diff --git a/ast-generator/src/build_fn_gen.rs b/ast-generator/src/build_fn_gen.rs
index f5cb49e..3b9c650 100644
--- a/ast-generator/src/build_fn_gen.rs
+++ b/ast-generator/src/build_fn_gen.rs
@@ -90,6 +90,57 @@ fn make_rule_matcher(child_spec: &ChildSpec) -> TokenStream {
     }
 }
 
+fn make_child_arg(child_spec: &ChildSpec) -> Option<TokenStream> {
+    match child_spec {
+        ChildSpec::SkipChild(_) => None,
+        ChildSpec::VecChild(vec_child) => {
+            let child_ident = match vec_child.build() {
+                VecChildToBuild::Type(vec_type_child) => format_ident!("{}", vec_type_child.var_name())
+            };
+            Some(quote! { #child_ident })
+        },
+        ChildSpec::SingleChild(single_child) => {
+            match single_child.build() {
+                SingleChildToBuild::Type(single_type_child) => {
+                    let child_ident = format_ident!("{}", single_type_child.var_name());
+                    if single_type_child.optional() {
+                        Some(quote! { #child_ident })
+                    } else if let Some(or_else) = single_type_child.or_else()  {
+                        let child_type_ident = format_ident!("{}", single_type_child.build());
+                        let or_else_ident = format_ident!("{}", or_else);
+                        Some(quote! {
+                            #child_ident.unwrap_or_else(|| Box::new(#child_type_ident::#or_else_ident()))
+                        })
+                    } else {
+                        Some(quote! { #child_ident.unwrap() })                        
+                    }
+                },
+                SingleChildToBuild::Boolean(single_boolean_child) => {
+                    let child_ident = format_ident!("{}", single_boolean_child.var_name());
+                    Some(quote! { #child_ident })
+                }
+            }
+        }
+    }
+}
+
+fn make_return_value_stream(build_spec: &StructBuildSpec) -> TokenStream {
+    let type_ident = format_ident!("{}", build_spec.build());
+    let child_args = build_spec
+        .children()
+        .iter()
+        .map(|child| make_child_arg(child))
+        .filter(|child_arg| child_arg.is_some())
+        .map(|child_arg| child_arg.unwrap())
+        .collect::<Vec<_>>();
+
+    quote! {
+        #type_ident::new(
+            #(#child_args,)*
+        )
+    }
+}
+
 pub fn make_struct_build_fn(build_spec: &StructBuildSpec) -> TokenStream {
     let build_fn_ident = format_ident!("{}", build_spec.with());
     let pair_ident = format_ident!("{}_pair", build_spec.build().to_case(Case::Snake));
@@ -117,11 +168,15 @@ pub fn make_struct_build_fn(build_spec: &StructBuildSpec) -> TokenStream {
         }
     };
 
+    let new_stream = make_return_value_stream(build_spec);
+
     quote! {
         fn #build_fn_ident(#pair_ident: Pair<Rule>) -> #return_type_ident {
             #(#child_holders;)*
 
             #iter_stream
+
+            #new_stream
         }
     }
 }
diff --git a/ast-generator/src/deserialize.rs b/ast-generator/src/deserialize.rs
index f5bbffa..6230770 100644
--- a/ast-generator/src/deserialize.rs
+++ b/ast-generator/src/deserialize.rs
@@ -48,34 +48,56 @@ fn get_vec_child(name: &str, rule: &str, build: &Yaml) -> ChildSpec {
 
