auto merge of #5179 : alexcrichton/rust/default-warn-unused-import, r=graydon

I've found that unused imports can often start cluttering a project after a long time, and it's very useful to keep them under control. I don't like how Go forces a compiler error by default and it can't be changed, but I certainly want to know about them so I think that a warn is a good default.

Now that the `unused_imports` lint option is a bit smarter, I think it's possible to change the default level to warn. This commit also removes all unused imports throughout the compiler and libraries (500+).

The only odd things that I ran into were that some `use` statements had to have `#[cfg(notest)]` or `#[cfg(test)]` based on where they were. The ones with `notest` were mostly in core for modules like `cmp` whereas `cfg(test)` was for tests that weren't part of a normal `mod test` module.

Author: bors

src/compiletest/common.rs

@@ -10,8 +10,6 @@
 
 use core::prelude::*;
 
-use cmp;
-
 #[deriving_eq]
 pub enum mode {
     mode_compile_fail,

src/compiletest/compiletest.rc

@@ -32,7 +32,6 @@ pub mod errors;
 use std::getopts;
 use std::test;
 
-use core::{result, either};
 use core::result::{Ok, Err};
 
 use common::config;

src/compiletest/errors.rs

@@ -10,8 +10,6 @@
 
 use core::prelude::*;
 
-use common::config;
-
 use core::io;
 use core::io::ReaderUtil;
 use core::str;

src/compiletest/procsrv.rs

@@ -13,14 +13,11 @@ use core::prelude::*;
 use core::io::{ReaderUtil, WriterUtil};
 use core::io;
 use core::libc::{c_int, pid_t};
-use core::libc;
 use core::os;
-use core::pipes;
 use core::run::spawn_process;
 use core::run;
 use core::str;
 use core::task;
-use core::vec;
 
 #[cfg(target_os = "win32")]
 fn target_env(lib_path: ~str, prog: ~str) -> ~[(~str,~str)] {

src/compiletest/runtest.rs

@@ -10,14 +10,12 @@
 
 use core::prelude::*;
 
-use common;
 use common::mode_run_pass;
 use common::mode_run_fail;
 use common::mode_compile_fail;
 use common::mode_pretty;
 use common::config;
 use errors;
-use header;
 use header::load_props;
 use header::TestProps;
 use procsrv;

src/compiletest/util.rs

@@ -10,12 +10,10 @@
 
 use core::prelude::*;
 
-use common;
 use common::config;
 
 use core::io;
 use core::os::getenv;
-use core::os;
 
 pub fn make_new_path(path: ~str) -> ~str {
 

src/libcore/bool.rs

@@ -11,10 +11,8 @@
 
 //! Boolean logic
 
-use bool;
-use cmp;
-use cmp::Eq;
 use option::{None, Option, Some};
+#[cfg(notest)] use cmp;
 
 /// Negation / inverse
 pub pure fn not(v: bool) -> bool { !v }
@@ -82,7 +80,7 @@ impl cmp::Eq for bool {
 #[test]
 pub fn test_bool_from_str() {
     do all_values |v| {
-        assert Some(v) == from_str(bool::to_str(v))
+        assert Some(v) == from_str(to_str(v))
     }
 }
 

src/libcore/char.rs

@@ -10,14 +10,14 @@
 
 //! Utilities for manipulating the char type
 
-use char;
-use cmp::Eq;
 use option::{None, Option, Some};
 use str;
 use u32;
 use uint;
 use unicode;
 
+#[cfg(notest)] use cmp::Eq;
+
 /*
     Lu  Uppercase_Letter    an uppercase letter
     Ll  Lowercase_Letter    a lowercase letter
@@ -305,8 +305,8 @@ fn test_to_digit() {
 
 #[test]
 fn test_is_ascii() {
-   assert str::all(~"banana", char::is_ascii);
-   assert ! str::all(~"ประเทศไทย中华Việt Nam", char::is_ascii);
+   assert str::all(~"banana", is_ascii);
+   assert ! str::all(~"ประเทศไทย中华Việt Nam", is_ascii);
 }
 
 #[test]

src/libcore/dvec.rs

@@ -20,7 +20,6 @@ Note that recursive use is not permitted.
 */
 
 use cast;
-use cast::reinterpret_cast;
 use prelude::*;
 use ptr::null;
 use vec;

src/libcore/either.rs

@@ -11,7 +11,6 @@
 //! A type that represents one of two alternatives
 
 use cmp::Eq;
-use cmp;
 use kinds::Copy;
 use result::Result;
 use result;