Currently, rustc requires that a linkage be a product of 100% rlibs or 100%
dylibs. This is to satisfy the requirement that each object appear at most once
in the final output products. This is a bit limiting, and the upcoming libcore
library cannot exist as a dylib, so these rules must change.

The goal of this commit is to enable *some* use cases for mixing rlibs and
dylibs, primarily libcore's use case. It is not targeted at allowing an
exhaustive number of linkage flavors.

There is a new dependency_format module in rustc which calculates what format
each upstream library should be linked as in each output type of the current
unit of compilation. The module itself contains many gory details about what's
going on here.

cc #10729

This was accidentally left out of the recent logging improvements.

This was accidentally left out of the recent logging improvements.

Update the example to make the usage of `pub mod foo;` much more
apparent, as well as using an example where setting the visibility of
the module is actually necessary.

The `std::bitflags::bitflags!` macro did not provide support for
adding attributes to the generates structure, due to limitations in
the parser for macros. This patch works around the parser limitations
by requiring a `flags` keyword in the `bitflags!` invocations:

    bitflags!(
        #[deriving(Hash)]
        #[doc="Three flags"]
        flags Flags: u32 {
            FlagA       = 0x00000001,
            FlagB       = 0x00000010,
            FlagC       = 0x00000100
        }
    )

The intent of `std::bitflags` is to allow building type-safe wrappers
around C-style flags APIs. But in addition to construction these flags
from the Rust side, we need a way to convert them from the C
side. This patch adds a `from_bits` function, which is unsafe since
the bits in question may not represent a valid combination of flags.

Finally, this patch changes `std::io::FilePermissions` from an exposed
`u32` representation to a typesafe representation (that only allows valid
flag combinations) using the `std::bitflags`.

Closes #6085.

New attempt to generalize stats, after #12606.
Since #12355 did not get merged, i want go get first get my change done and the try to fix sum.

Update the example to make the usage of `pub mod foo;` much more
apparent, as well as using an example where setting the visibility of
the module is actually necessary.

Shamelessly adds myself as a contributor.

While there are various references to the work compositionality on the web, I can't find any reference to it being an actual word. My understanding is that composability is what's actually meant here anyway.

If an unbalanced [ exists in a string or comment, this should not be
considered when calculating the indent at the top level.

Similarly, when testing for ({/}) to see if we're at the top level to
begin with, strings and comments should be skipped.

Followup to some recent feedback in PR #13676.

By carefully distinguishing falling back to the default arm from moving
on to the next pattern, this patch adjusts the codegen logic for range
and guarded arms of pattern matching expression. It is a more
appropriate way of fixing #12582 and #13027 without causing regressions
such as #13867.
    
Closes #13867

Turning a `&T` into an `&mut T` is undefined behaviour, and needs to be
done very very carefully. Providing a convenience function for exactly
this task is a bad idea, just tempting people into doing the wrong
thing.

(The right thing is to use types like `Cell`, `RefCell` or `Unsafe`.)

cc https://github.com/mozilla/rust/issues/13933

The logging macros now create a LogRecord, and pass that to the Logger. This will allow custom loggers to change the formatting, and possible filter on more properties of the log record.

DefaultLogger's formatting was taken from Python's default formatting:
`LEVEL:from: message`

Also included: fmt::Arguments now implement Show, so they can be used to
extend format strings.

@alexcrichton r?

This patch changes `std::io::FilePermissions` from an exposed `u32`
representation to a typesafe representation (that only allows valid
flag combinations) using the `std::bitflags`, thus ensuring a greater
degree of safety on the Rust side.

Despite the change to the type, most code should continue to work
as-is, sincde the new type provides bit operations in the style of C
flags. To get at the underlying integer representation, use the `bits`
method; to (unsafely) convert to `FilePermissions`, use
`FilePermissions::from_bits`.

Closes #6085.

[breaking-change]

The intent of `std::bitflags` is to allow building type-safe wrappers
around C-style flags APIs. But in addition to construction these flags
from the Rust side, we need a way to convert them from the C
side. This patch adds a `from_bits` function, which is unsafe since
the bits in question may not represent a valid combination of flags.

The `std::bitflags::bitflags!` macro did not provide support for
adding attributes to the generated structure or flags, due to
limitations in the parser for macros. This patch works around the
parser limitations by requiring a `flags` keyword in the overall
`bitflags!` invocation, and a `static` keyword for each flag:

    bitflags!(
        #[deriving(Hash)]
        #[doc="Three flags"]
        flags Flags: u32 {
            #[doc="The first flag"]
            static FlagA       = 0x00000001,
            static FlagB       = 0x00000010,
            static FlagC       = 0x00000100
        }
    )

These often crop up when using default methods that don't actually bind their
argument names.

