diff --git a/ast-generator/src/deserialize/leaf_enum_spec.rs b/ast-generator/src/deserialize/leaf_enum_spec.rs
new file mode 100644
index 0000000..bb145ac
--- /dev/null
+++ b/ast-generator/src/deserialize/leaf_enum_spec.rs
@@ -0,0 +1,13 @@
+use yaml_rust2::Yaml;
+use crate::spec::leaf_enum_spec::LeafEnumBuildSpec;
+
+pub fn deserialize_leaf_enum(name: &str, props: &Yaml) -> LeafEnumBuildSpec {
+    let rules = props["rules"].as_vec()
+        .unwrap()
+        .iter()
+        .map(|rule_yaml| {
+            rule_yaml.as_str().unwrap().to_string()
+        })
+        .collect();
+    LeafEnumBuildSpec::new(name, rules)
+}
diff --git a/ast-generator/src/deserialize/leaf_struct_spec.rs b/ast-generator/src/deserialize/leaf_struct_spec.rs
new file mode 100644
index 0000000..5243eed
--- /dev/null
+++ b/ast-generator/src/deserialize/leaf_struct_spec.rs
@@ -0,0 +1,21 @@
+use crate::deserialize::util::unwrap_single_member_hash;
+use yaml_rust2::Yaml;
+use crate::spec::leaf_struct_spec::{LeafStructBuildSpec, LeafStructMember, LeafStructMemberKind};
+
+fn deserialize_member(member_name: &str) -> LeafStructMember {
+    LeafStructMember::new(member_name, LeafStructMemberKind::String)
+}
+
+pub fn deserialize_leaf_struct(name: &str, props: &Yaml) -> LeafStructBuildSpec {
+    let members = props["members"]
+        .as_vec()
+        .unwrap()
+        .iter()
+        .map(|member_hash| {
+            let (member_name, _props) = unwrap_single_member_hash(member_hash);
+            deserialize_member(&member_name)
+        })
+        .map(Box::new)
+        .collect();
+    LeafStructBuildSpec::new(name, members)
+}
diff --git a/ast-generator/src/deserialize/mod.rs b/ast-generator/src/deserialize/mod.rs
index acfcf4e..1608173 100644
--- a/ast-generator/src/deserialize/mod.rs
+++ b/ast-generator/src/deserialize/mod.rs
@@ -1,451 +1,67 @@
-use crate::spec::{
-    AlternativeAction, AlternativeBuild, AlternativeBuildChild, AlternativeChild, AlternativeTest,
-    BooleanChildToBuild, BuildSpec, EnumBuildSpec, EnumRule, EnumRuleChild, EnumRuleChildKind,
-    EnumRuleNodeChild, LeafEnumBuildSpec, LeafEnumRule, LeafStructBuildSpec, LeafStructMember,
-    LeafStructMemberKind, MemberChild, MemberChildToBuild, NameAndKind, NodeChildToBuild,
-    PolymorphicBuildAlternative, PolymorphicBuildBuildSpec, PolymorphicEnumBuildSpec,
-    PolymorphicEnumMember, PolymorphicEnumRule, PolymorphicTypeBuildSpec, ProductionBuildSpec,
-    ProductionKind, ProductionNodeKind, ProductionStringFrom, SkipChild, StructBuildSpec,
-    StructChildSpec, VecChild, VecChildToBuild, VecNodeChildToBuild,
-};
-use crate::util::make_build_fn_name;
-use convert_case::{Case, Casing};
+mod leaf_enum_spec;
+mod leaf_struct_spec;
+mod node_production_spec;
+mod polymorphic_enum_loop_spec;
+mod polymorphic_type_spec;
+mod production_spec;
+mod struct_spec;
+mod tree_enum_spec;
+pub(crate) mod util;
+
+use crate::deserialize::leaf_enum_spec::deserialize_leaf_enum;
+use crate::deserialize::leaf_struct_spec::deserialize_leaf_struct;
+use crate::deserialize::node_production_spec::deserialize_node_production;
+use crate::deserialize::polymorphic_enum_loop_spec::deserialize_polymorphic_enum_loop;
+use crate::deserialize::polymorphic_type_spec::deserialize_polymorphic_type;
+use crate::deserialize::production_spec::deserialize_production;
+use crate::deserialize::struct_spec::deserialize_struct_spec;
+use crate::deserialize::tree_enum_spec::deserialize_tree_enum;
+use crate::spec::BuildSpec;
 use yaml_rust2::{Yaml, YamlLoader};
 
-fn get_as_bool(yaml: &Yaml) -> bool {
-    yaml.as_bool().unwrap_or_else(|| false)
-}
-
-fn unwrap_single_member_hash(hash: &Yaml) -> (String, &Yaml) {
-    let as_hash = hash.as_hash().unwrap();
-    if as_hash.is_empty() {
-        panic!("empty hash");
-    } else if as_hash.len() > 1 {
-        panic!("hash contains more than one key");
-    }
-    let (member_key, member_value) = as_hash.iter().collect::<Vec<(&Yaml, &Yaml)>>()[0];
-    let key_as_string = member_key.as_str().unwrap().to_string();
-    (key_as_string, member_value)
-}
-
-fn deserialize_polymorphic_enum_build_spec(
-    name: &str,
-    build_spec: &Yaml,
-) -> PolymorphicEnumBuildSpec {
-    let return_type = build_spec["return_type"].as_str().unwrap();
-    let rules = build_spec["rules"]
-        .as_vec()
-        .unwrap()
-        .iter()
-        .map(|rule_yaml| {
-            let (rule_name, props) = unwrap_single_member_hash(rule_yaml);
-            if props["wrap"].is_hash() {
-                PolymorphicEnumRule::Wrap(NameAndKind::new(
-                    &rule_name,
-                    props["wrap"]["enum_variant"].as_str().unwrap(),
-                ))
-            } else if props["return_build"].is_hash() {
-                PolymorphicEnumRule::ReturnBuild(NameAndKind::new(
-                    &rule_name,
-                    props["return_build"]["kind"].as_str().unwrap(),
-                ))
-            } else {
-                panic!()
-            }
-        })
-        .map(Box::new)
-        .collect::<Vec<_>>();
-    PolymorphicEnumBuildSpec::new(name, return_type, rules)
-}
-
-fn deserialize_polymorphic_action(action_yaml: &Yaml) -> AlternativeAction {
-    if action_yaml["return_build"].is_hash() {
-        let kind = action_yaml["return_build"]["kind"].as_str().unwrap();
-        AlternativeAction::ReturnBuild(kind.to_string())
-    } else if action_yaml["build"].is_hash() {
-        let build_children = action_yaml["build"]["children"]
-            .as_vec()
-            .unwrap()
-            .iter()
-            .map(|child_yaml| {
-                let (child_name, child_props) = unwrap_single_member_hash(child_yaml);
-                if get_as_bool(&child_props["skip"]) {
-                    AlternativeChild::Skip
-                } else {
-                    let kind = child_props["kind"].as_str().unwrap();
-                    let rule = child_props["rule"].as_str().unwrap();
-                    AlternativeChild::Build(AlternativeBuildChild::new(&child_name, kind, rule))
-                }
-            })
-            .map(Box::new)
-            .collect();
-        let enum_variant = action_yaml["build"]["enum_variant"].as_str().unwrap();
-        let build = AlternativeBuild::new(enum_variant, build_children);
-        AlternativeAction::Build(build)
-    } else {
-        panic!("return_build or build is required for an alternative")
-    }
-}
-
-fn deserialize_polymorphic_build_build_spec(
-    name: &str,
-    polymorphic_build_yaml: &Yaml,
-) -> PolymorphicBuildBuildSpec {
-    let return_type = polymorphic_build_yaml["return_type"].as_str().unwrap();
-    let alternatives = polymorphic_build_yaml["alternatives"]
-        .as_vec()
-        .unwrap()
-        .iter()
-        .map(|alternative_yaml| {
-            let number_of_pairs = alternative_yaml["test"]["number_of_pairs"]
-                .as_i64()
-                .unwrap();
-            let action = deserialize_polymorphic_action(&alternative_yaml["action"]);
-            PolymorphicBuildAlternative::new(
-                AlternativeTest::NumberOfPairs(number_of_pairs),
-                action,
-            )
-        })
-        .map(Box::new)
-        .collect();
-    PolymorphicBuildBuildSpec::new(name, return_type, alternatives)
-}
-
-fn deserialize_polymorphic_enum_members(
-    enum_members_yaml: &Yaml,
-) -> Vec<Box<PolymorphicEnumMember>> {
-    enum_members_yaml
-        .as_vec()
-        .unwrap()
-        .iter()
-        .map(|enum_member_yaml| {
-            let (member_name, member_hash) = unwrap_single_member_hash(enum_member_yaml);
-            let inner_kind = member_hash["inner"]["kind"].as_str().unwrap();
-            PolymorphicEnumMember::new(&member_name, inner_kind)
-        })
-        .map(Box::new)
-        .collect()
-}
-
-fn deserialize_polymorphic_spec(name: &str, spec_props: &Yaml) -> PolymorphicTypeBuildSpec {
-    let enum_members = deserialize_polymorphic_enum_members(&spec_props["enum_members"]);
-    let build_kind = spec_props["build"]["kind"].as_str().unwrap();
-    PolymorphicTypeBuildSpec::new(name, enum_members, build_kind)
-}
-
-fn deserialize_production_spec(rule: &str, production_yaml: &Yaml) -> ProductionBuildSpec {
