Added documentation

Author: 1c3t3a

clippy_lints/src/semicolon_if_nothing_returned.rs

@@ -7,24 +7,31 @@ use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 declare_clippy_lint! {
-    /// **What it does:**
+    /// **What it does:** Looks for blocks of expressions and fires if the last expression returns `()`
+    /// but is not followed by a semicolon.
     ///
-    /// **Why is this bad?**
+    /// **Why is this bad?** The semicolon might be optional but when
+    /// extending the block with new code, it doesn't require a change in previous last line.
+    /// It's also more idiomatic.
     ///
     /// **Known problems:** None.
     ///
     /// **Example:**
     ///
     /// ```rust
-    /// // example code where clippy issues a warning
+    /// fn main() {
+    /// println!("Hello world")
+    /// }
     /// ```
     /// Use instead:
     /// ```rust
-    /// // example code which does not raise clippy warning
+    /// fn main() {
+    /// println!("Hello world");
+    /// }
     /// ```
     pub SEMICOLON_IF_NOTHING_RETURNED,
     pedantic,
-    "default lint description"
+    "add a semicolon if nothing is returned"
 }
 
 declare_lint_pass!(SemicolonIfNothingReturned => [SEMICOLON_IF_NOTHING_RETURNED]);