Add score/lifetimes/trait.md

src/SUMMARY.md

@@ -124,6 +124,7 @@
         - [Functions](scope/lifetime/fn.md)
         - [Methods](scope/lifetime/methods.md)
         - [Structs](scope/lifetime/struct.md)
+        - [Traits](scope/lifetime/trait.md)
         - [Bounds](scope/lifetime/lifetime_bounds.md)
         - [Coercion](scope/lifetime/lifetime_coercion.md)
         - [Static](scope/lifetime/static_lifetime.md)

src/scope/lifetime/trait.md

@@ -0,0 +1,33 @@
+# Traits
+
+Annotation of lifetimes in trait methods basically are similar to functions.
+Note that `impl` may have annotation of lifetimes too.
+
+```rust,editable
+// A struct with annotation of lifetimes.
+#[derive(Debug)]
+ struct Borrowed<'a> {
+     x: &'a i32,
+ }
+
+// Annotate lifetimes to impl.
+impl<'a> Default for Borrowed<'a> {
+    fn default() -> Self {
+        Self {
+            x: &10,
+        }
+    }
+}
+
+fn main() {
+    let b: Borrowed = Default::default();
+    println!("b is {:?}", b);
+}
+```
+
+### See also:
+
+[`trait`s][trait]
+
+
+[trait]: trait.html