 fn get_single_child_to_build(name: &str, rule: &str, optional: bool, build: &Yaml) -> SingleChildToBuild {
     if build.is_hash() {
-        let r#type = build["type"].as_str().unwrap();
-        let var_name = build["var"]
-            .as_str()
-            .map(|s| s.to_string())
-            .unwrap_or(name.to_string());
-        let on = build["on"].as_str().unwrap();
-        if r#type.eq("boolean") && on.eq("rule_present") {
-            SingleChildToBuild::Boolean(SingleBooleanChildToBuild::new(
-                &var_name,
-                BuildBooleanOn::RulePresent,
-            ))
-        } else {
-            todo!("currently on boolean types with on: rule_present are supported")
+        match build["type"].as_str() {
+            Some(r#type) => {
+                let var_name = build["var"]
+                    .as_str()
+                    .map(|s| s.to_string())
+                    .unwrap_or(name.to_string());
+                let on = build["on"].as_str().unwrap();
+                if r#type.eq("boolean") && on.eq("rule_present") {
+                    SingleChildToBuild::Boolean(SingleBooleanChildToBuild::new(
+                        &var_name,
+                        BuildBooleanOn::RulePresent,
+                    ))
+                } else {
+                    todo!("currently on boolean types with on: rule_present are supported")
+                }       
+            },
+            None => {
+                let or_else = build["or_else"]
+                    .as_str()
+                    .map(|s| s.to_string())
+                    .or_else(|| {
+                        let or_else_default = build["or_else_default"]
+                            .as_bool()
+                            .unwrap_or_else(|| false);
+                        if or_else_default {
+                            Some(String::from("default"))
+                        } else {
+                            None
+                        }
+                    });
+                SingleChildToBuild::Type(SingleTypeChildToBuild::from_build_or_rule(
+                    rule,
+                    or_else,
+                    optional,
+                ))
+            }
         }
     } else {
         match build.as_str() {
-            Some(s) => SingleChildToBuild::Type(SingleTypeChildToBuild::from_build_or_rule(s, optional)),
-            None => SingleChildToBuild::Type(SingleTypeChildToBuild::from_build_or_rule(rule, optional)),
+            Some(s) => SingleChildToBuild::Type(SingleTypeChildToBuild::from_build_or_rule(s, None, optional)),
+            None => SingleChildToBuild::Type(SingleTypeChildToBuild::from_build_or_rule(rule, None, optional)),
         }
     }
 }
 
-fn get_single_child(name: &str, rule: &str, optional: bool, or_else: Option<String>, build: &Yaml) -> ChildSpec {
+fn get_single_child(name: &str, rule: &str, optional: bool, build: &Yaml) -> ChildSpec {
     ChildSpec::SingleChild(SingleChild::new(
         name,
         rule,
         get_single_child_to_build(name, rule, optional, build),
-        or_else
     ))
 }
 
@@ -110,21 +132,8 @@ fn get_child_specs(children: &Yaml) -> Vec<ChildSpec> {
                     let optional = props["optional"]
                         .as_bool()
                         .unwrap_or_else(|| false);
-                    let or_else = props["or_else"]
-                        .as_str()
-                        .map(|s| s.to_string())
-                        .or_else(|| {
-                            let or_else_default = props["or_else_default"]
-                                .as_bool()
-                                .unwrap_or_else(|| false);
-                            if or_else_default {
-                                Some(String::from("default"))
-                            } else {
-                                None
-                            }
-                        });
                     
-                    get_single_child(name, &rule, optional, or_else, build)
+                    get_single_child(name, &rule, optional, build)
                 }
             } else {
                 ChildSpec::SingleChild(SingleChild::from_name_snake(child_spec.as_str().unwrap()))
diff --git a/ast-generator/src/lib.rs b/ast-generator/src/lib.rs
index c657e1c..6f5716a 100644
--- a/ast-generator/src/lib.rs
+++ b/ast-generator/src/lib.rs
@@ -9,6 +9,7 @@ use proc_macro2::TokenStream;
 use quote::quote;
 use spec::BuildSpec;
 use syn::File;
+use syn::spanned::Spanned;
 
 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 f42b85c..96e966a 100644
--- a/ast-generator/src/spec.rs
+++ b/ast-generator/src/spec.rs
@@ -224,7 +224,6 @@ pub struct SingleChild {
     name: String,
     rule: String,
     build: SingleChildToBuild,
-    or_else: Option<String>
 }
 
 impl SingleChild {
@@ -234,18 +233,17 @@ impl SingleChild {
             rule: name.to_case(Case::Pascal),
             build: SingleChildToBuild::Type(SingleTypeChildToBuild::from_build_or_rule(
                 &name.to_case(Case::Pascal),
+                None,
                 false,
             )),
-            or_else: None,
         }
     }
 
-    pub fn new(name: &str, rule: &str, build: SingleChildToBuild, or_else: Option<String>) -> Self {
+    pub fn new(name: &str, rule: &str, build: SingleChildToBuild) -> Self {
         Self {
             name: name.to_string(),
             rule: rule.to_string(),
             build,
-            or_else,
         }
     }
 
