Add "true" or "false" example

examples/README.md

@@ -72,3 +72,7 @@ How to use `#[structopt(skip)]`.
 ### [Aliases](subcommand_aliases.rs)
 
 How to use aliases
+
+### [`true` or `false`](true_or_false.rs)
+
+How to express "`"true"` or `"false"` argument.

examples/true_or_false.rs

@@ -0,0 +1,16 @@
+//! How to express "`"true"` or `"false"` argument.
+
+use structopt::StructOpt;
+
+type Bool = bool;
+
+#[derive(StructOpt, Debug)]
+struct Opt {
+    verbose: Bool,
+}
+
+fn main() {
+    assert!(Opt::from_iter_safe("test", "true").is_ok());
+    assert!(Opt::from_iter_safe("test", "false").is_ok());
+    assert!(Opt::from_iter_safe("test", "beauty").is_err()); // no beauty, only truth and falseness
+}

src/lib.rs

@@ -302,6 +302,17 @@
 //! If you would like to use a custom string parser other than `FromStr`, see
 //! the [same titled section](#custom-string-parsers) below.
 //!
+//! **Note:**
+//! _________________
+//! Pay attention that *only literal occurrence* of this types is special, for example
+//! `Option<T>` is special while `::std::option::Option<T>` is not.
+//!
+//! If you need to avoid special casing you can make a `type` alias and
+//! use it in place of the said type, see
+//! [this](https://github.com/TeXitoi/structopt/tree/master/examples/true_or_false.rs)
+//! for example.
+//! _________________
+//!
 //! Thus, the `speed` argument is generated as:
 //!
 //! ```