[Issue 21674] [REG v2.086] `alias this` triggers wrong deprecation message on function call

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21674

--- Comment #7 from Iain Buclaw <ibuclaw at gdcproject.org> ---
The cause of the regression is that the conditions that check this are looking
at the wrong thing.

---
if (Expression result = checkAliasThisForLhs(ad1, sc, e))
{
    // Problem #1
    //   + e = `m.data = "Hello World"`
    //   + result = `m.data.str("Hello World")
    // I think we should instead be looking at the `result{.e1}.op`, not the
    // original expression.
    if (e.op != EXP.assign || e.e1.op == EXP.type)
        return result;

    // Problem #2
    //   + ad1 = `S1`
    //   + result.var.parent = `EntryType`
    // I think we should instead be looking at the aggregate declaration for
    // the LHS of the rewritten `result`.
    if (ad1.fields.dim == 1 || (ad1.fields.dim == 2 && ad1.vthis))
    {
        if (var && var.type == ad1.fields[0].type)
            return result;

        if (tf.isref && ad1.fields[0].type == tf.next)
            return result;
    }
}
---

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