Closes #13775

Some minor clarifications and fixes.

The logging macros now create a LogRecord, and pass that to the
Logger, instead of passing a `level` and `args`. The new signature is:

    trait Logger {
        fn log(&mut self, record: &LogRecord);
    }

The LogRecord includes additional values that may be useful to custom
loggers, and also allows for further expansion if not values are found
useful.

DefaultLogger's formatting was taken from Python's default formatting:
`LEVEL:from: message`

Also included: fmt::Arguments now implement Show, so they can be used to
extend format strings.

[breaking-change]

This patch fixes issue #13186.

When generating constant expression for enum, it is possible that
alignment of expression may be not equal to alignment of type.  In that
case space after last struct field must be padded to match size of value
and size of struct. This commit adds that padding.

See detailed explanation in src/test/run-pass/trans-tag-static-padding.rs

This was removed because these could alias with `&const T` or `@mut T`
and those are now gone from the language. There are still aliasing
issues within local scopes, but this is correct for function parameters.

This also removes the no-op `noalias` marker on proc (not a pointer) and
leaves out the mention of #6750 because real type-based alias analysis
is not within the scope of best effort usage of the `noalias` attribute.

Test case:

    pub fn foo(x: &mut &mut u32) {
        **x = 5;
        **x = 5;
    }

Before:

    define void @_ZN3foo20h0ce94c9671b0150bdaa4v0.0E(i32** nocapture readonly) unnamed_addr #0 {
    entry-block:
      %1 = load i32** %0, align 8
      store i32 5, i32* %1, align 4
      %2 = load i32** %0, align 8
      store i32 5, i32* %2, align 4
      ret void
    }

After:

    define void @_ZN3foo20h0ce94c9671b0150bdaa4v0.0E(i32** noalias nocapture readonly) unnamed_addr #0 {
    entry-block:
      %1 = load i32** %0, align 8
      store i32 5, i32* %1, align 4
      ret void
    }

Closes #12436

Corrected example to to use Rand trait referenced in preceding
description and included an example using the Show trait to print ABC.

Combined redundant paragraphs about the match expression and removed a
redundant example.

Add a `graphviz` crate for making .dot files to layout and render graphs.

(This is a precursor to other work to render control-flow graphs from within rustc itself; but this crate should be independently usable, since it abstracts over the client's graph-representation and labeling method.)

By carefully distinguishing falling back to the default arm from moving
on to the next pattern, this patch adjusts the codegen logic for range
and guarded arms of pattern matching expression. It is a more
appropriate way of fixing #12582 and #13027 without causing regressions
such as #13867.

Closes #13867

It has been found that #13034 was flawed and caused regression #13867.
This patch reveres the changes made by it except the companion tests.

Version changed due to a newer requirement in LLVM.

Some cases were not correctly handled by this lint, for instance `let a = 42u8; a < 0` and `let a = 42u8; a > 255`.
It led to the discovery of two useless comparisons, which I removed.

Turning a `&T` into an `&mut T` carries a large risk of undefined
behaviour, and needs to be done very very carefully. Providing a
convenience function for exactly this task is a bad idea, just tempting
people into doing the wrong thing.

The right thing is to use types like `Cell`, `RefCell` or `Unsafe`.

For memory safety, Rust has that guarantee that `&mut` pointers do not
alias with any other pointer, that is, if you have a `&mut T` then that
is the only usable pointer to that `T`. This allows Rust to assume that
writes through a `&mut T` do not affect the values of any other `&` or
`&mut` references. `&` pointers have no guarantees about aliasing or
not, so it's entirely possible for the same pointer to be passed into
both arguments of a function like

    fn foo(x: &int, y: &int) { ... }

Converting either of `x` or `y` to a `&mut` pointer and modifying it
would affect the other value: invalid behaviour.

(Similarly, it's undefined behaviour to modify the value of an immutable
local, like `let x = 1;`.)

At a low-level, the *only* safe way to obtain an `&mut` out of a `&` is
using the `Unsafe` type (there are higher level wrappers around it, like
`Cell`, `RefCell`, `Mutex` etc.). The `Unsafe` type is registered with
the compiler so that it can reason a little about these `&` to `&mut`
casts, but it is still up to the user to ensure that the `&mut`s
obtained out of an `Unsafe` never alias.

(Note that *any* conversion from `&` to `&mut` can be invalid, including
a plain `transmute`, or casting `&T` -> `*T` -> `*mut T` -> `&mut T`.)

[breaking-change]

cc @pcwalton and @flaper87, this has box expressions and opt-in builtin kinds.