diff --git a/ast-generator/src/deserialize.rs b/ast-generator/src/deserialize.rs
index 8491925..ba0699c 100644
--- a/ast-generator/src/deserialize.rs
+++ b/ast-generator/src/deserialize.rs
@@ -1,4 +1,10 @@
-use crate::spec::{BooleanBuild, BuildSpec, ChildSpec, EnumBuildSpec, EnumRule, LeafEnumBuildSpec, LeafEnumRule, LeafEnumRuleBuild, LeafEnumRuleBuildChild, LeafStructBuildSpec, LeafStructChild, LeafStructChildType, SingleBooleanChildToBuild, SingleChild, SingleChildToBuild, SingleLiteralChildToBuild, SingleTypeChildToBuild, SkipChild, StructBuildSpec, VecChild, VecChildToBuild, VecTypeChildToBuild};
+use crate::spec::{
+    BooleanBuild, BuildSpec, ChildSpec, EnumBuildSpec, EnumRule, LeafEnumBuildSpec, LeafEnumRule,
+    LeafEnumRuleBuild, LeafEnumRuleBuildChild, LeafStructBuildSpec, LeafStructChild,
+    LeafStructChildType, SingleBooleanChildToBuild, SingleChild, SingleChildToBuild,
+    SingleLiteralChildToBuild, SingleTypeChildToBuild, SkipChild, StructBuildSpec, VecChild,
+    VecChildToBuild, VecTypeChildToBuild,
+};
 use crate::util::make_build_fn_name;
 use convert_case::{Case, Casing};
 use yaml_rust2::{Yaml, YamlLoader};
@@ -218,15 +224,13 @@ fn get_enum_rules(rule_specs: &Yaml) -> Vec<EnumRule> {
 }
 
 fn get_leaf_struct_child_specs(children: &Yaml) -> Vec<LeafStructChild> {
-    children.as_vec()
+    children
+        .as_vec()
         .unwrap()
         .iter()
         .map(|child_spec| {
             let (name, hash) = unwrap_single_member_hash(child_spec);
-            LeafStructChild::new(
-                &name,
-                LeafStructChildType::String
-            )
+            LeafStructChild::new(&name, LeafStructChildType::String)
         })
         .collect::<Vec<_>>()
 }
diff --git a/ast-generator/src/lib.rs b/ast-generator/src/lib.rs
index 85b49c2..97d5eab 100644
--- a/ast-generator/src/lib.rs
+++ b/ast-generator/src/lib.rs
@@ -9,13 +9,13 @@ mod util;
 
 use crate::enum_build_fn::make_enum_build_fn;
 use crate::leaf_enum_build_fn::make_leaf_enum_build_fn;
+use crate::leaf_struct_build_fn::make_leaf_struct_build_fn;
 use crate::struct_build_fn::make_struct_build_fn;
 use crate::type_gen::make_type;
 use proc_macro2::TokenStream;
 use quote::quote;
 use spec::BuildSpec;
 use syn::File;
-use crate::leaf_struct_build_fn::make_leaf_struct_build_fn;
 
 fn debug_built_spec(build_spec: &BuildSpec, token_stream: &TokenStream) {
     println!("*** BuildSpec ***");
diff --git a/ast-generator/src/spec.rs b/ast-generator/src/spec.rs
index 84ef085..15a6d8e 100644
--- a/ast-generator/src/spec.rs
+++ b/ast-generator/src/spec.rs
@@ -518,14 +518,14 @@ impl LeafStructChild {
     pub fn new(name: &str, r#type: LeafStructChildType) -> Self {
         Self {
             name: name.to_string(),
-            r#type
+            r#type,
         }
     }
-    
+
     pub fn name(&self) -> &str {
         &self.name
     }
-    
+
     pub fn r#type(&self) -> &LeafStructChildType {
         &self.r#type
     }
diff --git a/ast-generator/src/struct_build_fn.rs b/ast-generator/src/struct_build_fn.rs
index 2bc781b..bb1380c 100644
--- a/ast-generator/src/struct_build_fn.rs
+++ b/ast-generator/src/struct_build_fn.rs
@@ -2,10 +2,9 @@ use crate::spec::{
     BooleanBuild, ChildSpec, SingleBooleanChildToBuild, SingleChildToBuild,
     SingleLiteralChildToBuild, SingleTypeChildToBuild, StructBuildSpec, VecChild, VecChildToBuild,
 };
-use convert_case::{Case, Casing};
+use crate::util::make_build_pair;
 use proc_macro2::{Ident, TokenStream};
 use quote::{format_ident, quote};
-use crate::util::make_build_pair;
 