-    let kind = if production_yaml["node"].is_hash() {
-        let kind = production_yaml["node"]["kind"].as_str().unwrap();
-        let with = production_yaml["node"]["with"].as_str().unwrap();
-        ProductionKind::Node(ProductionNodeKind::new(kind, with))
-    } else {
-        match production_yaml["kind"].as_str().unwrap() {
-            "int" => ProductionKind::Int,
-            "long" => ProductionKind::Long,
-            "double" => ProductionKind::Double,
-            "boolean" => ProductionKind::Boolean,
-            "string" => {
-                let from = match production_yaml["from"].as_str().unwrap() {
-                    "string_inner" => ProductionStringFrom::StringInner,
-                    "whole_pair" => ProductionStringFrom::WholePair,
-                    _ => panic!(
-                        "invalid from: {}",
-                        production_yaml["from"].as_str().unwrap()
-                    ),
-                };
-                ProductionKind::String(from)
-            }
-            _ => panic!(
-                "invalid kind: {}",
-                production_yaml["kind"].as_str().unwrap()
-            ),
-        }
-    };
-    ProductionBuildSpec::new(rule, kind)
-}
-
-fn deserialize_leaf_enum_rule(rule_yaml: &Yaml) -> Box<LeafEnumRule> {
-    Box::new(LeafEnumRule::new(rule_yaml.as_str().unwrap()))
-}
-
-fn deserialize_leaf_enum_rules(rules_yaml: &Yaml) -> Vec<Box<LeafEnumRule>> {
-    rules_yaml
-        .as_vec()
-        .unwrap()
-        .iter()
-        .map(|rule_yaml| deserialize_leaf_enum_rule(rule_yaml))
-        .collect()
-}
-
-fn deserialize_enum_rule_custom_child(rule_props: &Yaml) -> Option<Box<EnumRuleChild>> {
-    if !rule_props["child"].as_bool().unwrap_or(true) {
-        None
-    } else {
-        let kind = match rule_props["kind"].as_str().unwrap() {
-            "int" => EnumRuleChildKind::Int,
-            "long" => EnumRuleChildKind::Long,
-            "double" => EnumRuleChildKind::Double,
-            "usize" => EnumRuleChildKind::USize,
-            "string" => EnumRuleChildKind::String,
-            "boolean" => EnumRuleChildKind::Boolean,
-            _ => panic!(
-                "unsupported enum rule kind: {}",
-                rule_props["kind"].as_str().unwrap()
-            ),
-        };
-        Some(Box::new(EnumRuleChild::new(Box::new(kind))))
-    }
-}
-
-fn deserialize_enum_rule_node_child(rule: &str) -> Box<EnumRuleChild> {
-    Box::new(EnumRuleChild::new(Box::new(EnumRuleChildKind::Node(
-        EnumRuleNodeChild::new(rule),
-    ))))
-}
-
-fn deserialize_enum_rule(rule_yaml: &Yaml) -> Box<EnumRule> {
-    if rule_yaml.is_hash() {
-        let (rule, rule_props) = unwrap_single_member_hash(rule_yaml);
-        Box::new(EnumRule::new(
-            &rule,
-            deserialize_enum_rule_custom_child(rule_props),
-        ))
-    } else {
-        let rule_as_str = rule_yaml.as_str().unwrap();
-        Box::new(EnumRule::new(
-            rule_as_str,
-            Some(deserialize_enum_rule_node_child(rule_as_str)),
-        ))
-    }
-}
-
-fn deserialize_enum_rules(rules_yaml: &Yaml) -> Vec<Box<EnumRule>> {
-    rules_yaml
-        .as_vec()
-        .unwrap()
-        .iter()
-        .map(|rule_yaml| deserialize_enum_rule(rule_yaml))
-        .collect()
-}
-
-fn deserialize_leaf_struct_member(name: &str, props: &Yaml) -> Box<LeafStructMember> {
-    let kind = props["kind"].as_str().unwrap();
-    if kind == "string" {
-        Box::new(LeafStructMember::new(name, LeafStructMemberKind::String))
-    } else {
-        panic!("invalid member kind: {}", kind);
-    }
-}
-
-fn deserialize_leaf_struct_members(members_yaml: &Yaml) -> Vec<Box<LeafStructMember>> {
-    members_yaml
-        .as_vec()
-        .unwrap()
-        .iter()
-        .map(|member| {
-            let (member_name, member_props) = unwrap_single_member_hash(member);
-            deserialize_leaf_struct_member(&member_name, member_props)
-        })
-        .collect()
-}
-
-fn deserialize_member_node_to_build(
-    rule: &str,
-    build_props: &Yaml,
-    optional: bool,
-) -> Box<MemberChildToBuild> {
-    let or_else = build_props["or_else"]
-        .as_str()
-        .or_else(|| {
-            if get_as_bool(&build_props["or_else_default"]) {
-                Some("default")
-            } else {
-                None
-            }
-        })
-        .map(ToString::to_string);
-
-    let kind = build_props["kind"]
-        .as_str()
-        .map(ToString::to_string)
-        .unwrap_or_else(|| make_build_fn_name(rule));
-
-    let with = build_props["with"]
-        .as_str()
-        .map(ToString::to_string)
-        .unwrap_or_else(|| make_build_fn_name(rule));
-
-    Box::new(MemberChildToBuild::Node(NodeChildToBuild::new(
-        &kind, &with, or_else, optional,
-    )))
-}
-
-fn deserialize_member_boolean_to_build(name: &str) -> Box<MemberChildToBuild> {
-    Box::new(MemberChildToBuild::Boolean(BooleanChildToBuild::new(name)))
-}
-
-fn deserialize_member_child_to_build(
-    name: &str,
-    rule: &str,
-    props: &Yaml,
-    optional: bool,
-) -> Box<MemberChildToBuild> {
-    if props["build"].is_hash() {
-        let build_props = &props["build"];
-        let kind = build_props["kind"].as_str().or(Some("node")).unwrap();
-        if kind == "node" {
-            deserialize_member_node_to_build(rule, build_props, optional)
-        } else if kind == "boolean" {
-            deserialize_member_boolean_to_build(name)
-        } else {
-            panic!("unsupported kind: {}", kind)
-        }
-    } else {
-        let optional = get_as_bool(&props["optional"]);
-        let with = props["with"]
-            .as_str()
-            .map(ToString::to_string)
-            .unwrap_or_else(|| make_build_fn_name(rule));
-
-        Box::new(MemberChildToBuild::Node(NodeChildToBuild::new(
-            rule, &with, None, optional,
-        )))
-    }
-}
-
-fn deserialize_member_child(
-    name: &str,
-    rule: &str,
-    optional: bool,
-    props: &Yaml,
-) -> Box<StructChildSpec> {
-    Box::new(StructChildSpec::MemberChild(MemberChild::new(
-        name,
-        rule,
-        deserialize_member_child_to_build(name, rule, props, optional),
-    )))
-}
-
-fn deserialize_vec_node_child(name: &str, props: &Yaml) -> Box<StructChildSpec> {
-    let rule = props["rule"].as_str().unwrap();
-    Box::new(StructChildSpec::VecChild(VecChild::new(
-        name,
-        rule,
-        Box::new(VecChildToBuild::Node(VecNodeChildToBuild::new(rule))),
-    )))
-}
-
-fn deserialize_vec_string_child(name: &str, props: &Yaml) -> Box<StructChildSpec> {
-    let rule = props["rule"].as_str().unwrap();
-    Box::new(StructChildSpec::VecChild(VecChild::new(
-        name,
-        rule,
-        Box::new(VecChildToBuild::String),
-    )))
-}
-
-fn deserialize_vec_child(name: &str, props: &Yaml) -> Box<StructChildSpec> {
-    let kind = props["kind"].as_str().or_else(|| Some("node")).unwrap();
-    if kind == "node" {
-        deserialize_vec_node_child(name, props)
-    } else if kind == "string" {
-        deserialize_vec_string_child(name, props)
-    } else {
-        panic!("invalid kind: {}", kind);
-    }
-}
-
-fn deserialize_skip_child(name: &str, rule: &str) -> Box<StructChildSpec> {
-    Box::new(StructChildSpec::SkipChild(SkipChild::new(name, rule)))
-}
-
-fn deserialize_struct_hash_child(child: &Yaml) -> Box<StructChildSpec> {
-    let (name, props) = unwrap_single_member_hash(child);
-
-    let rule = props["rule"]
-        .as_str()
-        .map(|s| s.to_string())
-        .unwrap_or(name.to_case(Case::Pascal));
-
-    if get_as_bool(&props["skip"]) {
-        deserialize_skip_child(&name, &rule)
-    } else {
-        if get_as_bool(&props["vec"]) {
-            deserialize_vec_child(&name, props)
-        } else {
-            let optional = get_as_bool(&props["optional"]);
-            deserialize_member_child(&name, &rule, optional, props)
-        }
-    }
-}
-
-fn deserialize_struct_string_child(child: &Yaml) -> Box<StructChildSpec> {
-    let child_as_str = child.as_str().unwrap();
-    let child_name_pascal = child_as_str.to_case(Case::Pascal);
-    Box::new(StructChildSpec::MemberChild(MemberChild::new(
