Before introducing slots it was hard to change global variables
preserving changes across multiple function calls.
This commit implements such possibility.
Closes#638.
1. Slot is a new mechanism for storing variables during execution
which is more convenient than alt.stack. This commit implements
support for slot opcodes in both vm and compiler.
2. Remove old alt.stack opcodes.
3. Do not process globals at the start of every function, but instead
load them single time at main.
A part of integration with NEO Blockchain Toolkit (see #902). To be
able to deploy smart-contract compiled with neo-go compiler via NEO
Express, we have to generate additional .abi.json file. This file
contains the following information:
- hash of the compiled contract
- smart-contract metadata (title, description, version, author,
email, has-storage, has-dynamic-invoke, is-payable)
- smart-contract entry point
- functions
- events
However, this .abi.json file is slightly different from the one,
described in manifest.go, so we have to add auxilaury stractures for
json marshalling. The .abi.json format used by NEO-Express is described
[here](https://github.com/neo-project/neo-devpack-dotnet/blob/master/src/Neo.Compiler.MSIL/FuncExport.cs#L66).
Method `methodInfoFromScope(...)` always returned an empty parameters
set, so we were missing this information in both .abi.json and
.debug.json files. Fixed now.
Sequence points is a way to map a specific instruction offset
from a compiled contract to a text span in a source file.
This commit implements mapping only for `return` statements.
Further improvements are straight-forward.
Previously, struct variables were initialize with VM's nil value
which is of primitive type. Thus SETITEM used for struct's field
updating wasn't working.
Previously this declarations were ignored which resulted
in runtime errors, because VM's nil is an element of primitive type
and can't be converted to an array.
When `return` or `break` statement is encountered inside
a for/range/switch statement, top stack items can be auxilliary.
They need to be cleaned up before returning from the function.
Current implementation of short-circuting is just plain wrong
as it uses `last` or `before-last` labels which meaning depend
on context. It doesn't even handle simple assignements like
`a := x == 1 && y == 2`.
This commit makes all jumps in such conditions local
and adds tests.
Closes#699, #700.
