fmt::Show is for debugging, and can and should be implemented for
all public types. This trait is used with `{:?}` syntax. There still
exists #[derive(Show)].
fmt::String is for types that faithfully be represented as a String.
Because of this, there is no way to derive fmt::String, all
implementations must be purposeful. It is used by the default format
syntax, `{}`.
This will break most instances of `{}`, since that now requires the type
to impl fmt::String. In most cases, replacing `{}` with `{:?}` is the
correct fix. Types that were being printed specifically for users should
receive a fmt::String implementation to fix this.
Part of #20013
[breaking-change]
This removes a large array of deprecated functionality, regardless of how
recently it was deprecated. The purpose of this commit is to clean out the
standard libraries and compiler for the upcoming alpha release.
Some notable compiler changes were to enable warnings for all now-deprecated
command line arguments (previously the deprecated versions were silently
accepted) as well as removing deriving(Zero) entirely (the trait was removed).
The distribution no longer contains the libtime or libregex_macros crates. Both
of these have been deprecated for some time and are available externally.
Closes#8142.
This is not the semantics we want long-term. You can continue to use
`#[unsafe_destructor]`, but you'll need to add
`#![feature(unsafe_destructor)]` to the crate attributes.
[breaking-change]
This removes all remnants of `@` pointers from rustc. Additionally, this removes
the `GC` structure from the prelude as it seems odd exporting an experimental
type in the prelude by default.
Closes#14193
[breaking-change]
This commit moves reflection (as well as the {:?} format modifier) to a new
libdebug crate, all of which is marked experimental.
This is a breaking change because it now requires the debug crate to be
explicitly linked if the :? format qualifier is used. This means that any code
using this feature will have to add `extern crate debug;` to the top of the
crate. Any code relying on reflection will also need to do this.
Closes#12019
[breaking-change]
This commit moves all logging out of the standard library into an external
crate. This crate is the new crate which is responsible for all logging macros
and logging implementation. A few reasons for this change are:
* The crate map has always been a bit of a code smell among rust programs. It
has difficulty being loaded on almost all platforms, and it's used almost
exclusively for logging and only logging. Removing the crate map is one of the
end goals of this movement.
* The compiler has a fair bit of special support for logging. It has the
__log_level() expression as well as generating a global word per module
specifying the log level. This is unfairly favoring the built-in logging
system, and is much better done purely in libraries instead of the compiler
itself.
* Initialization of logging is much easier to do if there is no reliance on a
magical crate map being available to set module log levels.
* If the logging library can be written outside of the standard library, there's
no reason that it shouldn't be. It's likely that we're not going to build the
highest quality logging library of all time, so third-party libraries should
be able to provide just as high-quality logging systems as the default one
provided in the rust distribution.
With a migration such as this, the change does not come for free. There are some
subtle changes in the behavior of liblog vs the previous logging macros:
* The core change of this migration is that there is no longer a physical
log-level per module. This concept is still emulated (it is quite useful), but
there is now only a global log level, not a local one. This global log level
is a reflection of the maximum of all log levels specified. The previously
generated logging code looked like:
if specified_level <= __module_log_level() {
println!(...)
}
The newly generated code looks like:
if specified_level <= ::log::LOG_LEVEL {
if ::log::module_enabled(module_path!()) {
println!(...)
}
}
Notably, the first layer of checking is still intended to be "super fast" in
that it's just a load of a global word and a compare. The second layer of
checking is executed to determine if the current module does indeed have
logging turned on.
This means that if any module has a debug log level turned on, all modules
with debug log levels get a little bit slower (they all do more expensive
dynamic checks to determine if they're turned on or not).
Semantically, this migration brings no change in this respect, but
runtime-wise, this will have a perf impact on some code.
* A `RUST_LOG=::help` directive will no longer print out a list of all modules
that can be logged. This is because the crate map will no longer specify the
log levels of all modules, so the list of modules is not known. Additionally,
warnings can no longer be provided if a malformed logging directive was
supplied.
The new "hello world" for logging looks like:
#[phase(syntax, link)]
extern crate log;
fn main() {
debug!("Hello, world!");
}
values to be copied. Rewrite kind computation so that instead of directly
computing the kind it computes what kinds of values are present in the type,
and then derive kinds based on that. I find this easier to think about.
Fixes#4821.
Changes:
- Refactor move mode computation
- Removes move mode arguments, unary move, capture clauses
(though they still parse for backwards compatibility)
- Simplify how moves are handled in trans
- Fix a number of illegal copies that cropped up
- Workaround for bug involving def-ids in params
(see details below)
Future work (I'll open bugs for these...):
- Improve error messages for moves that are due
to bindings
- Add support for moving owned content like a.b.c
to borrow check, test in trans (but I think it'll
"just work")
- Proper fix for def-ids in params
Def ids in params:
Move captures into a map instead of recomputing.
This is a workaround for a larger bug having to do with the def-ids associated
with ty_params, which are not always properly preserved when inlining. I am
not sure of my preferred fix for the larger bug yet. This current fix removes
the only code in trans that I know of which relies on ty_param def-ids, but
feels fragile.
