Auto merge of #30458 - fhahn:fix-warnings-tests-stdlib, r=sanxiyn

This PR siliences some warnings when compiling stdlib with --test. Mostly remove some unused imports and added a few `#[allow(..)]`.

I also marked some signal handling functions with `#[cfg(not(test))]`, because they are only called through `rt::lang_start`, which is also marked as  `#[cfg(not(test))]`

4 files changed, 5 insertions, 3 deletions

diff --git a/src/libstd/io/buffered.rs b/src/libstd/io/buffered.rs
index 79eedbeda2c..16ce05ef2dc 100644
--- a/src/libstd/io/buffered.rs
+++ b/src/libstd/io/buffered.rs
@@ -791,7 +791,7 @@ impl<W: Read + Write> Read for InternalBufWriter<W> {
 mod tests {
     use prelude::v1::*;
     use io::prelude::*;
-    use io::{self, BufReader, BufWriter, Cursor, LineWriter, SeekFrom};
+    use io::{self, BufReader, BufWriter, LineWriter, SeekFrom};
     use test;
 
     /// A dummy reader intended at testing short-reads propagation.
diff --git a/src/libstd/io/error.rs b/src/libstd/io/error.rs
index 1dd96f5ddfc..e3f17c839f1 100644
--- a/src/libstd/io/error.rs
+++ b/src/libstd/io/error.rs
@@ -377,7 +377,7 @@ mod test {
         struct TestError;
 
         impl fmt::Display for TestError {
-            fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+            fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
                 Ok(())
             }
         }
diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index 7be0f467ac9..2ad45e80dd1 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -1983,7 +1983,7 @@ mod tests {
         b.iter(|| {
             let mut lr = repeat(1).take(10000000);
             let mut vec = Vec::with_capacity(1024);
-            super::read_to_end(&mut lr, &mut vec);
+            super::read_to_end(&mut lr, &mut vec)
         });
     }
 }
diff --git a/src/libstd/io/util.rs b/src/libstd/io/util.rs
index 07a9548224a..e05a0d577ff 100644
--- a/src/libstd/io/util.rs
+++ b/src/libstd/io/util.rs
@@ -199,6 +199,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(deprecated)]
     fn tee() {
         let mut buf = [0; 10];
         {
@@ -209,6 +210,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(deprecated)]
     fn broadcast() {
         let mut buf1 = [0; 10];
         let mut buf2 = [0; 10];