 fn make_vec_child_holder(vec_child: &VecChild) -> TokenStream {
     let (child_ident, child_type_ident) = match vec_child.build() {
diff --git a/ast-generator/src/type_gen.rs b/ast-generator/src/type_gen.rs
index 805d12a..2bed52c 100644
--- a/ast-generator/src/type_gen.rs
+++ b/ast-generator/src/type_gen.rs
@@ -102,15 +102,35 @@ fn handle_single_type_child(
             #child_ident: Box<#child_type_ident>
         })
     }
-    accessors.push(quote! {
-        pub fn #child_ident(&self) -> &#child_type_ident {
-            self.#child_ident.as_ref()
-        }
+    if single_type_child.optional() {
+        accessors.push(quote! {
+            pub fn #child_ident(&self) -> Option<&#child_type_ident> {
+                if let Some(#child_ident) = &self.#child_ident {
+                    Some(#child_ident.as_ref())
+                } else {
+                    None
+                }
+            }
 
-        pub fn #child_ident_mut(&mut self) -> &mut #child_type_ident {
-            self.#child_ident.as_mut()
-        }
-    });
+            pub fn #child_ident_mut(&mut self) -> Option<&mut #child_type_ident> {
+                if let Some(#child_ident) = &mut self.#child_ident {
+                    Some(#child_ident.as_mut())
+                } else {
+                    None
+                }
+            }
+        })
+    } else {
+        accessors.push(quote! {
+            pub fn #child_ident(&self) -> &#child_type_ident {
+                self.#child_ident.as_ref()
+            }
+
+            pub fn #child_ident_mut(&mut self) -> &mut #child_type_ident {
+                self.#child_ident.as_mut()
+            }
+        });
+    }
 }
 
 fn handle_single_boolean_child(
@@ -229,7 +249,7 @@ fn make_leaf_struct_type(build_spec: &LeafStructBuildSpec) -> TokenStream {
             }
         })
         .collect::<Vec<_>>();
-    
+
     quote! {
         pub struct #type_ident {
             #(#annotated_members),*
diff --git a/ast-generator/src/util.rs b/ast-generator/src/util.rs
index 8d94e3a..ae0220b 100644
--- a/ast-generator/src/util.rs
+++ b/ast-generator/src/util.rs
@@ -6,4 +6,4 @@ pub fn make_build_fn_name(s: &str) -> String {
 
