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

2 files changed, 2 insertions, 0 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 105f911dd57..40c8ba93bd5 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -362,6 +362,7 @@ impl Generics {
 }
 
 impl Default for Generics {
+    /// Creates an instance of `Generics`.
     fn default() ->  Generics {
         Generics {
             lifetimes: Vec::new(),
diff --git a/src/libsyntax/ptr.rs b/src/libsyntax/ptr.rs
index c3f8a977a65..58750158931 100644
--- a/src/libsyntax/ptr.rs
+++ b/src/libsyntax/ptr.rs
@@ -154,6 +154,7 @@ impl<T> P<[T]> {
 }
 
 impl<T> Default for P<[T]> {
+    /// Creates an empty `P<[T]>`.
     fn default() -> P<[T]> {
         P::new()
     }