Loadable syntax extensions don't work when cross compiling (see #12102), so the
fourcc tests all need to be ignored. They're valuable tests, so they shouldn't
be outright ignored, so they're now flagged with ignore-cross-compile
This resolves issue #12157. Does that do it already or is there something else that needs taking care of?
As a side note, there seems to be some documentation, in which the old existence of the do keyword is explained. The list of keywords is not up-to-date either. But these are certainly separate issues.
Resolves issue #12157. `do` is hereby reinstated as a keyword; no syntax is
associated with it though. Along the way, a unit test had to be adapted, since
it was using `do` as a method identifier.
Breaking changes:
- Any code using `do` as an identifier will no longer work.
The previous definition was actually describing covariance.
Fixing to describe contravariance while keeping 'static in the definition was tricky so just changed to use 'short and 'long.
Repair a rather embarassingly obvious hole that I created as part of #9629. In particular, prevent `&mut` borrows of data in an aliasable location. This used to be prevented through the restrictions mechanism, but in #9629 I modified those rules incorrectly.
r? @pcwalton
Fixes#11913
It was decided that a consistent result across platforms would be the
most useful and least surprising. A "target" option has been added to
get the old behaviour of using the target platform's endianess.
fourcc!() allows you to embed FourCC (or OSType) values that are
evaluated as u32 literals. It takes a 4-byte ASCII string and produces
the u32 resulting in interpreting those 4 bytes as a u32, using either
the platform-native endianness, or explicitly as big or little endian.
This pull request tries to fix#12050.
I went after these wrong errors quite aggressively so it might be that I also changed some strings that are not actual errors.
Please point those out and I will update this pull request accordingly.
Error messages cleaned in librustc/middle
Error messages cleaned in libsyntax
Error messages cleaned in libsyntax more agressively
Error messages cleaned in librustc more aggressively
Fixed affected tests
Fixed other failing tests
Last failing tests fixed
Declare a `type SendStr = MaybeOwned<'static>` to ease readibility of
types that needed the old SendStr behavior.
Implement all the traits for MaybeOwned that SendStr used to implement.
- Convert the formatting traits to `&self` rather than `_: &Self`
- Rejig `syntax::ext::{format,deriving}` a little in preparation
- Implement `#[deriving(Show)]`
This has been a long time coming. Conditions in rust were initially envisioned
as being a good alternative to error code return pattern. The idea is that all
errors are fatal-by-default, and you can opt-in to handling the error by
registering an error handler.
While sounding nice, conditions ended up having some unforseen shortcomings:
* Actually handling an error has some very awkward syntax:
let mut result = None;
let mut answer = None;
io::io_error::cond.trap(|e| { result = Some(e) }).inside(|| {
answer = Some(some_io_operation());
});
match result {
Some(err) => { /* hit an I/O error */ }
None => {
let answer = answer.unwrap();
/* deal with the result of I/O */
}
}
This pattern can certainly use functions like io::result, but at its core
actually handling conditions is fairly difficult
* The "zero value" of a function is often confusing. One of the main ideas
behind using conditions was to change the signature of I/O functions. Instead
of read_be_u32() returning a result, it returned a u32. Errors were notified
via a condition, and if you caught the condition you understood that the "zero
value" returned is actually a garbage value. These zero values are often
difficult to understand, however.
One case of this is the read_bytes() function. The function takes an integer
length of the amount of bytes to read, and returns an array of that size. The
array may actually be shorter, however, if an error occurred.
Another case is fs::stat(). The theoretical "zero value" is a blank stat
struct, but it's a little awkward to create and return a zero'd out stat
struct on a call to stat().
In general, the return value of functions that can raise error are much more
natural when using a Result as opposed to an always-usable zero-value.
* Conditions impose a necessary runtime requirement on *all* I/O. In theory I/O
is as simple as calling read() and write(), but using conditions imposed the
restriction that a rust local task was required if you wanted to catch errors
with I/O. While certainly an surmountable difficulty, this was always a bit of
a thorn in the side of conditions.
* Functions raising conditions are not always clear that they are raising
conditions. This suffers a similar problem to exceptions where you don't
actually know whether a function raises a condition or not. The documentation
likely explains, but if someone retroactively adds a condition to a function
there's nothing forcing upstream users to acknowledge a new point of task
failure.
* Libaries using I/O are not guaranteed to correctly raise on conditions when an
error occurs. In developing various I/O libraries, it's much easier to just
return `None` from a read rather than raising an error. The silent contract of
"don't raise on EOF" was a little difficult to understand and threw a wrench
into the answer of the question "when do I raise a condition?"