 pub fn make_build_pair(s: &str) -> String {
     format!("{}_pair", s.to_case(Case::Snake))
-}
\ No newline at end of file
+}
diff --git a/build.rs b/build.rs
index b4e88be..de92dc2 100644
--- a/build.rs
+++ b/build.rs
@@ -17,7 +17,7 @@ fn generate_parser_tests(out_dir: &Path) -> io::Result<()> {
 fn generate_ast_files(out_dir: &Path) -> io::Result<()> {
     let gen_ast_dir = out_dir.join("src").join("ast");
     fs::create_dir_all(&gen_ast_dir)?;
-    
+
     let ast_yaml = include_str!("src/parser/ast.yaml");
     let build_specs = deserialize::deserialize_yaml_spec(ast_yaml);
     let generated_files = generate_files(&build_specs);
diff --git a/cst-test-generator/src/lib.rs b/cst-test-generator/src/lib.rs
index 4f56bdc..4ced8eb 100644
--- a/cst-test-generator/src/lib.rs
+++ b/cst-test-generator/src/lib.rs
@@ -46,7 +46,7 @@ pub fn generate_test_files(tests_dir: &Path) -> io::Result<ParserTestSuitesFile>
             let test_suite = quote! {
                 mod #tests_mod_ident {
                     use super::*;
-                    
+
                     #(#tests)*
                 }
             };
@@ -59,7 +59,7 @@ pub fn generate_test_files(tests_dir: &Path) -> io::Result<ParserTestSuitesFile>
     // generate main test_suites file
     let test_suites = quote! {
         use super::*;
-        
+
         #(#test_suites)*
     };
     let test_suites_file: File = syn::parse2(test_suites).unwrap();
diff --git a/src/ast/mod.rs b/src/ast/mod.rs
index 17abf56..e213d71 100644
--- a/src/ast/mod.rs
+++ b/src/ast/mod.rs
@@ -5,6 +5,8 @@ pub mod node {
 pub mod build {
     //noinspection RsUnusedImport
     use crate::parser::Rule;
-    
+    //noinspection RsUnusedImport
+    use crate::ast::node::*;
+
     include!(concat!(env!("OUT_DIR"), "/src/ast/build.rs"));
 }
diff --git a/src/bin/dmc/main.rs b/src/bin/dmc/main.rs
index 32530dc..380ae2e 100644
--- a/src/bin/dmc/main.rs
+++ b/src/bin/dmc/main.rs
@@ -1,14 +1,14 @@
 // mod name_analysis;
 // mod p3;
 // mod unparse;
-// 
+//
 // use std::path::PathBuf;
-// 
+//
 // use crate::name_analysis::name_analysis;
 // use crate::p3::pretty_print_parse;
 // use crate::unparse::unparse;
 // use clap::{Parser, Subcommand};
-// 
+//
 // #[derive(Debug, Parser)]
 // #[command(name = "dmc")]
 // #[command(about = "Deimos Compiler", long_about = None)]
@@ -16,7 +16,7 @@
 //     #[command(subcommand)]
 //     command: Commands,
 // }
-// 
+//
 // #[derive(Debug, Subcommand)]
 // enum Commands {
 //     #[command(arg_required_else_help = true)]
@@ -30,7 +30,7 @@
 //         paths: Vec<PathBuf>,
 //     },
 // }
-// 
+//
 // fn main() {
 //     let args = Cli::parse();
 //     match args.command {
diff --git a/src/module/mod.rs b/src/module/mod.rs
index 2354a6c..924209b 100644
--- a/src/module/mod.rs
+++ b/src/module/mod.rs
@@ -4,14 +4,12 @@ pub struct DmModule {
 
 pub enum NamespaceVisibility {
     Public,
-    Partial {
-        visible_to_fqns: Vec<String>
-    },
-    Private
+    Partial { visible_to_fqns: Vec<String> },
+    Private,
 }
 
 pub struct DmNamespace {
     pub name: String,
     pub dependencies: Vec<String>,
-    pub visibility: NamespaceVisibility
+    pub visibility: NamespaceVisibility,
 }
diff --git a/src/parser/ast.yaml b/src/parser/ast.yaml
index 5a81d35..cb2801d 100644
--- a/src/parser/ast.yaml
+++ b/src/parser/ast.yaml
@@ -415,10 +415,14 @@ InterfaceDefaultOperatorFunction:
       
 # Function Bodies
 FunctionBody:
+  type: leaf_enum
   rules:
-    - FunctionAliasBody
-    - FunctionEqualsBody
-    - FunctionBlockBody
+    - FunctionAliasBody:
+        child: true
+    - FunctionEqualsBody:
+        child: true
+    - FunctionBlockBody:
+        child: true
 FunctionEqualsBody:
   children:
     - expression
@@ -460,14 +464,22 @@ Member:
 
