`get` keyword behaves exactly like `method_id` (auto-calc hash),
but it's placed on the left, similar to Tact: `get T name()`.
`method_id(n)` is still valid, considering it can't be invoked by name,
since a client will compute another hash.
It's supposed it will be still used in tests and in low-level code
(not to be called externally, but to be called after replacing c3).
`get(hash)` is invalid, this keyword does not accept anything.
* Add special string literals "..."? (s,a,u,h,)
* Add string literal H (256-bit hash)
* Add string literal c (crc32)
* Use td::hex_encode instead of homebrew function and add test
* Fix error codes and use more generic address
* Add support for int and slice constants
* Add support for strongly typed constants
* Add support for precompiled constant expressions (hard!)
Co-authored-by: starlightduck <starlightduck@gmail.com>
