Fix Issue 20367 - Postblit cannot be disabled when copy ctor is defined

[RazvanN7]

If a struct defines both a postblit and a copy constructor and the postblit is disabled, go with the copy constructor.

[dlang-bot]

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	20367	normal	Postblit cannot be disabled when copy ctor is defined

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub fetch digger
dub run digger -- build "master + dmd#10557"

[thewilsonator]

Auto-merge toggled on

[SSoulaimane]

I remembered this function.

dmd/src/dmd/mtype.d

Lines 6748 to 6765 in a140329

	/***************************************************
	* Determine if type t is copyable.
	* Params:
	* t = type to check
	* Returns:
	* true if we can copy it
	*/
	bool isCopyable(const Type t) pure nothrow @nogc
	{
	//printf("isCopyable() %s\n", t.toChars());
	if (auto ts = t.isTypeStruct())
	{
	if (ts.sym.postblit &&
	ts.sym.postblit.storage_class & STC.disable)
	return false;
	}
	return true;
	}

You may want to look into it.