The `declare_program!` and `declare_loader!` macros both expand to
new macro definitions (based on the `$name` argument). These 'inner'
macros make use of the special `$crate` metavariable to access items in
the crate where the 'inner' macros is defined.
However, this only works due to a bug in rustc. When a macro is
expanded, all `$crate` tokens in its output are 'marked' as being
resolved in the defining crate of that macro. An inner macro (including
the body of its arms) is 'just' another set of tokens that appears in
the body of the outer macro, so any `$crate` identifiers used there are
resolved relative to the 'outer' macro.
For example, consider the following code:
```rust
macro_rules! outer {
() => {
macro_rules! inner {
() => {
$crate::Foo
}
}
}
}
```
The path `$crate::Foo` will be resolved relative to the crate that defines `outer`,
**not** the crate which defines `inner`.
However, rustc currently loses this extra resolution information
(referred to as 'hygiene' information) when a crate is serialized.
In the above example, this means that the macro `inner` (which gets
defined in whatever crate invokes `outer!`) will behave differently
depending on which crate it is invoked from:
When `inner` is invoked from the same crate in which it is defined,
the hygiene information will still be available,
which will cause `$crate::Foo` to be resolved in the crate which defines 'outer'.
When `inner` is invoked from a different crate, it will be loaded from
the metadata of the crate which defines 'inner'. Since the hygiene
information is currently lost, rust will 'forget' that `$crate::Foo` is
supposed to be resolved in the context of 'outer'. Instead, it will be
resolved relative to the crate which defines 'inner', which can cause
incorrect code to compile.
This bug will soon be fixed in rust (see https://github.com/rust-lang/rust/pull/72121),
which will break `declare_program!` and `declare_loader!`. Fortunately,
it's possible to obtain the desired behavior (`$crate` resolving in the
context of the 'inner' macro) by use of a procedural macro.
This commit adds a `respan!` proc-macro to the `sdk/macro` crate.
Using the newly-stabilized (on Nightly) `Span::resolved_at` method,
the `$crate` identifier can be made to be resolved in the context of the
proper crate.
Since `Span::resolved_at` is only stable on the latest nightly,
referencing it on an earlier version of Rust will cause a compilation error.
This requires the `rustversion` crate to be used, which allows conditionally
compiling code epending on the Rust compiler version in use. Since this method is already
stabilized in the latest nightly, there will never be a situation where
the hygiene bug is fixed (e.g. https://github.com/rust-lang/rust/pull/72121)
is merged but we are unable to call `Span::resolved_at`.
* Make Message::new_with_payer the default constructor
* Remove Transaction::new_[un]signed_instructions
These guess the fee-payer instead of stating it explicitly
* Fixup commitment-aggregation metric
* Trigger notifications after commitment-cache update
* Fixup fn name
* Add single-confirmation commitment level
* Rename to highest_confirmed_slot
* Pass commitment-cache info directly to notifications
* Use match
* Update commitment docs
* Update out of date pubsub docs
* lamports->SOL in user-facing error msg
* Check for sufficient balance for spend and fee
* Add ALL option to solana transfer
* Rework TransferAmount to check for sign_only in parse
* Refactor TransferAmount & fee-check handling to be more general
* Add addl checks mechanism
* Move checks out of cli.rs
* Rename to SpendAmount to be more general & move
* Impl ALL/spend helpers for create-nonce-account
* Impl spend helpers for create-vote-account
* Impl ALL/spend helpers for create-stake-account
* Impl spend helpers for ping
* Impl ALL/spend helpers for pay
* Impl spend helpers for validator-info
* Remove unused fns
* Remove retry_get_balance
* Add a couple unit tests
* Rework send_util fn signatures
* Switch AccountsIndex.account_maps from HashMap to BTreeMap
* Introduce eager rent collection
* Start to add tests
* Avoid too short eager rent collection cycles
* Add more tests
* Add more tests...
* Refacotr!!!!!!
* Refactoring follow up
* More tiny cleanups
* Don't rewrite 0-lamport accounts to be deterministic
* Refactor a bit
* Do hard fork, restore tests, and perf. mitigation
* Fix build...
* Refactor and add switch over for testnet (TdS)
* Use to_be_bytes
* cleanup
* More tiny cleanup
* Rebase cleanup
* Set Bank::genesis_hash when resuming from snapshot
* Reorder fns and clean ups
* Better naming and commenting
* Yet more naming clarifications
* Make prefix width strictly uniform for 2-base partition_count
* Fix typo...
* Revert cluster-dependent gate
* kick ci?
* kick ci?
* kick ci?
