var.this

this(ref return scope inout var rhs) inout scope @safe

Copy constructor for same-constness copies (mutable→mutable,

const→const, immutable→immutable, and compiler-generated inout copies
in structs that embed var): shallow payload copy, matching the
documented var a = b; aliasing semantics.

this(ref return scope const var rhs) @safe

Copy constructor from a const var into a mutable one: deep copy. A shallow blit would hand back a mutable alias to the const payload, letting @safe callers mutate "const" data (and race on shared snapshots).

this(ref return scope immutable var rhs) @safe

Copy constructor from an immutable var into a mutable one: deep copy (see the const overload).

this(ref return scope const var rhs) const scope @safe

Copy constructor from a const var into a const one: shallow copy. A const destination cannot be used to mutate the payload, so aliasing is sound.

this(ref return scope immutable var rhs) const scope @safe

Copy constructor from an immutable var into a const one: shallow copy (a const view of immutable data; nobody can mutate it).

this(T arg) @safe

Construct a var from another value arg.

This constructor delegates to opAssign for non-var arguments to normalize behavior. var-to-var copies are handled exclusively by the copy constructors above (D forbids an rvalue constructor alongside a copy constructor).