Which greatly simplifies reuse of these packages (and they're expected to be
reused since real tokens implement standards and also add something of their
own) and allows to avoid effects like
doc_test.go:68:28: ambiguous selector neoContract.BalanceOf
when neo.Contract is used. Avoids duplication in NEP-11 implementation as
well.
So that (*codegen).Visit is able to omit code generation for these
unused global vars. The most tricky part is to detect unused global
variables, it is done in several steps:
1. Collect the set of named used/unused global vars.
2. Collect the set of globally declared expressions that contain
function calls.
3. Pick up global vars from the set made at step 2.
4. Traverse used functions and puck up those global vars that are used
from these functions.
5. Rename all globals that are presented in the set made at step 1
but are not presented in the set made on step 3 or step 4.
Move all auxiliary function declaration after Main, so that INITSLOT
instructions counter works properly. `vmAndCompileInterop` loads program
and moves nextIP to the Main function offset if there's no _init
function. If _init is there, then nextIP will be moved to the start of
_init. In TestInline we don't handle instructions properly (CALL/JMP
don't change nextIP), we just perform instruction traversal from the
start point via Next(), thus INITSLOT counter value depends on the
starting instruction, which depends on _init presence.
If variable is unnamed and does not contain function call then it's
treated as unused and code generation may be omitted for it
initialization/declaration.
In case if global var is unnamed (and, as a consequence, unused) and
contains a function call inside its value specification, we need to emit
code for this var to be able to call the function as it can have
side-effects. See the example:
```
package foo
import "github.com/nspcc-dev/neo-go/pkg/interop/runtime"
var A = f()
func Main() int {
return 3
}
func f() int {
runtime.Notify("Valuable notification", 1)
return 2
}
```
NEP-6 has a notion of locked acccounts and SignTx must respect this user's
choice. For some reason this setting was inappropriately used by our RPC
client tests (probably a different kind of lock was meant).
* each account must have an appropriate signer, if there is no signer for
this account in the tx it's an error
* we can only safely append to Scripts when account belongs to the next
signer (we don't have appropriate verification scripts for other signers)
* when contract has one parameter, the signature shouldn't be appended to
other data
I think these rules allow to handle more cases and do that safer. We have more
complex scenarios though, like non-signature parameters or mixed-parameter
invocation scripts, but that's out of scope for now.
