Bug 21665 – Void initialization should not be allowed for instances of struct with invariant

struct ShortString { private ubyte length; private char[15] data; @safe this(const(char)[] src) { length = cast(ubyte) src.length; data[0 .. src.length] = src[]; } @trusted const(char)[] opIndex() const { // should be ok to skip the bounds check here return data.ptr[0 .. length]; } invariant { assert(length <= data.length); } } If this is void initialized, @safe test() { ShortString s = void; char c = s[16]; } Then the value in .length is unpredictable, so the invariant may not be satisfied. So, in @safe code, void initializations of struct objects when the struct has an invariant should not be allowed. The same holds true for unions, such as: union U { int n; ShortString s; } Examples by Dennis Korpel and Paul Backus.

@WalterBright created dlang/dmd pull request #12326 "fix Issue 21665 - Void initialization should not be allowed for insta…" fixing this issue: - fix Issue 21665 - Void initialization should not be allowed for instances of struct with invariant https://github.com/dlang/dmd/pull/12326

dlang/dmd pull request #12326 "fix Issue 21665 - Void initialization should not be allowed for insta…" was merged into master: - 72b737a626e3088b829cdde29ed51c6c00a308e8 by Walter Bright: fix Issue 21665 - Void initialization should not be allowed for instances of struct with invariant https://github.com/dlang/dmd/pull/12326