Bug 18313 – Default initializer for class isn't always called

When working with dlib library (gamedev oriented library) I've noticed a strange behaviour, which seems unexpected to me: For this example code (add "dlib": "~>0.12.2" to dub dependency to build): import std.stdio; import dlib.math; class Foo { Matrix4f mat1; Matrix4f mat2 = Matrix4f.zero(); Quaternionf q1; Quaternionf q2 = Quaternionf.identity();; } void main() { Foo foo = new Foo(); writeln(foo.mat1); writeln(foo.mat2); writeln(foo.q1); writeln(foo.q2); Matrix4f mat3; Matrix4f mat4 = Matrix4f.zero(); writeln(mat3); writeln(mat4); } The expectation is that foo.mat2 gets initialized to Matrix4f.zero() value, just like it works with foo.q2 and mat4 variable. But for some reason, foo.mat2 stays uninitialized (filled with NaNs rather than zeroes).

*** This issue has been marked as a duplicate of issue 15205 ***