-        child_as_str,
-        &child_name_pascal,
-        Box::new(MemberChildToBuild::Node(NodeChildToBuild::new(
-            &child_name_pascal,
-            &make_build_fn_name(&child_name_pascal),
-            None,
-            false,
-        ))),
-    )))
-}
-
-fn deserialize_struct_children(children: &Yaml) -> Vec<Box<StructChildSpec>> {
-    children
-        .as_vec()
-        .unwrap()
-        .iter()
-        .map(|child_spec| {
-            if child_spec.is_hash() {
-                deserialize_struct_hash_child(child_spec)
-            } else {
-                deserialize_struct_string_child(child_spec)
-            }
-        })
-        .collect()
-}
-
 fn deserialize_build_spec(build_spec_name: &str, build_spec: &Yaml) -> BuildSpec {
-    if build_spec["children"].is_array() {
-        let children = deserialize_struct_children(&build_spec["children"]);
-        BuildSpec::Struct(StructBuildSpec::new(build_spec_name, children))
-    } else if build_spec["members"].is_array() {
-        let members = deserialize_leaf_struct_members(&build_spec["members"]);
-        BuildSpec::LeafStruct(LeafStructBuildSpec::new(build_spec_name, members))
-    } else if build_spec["rules"].is_array() {
-        let rules = deserialize_enum_rules(&build_spec["rules"]);
-        BuildSpec::Enum(EnumBuildSpec::new(build_spec_name, rules))
-    } else if build_spec["leaf_rules"].is_array() {
-        let leaf_rules = deserialize_leaf_enum_rules(&build_spec["leaf_rules"]);
-        BuildSpec::LeafEnum(LeafEnumBuildSpec::new(build_spec_name, leaf_rules))
-    } else if build_spec["produce"].is_hash() {
-        BuildSpec::Production(deserialize_production_spec(
+    if build_spec["struct"].is_hash() {
+        BuildSpec::Struct(deserialize_struct_spec(
             build_spec_name,
-            &build_spec["produce"],
+            &build_spec["struct"],
+        ))
+    } else if build_spec["leaf_struct"].is_hash() {
+        BuildSpec::LeafStruct(deserialize_leaf_struct(
+            build_spec_name,
+            &build_spec["leaf_struct"],
+        ))
+    } else if build_spec["tree_enum"].is_hash() {
+        BuildSpec::Enum(deserialize_tree_enum(
+            build_spec_name,
+            &build_spec["tree_enum"],
+        ))
+    } else if build_spec["leaf_enum"].is_hash() {
+        BuildSpec::LeafEnum(deserialize_leaf_enum(
+            build_spec_name,
+            &build_spec["leaf_enum"],
+        ))
+    } else if build_spec["production"].is_hash() {
+        BuildSpec::Production(deserialize_production(
+            build_spec_name,
+            &build_spec["production"],
+        ))
+    } else if build_spec["node_production"].is_hash() {
+        BuildSpec::NodeProduction(deserialize_node_production(
+            build_spec_name,
+            &build_spec["node_production"],
         ))
     } else if build_spec["polymorphic_type"].is_hash() {
-        BuildSpec::Polymorphic(deserialize_polymorphic_spec(
+        BuildSpec::PolymorphicType(deserialize_polymorphic_type(
             build_spec_name,
             &build_spec["polymorphic_type"],
         ))
-    } else if build_spec["polymorphic_build"].is_hash() {
-        BuildSpec::PolymorphicBuild(deserialize_polymorphic_build_build_spec(
+    } else if build_spec["polymorphic_enum_loop_build"].is_hash() {
+        BuildSpec::PolymorphicEnumLoop(deserialize_polymorphic_enum_loop(
             build_spec_name,
-            &build_spec["polymorphic_build"],
-        ))
-    } else if build_spec["polymorphic_enum"].is_hash() {
-        BuildSpec::PolymorphicEnum(deserialize_polymorphic_enum_build_spec(
-            build_spec_name,
-            &build_spec["polymorphic_enum"],
+            &build_spec["polymorphic_enum_loop_build"],
         ))
     } else {
-        panic!(
-            "Expected a node spec for either a struct, leaf_struct, enum, leaf_enum node type, production, polymorphic type, or polymorphic build type."
-        );
+        panic!("Missing or incorrect build type for {}", build_spec_name);
     }
 }
 
diff --git a/ast-generator/src/deserialize/node_production_spec.rs b/ast-generator/src/deserialize/node_production_spec.rs
new file mode 100644
index 0000000..b016331
--- /dev/null
+++ b/ast-generator/src/deserialize/node_production_spec.rs
@@ -0,0 +1,9 @@
+use crate::deserialize::util::make_build_fn_name;
+use crate::spec::node_production_spec::NodeProductionBuildSpec;
+use yaml_rust2::Yaml;
+
+pub fn deserialize_node_production(name: &str, props: &Yaml) -> NodeProductionBuildSpec {
+    let kind = props["kind"].as_str().unwrap();
+    let with = make_build_fn_name(props["with"].as_str().unwrap());
+    NodeProductionBuildSpec::new(name, kind, &with)
+}
diff --git a/ast-generator/src/deserialize/polymorphic_enum_loop_spec.rs b/ast-generator/src/deserialize/polymorphic_enum_loop_spec.rs
new file mode 100644
index 0000000..a26c3c9
--- /dev/null
+++ b/ast-generator/src/deserialize/polymorphic_enum_loop_spec.rs
@@ -0,0 +1,74 @@
+use crate::deserialize::util::{make_build_fn_name, unwrap_single_member_hash};
+use crate::spec::polymorphic_enum_loop_spec::{
+    PolymorphicEnumLoopBuildSpec, PolymorphicEnumLoopChildUseCurrent, PolymorphicEnumLoopRule,
+    PolymorphicEnumLoopRuleBuild, PolymorphicEnumLoopRuleBuildChild,
+    PolymorphicEnumLoopRuleChildOnEach, PolymorphicEnumLoopRulePassThrough,
+};
+use yaml_rust2::Yaml;
+
+fn deserialize_build_child(child_name: &str, props: &Yaml) -> PolymorphicEnumLoopRuleBuildChild {
+    if props["use_current"].is_hash() {
+        let kind = props["use_current"]["kind"].as_str().unwrap();
+        PolymorphicEnumLoopRuleBuildChild::UseCurrent(PolymorphicEnumLoopChildUseCurrent::new(
+            child_name, kind,
+        ))
+    } else if props["on_each"].is_hash() {
+        let rule = props["on_each"]["rule"].as_str().unwrap();
+        PolymorphicEnumLoopRuleBuildChild::OnEach(PolymorphicEnumLoopRuleChildOnEach::new(
+            child_name, rule,
+        ))
+    } else {
+        panic!("Expected 'use_current' or 'on_each' hash for polymorphic enum loop build child");
+    }
+}
+
+fn deserialize_build(name: &str, props: &Yaml) -> PolymorphicEnumLoopRuleBuild {
+    let variant = props["variant"].as_str().unwrap();
+    let children = props["children"]
+        .as_vec()
+        .unwrap()
+        .iter()
+        .map(|child_yaml| {
+            let (child_name, child_props) = unwrap_single_member_hash(child_yaml);
+            deserialize_build_child(&child_name, child_props)
+        })
+        .map(Box::new)
+        .collect();
+
+    PolymorphicEnumLoopRuleBuild::new(name, variant, children)
+}
+
+fn deserialize_pass_through(name: &str, props: &Yaml) -> PolymorphicEnumLoopRulePassThrough {
+    let kind = props["kind"].as_str().unwrap();
+    let with = make_build_fn_name(props["with"].as_str().unwrap());
+    PolymorphicEnumLoopRulePassThrough::new(name, kind, &with)
+}
+
+fn deserialize_rule(rule_name: &str, props: &Yaml) -> PolymorphicEnumLoopRule {
+    if props["pass_through"].is_hash() {
+        PolymorphicEnumLoopRule::PassThrough(deserialize_pass_through(
+            rule_name,
+            &props["pass_through"],
+        ))
+    } else if props["build"].is_hash() {
+        PolymorphicEnumLoopRule::Build(deserialize_build(rule_name, &props["build"]))
+    } else {
+        panic!("Polymorphic enum loop rule must have 'pass_through' or 'build' hash.");
+    }
+}
+
+pub fn deserialize_polymorphic_enum_loop(name: &str, props: &Yaml) -> PolymorphicEnumLoopBuildSpec {
+    let kind = props["kind"].as_str().unwrap();
+    let rules = props["rules"]
+        .as_vec()
+        .unwrap()
+        .iter()
+        .map(|rule_yaml| {
+            let (rule_name, rule_props) = unwrap_single_member_hash(rule_yaml);
+            deserialize_rule(&rule_name, rule_props)
+        })
+        .map(Box::new)
+        .collect();
+
+    PolymorphicEnumLoopBuildSpec::new(name, kind, rules)
+}
diff --git a/ast-generator/src/deserialize/polymorphic_type_spec.rs b/ast-generator/src/deserialize/polymorphic_type_spec.rs
new file mode 100644
index 0000000..54d34c8
--- /dev/null
+++ b/ast-generator/src/deserialize/polymorphic_type_spec.rs
