Rollup merge of #36396 - athulappadan:Default-docs, r=bluss

Documentation of what Default does for each type

Addresses #36265
I haven't changed the following types due to doubts:

1)src/libstd/ffi/c_str.rs
2)src/libcore/iter/sources.rs
3)src/libcore/hash/mod.rs
4)src/libcore/hash/mod.rs
5)src/librustc/middle/privacy.rs

r? @steveklabnik

7 files changed, 9 insertions, 0 deletions

diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
index 4eb2c8f0644..eb1653f18cb 100644
--- a/src/libstd/collections/hash/map.rs
+++ b/src/libstd/collections/hash/map.rs
@@ -1218,6 +1218,7 @@ impl<K, V, S> Default for HashMap<K, V, S>
     where K: Eq + Hash,
           S: BuildHasher + Default,
 {
+    /// Creates an empty `HashMap<K, V, S>`, with the `Default` value for the hasher.
     fn default() -> HashMap<K, V, S> {
         HashMap::with_hasher(Default::default())
     }
@@ -2026,6 +2027,7 @@ impl Hasher for DefaultHasher {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Default for RandomState {
+    /// Constructs a new `RandomState`.
     #[inline]
     fn default() -> RandomState {
         RandomState::new()
diff --git a/src/libstd/collections/hash/set.rs b/src/libstd/collections/hash/set.rs
index ca5137e9573..ff56747fee6 100644
--- a/src/libstd/collections/hash/set.rs
+++ b/src/libstd/collections/hash/set.rs
@@ -665,6 +665,7 @@ impl<T, S> Default for HashSet<T, S>
     where T: Eq + Hash,
           S: BuildHasher + Default,
 {
+    /// Creates an empty `HashSet<T, S>` with the `Default` value for the hasher.
     fn default() -> HashSet<T, S> {
         HashSet::with_hasher(Default::default())
     }
diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index 2d5e8c04194..1c449712e1f 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -361,6 +361,7 @@ impl<'a> Default for &'a CStr {
 
 #[stable(feature = "cstr_default", since = "1.10.0")]
 impl Default for CString {
+    /// Creates an empty `CString`.
     fn default() -> CString {
         let a: &CStr = Default::default();
         a.to_owned()
diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs
index 36cf4ef758d..d93d3c73622 100644
--- a/src/libstd/ffi/os_str.rs
+++ b/src/libstd/ffi/os_str.rs
@@ -170,6 +170,7 @@ impl ops::Deref for OsString {
 
 #[stable(feature = "osstring_default", since = "1.9.0")]
 impl Default for OsString {
+    /// Constructs an empty `OsString`.
     #[inline]
     fn default() -> OsString {
         OsString::new()
@@ -342,6 +343,7 @@ impl OsStr {
 
 #[stable(feature = "osstring_default", since = "1.9.0")]
 impl<'a> Default for &'a OsStr {
+    /// Creates an empty `OsStr`.
     #[inline]
     fn default() -> &'a OsStr {
         OsStr::new("")
diff --git a/src/libstd/sync/condvar.rs b/src/libstd/sync/condvar.rs
index 4c946e613ea..3db8b05b954 100644
--- a/src/libstd/sync/condvar.rs
+++ b/src/libstd/sync/condvar.rs
@@ -241,6 +241,7 @@ impl Condvar {
 
 #[stable(feature = "condvar_default", since = "1.9.0")]
 impl Default for Condvar {
+    /// Creates a `Condvar` which is ready to be waited on and notified.
     fn default() -> Condvar {
         Condvar::new()
     }
diff --git a/src/libstd/sync/mutex.rs b/src/libstd/sync/mutex.rs
index c8ae88c2331..098a3e44258 100644
--- a/src/libstd/sync/mutex.rs
+++ b/src/libstd/sync/mutex.rs
@@ -287,6 +287,7 @@ impl<T: ?Sized> Drop for Mutex<T> {
 
 #[stable(feature = "mutex_default", since = "1.9.0")]
 impl<T: ?Sized + Default> Default for Mutex<T> {
+    /// Creates a `Mutex<T>`, with the `Default` value for T.
     fn default() -> Mutex<T> {
         Mutex::new(Default::default())
     }
diff --git a/src/libstd/sync/rwlock.rs b/src/libstd/sync/rwlock.rs
index 4801bcffd08..7f053c6704b 100644
--- a/src/libstd/sync/rwlock.rs
+++ b/src/libstd/sync/rwlock.rs
@@ -311,6 +311,7 @@ impl<T: ?Sized + fmt::Debug> fmt::Debug for RwLock<T> {
 
 #[stable(feature = "rw_lock_default", since = "1.9.0")]
 impl<T: Default> Default for RwLock<T> {
+    /// Creates a new `RwLock<T>`, with the `Default` value for T.
     fn default() -> RwLock<T> {
         RwLock::new(Default::default())
     }