[Issue 14639] Assigning init value to struct uses stack, causing segfault

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14639

--- Comment #3 from Walter Bright <bugzilla at digitalmars.com> ---
The code:

    biggy = Biggy.init;

gets rewritten to be:

    biggy = Biggy([0LU, ...]);

which is a construction. The postblit caused an opAssign() to be created, and
the expression is further rewritten to:

    biggy.opAssign(Biggy([0LU, ...]));

which blows up the parameter stack because Biggy([0LU, ...]) is too big for it.
The operation is not disabled because it gets constructed in place - a copy is
not being made.

A possible compiler fix is to figure out that the generated opAssign is trivial
and can be replaced with a bit copy. The code in opover.d:

                if (sd && !sd.hasIdentityAssign)
                {
                    /* This is bitwise struct assignment. */
                    return;
                }

can be modified to test for triviality of identity assign, and use a bitwise
copy.

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