An init-capture inhabits the scope of the lambda-expression's compound-statement. An init-capture without ellipsis behaves as if it declares and explicitly captures a variable of the form “auto init-capture ;”, except that:

• [...]

Assume we have an init-capture x = x, the behavior would be as if it looks like

auto x = x;

According to [basic.scope.pdecl] p1 and [dcl.spec.auto.general] p11, the specified behavior is ill-formed.