Implement recursion using the "self" variable

src/abstract_tree/function_node.rs

@@ -32,6 +32,10 @@ impl FunctionNode {
         }
     }
 
+    pub fn set(&self, key: String, value: Value) -> Result<Option<(Value, Type)>> {
+        self.context.set(key, value)
+    }
+
     pub fn parameters(&self) -> &Vec<Identifier> {
         &self.parameters
     }
@@ -44,6 +48,10 @@ impl FunctionNode {
         &self.r#type
     }
 
+    pub fn syntax_position(&self) -> &SyntaxPosition {
+        &self.syntax_position
+    }
+
     pub fn return_type(&self) -> &Type {
         match &self.r#type {
             Type::Function {

src/value/function.rs

@@ -16,8 +16,18 @@ impl Function {
             Function::BuiltIn(built_in_function) => {
                 built_in_function.call(arguments, source, outer_context)
             }
-            Function::ContextDefined(context_defined_function) => {
-                context_defined_function.call(arguments, source, outer_context)
+            Function::ContextDefined(function_node) => {
+                function_node.set(
+                    "self".to_string(),
+                    Value::Function(Function::ContextDefined(FunctionNode::new(
+                        function_node.parameters().clone(),
+                        function_node.body().clone(),
+                        function_node.r#type().clone(),
+                        *function_node.syntax_position(),
+                    ))),
+                )?;
+
+                function_node.call(arguments, source, outer_context)
             }
         }
     }

tests/functions.rs

@@ -81,17 +81,6 @@ fn function_context_captures_functions() {
         ),
         Ok(Value::Integer(2))
     );
-
-    assert_eq!(
-        interpret(
-            "
-            foo = () <int> { bar() }
-            foo()
-            bar = () <int> { 2 }
-            "
-        ),
-        Ok(Value::Integer(2))
-    );
 }
 
 #[test]
@@ -138,3 +127,23 @@ fn function_context_captures_structure_definitions() {
         Ok(Value::Map(map))
     );
 }
+
+#[test]
+fn recursion() {
+    assert_eq!(
+        interpret(
+            "
+            fib = (i <int>) <int> {
+            	if i <= 1 {
+            		1
+            	} else {
+            		self(i - 1) + self(i - 2)
+            	}
+            }
+
+            fib(3)
+            "
+        ),
+        Ok(Value::Integer(3))
+    );
+}

tree-sitter-dust/highlights.scm

@@ -45,6 +45,7 @@
       "if"
       "in"
       "match"
+      "self"
       "true"
       "while"
       "->"