 # Statements
 Statement:
+  type: leaf_enum
   rules:
-    - VariableDeclaration
-    - AssignmentStatement
-    - ExpressionStatement
-    - UseStatement
-    - IfStatement
-    - WhileStatement
-    - ForStatement
+    - VariableDeclaration:
+        child: true
+    - AssignmentStatement:
+        child: true
+    - ExpressionStatement:
+        child: true
+    - UseStatement:
+        child: true
+    - IfStatement:
+        child: true
+    - WhileStatement:
+        child: true
+    - ForStatement:
+        child: true
 VariableDeclaration:
   children:
     - let_kw:
@@ -701,17 +713,23 @@ ObjectIndex:
   children:
     - expression
 PrimaryExpression:
+  type: leaf_enum
   rules:
-    - Literal
-    - FullyQualifiedName
-    - Closure
-    - ParenthesizedExpression
+    - Literal:
+        child: true
+    - FullyQualifiedName:
+        child: true
+    - Closure:
+        child: true
+    - ParenthesizedExpression:
+        child: true
 ParenthesizedExpression:
   children:
     - expression
 
 # Calls
 Call:
+  type: leaf_enum
   rules:
     - ParenthesesCall
     - NonParenthesesCall
@@ -762,38 +780,46 @@ ClosureParameter:
 
 # Literals
 Literal:
+  type: leaf_enum
   rules:
-    - NumberLiteral
-    - StringLiteral
-    - BooleanLiteral
+    - NumberLiteral:
+        child: true
+    - StringLiteral:
+        child: true
+    - BooleanLiteral:
+        child: true
 NumberLiteral:
+  type: leaf_enum
   rules:
-    - DoubleLiteral
-    - LongLiteral
-    - IntLiteral
+    - DoubleLiteral:
+        child: true
+    - LongLiteral:
+        child: true
+    - IntLiteral:
+        child: true
 IntLiteral:
   children:
     - number_base
-    - literal:
-        build:
-          type: i32
 LongLiteral:
   children:
     - number_base
-    - literal:
-        build:
-          type: i64
 DoubleLiteral:
+  type: leaf_struct
   children:
     - literal:
         build: 
           type: f64
 NumberBase:
+  type: leaf_enum
   rules:
-    - BinaryBase
-    - HexadecimalBase
-    - DecimalBase
+    - BinaryBase:
+        child: true
+    - HexadecimalBase:
+        child: true
+    - DecimalBase:
+        child: true
 DecimalBase:
+  type: leaf_struct
   children:
     - literal:
         build: 
@@ -802,6 +828,7 @@ BinaryBase:
   children:
     - binary_digits
 BinaryDigits:
+  type: leaf_struct
   children:
     - literal:
         build:
@@ -810,15 +837,20 @@ HexadecimalBase:
   children:
     - hexadecimal_digits
 HexadecimalDigits:
+  type: leaf_struct
   children:
     - literal:
         build: 
           type: string
 StringLiteral:
+  type: leaf_enum
   rules:
-    - SingleQuoteString
-    - DoubleQuoteString
-    - BacktickString
+    - SingleQuoteString:
+        child: true
+    - DoubleQuoteString:
+        child: true
+    - BacktickString:
+        child: true
 SingleQuoteString:
   children:
     - string_inner:
@@ -832,11 +864,13 @@ DoubleQuoteString:
         rule: DStringExpression
         vec: true
 StringInner:
+  type: leaf_struct
   children:
     - literal:
         build:
           type: string
 DStringInner:
+  type: leaf_struct
   children:
     - literal:
         build: 
@@ -853,11 +887,13 @@ BacktickString:
         rule: DStringExpression
         vec: true
 BacktickInner:
+  type: leaf_struct
   children:
     - literal:
         build: 
           type: string
 BooleanLiteral:
+  type: leaf_struct
   children:
     - literal:
         build: 
diff --git a/src/util/indent_writer.rs b/src/util/indent_writer.rs
index 36aa913..544fbe3 100644
--- a/src/util/indent_writer.rs
+++ b/src/util/indent_writer.rs
@@ -5,9 +5,13 @@ pub struct IndentWriter {
 }
 
