[Issue 21104] New: certain array operations fail during CTFE when used to initialize a static array

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21104

          Issue ID: 21104
           Summary: certain array operations fail during CTFE when used to
                    initialize a static array
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: elpenguino+D at gmail.com

Example:
```
enum b = f();

int[4] f() {
    int[4] x = [1,2,3,4] * [1,2,3,4];
    return x;
}
```

f() works fine at runtime, but fails during CTFE with `Error: variable x cannot
be read at compile time`.

Looking at the -vcg-ast output, it becomes clear why: `int[4] x = arrayOp(x[],
[1, 2, 3, 4], [1, 2, 3, 4]);`. The presence of x in that statement is illegal.

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