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rust/src/libstd/lib.rs
Nick Cameron 95602a759d Add trivial cast lints. 
This permits all coercions to be performed in casts, but adds lints to warn in those cases.

Part of this patch moves cast checking to a later stage of type checking. We acquire obligations to check casts as part of type checking where we previously checked them. Once we have type checked a function or module, then we check any cast obligations which have been acquired. That means we have more type information available to check casts (this was crucial to making coercions work properly in place of some casts), but it means that casts cannot feed input into type inference.

[breaking change]

* Adds two new lints for trivial casts and trivial numeric casts, these are warn by default, but can cause errors if you build with warnings as errors. Previously, trivial numeric casts and casts to trait objects were allowed.
* The unused casts lint has gone.
* Interactions between casting and type inference have changed in subtle ways. Two ways this might manifest are:
- You may need to 'direct' casts more with extra type information, for example, in some cases where `foo as _ as T` succeeded, you may now need to specify the type for `_`
- Casts do not influence inference of integer types. E.g., the following used to type check:

```
let x = 42;
let y = &x as *const u32;
```

Because the cast would inform inference that `x` must have type `u32`. This no longer applies and the compiler will fallback to `i32` for `x` and thus there will be a type error in the cast. The solution is to add more type information:

```
let x: u32 = 42;
let y = &x as *const u32;
```
2015-03-25 10:03:57 +13:00

