Update book for methods calls

book/src/template_syntax.md

@@ -245,13 +245,11 @@ struct MyTemplate;
 
 ### Struct / trait implementations
 
-Finally, we can invoke functions that are implementation methods of our
-template struct, by referencing `Self` (note the uppercase `S`) as the path,
-before calling our function:
+Finally, we can call methods of our template struct:
 
 ```rust
 #[derive(Template)]
-#[template(source = "{{ Self::foo(self, 123) }}", ext = "txt")]
+#[template(source = "{{ foo(123) }}", ext = "txt")]
 struct MyTemplate {
   count: u32,
 };
@@ -263,9 +261,8 @@ impl MyTemplate {
 }
 ```
 
-If the implemented method requires a reference to the struct itself,
-such as is demonstrated in the above example, we can pass `self`
-(note the lowercase `s`) as the first argument.
+You can also use `self.foo(123)`, or even `Self::foo(self, 123)`, as you see
+fit.
 
 Similarly, using the `Self` path, we can also call any method belonging
 to a trait that has been implemented for our template struct:
@@ -286,6 +283,32 @@ impl Hello for MyTemplate {
 }
 ```
 
+If you want to call a closure which is a field, you'll need to follow Rust's
+syntax by surrounding the call with parens:
+
+```rust
+#[derive(Template)]
+#[template(source = "{{ (closure)(12) }}", ext = "txt")]
+struct MyTemplate {
+    closure: fn(i32) -> i32,
+}
+```
+
+## Calling functions
+
+If you only provide a function name, `rinja` will assume it's a method. If
+you want to call a method, you will need to use a path instead:
+
+```jinja
+{# This is the equivalent of `self.method()`. #}
+{{ method() }}
+{# This is the equivalent of `self::function()`, which will call the
+`function` function from the current module. #}
+{{ self::function() }}
+{# This is the equivalent of `super::b::f()`. #}
+{{ super::b::f() }}
+```
+
 ## Template inheritance
 
 Template inheritance allows you to build a base template with common