@@ -0,0 +1,23 @@
+use crate::deserialize::util::unwrap_single_member_hash;
+use crate::spec::polymorphic_type_spec::{PolymorphicTypeBuildSpec, PolymorphicTypeVariant};
+use yaml_rust2::Yaml;
+
+fn deserialize_variant(variant_name: &str, props: &Yaml) -> PolymorphicTypeVariant {
+    let inner_kind = props["inner"]["kind"].as_str().unwrap();
+    PolymorphicTypeVariant::new(variant_name, inner_kind)    
+}
+
+pub fn deserialize_polymorphic_type(name: &str, props: &Yaml) -> PolymorphicTypeBuildSpec {
+    let variants = props["variants"]
+        .as_vec()
+        .unwrap()
+        .iter()
+        .map(|variant_yaml| {
+            let (variant_name, variant_props) = unwrap_single_member_hash(variant_yaml);
+            deserialize_variant(&variant_name, variant_props)
+        })
+        .map(Box::new)
+        .collect();
+    let kind = props["build"]["kind"].as_str().unwrap();
+    PolymorphicTypeBuildSpec::new(name, variants, kind)
+}
\ No newline at end of file
diff --git a/ast-generator/src/deserialize/production_spec.rs b/ast-generator/src/deserialize/production_spec.rs
new file mode 100644
index 0000000..34ea86c
--- /dev/null
+++ b/ast-generator/src/deserialize/production_spec.rs
@@ -0,0 +1,21 @@
+use crate::spec::production_spec::{ProductionBooleanFrom, ProductionBuildSpec, ProductionKind, ProductionStringFrom};
+use yaml_rust2::Yaml;
+
+pub fn deserialize_production(name: &str, props: &Yaml) -> ProductionBuildSpec {
+    let kind = match props["kind"].as_str().unwrap() {
+        "int" => ProductionKind::Int,
+        "long" => ProductionKind::Long,
+        "double" => ProductionKind::Double,
+        "string" => {
+            let from = match props["from"].as_str().unwrap() {
+                "string_inner" => ProductionStringFrom::StringInner,
+                "whole_pair" => ProductionStringFrom::WholePair,
+                _ => panic!("Unknown string production from: {}", props["from"].as_str().unwrap())
+            };
+            ProductionKind::String(from)
+        },
+        "boolean" => ProductionKind::Boolean(ProductionBooleanFrom::ParseWholePair),
+        _ => panic!("Unknown production kind: {}", props["kind"].as_str().unwrap()),
+    };
+    ProductionBuildSpec::new(name, kind)
+}
diff --git a/ast-generator/src/deserialize/struct_spec.rs b/ast-generator/src/deserialize/struct_spec.rs
new file mode 100644
index 0000000..e03aee5
--- /dev/null
+++ b/ast-generator/src/deserialize/struct_spec.rs
@@ -0,0 +1,140 @@
+use crate::deserialize_error;
+use convert_case::{Case, Casing};
+
+use crate::deserialize::util::{get_as_bool, make_build_fn_name, unwrap_single_member_hash};
+use crate::spec::struct_spec::*;
+use yaml_rust2::Yaml;
+
+fn deserialize_skip_child(props: &Yaml) -> StructChild {
+    let rule = props["rule"].as_str().unwrap();
+    StructChild::SkipChild(SkipChild::new(rule))
+}
+
+fn deserialize_vec_child(child_name: &str, props: &Yaml) -> StructChild {
+    let rule = props["rule"].as_str().unwrap();
+    let kind = props["kind"].as_str()
+        .unwrap_or(rule);
+    StructChild::VecChild(VecChild::new(child_name, rule, kind))
+}
+
+fn deserialize_member_build(child_name: &str, rule: &str, props: &Yaml) -> MemberChildBuild {
+    if props["node"].is_hash() {
+        let node_props = &props["node"];
+        let kind = node_props["kind"].as_str().unwrap_or(rule);
+        let with = node_props["with"]
+            .as_str()
+            .map(ToString::to_string)
+            .unwrap_or_else(|| make_build_fn_name(kind));
+
+        let or_else = if get_as_bool(&node_props["or_else_default"]) {
+            Some(String::from("default"))
+        } else if let Some(or_else) = node_props["or_else"].as_str() {
+            Some(or_else.to_string())
+        } else {
+            None
+        };
+
+        MemberChildBuild::Node(NodeMemberBuild::new(kind, &with, or_else))
+    } else if props["boolean"].is_hash() {
+        let boolean_props = &props["boolean"];
+        if let Some(on) = boolean_props["on"].as_str() {
+            if on == "rule_present" {
+                MemberChildBuild::Boolean(BooleanMemberBuild::new(
+                    BooleanMemberBuildOn::RulePresent,
+                ))
+            } else {
+                panic!(
+                    "Expected 'on' in 'boolean' in 'build' in {} to be 'rule_present'",
+                    child_name
+                );
+            }
+        } else {
+            panic!("Expected 'on' in 'boolean' in 'build' in {}", child_name);
+        }
+    } else {
+        panic!(
+            "Expected either of 'node' or 'boolean' in 'build' in {}",
+            child_name
+        );
+    }
+}
+
+fn deserialize_member_child(child_name: &str, props: &Yaml) -> StructChild {
+    let rule = props["rule"]
+        .as_str()
+        .map(ToString::to_string)
+        .unwrap_or_else(|| child_name.to_case(Case::Pascal));
+    let optional = get_as_bool(&props["optional"]);
+    if props["build"].is_hash() {
+        let build = deserialize_member_build(child_name, &rule, &props["build"]);
+        StructChild::MemberChild(MemberChild::new(
+            child_name,
+            &rule,
+            optional,
+            Box::new(build),
+        ))
+    } else {
+        StructChild::MemberChild(MemberChild::new(
+            child_name,
+            &rule,
+            optional,
+            Box::new(MemberChildBuild::Node(NodeMemberBuild::new(
+                &rule,
+                &make_build_fn_name(&rule),
+                None,
+            ))),
+        ))
+    }
+}
+
+fn deserialize_hash_child(name: &str, props: &Yaml) -> StructChild {
+    if props["skip"].is_hash() {
+        deserialize_skip_child(&props["skip"])
+    } else if props["vec"].is_hash() {
+        deserialize_vec_child(name, &props["vec"])
+    } else if props["member"].is_hash() {
+        deserialize_member_child(name, &props["member"])
+    } else {
+        panic!("Expected 'skip' or 'vec' in 'member' in {}", name);
+    }
+}
+
+fn deserialize_string_child(name: &str) -> StructChild {
+    let name_pascal = name.to_case(Case::Pascal);
+    StructChild::MemberChild(MemberChild::new(
+        name,
+        &name_pascal,
+        false,
+        Box::new(MemberChildBuild::Node(NodeMemberBuild::new(
+            &name_pascal,
+            &make_build_fn_name(name),
+            None,
+        ))),
+    ))
+}
+
+fn deserialize_children(children_yaml: &Yaml) -> Vec<Box<StructChild>> {
+    children_yaml
+        .as_vec()
+        .unwrap()
+        .iter()
+        .map(|child_yaml| {
+            if let Some(name) = child_yaml.as_str() {
+                deserialize_string_child(name)
+            } else {
+                let (child_name, child_props) = unwrap_single_member_hash(child_yaml);
+                deserialize_hash_child(&child_name, child_props)
+            }
+        })
+        .map(Box::new)
+        .collect()
+}
+
+pub fn deserialize_struct_spec(name: &str, struct_yaml: &Yaml) -> StructSpec {
+    let children = if struct_yaml["children"].is_array() {
+        deserialize_children(&struct_yaml["children"])
+    } else {
+        deserialize_error!("array", "children", name);
+    };
+    StructSpec::new(name, children)
+}
diff --git a/ast-generator/src/deserialize/tree_enum_spec.rs b/ast-generator/src/deserialize/tree_enum_spec.rs
new file mode 100644
index 0000000..016fc2e
--- /dev/null
+++ b/ast-generator/src/deserialize/tree_enum_spec.rs
@@ -0,0 +1,50 @@
+use crate::deserialize::util::{get_as_bool_or, unwrap_single_member_hash};
+use crate::spec::tree_enum_spec::{
+    EnumRuleChild, EnumRuleChildKind, TreeEnumBuildSpec, TreeEnumRule,
+};
+use yaml_rust2::Yaml;
+
+fn deserialize_hash_enum_rule(rule: &str, props: &Yaml) -> TreeEnumRule {
+    if get_as_bool_or(&props["child"], true) {
+        let kind = match props["kind"].as_str().unwrap() {
+            "int" => EnumRuleChildKind::Int,
+            "long" => EnumRuleChildKind::Long,
+            "double" => EnumRuleChildKind::Double,
+            "string" => EnumRuleChildKind::String,
+            "boolean" => EnumRuleChildKind::Boolean,
+            _ => panic!("Invalid kind: {}", props["kind"].as_str().unwrap()),
+        };
