MSL follows C++ standard convention, and such variable declarations within switch statements must have their scope localised within each case. Adding braces in all cases ensures correct behaviour and avoids 'case ... bypass initialization of local variable' compilation error.
struct initialisation to follow C++ rules for Metal. Implicit constructors replaced with either explicit constructors or list-initialization where appropriate.
Ref T96261
Authored by Apple: Michael Parkin-White
Reviewed By: fclem
Maniphest Tasks: T96261
Differential Revision: https://developer.blender.org/D14451
e28f07b5c8