On Monday, 5 March 2018 at 10:57:35 UTC, Jonathan M Davis wrote (in the article):
The problem is that the entire object must be fully initialized before the body of the postblit constructor is run. That means that any member variables which are const or immutable are stuck at whatever they were in the original object, because it would violate the type system to mutate them. And if an object is const or immutable, then that's all of the members.

I think we have a misunderstanding here. According to that, this would not compile (imports left out):

struct placeAtWorldMap
{   char[] title;
    int[2] coordsMicroDeg;

    {   title = title.dup;
void main()
{   char[] title = "London bridge".dup;
    const place = placeAtWorldMap(title, [51_508_038, -87_693]);
    const samePlace = place;
    "falling down ".copy(title);
    place.title.writeln; // falling down
    samePlace.title.writeln; // London bridge

...but it compiles and correctly runs, and I'm happy about that.

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