+        TreeEnumRule::new(rule, Some(Box::new(EnumRuleChild::new(Box::new(kind)))))
+    } else {
+        // no child
+        TreeEnumRule::new(rule, None)
+    }
+}
+
+fn deserialize_string_enum_rule(rule: &str) -> TreeEnumRule {
+    TreeEnumRule::new(
+        rule,
+        Some(Box::new(EnumRuleChild::new(Box::new(
+            EnumRuleChildKind::Node,
+        )))),
+    )
+}
+
+pub fn deserialize_tree_enum(name: &str, props: &Yaml) -> TreeEnumBuildSpec {
+    let rules = props["rules"]
+        .as_vec()
+        .unwrap()
+        .iter()
+        .map(|rule_yaml| {
+            if let Some(rule) = rule_yaml.as_str() {
+                deserialize_string_enum_rule(rule)
+            } else {
+                let (rule, props) = unwrap_single_member_hash(rule_yaml);
+                deserialize_hash_enum_rule(&rule, props)
+            }
+        })
+        .map(Box::new)
+        .collect();
+
+    TreeEnumBuildSpec::new(name, rules)
+}
diff --git a/ast-generator/src/deserialize/util.rs b/ast-generator/src/deserialize/util.rs
new file mode 100644
index 0000000..345d8e8
--- /dev/null
+++ b/ast-generator/src/deserialize/util.rs
@@ -0,0 +1,37 @@
+use convert_case::{Case, Casing};
+use yaml_rust2::Yaml;
+
+#[macro_export]
+macro_rules! deserialize_error {
+    ($kind:expr, $key:expr, $name:expr) => {
+        panic!("Expected {} '{}' in {}.", $kind, $key, $name);
+    };
+}
+
+pub fn make_build_fn_name(s: &str) -> String {
+    format!("build_{}", s.to_case(Case::Snake))
+}
+
+pub fn make_build_pair(s: &str) -> String {
+    format!("{}_pair", s.to_case(Case::Snake))
+}
+
+pub fn unwrap_single_member_hash(hash: &Yaml) -> (String, &Yaml) {
+    let as_hash = hash.as_hash().unwrap();
+    if as_hash.is_empty() {
+        panic!("empty hash");
+    } else if as_hash.len() > 1 {
+        panic!("hash contains more than one key");
+    }
+    let (member_key, member_value) = as_hash.iter().collect::<Vec<(&Yaml, &Yaml)>>()[0];
+    let key_as_string = member_key.as_str().unwrap().to_string();
+    (key_as_string, member_value)
+}
+
+pub fn get_as_bool(yaml: &Yaml) -> bool {
+    yaml.as_bool().unwrap_or(false)
+}
+
+pub fn get_as_bool_or(yaml: &Yaml, or: bool) -> bool {
+    yaml.as_bool().unwrap_or(or)
+}
diff --git a/ast-generator/src/spec/leaf_enum_spec.rs b/ast-generator/src/spec/leaf_enum_spec.rs
new file mode 100644
index 0000000..5c687fc
--- /dev/null
+++ b/ast-generator/src/spec/leaf_enum_spec.rs
@@ -0,0 +1,21 @@
+pub struct LeafEnumBuildSpec {
+    build: String,
+    rules: Vec<String>,
+}
+
+impl LeafEnumBuildSpec {
+    pub fn new(build: &str, rules: Vec<String>) -> Self {
+        Self {
+            build: build.to_string(),
+            rules,
+        }
+    }
+
+    pub fn build(&self) -> &str {
+        &self.build
+    }
+
+    pub fn rules(&self) -> impl Iterator<Item = &str> {
+        self.rules.iter().map(AsRef::as_ref)
+    }
+}
\ No newline at end of file
diff --git a/ast-generator/src/spec/leaf_struct_spec.rs b/ast-generator/src/spec/leaf_struct_spec.rs
new file mode 100644
index 0000000..0c12df4
--- /dev/null
+++ b/ast-generator/src/spec/leaf_struct_spec.rs
@@ -0,0 +1,47 @@
+pub struct LeafStructBuildSpec {
+    build: String,
+    members: Vec<Box<LeafStructMember>>,
+}
+
+impl LeafStructBuildSpec {
+    pub fn new(build: &str, members: Vec<Box<LeafStructMember>>) -> Self {
+        Self {
+            build: build.to_string(),
+            members,
+        }
+    }
+
+    pub fn build(&self) -> &str {
+        &self.build
+    }
+
+    pub fn members(&self) -> impl Iterator<Item = &LeafStructMember> {
+        self.members.iter().map(Box::as_ref)
+    }
+}
+
+pub struct LeafStructMember {
+    name: String,
+    kind: LeafStructMemberKind,
+}
+
+impl LeafStructMember {
+    pub fn new(name: &str, kind: LeafStructMemberKind) -> Self {
+        Self {
+            name: name.to_string(),
+            kind,
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn kind(&self) -> &LeafStructMemberKind {
+        &self.kind
+    }
+}
+
+pub enum LeafStructMemberKind {
+    String,
+}
diff --git a/ast-generator/src/spec/mod.rs b/ast-generator/src/spec/mod.rs
index 955e485..7a83e08 100644
--- a/ast-generator/src/spec/mod.rs
+++ b/ast-generator/src/spec/mod.rs
@@ -1,700 +1,28 @@
+use crate::spec::node_production_spec::NodeProductionBuildSpec;
+use leaf_enum_spec::LeafEnumBuildSpec;
+use leaf_struct_spec::LeafStructBuildSpec;
+use polymorphic_type_spec::PolymorphicTypeBuildSpec;
+use production_spec::ProductionBuildSpec;
+use struct_spec::StructSpec;
+use tree_enum_spec::TreeEnumBuildSpec;
+use crate::spec::polymorphic_enum_loop_spec::PolymorphicEnumLoopBuildSpec;
+
+pub(crate) mod leaf_enum_spec;
+pub(crate) mod leaf_struct_spec;
+pub(crate) mod node_production_spec;
+pub(crate) mod polymorphic_enum_loop_spec;
+pub(crate) mod polymorphic_type_spec;
+pub(crate) mod production_spec;
+pub(crate) mod struct_spec;
+pub(crate) mod tree_enum_spec;
+
 pub enum BuildSpec {
-    Enum(EnumBuildSpec),
+    Enum(TreeEnumBuildSpec),
     LeafEnum(LeafEnumBuildSpec),
-    Struct(StructBuildSpec),
+    Struct(StructSpec),
     LeafStruct(LeafStructBuildSpec),
     Production(ProductionBuildSpec),
-    Polymorphic(PolymorphicTypeBuildSpec),
-    PolymorphicBuild(PolymorphicBuildBuildSpec),
-    PolymorphicEnum(PolymorphicEnumBuildSpec),
-}
-
-// Enum build spec
-
-pub struct EnumBuildSpec {
-    build: String,
-    rules: Vec<Box<EnumRule>>,
-}
-
-impl EnumBuildSpec {
-    pub fn new(build: &str, rules: Vec<Box<EnumRule>>) -> Self {
-        EnumBuildSpec {
-            build: build.to_string(),
-            rules,
-        }
-    }
-
-    /// The enum type to be built, in Pascal case.
-    pub fn build(&self) -> &str {
-        &self.build
-    }
-
-    /// The individual rule specs.
-    pub fn rules(&self) -> impl Iterator<Item = &EnumRule> {
-        self.rules.iter().map(Box::as_ref)
-    }
-}
-
-pub struct EnumRule {
-    rule: String,
-    child: Option<Box<EnumRuleChild>>,
-}
-
-impl EnumRule {
-    pub fn new(rule: &str, child: Option<Box<EnumRuleChild>>) -> Self {
-        Self {
-            rule: rule.to_string(),
-            child,
-        }
-    }
-
-    /// The enum rule to match, in Pascal case.
-    pub fn rule(&self) -> &str {
-        &self.rule
-    }
-
-    pub fn child(&self) -> Option<&EnumRuleChild> {
-        if let Some(child) = &self.child {
-            Some(child.as_ref())
-        } else {
-            None
-        }
-    }
-}
-
-pub struct EnumRuleChild {
-    kind: Box<EnumRuleChildKind>,
-}
-
-impl EnumRuleChild {
-    pub fn new(kind: Box<EnumRuleChildKind>) -> Self {
-        Self { kind }
-    }
-
-    pub fn kind(&self) -> &EnumRuleChildKind {
-        &self.kind
-    }
-}
-
-pub enum EnumRuleChildKind {
-    Node(EnumRuleNodeChild),
-    Int,
-    Long,
-    Double,
-    USize,
-    String,
-    Boolean,
-}
-
-pub struct EnumRuleNodeChild {
-    build: String,
-}
-
-impl EnumRuleNodeChild {
-    pub fn new(build: &str) -> Self {
-        Self {
-            build: build.to_string(),
-        }
-    }
-
-    pub fn build(&self) -> &str {
-        &self.build
-    }
-}
-
-// Leaf enum build spec
-
-pub struct LeafEnumBuildSpec {
-    build: String,
-    rules: Vec<Box<LeafEnumRule>>,
-}
-
-impl LeafEnumBuildSpec {
-    pub fn new(build: &str, rules: Vec<Box<LeafEnumRule>>) -> Self {
-        Self {
-            build: build.to_string(),
-            rules,
-        }
-    }
-
-    pub fn build(&self) -> &str {
-        &self.build
-    }
-
-    pub fn rules(&self) -> impl Iterator<Item = &LeafEnumRule> {
-        self.rules.iter().map(Box::as_ref)
-    }
-}
-
-pub struct LeafEnumRule {
-    rule: String,
-}
-
-impl LeafEnumRule {
-    pub fn new(rule: &str) -> Self {
-        Self {
-            rule: rule.to_string(),
-        }
-    }
-
-    pub fn rule(&self) -> &str {
-        &self.rule
-    }
-}
-
-// Struct build spec
-
-pub struct StructBuildSpec {
-    build: String,
-    children: Vec<Box<StructChildSpec>>,
-}
-
-impl StructBuildSpec {
-    pub fn new(build: &str, children: Vec<Box<StructChildSpec>>) -> Self {
-        Self {
-            build: build.to_string(),
-            children,
-        }
-    }
-
-    /// The type to be built, in Pascal case.