Many of these difficulties can be overcome through documentation, examples, and
general practice. In the end, all of these difficulties added together ended up
being too overwhelming and improving various aspects didn't end up helping that
much.
A result-based I/O error handling strategy also has shortcomings, but the
cognitive burden is much smaller. The tooling necessary to make this strategy as
usable as conditions were is much smaller than the tooling necessary for
conditions.
Perhaps conditions may manifest themselves as a future entity, but for now
we're going to remove them from the standard library.
Closes#9795Closes#8968
This has been a long time coming. Conditions in rust were initially envisioned
as being a good alternative to error code return pattern. The idea is that all
errors are fatal-by-default, and you can opt-in to handling the error by
registering an error handler.
While sounding nice, conditions ended up having some unforseen shortcomings:
* Actually handling an error has some very awkward syntax:
let mut result = None;
let mut answer = None;
io::io_error::cond.trap(|e| { result = Some(e) }).inside(|| {
answer = Some(some_io_operation());
});
match result {
Some(err) => { /* hit an I/O error */ }
None => {
let answer = answer.unwrap();
/* deal with the result of I/O */
}
}
This pattern can certainly use functions like io::result, but at its core
actually handling conditions is fairly difficult
* The "zero value" of a function is often confusing. One of the main ideas
behind using conditions was to change the signature of I/O functions. Instead
of read_be_u32() returning a result, it returned a u32. Errors were notified
via a condition, and if you caught the condition you understood that the "zero
value" returned is actually a garbage value. These zero values are often
difficult to understand, however.
One case of this is the read_bytes() function. The function takes an integer
length of the amount of bytes to read, and returns an array of that size. The
array may actually be shorter, however, if an error occurred.
Another case is fs::stat(). The theoretical "zero value" is a blank stat
struct, but it's a little awkward to create and return a zero'd out stat
struct on a call to stat().
In general, the return value of functions that can raise error are much more
natural when using a Result as opposed to an always-usable zero-value.
* Conditions impose a necessary runtime requirement on *all* I/O. In theory I/O
is as simple as calling read() and write(), but using conditions imposed the
restriction that a rust local task was required if you wanted to catch errors
with I/O. While certainly an surmountable difficulty, this was always a bit of
a thorn in the side of conditions.
* Functions raising conditions are not always clear that they are raising
conditions. This suffers a similar problem to exceptions where you don't
actually know whether a function raises a condition or not. The documentation
likely explains, but if someone retroactively adds a condition to a function
there's nothing forcing upstream users to acknowledge a new point of task
failure.
* Libaries using I/O are not guaranteed to correctly raise on conditions when an
error occurs. In developing various I/O libraries, it's much easier to just
return `None` from a read rather than raising an error. The silent contract of
"don't raise on EOF" was a little difficult to understand and threw a wrench
into the answer of the question "when do I raise a condition?"
Many of these difficulties can be overcome through documentation, examples, and
general practice. In the end, all of these difficulties added together ended up
being too overwhelming and improving various aspects didn't end up helping that
much.
A result-based I/O error handling strategy also has shortcomings, but the
cognitive burden is much smaller. The tooling necessary to make this strategy as
usable as conditions were is much smaller than the tooling necessary for
conditions.
Perhaps conditions may manifest themselves as a future entity, but for now
we're going to remove them from the standard library.
Closes#9795Closes#8968
This commit removes the -c, --emit-llvm, -s, --rlib, --dylib, --staticlib,
--lib, and --bin flags from rustc, adding the following flags:
* --emit=[asm,ir,bc,obj,link]
* --crate-type=[dylib,rlib,staticlib,bin,lib]
The -o option has also been redefined to be used for *all* flavors of outputs.
This means that we no longer ignore it for libraries. The --out-dir remains the
same as before.
The new logic for files that rustc emits is as follows:
1. Output types are dictated by the --emit flag. The default value is
--emit=link, and this option can be passed multiple times and have all options
stacked on one another.
2. Crate types are dictated by the --crate-type flag and the #[crate_type]
attribute. The flags can be passed many times and stack with the crate
attribute.
3. If the -o flag is specified, and only one output type is specified, the
output will be emitted at this location. If more than one output type is
specified, then the filename of -o is ignored, and all output goes in the
directory that -o specifies. The -o option always ignores the --out-dir
option.
4. If the --out-dir flag is specified, all output goes in this directory.
5. If -o and --out-dir are both not present, all output goes in the directory of
the crate file.
6. When multiple output types are specified, the filestem of all output is the
same as the name of the CrateId (derived from a crate attribute or from the
filestem of the crate file).
Closes#7791Closes#11056Closes#11667
