Document opaque types

Closes https://github.com/gleam-lang/language-tour/issues/63

2 files changed, 21 insertions, 0 deletions

diff --git a/src/content/chapter5_advanced_features/lesson03_todo/code.gleam b/src/content/chapter5_advanced_features/lesson03_todo/code.gleam
new file mode 100644
index 0000000..d5abe8f
--- /dev/null
+++ b/src/content/chapter5_advanced_features/lesson03_todo/code.gleam
@@ -0,0 +1,7 @@
+pub fn main() {
+  todo as "I haven't written this code yet!"
+}
+
+pub fn todo_without_reason() {
+  todo
+}
diff --git a/src/content/chapter5_advanced_features/lesson03_todo/en.html b/src/content/chapter5_advanced_features/lesson03_todo/en.html
new file mode 100644
index 0000000..4a2c433
--- /dev/null
+++ b/src/content/chapter5_advanced_features/lesson03_todo/en.html
@@ -0,0 +1,14 @@
+<p>
+  The <code>todo</code> keyword is used to specify that some code is not yet
+  implemented.
+</p>
+<p>
+  The <code>as "some string"</code> is optional, though you may wish to include
+  the message if you have more than one code block marked as
+  <code>todo</code> in your code.
+</p>
+<p>
+  When used the Gleam compiler will print a warning to remind you the code is
+  unfinished, and if the code is run then the program will crash with the given
+  message.
+</p>