-    pub fn build(&self) -> &str {
-        &self.build
-    }
-
-    /// The children for this build spec.
-    pub fn children(&self) -> impl Iterator<Item = &StructChildSpec> {
-        self.children.iter().map(Box::as_ref)
-    }
-}
-
-pub enum StructChildSpec {
-    SkipChild(SkipChild),
-    VecChild(VecChild),
-    MemberChild(MemberChild),
-}
-
-pub struct SkipChild {
-    name: String,
-    rule: String,
-}
-
-impl SkipChild {
-    pub fn new(name: &str, rule: &str) -> Self {
-        Self {
-            name: name.to_string(),
-            rule: rule.to_string(),
-        }
-    }
-
-    /// The name of this child spec.
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-
-    /// The grammar rule to match.
-    pub fn rule(&self) -> &str {
-        &self.rule
-    }
-}
-
-pub struct VecChild {
-    name: String,
-    rule: String,
-    build: Box<VecChildToBuild>,
-}
-
-impl VecChild {
-    pub fn new(name: &str, rule: &str, build: Box<VecChildToBuild>) -> Self {
-        Self {
-            name: name.to_string(),
-            rule: rule.to_string(),
-            build,
-        }
-    }
-
-    /// The name of this child.
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-
-    /// The rule to match to build this child.
-    pub fn rule(&self) -> &str {
-        &self.rule
-    }
-
-    /// The build info for this child.
-    pub fn build(&self) -> &VecChildToBuild {
-        &self.build
-    }
-}
-
-#[derive(Debug)]
-pub enum VecChildToBuild {
-    Node(VecNodeChildToBuild),
-    String,
-}
-
-#[derive(Debug)]
-pub struct VecNodeChildToBuild {
-    build: String,
-}
-
-impl VecNodeChildToBuild {
-    pub fn new(build: &str) -> Self {
-        Self {
-            build: build.to_string(),
-        }
-    }
-
-    /// The type to build, in Pascal case.
-    pub fn build(&self) -> &str {
-        &self.build
-    }
-}
-
-#[derive(Debug)]
-pub struct MemberChild {
-    name: String,
-    rule: String,
-    build: Box<MemberChildToBuild>,
-}
-
-impl MemberChild {
-    pub fn new(name: &str, rule: &str, build: Box<MemberChildToBuild>) -> Self {
-        Self {
-            name: name.to_string(),
-            rule: rule.to_string(),
-            build,
-        }
-    }
-
-    /// The name of this child in the yaml file, in snake case.
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-
-    /// The grammar rule to match to build this child.
-    pub fn rule(&self) -> &str {
-        &self.rule
-    }
-
-    /// The specification for what to actually build.
-    pub fn build(&self) -> &MemberChildToBuild {
-        &self.build
-    }
-}
-
-#[derive(Debug)]
-pub enum MemberChildToBuild {
-    Node(NodeChildToBuild),
-    Boolean(BooleanChildToBuild),
-}
-
-#[derive(Debug)]
-pub struct NodeChildToBuild {
-    kind: String,
-    with: String,
-    or_else: Option<String>,
-    optional: bool,
-}
-
-impl NodeChildToBuild {
-    pub fn new(kind: &str, with: &str, or_else: Option<String>, optional: bool) -> Self {
-        Self {
-            kind: kind.to_string(),
-            with: with.to_string(),
-            or_else,
-            optional,
-        }
-    }
-
-    /// The type to build, in Pascal case.
-    pub fn kind(&self) -> &str {
-        &self.kind
-    }
-
-    pub fn with(&self) -> &str {
-        &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
-    }
-}
-
-#[derive(Debug)]
-pub struct BooleanChildToBuild {
-    name: String,
-}
-
-impl BooleanChildToBuild {
-    pub fn new(name: &str) -> Self {
-        Self {
-            name: name.to_string(),
-        }
-    }
-
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-}
-
-// Leaf Struct build spec
-
-pub struct LeafStructBuildSpec {
-    build: String,
-    members: Vec<Box<LeafStructMember>>,
-}
-
-impl LeafStructBuildSpec {
-    pub fn new(build: &str, members: Vec<Box<LeafStructMember>>) -> Self {
-        Self {
-            build: build.to_string(),
-            members,
-        }
-    }
-
-    pub fn build(&self) -> &str {
-        &self.build
-    }
-
-    pub fn members(&self) -> impl Iterator<Item = &LeafStructMember> {
-        self.members.iter().map(Box::as_ref)
-    }
-}
-
-pub struct LeafStructMember {
-    name: String,
-    kind: LeafStructMemberKind,
-}
-
-impl LeafStructMember {
-    pub fn new(name: &str, kind: LeafStructMemberKind) -> Self {
-        Self {
-            name: name.to_string(),
-            kind,
-        }
-    }
-
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-
-    pub fn kind(&self) -> &LeafStructMemberKind {
-        &self.kind
-    }
-}
-
-pub enum LeafStructMemberKind {
-    String,
-}
-
-pub struct ProductionBuildSpec {
-    rule: String,
-    kind: ProductionKind,
-}
-
-impl ProductionBuildSpec {
-    pub fn new(rule: &str, kind: ProductionKind) -> Self {
-        Self {
-            rule: rule.to_string(),
-            kind,
-        }
-    }
-
-    pub fn rule(&self) -> &str {
-        &self.rule
-    }
-
-    pub fn kind(&self) -> &ProductionKind {
-        &self.kind
-    }
-}
-
-pub enum ProductionKind {
-    Int,
-    Long,
-    Double,
-    String(ProductionStringFrom),
-    Boolean,
-    Node(ProductionNodeKind),
-}
-
-pub struct ProductionNodeKind {
-    kind: String,
-    with: String,
-}
-
-impl ProductionNodeKind {
-    pub fn new(kind: &str, with: &str) -> Self {
-        Self {
-            kind: kind.to_string(),
-            with: with.to_string(),
-        }
-    }
-
-    pub fn kind(&self) -> &str {
-        &self.kind
-    }
-
-    pub fn with(&self) -> &str {
-        &self.with
-    }
-}
-
-pub enum ProductionStringFrom {
-    StringInner,
-    WholePair,
-}
-
-// Polymorphic build spec
-
-pub struct PolymorphicTypeBuildSpec {
-    name: String,
-    enum_members: Vec<Box<PolymorphicEnumMember>>,
-    build_kind: String,
-}
-
-impl PolymorphicTypeBuildSpec {
-    pub fn new(
-        name: &str,
-        enum_members: Vec<Box<PolymorphicEnumMember>>,
-        build_kind: &str,
-    ) -> Self {
-        Self {
-            name: name.to_string(),
-            enum_members,
-            build_kind: build_kind.to_string(),
-        }
-    }
-
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-
-    pub fn enum_members(&self) -> impl Iterator<Item = &PolymorphicEnumMember> {
-        self.enum_members.iter().map(Box::as_ref)
-    }
-
-    pub fn build_kind(&self) -> &str {
-        self.build_kind.as_str()
-    }
-}
-
-pub struct PolymorphicEnumMember {
-    name: String,
-    inner_kind: String,
-}
-
-impl PolymorphicEnumMember {
-    pub fn new(name: &str, inner_kind: &str) -> Self {
-        Self {
-            name: name.to_string(),
-            inner_kind: inner_kind.to_string(),
-        }
-    }
-
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-
-    pub fn inner_kind(&self) -> &str {
-        &self.inner_kind
-    }
-}
-
-pub struct PolymorphicBuildBuildSpec {
-    name: String,
-    return_type: String,
-    alternatives: Vec<Box<PolymorphicBuildAlternative>>,
-}
-
-impl PolymorphicBuildBuildSpec {
-    pub fn new(
-        name: &str,
-        return_type: &str,
-        alternatives: Vec<Box<PolymorphicBuildAlternative>>,
-    ) -> Self {
-        Self {
-            name: name.to_string(),
-            return_type: return_type.to_string(),
-            alternatives,
-        }
-    }
-
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-
-    pub fn return_type(&self) -> &str {
-        &self.return_type
-    }
-
-    pub fn alternatives(&self) -> impl Iterator<Item = &PolymorphicBuildAlternative> {
-        self.alternatives.iter().map(Box::as_ref)
-    }
-
-    pub fn primary_alternative(&self) -> (&AlternativeTest, &AlternativeBuild) {
-        let primary_build_alternative = self
-            .alternatives
-            .iter()
-            .find(|alternative| match alternative.action {
-                AlternativeAction::Build(_) => true,
-                _ => false,
-            })
-            .map(Box::as_ref)
-            .unwrap();
-        let alternative_build =
-            if let AlternativeAction::Build(build) = &primary_build_alternative.action {
-                build
-            } else {
-                unreachable!();
-            };
-        (primary_build_alternative.test(), alternative_build)
-    }
-}
-
-pub struct PolymorphicBuildAlternative {
-    test: AlternativeTest,
-    action: AlternativeAction,
-}
-
-impl PolymorphicBuildAlternative {
-    pub fn new(test: AlternativeTest, action: AlternativeAction) -> Self {
-        Self { test, action }
-    }
-
-    pub fn test(&self) -> &AlternativeTest {
-        &self.test
-    }
-
-    pub fn action(&self) -> &AlternativeAction {
-        &self.action
-    }
-}
-
-pub enum AlternativeTest {
-    NumberOfPairs(i64),
-}
-
-pub enum AlternativeAction {
-    ReturnBuild(String),
-    Build(AlternativeBuild),
-}
-
-pub struct AlternativeBuild {
-    enum_variant: String,
-    children: Vec<Box<AlternativeChild>>,
-}
-
-impl AlternativeBuild {
