local variables are now created automatically when they are first assigned to.
the global keyword can be used to declare that a name refers to a global variable instead,
at which point, assigning to the name results in the assignment referencing the global variable
instead of allocating a new global variable.
IVY_KW_VAR is not treated as an expression start token (as variable declarations are not
strictly expressions). so the lambda parser did not create a block parser context
when it encountered this keyword.
