemBin(BinExp be, int op)`

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