-    pub fn new(enum_variant: &str, children: Vec<Box<AlternativeChild>>) -> Self {
-        Self {
-            enum_variant: enum_variant.to_string(),
-            children,
-        }
-    }
-
-    pub fn enum_variant(&self) -> &str {
-        &self.enum_variant
-    }
-
-    pub fn children(&self) -> impl Iterator<Item = &AlternativeChild> {
-        self.children.iter().map(Box::as_ref)
-    }
-}
-
-pub enum AlternativeChild {
-    Skip,
-    Build(AlternativeBuildChild),
-}
-
-pub struct AlternativeBuildChild {
-    name: String,
-    kind: String,
-    rule: String,
-}
-
-impl AlternativeBuildChild {
-    pub fn new(name: &str, kind: &str, rule: &str) -> Self {
-        Self {
-            name: name.to_string(),
-            kind: kind.to_string(),
-            rule: rule.to_string(),
-        }
-    }
-
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-
-    pub fn kind(&self) -> &str {
-        &self.kind
-    }
-
-    pub fn rule(&self) -> &str {
-        &self.rule
-    }
-}
-
-pub struct PolymorphicEnumBuildSpec {
-    name: String,
-    return_type: String,
-    rules: Vec<Box<PolymorphicEnumRule>>,
-}
-
-impl PolymorphicEnumBuildSpec {
-    pub fn new(name: &str, return_type: &str, rules: Vec<Box<PolymorphicEnumRule>>) -> Self {
-        Self {
-            name: name.to_string(),
-            return_type: return_type.to_string(),
-            rules,
-        }
-    }
-
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-
-    pub fn return_type(&self) -> &str {
-        &self.return_type
-    }
-
-    pub fn rules(&self) -> impl Iterator<Item = &PolymorphicEnumRule> {
-        self.rules.iter().map(Box::as_ref)
-    }
-}
-
-pub enum PolymorphicEnumRule {
-    Wrap(NameAndKind),
-    ReturnBuild(NameAndKind),
-}
-
-pub struct NameAndKind {
-    name: String,
-    kind: String,
-}
-
-impl NameAndKind {
-    pub fn new(name: &str, kind: &str) -> Self {
-        Self {
-            name: name.to_string(),
-            kind: kind.to_string(),
-        }
-    }
-
-    pub fn name(&self) -> &str {
-        &self.name
-    }
-
-    pub fn kind(&self) -> &str {
-        &self.kind
-    }
+    NodeProduction(NodeProductionBuildSpec),
+    PolymorphicType(PolymorphicTypeBuildSpec),
+    PolymorphicEnumLoop(PolymorphicEnumLoopBuildSpec),
 }
diff --git a/ast-generator/src/spec/node_production_spec.rs b/ast-generator/src/spec/node_production_spec.rs
new file mode 100644
index 0000000..2f019a6
--- /dev/null
+++ b/ast-generator/src/spec/node_production_spec.rs
@@ -0,0 +1,27 @@
+pub struct NodeProductionBuildSpec {
+    name: String,
+    kind: String,
+    with: String
+}
+
+impl NodeProductionBuildSpec {
+    pub fn new(name: &str, kind: &str, with: &str) -> Self {
+        Self {
+            name: name.to_string(),
+            kind: kind.to_string(),
+            with: with.to_string()
+        }
+    }
+    
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+    
+    pub fn kind(&self) -> &str {
+        &self.kind
+    }
+    
+    pub fn with(&self) -> &str {
+        &self.with
+    }
+}
\ No newline at end of file
diff --git a/ast-generator/src/spec/polymorphic_enum_loop_spec.rs b/ast-generator/src/spec/polymorphic_enum_loop_spec.rs
new file mode 100644
index 0000000..25312dd
--- /dev/null
+++ b/ast-generator/src/spec/polymorphic_enum_loop_spec.rs
@@ -0,0 +1,133 @@
+pub struct PolymorphicEnumLoopBuildSpec {
+    name: String,
+    kind: String,
+    rules: Vec<Box<PolymorphicEnumLoopRule>>,
+}
+
+impl PolymorphicEnumLoopBuildSpec {
+    pub fn new(name: &str, kind: &str, rules: Vec<Box<PolymorphicEnumLoopRule>>) -> Self {
+        Self {
+            name: name.to_string(),
+            kind: kind.to_string(),
+            rules,
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn kind(&self) -> &str {
+        &self.kind
+    }
+
+    pub fn rules(&self) -> impl Iterator<Item = &PolymorphicEnumLoopRule> {
+        self.rules.iter().map(Box::as_ref)
+    }
+}
+
+pub enum PolymorphicEnumLoopRule {
+    PassThrough(PolymorphicEnumLoopRulePassThrough),
+    Build(PolymorphicEnumLoopRuleBuild),
+}
+
+pub struct PolymorphicEnumLoopRulePassThrough {
+    name: String,
+    kind: String,
+    with: String,
+}
+
+impl PolymorphicEnumLoopRulePassThrough {
+    pub fn new(name: &str, kind: &str, with: &str) -> Self {
+        Self {
+            name: name.to_string(),
+            kind: kind.to_string(),
+            with: with.to_string(),
+        }
+    }
+    
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+    
+    pub fn kind(&self) -> &str {
+        &self.kind
+    }
+    
+    pub fn with(&self) -> &str {
+        &self.with
+    }
+}
+
+pub struct PolymorphicEnumLoopRuleBuild {
+    name: String,
+    variant: String,
+    children: Vec<Box<PolymorphicEnumLoopRuleBuildChild>>,
+}
+
+impl PolymorphicEnumLoopRuleBuild {
+    pub fn new(name: &str, variant: &str, children: Vec<Box<PolymorphicEnumLoopRuleBuildChild>>) -> Self {
+        Self {
+            name: name.to_string(),
+            variant: variant.to_string(),
+            children,
+        }
+    }
+
+    pub fn variant(&self) -> &str {
+        &self.variant
+    }
+
+    pub fn children(&self) -> impl Iterator<Item = &PolymorphicEnumLoopRuleBuildChild> {
+        self.children.iter().map(Box::as_ref)
+    }
+}
+
+pub enum PolymorphicEnumLoopRuleBuildChild {
+    UseCurrent(PolymorphicEnumLoopChildUseCurrent),
+    OnEach(PolymorphicEnumLoopRuleChildOnEach),
+}
+
+pub struct PolymorphicEnumLoopChildUseCurrent {
+    name: String,
+    kind: String,
+}
+
+impl PolymorphicEnumLoopChildUseCurrent {
+    pub fn new(name: &str, kind: &str) -> Self {
+        Self {
+            name: name.to_string(),
+            kind: kind.to_string(),
+        }
+    }
+    
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn kind(&self) -> &str {
+        &self.kind
+    }
+}
+
+pub struct PolymorphicEnumLoopRuleChildOnEach {
+    name: String,
+    rule: String,
+}
+
+impl PolymorphicEnumLoopRuleChildOnEach {
+    pub fn new(name: &str, rule: &str) -> Self {
+        Self {
+            name: name.to_string(),
+            rule: rule.to_string(),
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+    
+    pub fn rule(&self) -> &str {
+        &self.rule
+    }
+}
diff --git a/ast-generator/src/spec/polymorphic_type_spec.rs b/ast-generator/src/spec/polymorphic_type_spec.rs
new file mode 100644
index 0000000..97eee0e
--- /dev/null
+++ b/ast-generator/src/spec/polymorphic_type_spec.rs
@@ -0,0 +1,49 @@
+pub struct PolymorphicTypeBuildSpec {
+    name: String,
+    variants: Vec<Box<PolymorphicTypeVariant>>,
+    kind: String,
+}
+
+impl PolymorphicTypeBuildSpec {
+    pub fn new(name: &str, variants: Vec<Box<PolymorphicTypeVariant>>, kind: &str) -> Self {
+        Self {
+            name: name.to_string(),
+            variants,
+            kind: kind.to_string(),
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn variants(&self) -> impl Iterator<Item = &PolymorphicTypeVariant> {
+        self.variants.iter().map(Box::as_ref)
+    }
+
+    pub fn kind(&self) -> &str {
+        self.kind.as_str()
+    }
+}
+
+pub struct PolymorphicTypeVariant {
+    name: String,
+    inner_kind: String,
+}
+
+impl PolymorphicTypeVariant {
+    pub fn new(name: &str, inner_kind: &str) -> Self {
+        Self {
+            name: name.to_string(),
+            inner_kind: inner_kind.to_string(),
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn inner_kind(&self) -> &str {
+        &self.inner_kind
+    }
+}
diff --git a/ast-generator/src/spec/production_spec.rs b/ast-generator/src/spec/production_spec.rs
new file mode 100644
index 0000000..31714be
--- /dev/null
+++ b/ast-generator/src/spec/production_spec.rs
@@ -0,0 +1,38 @@
+pub struct ProductionBuildSpec {
+    name: String,
+    kind: ProductionKind,
+}
+
+impl ProductionBuildSpec {
+    pub fn new(name: &str, kind: ProductionKind) -> Self {
+        Self {
+            name: name.to_string(),
+            kind,
+        }
+    }
+
+    pub fn rule(&self) -> &str {
+        &self.name
+    }
+
+    pub fn kind(&self) -> &ProductionKind {
+        &self.kind
+    }
+}
+
+pub enum ProductionKind {
+    Int,
+    Long,
+    Double,
+    String(ProductionStringFrom),
+    Boolean(ProductionBooleanFrom),
+}
+
+pub enum ProductionStringFrom {
+    StringInner,
+    WholePair,
+}
+
+pub enum ProductionBooleanFrom {
+    ParseWholePair,
+}
diff --git a/ast-generator/src/spec/struct_spec.rs b/ast-generator/src/spec/struct_spec.rs
new file mode 100644
index 0000000..56acd01
--- /dev/null
+++ b/ast-generator/src/spec/struct_spec.rs
@@ -0,0 +1,171 @@
+pub struct StructSpec {
+    build: String,
+    children: Vec<Box<StructChild>>,
+}
+
+impl StructSpec {
+    pub fn new(build: &str, children: Vec<Box<StructChild>>) -> Self {
+        Self {
+            build: build.to_string(),
+            children,
+        }
+    }
+
+    /// The type to be built, in Pascal case.