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// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! # The Rust Standard Library
//!
//! The Rust Standard Library provides the essential runtime
//! functionality for building portable Rust software.
//! It is linked to all Rust crates by default.
//!
//! ## Intrinsic types and operations
//!
//! The [`ptr`](ptr/index.html) and [`mem`](mem/index.html)
//! modules deal with unsafe pointers and memory manipulation.
//! [`marker`](marker/index.html) defines the special built-in traits,
//! and [`raw`](raw/index.html) the runtime representation of Rust types.
//! These are some of the lowest-level building blocks in Rust.
//!
//! ## Math on primitive types and math traits
//!
//! Although basic operations on primitive types are implemented
//! directly by the compiler, the standard library additionally
//! defines many common operations through traits defined in
//! mod [`num`](num/index.html).
//!
//! ## Pervasive types
//!
//! The [`option`](option/index.html) and [`result`](result/index.html)
//! modules define optional and error-handling types, `Option` and `Result`.
//! [`iter`](iter/index.html) defines Rust's iterator protocol
//! along with a wide variety of iterators.
//! [`Cell` and `RefCell`](cell/index.html) are for creating types that
//! manage their own mutability.
//!
//! ## Vectors, slices and strings
//!
//! The common container type, `Vec`, a growable vector backed by an array,
//! lives in the [`vec`](vec/index.html) module. Contiguous, unsized regions
//! of memory, `[T]`, commonly called "slices", and their borrowed versions,
//! `&[T]`, commonly called "borrowed slices", are built-in types for which the
//! for which the [`slice`](slice/index.html) module defines many methods.
//!
//! `&str`, a UTF-8 string, is a built-in type, and the standard library
//! defines methods for it on a variety of traits in the
//! [`str`](str/index.html) module. Rust strings are immutable;
//! use the `String` type defined in [`string`](string/index.html)
//! for a mutable string builder.
//!
//! For converting to strings use the [`format!`](fmt/index.html)
//! macro, and for converting from strings use the
//! [`FromStr`](str/trait.FromStr.html) trait.
//!
//! ## Platform abstractions
//!
//! Besides basic data types, the standard library is largely concerned
//! with abstracting over differences in common platforms, most notably
//! Windows and Unix derivatives. The [`os`](os/index.html) module
//! provides a number of basic functions for interacting with the
//! operating environment, including program arguments, environment
//! variables, and directory navigation. The [`path`](path/index.html)
//! module encapsulates the platform-specific rules for dealing
//! with file paths.
//!
//! `std` also includes modules for interoperating with the
//! C language: [`c_str`](c_str/index.html) and
//! [`c_vec`](c_vec/index.html).
//!
//! ## Concurrency, I/O, and the runtime
//!
//! The [`thread`](thread/index.html) module contains Rust's threading abstractions.
//! [`sync`](sync/index.html) contains further, primitive, shared memory types,
//! including [`atomic`](sync/atomic/index.html), and [`mpsc`](sync/mpsc/index.html),
//! which contains the channel types for message passing.
//!
//! Common types of I/O, including files, TCP, UDP, pipes, Unix domain sockets,
//! timers, and process spawning, are defined in the
//! [`old_io`](old_io/index.html) module.
//!
//! Rust's I/O and concurrency depends on a small runtime interface
//! that lives, along with its support code, in mod [`rt`](rt/index.html).
//! While a notable part of the standard library's architecture, this
//! module is not intended for public use.
//!
//! ## The Rust prelude and macros
//!
//! Finally, the [`prelude`](prelude/index.html) defines a
//! common set of traits, types, and functions that are made available
//! to all code by default. [`macros`](macros/index.html) contains
//! all the standard macros, such as `assert!`, `panic!`, `println!`,
//! and `format!`, also available to all Rust code.
// Do not remove on snapshot creation. Needed for bootstrap. (Issue #22364)
#![cfg_attr(stage0, feature(custom_attribute))]
#![crate_name = "std"]
#![stable(feature = "rust1", since = "1.0.0")]
#![staged_api]
#![crate_type = "rlib"]
#![crate_type = "dylib"]
#![doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
html_favicon_url = "http://www.rust-lang.org/favicon.ico",
html_root_url = "http://doc.rust-lang.org/nightly/",
html_playground_url = "http://play.rust-lang.org/")]
#![doc(test(no_crate_inject))]
#![feature(alloc)]
#![feature(box_syntax)]
#![feature(collections)]
#![feature(core)]
#![feature(lang_items)]
#![feature(libc)]
#![feature(linkage, thread_local, asm)]
#![feature(old_impl_check)]
#![feature(optin_builtin_traits)]
#![feature(rand)]
#![feature(staged_api)]
#![feature(unboxed_closures)]
#![feature(unicode)]
#![feature(unsafe_destructor)]
#![feature(unsafe_no_drop_flag)]
#![feature(macro_reexport)]
#![feature(int_uint)]
#![feature(unique)]
#![feature(convert)]
#![feature(allow_internal_unstable)]
#![feature(str_char)]
#![feature(into_cow)]
#![cfg_attr(test, feature(test, rustc_private, std_misc))]
// Don't link to std. We are std.
#![feature(no_std)]
#![no_std]
#![allow(trivial_cast)]
#![allow(trivial_numeric_cast)]
#![deny(missing_docs)]
#[cfg(test)] extern crate test;
#[cfg(test)] #[macro_use] extern crate log;
#[macro_use]
#[macro_reexport(assert, assert_eq, debug_assert, debug_assert_eq,
unreachable, unimplemented, write, writeln)]
extern crate core;
#[macro_use]
#[macro_reexport(vec, format)]
extern crate "collections" as core_collections;
#[allow(deprecated)] extern crate "rand" as core_rand;
extern crate alloc;
extern crate unicode;
extern crate libc;
#[macro_use] #[no_link] extern crate rustc_bitflags;
// Make std testable by not duplicating lang items. See #2912
#[cfg(test)] extern crate "std" as realstd;
#[cfg(test)] pub use realstd::marker;
#[cfg(test)] pub use realstd::ops;
#[cfg(test)] pub use realstd::cmp;
#[cfg(test)] pub use realstd::boxed;
// NB: These reexports are in the order they should be listed in rustdoc
pub use core::any;
pub use core::cell;
pub use core::clone;
#[cfg(not(test))] pub use core::cmp;
pub use core::convert;
pub use core::default;
#[allow(deprecated)]
pub use core::finally;
pub use core::hash;
pub use core::intrinsics;
pub use core::iter;
#[cfg(not(test))] pub use core::marker;
pub use core::mem;
#[cfg(not(test))] pub use core::ops;
pub use core::ptr;
pub use core::raw;
pub use core::simd;
pub use core::result;
pub use core::option;
pub use core::error;
#[cfg(not(test))] pub use alloc::boxed;
pub use alloc::rc;
pub use core_collections::borrow;
pub use core_collections::fmt;
pub use core_collections::slice;
pub use core_collections::str;
pub use core_collections::string;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core_collections::vec;
pub use unicode::char;
/* Exported macros */
#[macro_use]
mod macros;
mod rtdeps;
/* The Prelude. */
pub mod prelude;
/* Primitive types */
// NB: slice and str are primitive types too, but their module docs + primitive doc pages
// are inlined from the public re-exports of core_collections::{slice, str} above.
#[path = "num/float_macros.rs"]
#[macro_use]
mod float_macros;
#[path = "num/int_macros.rs"]
#[macro_use]
mod int_macros;
#[path = "num/uint_macros.rs"]
#[macro_use]
mod uint_macros;
#[path = "num/isize.rs"] pub mod isize;
#[path = "num/i8.rs"] pub mod i8;
#[path = "num/i16.rs"] pub mod i16;
#[path = "num/i32.rs"] pub mod i32;
#[path = "num/i64.rs"] pub mod i64;
#[path = "num/usize.rs"] pub mod usize;
#[path = "num/u8.rs"] pub mod u8;
#[path = "num/u16.rs"] pub mod u16;
#[path = "num/u32.rs"] pub mod u32;
#[path = "num/u64.rs"] pub mod u64;
#[path = "num/f32.rs"] pub mod f32;
#[path = "num/f64.rs"] pub mod f64;
pub mod ascii;
pub mod thunk;
/* Common traits */
pub mod num;
/* Runtime and platform support */
#[macro_use]
pub mod thread;
pub mod collections;
pub mod dynamic_lib;
pub mod env;
pub mod ffi;
pub mod fs;
pub mod io;
pub mod net;
pub mod old_io;
pub mod old_path;
pub mod os;
pub mod path;
pub mod process;
pub mod rand;
pub mod sync;
pub mod time;
#[macro_use]
#[path = "sys/common/mod.rs"] mod sys_common;
#[cfg(unix)]
#[path = "sys/unix/mod.rs"] mod sys;
#[cfg(windows)]
#[path = "sys/windows/mod.rs"] mod sys;
pub mod rt;
mod panicking;
// Modules that exist purely to document + host impl docs for primitive types
mod array;
mod bool;
mod unit;
mod tuple;
// A curious inner-module that's not exported that contains the binding
// 'std' so that macro-expanded references to std::error and such
// can be resolved within libstd.
#[doc(hidden)]
mod std {
pub use sync; // used for select!()
pub use error; // used for try!()
pub use fmt; // used for any formatting strings
#[allow(deprecated)]
pub use old_io; // used for println!()
pub use option; // used for bitflags!{}
pub use rt; // used for panic!()
pub use vec; // used for vec![]
pub use cell; // used for tls!
pub use thread; // used for thread_local!
pub use marker; // used for tls!
pub use ops; // used for bitflags!
// The test runner calls ::std::env::args() but really wants realstd
#[cfg(test)] pub use realstd::env as env;
// The test runner requires std::slice::Vector, so re-export std::slice just for it.
//
// It is also used in vec![]
pub use slice;
pub use boxed; // used for vec![]
}
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