Reduce unnecessary COW on Vector by make writing explicit

This commit makes operator[] on Vector const and adds a write proxy to it.  From
now on writes to Vectors need to happen through the .write proxy. So for
instance:

Vector<int> vec;
vec.push_back(10);
std::cout << vec[0] << std::endl;
vec.write[0] = 20;

Failing to use the .write proxy will cause a compilation error.

In addition COWable datatypes can now embed a CowData pointer to their data.
This means that String, CharString, and VMap no longer use or derive from
Vector.

_ALWAYS_INLINE_ and _FORCE_INLINE_ are now equivalent for debug and non-debug
builds. This is a lot faster for Vector in the editor and while running tests.
The reason why this difference used to exist is because force-inlined methods
used to give a bad debugging experience. After extensive testing with modern
compilers this is no longer the case.

1 files changed, 1 insertions, 1 deletions

diff --git a/scene/2d/line_2d.cpp b/scene/2d/line_2d.cpp
index e9e895b5bb..ad9775c0b7 100644
--- a/scene/2d/line_2d.cpp
+++ b/scene/2d/line_2d.cpp
@@ -239,7 +239,7 @@ void Line2D::_draw() {
 	{
 		PoolVector<Vector2>::Read points_read = _points.read();
 		for (int i = 0; i < len; ++i) {
-			points[i] = points_read[i];
+			points.write[i] = points_read[i];
 		}
 	}