@@ -276,15 +274,21 @@ pub struct SingleTypeChildToBuild {
     build: String,
     var_name: String,
     with: String,
+    or_else: Option<String>,
     optional: bool,
 }
 
 impl SingleTypeChildToBuild {
-    pub fn from_build_or_rule(build_or_rule: &str, optional: bool) -> Self {
+    pub fn from_build_or_rule(
+        build_or_rule: &str,
+        or_else: Option<String>,
+        optional: bool,
+    ) -> Self {
         Self {
             build: build_or_rule.to_string(),
             var_name: build_or_rule.to_case(Case::Snake),
             with: make_build_fn_name(build_or_rule),
+            or_else,
             optional,
         }
     }
@@ -304,6 +308,11 @@ impl SingleTypeChildToBuild {
         &self.with
     }
 
+    /// The default fn to call when unwrapping the child (before passing as arg to new).
+    pub fn or_else(&self) -> Option<&str> {
+        self.or_else.as_deref()
+    }
+
     /// If the type should be wrapped in an Option.
     pub fn optional(&self) -> bool {
         self.optional
diff --git a/src/parser/ast.schema.yaml b/src/parser/ast.schema.yaml
index a62f4ca..d8081f7 100644
--- a/src/parser/ast.schema.yaml
+++ b/src/parser/ast.schema.yaml
@@ -82,12 +82,6 @@ $defs:
       optional:
         type: boolean
         description: If true, this child will be stored as an Option.
-      or_else:
-        type: string
-        description: The method name to call upon the built-type if the rule is not found. Takes precedence over "or_else_default".
-      or_else_default:
-        type: boolean
-        description: Whether to call the default method on the built-type if the rule is not found.
       build:
         oneOf:
           - type: string
@@ -97,7 +91,19 @@ $defs:
     additionalProperties: false
     description: A definition of what exactly to build for a given child rule.
     oneOf:
+      - $ref: "#/$defs/BuildSingleTypeChild"
       - $ref: "#/$defs/BuildBooleanChild"
+  BuildSingleTypeChild:
+    type: object
+    additionalProperties: false
+    description: A definition of a single-type child to build.
+    properties:
+      or_else:
+        type: string
+        description: The method name to call upon the built-type if the rule is not found. Takes precedence over "or_else_default".
+      or_else_default:
+        type: boolean
+        description: Whether to call the default method on the built-type if the rule is not found.
   BuildBooleanChild:
     type: object
     additionalProperties: false
diff --git a/src/parser/ast.yaml b/src/parser/ast.yaml
index 41b1894..d4f58ce 100644
--- a/src/parser/ast.yaml
+++ b/src/parser/ast.yaml
@@ -112,9 +112,11 @@ Interface:
         skip: true
     - identifier
     - generic_parameters:
-        or_else_default: true
+        build:
+          or_else_default: true
     - implements_list:
-        or_else_default: true
+        build:
+          or_else_default: true
     - declarations:
         rule: InterfaceLevelDeclaration
         vec: true
@@ -133,11 +135,14 @@ Class:
         skip: true
     - identifier
     - generic_parameters:
-        or_else_default: true
+        build:
+          or_else_default: true
     - class_constructor:
-        or_else_default: true
+        build:
+          or_else_default: true
     - implements_list:
-        or_else_default: true
+        build:
+          or_else_default: true
     - class_level_declarations:
         rule: ClassLevelDeclaration
         vec: true
@@ -155,11 +160,11 @@ Function:
         skip: true
     - generics:
         rule: GenericParameters
-        or_else_default: true
     - identifier
     - parameters
     - return_type:
-        or_else: void
+        build:
+          or_else: void
     - function_body
 OperatorFunction:
   children:
@@ -173,11 +178,13 @@ OperatorFunction:
         skip: true
     - generics:
         rule: GenericParameters
-        or_else_default: true
+        build:
+          or_else_default: true
     - operator
     - parameters
     - return_type:
-        or_else: void
+        build:
+          or_else: void
     - function_body
 PlatformFunction:
   children:
@@ -194,7 +201,8 @@ PlatformFunction:
         skip: true
     - generics:
         rule: GenericParameters
-        or_else_default: true
+        build:
+          or_else_default: true
     - identifier
     - parameters
     - return_type