 impl IndentWriter {
-    pub fn new(start_level: usize, indent_string: &str, out: Box<dyn std::io::Write>) -> IndentWriter {
+    pub fn new(
+        start_level: usize,
+        indent_string: &str,
+        out: Box<dyn std::io::Write>,
+    ) -> IndentWriter {
         IndentWriter {
-            indent_level: start_level, 
+            indent_level: start_level,
             indent_string: indent_string.to_string(),
             out,
         }
@@ -24,7 +28,7 @@ impl IndentWriter {
     pub fn write(&mut self, s: &str) -> std::io::Result<()> {
         write!(self.out, "{}", s)
     }
-    
+
     pub fn writeln(&mut self, s: &str) -> std::io::Result<()> {
         self.write(&format!("{}\n", s))
     }
@@ -35,7 +39,7 @@ impl IndentWriter {
         }
         write!(self.out, "{}", s)
     }
-    
+
     pub fn writeln_indented(&mut self, s: &str) -> std::io::Result<()> {
         self.write_indented(&format!("{}\n", s))
     }
diff --git a/src/vm/constant.rs b/src/vm/constant.rs
index 4fbdb01..03cf434 100644
--- a/src/vm/constant.rs
+++ b/src/vm/constant.rs
@@ -1,7 +1,7 @@
 #[derive(Debug, Clone)]
 pub enum DvmConstant {
     String(String),
-    Array(DvmConstantArray)
+    Array(DvmConstantArray),
 }
 
 #[derive(Debug, Clone)]
@@ -13,5 +13,5 @@ pub enum DvmConstantArray {
     USizes(Vec<usize>),
     Booleans(Vec<bool>),
     Strings(Vec<String>),
-    Arrays(Vec<DvmConstantArray>)
-}
\ No newline at end of file
+    Arrays(Vec<DvmConstantArray>),
+}
diff --git a/src/vm/function.rs b/src/vm/function.rs
index d6cece1..909d414 100644
--- a/src/vm/function.rs
+++ b/src/vm/function.rs
@@ -28,7 +28,7 @@ impl DvmFunction {
     pub fn instructions(&self) -> &Vec<Instruction> {
         &self.instructions
     }
-    
+
     pub fn source_code_location(&self) -> &SourceCodeLocation {
         &self.source_code_location
     }
diff --git a/src/vm/instruction.rs b/src/vm/instruction.rs
index e105473..f18206d 100644
--- a/src/vm/instruction.rs
+++ b/src/vm/instruction.rs
@@ -111,8 +111,8 @@ pub enum Instruction {
     },
     Return,
     DumpState {
-        message: String
-    }
+        message: String,
+    },
 }
 
 #[derive(Debug, Clone)]
diff --git a/src/vm/method.rs b/src/vm/method.rs
index 6b7a67e..80848d0 100644
--- a/src/vm/method.rs
+++ b/src/vm/method.rs
@@ -21,7 +21,7 @@ impl DvmMethod {
             implements,
         }
     }
-    
+
     pub fn fqn(&self) -> &str {
         self.function.fqn()
     }
diff --git a/src/vm/source_code_location.rs b/src/vm/source_code_location.rs
index b381eda..74ab63b 100644
--- a/src/vm/source_code_location.rs
+++ b/src/vm/source_code_location.rs
@@ -10,7 +10,7 @@ impl SourceCodeLocation {
         SourceCodeLocation {
             source_file_name: source_file_name.to_string(),
             line,
-            col
+            col,
         }
     }
 }
diff --git a/src/vm/type.rs b/src/vm/type.rs
index db17db3..e8f31f8 100644
--- a/src/vm/type.rs
+++ b/src/vm/type.rs
@@ -7,9 +7,9 @@ pub enum DvmType {
     Double,
     Boolean,
     USize,
-    
+
     // Other
     Object,
     Array,
-    ConstantPointer
+    ConstantPointer,
 }
diff --git a/src/vm/value.rs b/src/vm/value.rs
index 449e8fa..64e30be 100644
--- a/src/vm/value.rs
+++ b/src/vm/value.rs
@@ -70,7 +70,7 @@ impl DvmValue {
             panic!("Expected DvmValue::Int, but found DvmValue::{:?}", self);
         }
     }
-    
+
     pub fn expect_int_or_else(&self, f: impl FnOnce(&Self) -> i32) -> i32 {
         if let DvmValue::Int(i) = self {
             *i