+    pub fn build(&self) -> &str {
+        &self.build
+    }
+
+    /// The children for this build spec.
+    pub fn children(&self) -> impl Iterator<Item = &StructChild> {
+        self.children.iter().map(Box::as_ref)
+    }
+}
+
+pub enum StructChild {
+    SkipChild(SkipChild),
+    VecChild(VecChild),
+    MemberChild(MemberChild),
+}
+
+pub struct SkipChild {
+    rule: String,
+}
+
+impl SkipChild {
+    pub fn new(rule: &str) -> Self {
+        Self {
+            rule: rule.to_string(),
+        }
+    }
+
+    /// The grammar rule to match.
+    pub fn rule(&self) -> &str {
+        &self.rule
+    }
+}
+
+pub struct VecChild {
+    name: String,
+    rule: String,
+    kind: String,
+}
+
+impl VecChild {
+    pub fn new(name: &str, rule: &str, kind: &str) -> Self {
+        Self {
+            name: name.to_string(),
+            rule: rule.to_string(),
+            kind: kind.to_string(),
+        }
+    }
+
+    /// The name of this child.
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// The rule to match to build this child.
+    pub fn rule(&self) -> &str {
+        &self.rule
+    }
+
+    pub fn kind(&self) -> &str {
+        &self.kind
+    }
+}
+
+#[derive(Debug)]
+pub struct MemberChild {
+    name: String,
+    rule: String,
+    optional: bool,
+    build: Box<MemberChildBuild>,
+}
+
+impl MemberChild {
+    pub fn new(name: &str, rule: &str, optional: bool, build: Box<MemberChildBuild>) -> Self {
+        Self {
+            name: name.to_string(),
+            rule: rule.to_string(),
+            optional,
+            build,
+        }
+    }
+
+    /// The name of this child in the yaml file, in snake case.
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// The grammar rule to match to build this child.
+    pub fn rule(&self) -> &str {
+        &self.rule
+    }
+
+    pub fn optional(&self) -> bool {
+        self.optional
+    }
+
+    /// The specification for what to actually build.
+    pub fn build(&self) -> &MemberChildBuild {
+        &self.build
+    }
+}
+
+#[derive(Debug)]
+pub enum MemberChildBuild {
+    Node(NodeMemberBuild),
+    Boolean(BooleanMemberBuild),
+}
+
+#[derive(Debug)]
+pub struct NodeMemberBuild {
+    kind: String,
+    with: String,
+    or_else: Option<String>,
+}
+
+impl NodeMemberBuild {
+    pub fn new(kind: &str, with: &str, or_else: Option<String>) -> Self {
+        Self {
+            kind: kind.to_string(),
+            with: with.to_string(),
+            or_else,
+        }
+    }
+
+    /// The type to build, in Pascal case.
+    pub fn kind(&self) -> &str {
+        &self.kind
+    }
+
+    pub fn with(&self) -> &str {
+        &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()
+    }
+}
+
+#[derive(Debug)]
+pub struct BooleanMemberBuild {
+    on: BooleanMemberBuildOn,
+}
+
+impl BooleanMemberBuild {
+    pub fn new(on: BooleanMemberBuildOn) -> Self {
+        Self { on }
+    }
+    
+    pub fn on(&self) -> &BooleanMemberBuildOn {
+        &self.on
+    }
+}
+
+#[derive(Debug)]
+pub enum BooleanMemberBuildOn {
+    RulePresent
+}
\ No newline at end of file
diff --git a/ast-generator/src/spec/tree_enum_spec.rs b/ast-generator/src/spec/tree_enum_spec.rs
new file mode 100644
index 0000000..56301c8
--- /dev/null
+++ b/ast-generator/src/spec/tree_enum_spec.rs
@@ -0,0 +1,73 @@
+pub struct TreeEnumBuildSpec {
+    build: String,
+    rules: Vec<Box<TreeEnumRule>>,
+}
+
+impl TreeEnumBuildSpec {
+    pub fn new(build: &str, rules: Vec<Box<TreeEnumRule>>) -> Self {
+        TreeEnumBuildSpec {
+            build: build.to_string(),
+            rules,
+        }
+    }
+
+    /// The enum type to be built, in Pascal case.
+    pub fn build(&self) -> &str {
+        &self.build
+    }
+
+    /// The individual rule specs.
+    pub fn rules(&self) -> impl Iterator<Item = &TreeEnumRule> {
+        self.rules.iter().map(Box::as_ref)
+    }
+}
+
+pub struct TreeEnumRule {
+    rule: String,
+    child: Option<Box<EnumRuleChild>>,
+}
+
+impl TreeEnumRule {
+    pub fn new(rule: &str, child: Option<Box<EnumRuleChild>>) -> Self {
+        Self {
+            rule: rule.to_string(),
+            child,
+        }
+    }
+
+    /// The enum rule to match, in Pascal case.
+    pub fn rule(&self) -> &str {
+        &self.rule
+    }
+
+    pub fn child(&self) -> Option<&EnumRuleChild> {
+        if let Some(child) = &self.child {
+            Some(child.as_ref())
+        } else {
+            None
+        }
+    }
+}
+
+pub struct EnumRuleChild {
+    kind: Box<EnumRuleChildKind>,
+}
+
+impl EnumRuleChild {
+    pub fn new(kind: Box<EnumRuleChildKind>) -> Self {
+        Self { kind }
+    }
+
+    pub fn kind(&self) -> &EnumRuleChildKind {
+        &self.kind
+    }
+}
+
+pub enum EnumRuleChildKind {
+    Node,
+    Int,
+    Long,
+    Double,
+    String,
+    Boolean,
+}
diff --git a/ast-generator/src/util.rs b/ast-generator/src/util.rs
deleted file mode 100644
index ae0220b..0000000
--- a/ast-generator/src/util.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-use convert_case::{Case, Casing};
-
-pub fn make_build_fn_name(s: &str) -> String {
-    format!("build_{}", s.to_case(Case::Snake))
-}
-
-pub fn make_build_pair(s: &str) -> String {
-    format!("{}_pair", s.to_case(Case::Snake))
-}
diff --git a/src/parser/ast.schema.yaml b/src/parser/ast.schema.yaml
index cf16fb5..30292db 100644
--- a/src/parser/ast.schema.yaml
+++ b/src/parser/ast.schema.yaml
@@ -171,7 +171,9 @@ $defs:
     additionalProperties: false
     properties:
       boolean:
-        $ref: "#/$defs/StructChildMemberBuildBooleanProps"
+        $ref: "#/$defs/StructChildMemberBuildBooleanProps"'
+    required:
+      - boolean
   StructChildMemberBuildBooleanProps:
     type: object
     additionalProperties: false
@@ -181,6 +183,8 @@ $defs:
         type: string
         enum:
           - rule_present
+    required:
+      - on
 
   # Leaf Struct Node
   LeafStructNodeDefinition:
@@ -219,12 +223,8 @@ $defs:
       kind:
         enum:
           - string
-      from:
-        enum:
-          - whole_pair
     required:
       - kind
-      - from
 
   # Enum node
   EnumNodeDefinition:
diff --git a/src/parser/ast.yaml b/src/parser/ast.yaml
index 58debfc..da89d98 100644
--- a/src/parser/ast.yaml
+++ b/src/parser/ast.yaml
@@ -33,7 +33,6 @@ Identifier:
     members:
       - name:
           kind: string
-          from: whole_pair
 FullyQualifiedName:
   struct:
     children:
@@ -801,6 +800,7 @@ OrRhs:
             build:
               node:
                 kind: Expression
+                with: AndExpression
 
 # And
 AndExpression: