diff --git a/ast-generator/src/build_fn_gen.rs b/ast-generator/src/build_fn_gen.rs
new file mode 100644
index 0000000..f5cb49e
--- /dev/null
+++ b/ast-generator/src/build_fn_gen.rs
@@ -0,0 +1,127 @@
+use crate::spec::{
+    BuildBooleanOn, ChildSpec, SingleChildToBuild, StructBuildSpec, VecChildToBuild,
+};
+use convert_case::{Case, Casing};
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+
+pub fn make_build_fn_name(s: &str) -> String {
+    format!("build_{}", s.to_case(Case::Snake))
+}
+
+fn make_child_holder(child_spec: &ChildSpec) -> Option<TokenStream> {
+    match child_spec {
+        ChildSpec::SkipChild(_) => None,
+        ChildSpec::VecChild(vec_child) => {
+            let (child_ident, child_type_ident) = match vec_child.build() {
+                VecChildToBuild::Type(vec_type_child) => (
+                    format_ident!("{}", vec_type_child.var_name()),
+                    format_ident!("{}", vec_type_child.build()),
+                ),
+            };
+            Some(quote! {
+                let mut #child_ident: Vec<#child_type_ident> = vec![]
+            })
+        }
+        ChildSpec::SingleChild(single_child) => match single_child.build() {
+            SingleChildToBuild::Type(single_type_child) => {
+                let child_ident = format_ident!("{}", single_type_child.var_name());
+                let child_type_ident = format_ident!("{}", single_type_child.build());
+                Some(quote! {
+                    let mut #child_ident: Option<#child_type_ident> = None;
+                })
+            }
+            SingleChildToBuild::Boolean(boolean_child) => {
+                let child_ident = format_ident!("{}", boolean_child.var_name());
+                Some(quote! {
+                    let #child_ident: bool = false
+                })
+            }
+        },
+    }
+}
+
+fn make_match_action(child_spec: &ChildSpec) -> TokenStream {
+    match child_spec {
+        ChildSpec::SkipChild(_) => quote! {},
+        ChildSpec::VecChild(vec_child) => {
+            let (child_name_ident, build_fn_ident) = match vec_child.build() {
+                VecChildToBuild::Type(vec_type_child) => (
+                    format_ident!("{}", vec_type_child.var_name()),
+                    format_ident!("{}", vec_type_child.with()),
+                ),
+            };
+            quote! {
+                #child_name_ident.push(#build_fn_ident(inner_pair))
+            }
+        }
+        ChildSpec::SingleChild(single_child) => match single_child.build() {
+            SingleChildToBuild::Type(single_type_child) => {
+                let child_name_ident = format_ident!("{}", single_type_child.var_name());
+                let build_fn_ident = format_ident!("{}", single_type_child.with());
+                quote! {
+                    #child_name_ident = Some(#build_fn_ident(inner_pair))
+                }
+            }
+            SingleChildToBuild::Boolean(single_boolean_child) => {
+                let child_name_ident = format_ident!("{}", single_boolean_child.var_name());
+                match single_boolean_child.on() {
+                    BuildBooleanOn::RulePresent => quote! {
+                        #child_name_ident = true
+                    },
+                }
+            }
+        },
+    }
+}
+
+fn make_rule_matcher(child_spec: &ChildSpec) -> TokenStream {
+    let rule_ident = match child_spec {
+        ChildSpec::SkipChild(skip_child) => format_ident!("{}", skip_child.rule()),
+        ChildSpec::VecChild(vec_child) => format_ident!("{}", vec_child.rule()),
+        ChildSpec::SingleChild(single_child) => format_ident!("{}", single_child.rule()),
+    };
+    let action = make_match_action(child_spec);
+
+    quote! {
+        Rule::#rule_ident => {
+            #action;
+        }
+    }
+}
+
+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));
+    let return_type_ident = format_ident!("{}", build_spec.build());
+
+    let child_holders = build_spec
+        .children()
+        .iter()
+        .map(|child_spec| make_child_holder(child_spec))
+        .filter(|child_holder| child_holder.is_some())
+        .map(|child_holder| child_holder.unwrap())
+        .collect::<Vec<_>>();
+
+    let rule_matchers = build_spec
+        .children()
+        .iter()
+        .map(|child_spec| make_rule_matcher(child_spec))
+        .collect::<Vec<_>>();
+
+    let iter_stream = quote! {
+        for inner_pair in #pair_ident.into_inner() {
+            match inner_pair.as_rule() {
+                #(#rule_matchers)*
+            }
+        }
+    };
+
+    quote! {
+        fn #build_fn_ident(#pair_ident: Pair<Rule>) -> #return_type_ident {
+            #(#child_holders;)*
+
+            #iter_stream
+        }
+    }
+}
diff --git a/ast-generator/src/deserialize.rs b/ast-generator/src/deserialize.rs
new file mode 100644
index 0000000..869a2e7
--- /dev/null
+++ b/ast-generator/src/deserialize.rs
@@ -0,0 +1,167 @@
+use crate::build_fn_gen::make_build_fn_name;
+use crate::spec::{
+    BuildBooleanOn, BuildSpec, ChildSpec, EnumBuildSpec, EnumRule, SingleBooleanChildToBuild,
+    SingleChild, SingleChildToBuild, SingleTypeChildToBuild, SkipChild, StructBuildSpec, VecChild,
+    VecChildToBuild, VecTypeChildToBuild,
+};
+use convert_case::{Case, Casing};
+use yaml_rust2::{Yaml, YamlLoader};
+
+fn get_skip(skip: &Yaml) -> bool {
+    skip.as_bool().unwrap_or_else(|| false)
+}
+
+fn get_vec(vec: &Yaml) -> bool {
+    vec.as_bool().unwrap_or_else(|| false)
+}
+
+fn get_vec_child_to_build(build: &Yaml, rule: &str) -> VecChildToBuild {
+    if build.is_hash() {
+        let build_type = build["build"].as_str().unwrap();
+        let var_name = build["var"]
+            .as_str()
+            .map(|s| s.to_string())
+            .unwrap_or_else(|| build_type.to_case(Case::Snake));
+        let with = build["with"]
+            .as_str()
+            .map(|s| s.to_string())
+            .unwrap_or_else(|| make_build_fn_name(build_type));
+
+        VecChildToBuild::Type(VecTypeChildToBuild::new(build_type, &var_name, &with))
+    } else {
+        let build_as_str = build.as_str().unwrap_or(rule);
+        VecChildToBuild::Type(VecTypeChildToBuild::new(
+            build_as_str,
+            build_as_str.to_case(Case::Snake).as_str(),
+            make_build_fn_name(build_as_str).as_str(),
+        ))
+    }
+}
+
+fn get_vec_child(name: &str, rule: &str, build: &Yaml) -> ChildSpec {
+    ChildSpec::VecChild(VecChild::new(
+        name,
+        rule,
+        get_vec_child_to_build(build, rule),
+    ))
+}
+
+fn get_single_child_to_build(name: &str, rule: &str, 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")
+        }
+    } else {
+        match build.as_str() {
+            Some(s) => SingleChildToBuild::Type(SingleTypeChildToBuild::from_build_or_rule(s)),
+            None => SingleChildToBuild::Type(SingleTypeChildToBuild::from_build_or_rule(rule)),
+        }
+    }
+}
+
+fn get_single_child(name: &str, rule: &str, build: &Yaml) -> ChildSpec {
+    ChildSpec::SingleChild(SingleChild::new(
+        name,
+        rule,
+        get_single_child_to_build(name, rule, build),
+    ))
+}
+
+fn get_child_specs(children: &Yaml) -> Vec<ChildSpec> {
+    children
+        .as_vec()
+        .unwrap()
+        .iter()
+        .map(|child_spec| {
+            if child_spec.is_hash() {
+                let as_hash = child_spec.as_hash().unwrap();
+                let only_pair = as_hash.iter().next().unwrap();
+
+                let name = only_pair.0.as_str().unwrap();
+                let props = only_pair.1;
+
+                let rule = props["rule"].as_str().unwrap();
+
+                if get_skip(&props["skip"]) {
+                    return ChildSpec::SkipChild(SkipChild::new(name, rule));
+                }
+
+                let build = &props["build"];
+
+                if get_vec(&props["vec"]) {
+                    get_vec_child(name, rule, build)
+                } else {
+                    get_single_child(name, rule, build)
+                }
+            } else {
+                ChildSpec::SingleChild(SingleChild::from_name_snake(child_spec.as_str().unwrap()))
+            }
+        })
+        .collect()
+}
+
+fn get_enum_rule_specs(rule_specs: &Yaml) -> Vec<EnumRule> {
+    rule_specs
+        .as_vec()
+        .unwrap()
+        .iter()
+        .map(|rule_spec| {
+            if rule_spec.is_hash() {
+                let rule = rule_spec["rule"].as_str().unwrap();
+                let build = rule_spec["build"].as_str().unwrap();
+                let with = if !rule_spec["with"].is_badvalue() {
+                    rule_spec.as_str().unwrap().to_string()
+                } else {
+                    make_build_fn_name(build)
+                };
+
+                EnumRule::new(rule, build, &with)
+            } else {
+                EnumRule::from_rule(rule_spec.as_str().unwrap())
+            }
+        })
+        .collect()
+}
+
+fn deserialize_build_spec(build_spec_name: &Yaml, build_spec: &Yaml) -> BuildSpec {
+    let build_spec_name_pascal = build_spec_name.as_str().unwrap();
+    let children = &build_spec["children"];
+
+    if children.is_array() {
+        let child_specs = get_child_specs(children);
+        BuildSpec::Struct(StructBuildSpec::from_name(
+            build_spec_name_pascal,
+            child_specs,
+        ))
+    } else {
+        let rule_specs = &build_spec["rules"];
+        if rule_specs.is_array() {
+            let enum_rules = get_enum_rule_specs(rule_specs);
+            BuildSpec::Enum(EnumBuildSpec::from_name(build_spec_name_pascal, enum_rules))
+        } else {
+            panic!("either children or rules must be present on the build spec");
+        }
+    }
+}
+
+pub fn deserialize_yaml_spec(yaml: &str) -> Vec<BuildSpec> {
+    let docs = YamlLoader::load_from_str(yaml).unwrap();
+    let doc = &docs[0];
+
+    doc.as_hash()
+        .unwrap()
+        .iter()
+        .map(|(build_spec_name, build_spec)| deserialize_build_spec(build_spec_name, build_spec))
+        .collect()
+}
diff --git a/ast-generator/src/lib.rs b/ast-generator/src/lib.rs
index e8bde7b..c657e1c 100644
--- a/ast-generator/src/lib.rs
+++ b/ast-generator/src/lib.rs
@@ -1,310 +1,47 @@
-use convert_case::{Case, Casing};
-use proc_macro2::{Ident, TokenStream};
-use quote::{format_ident, quote};
-use yaml_rust2::YamlLoader;
+mod build_fn_gen;
+mod deserialize;
+mod spec;
+mod type_gen;
 
-enum BuildSpec {
-    Enum(EnumBuildSpec),
-    Struct(StructBuildSpec),
-}
+use crate::build_fn_gen::make_struct_build_fn;
+use crate::type_gen::make_type;
+use proc_macro2::TokenStream;
+use quote::quote;
+use spec::BuildSpec;
+use syn::File;
 
-struct EnumBuildSpec {
-    name: String,
-    build: String,
-    rules: Vec<EnumRule>,
-}
-
-struct EnumRule {
-    rule: String,
-    build: String,
-}
-
-impl EnumRule {
-    fn from_rule_name(rule_name: &str) -> Self {
-        Self {
-            rule: rule_name.to_string(),
-            build: rule_name.to_string(),
+fn debug_built_spec(build_spec: &BuildSpec, token_stream: &TokenStream) {
+    println!("*** BuildSpec ***");
+    match build_spec {
+        BuildSpec::Enum(enum_build_spec) => {
+            println!("Spec name: {}", enum_build_spec.name());
+        }
+        BuildSpec::Struct(struct_build_spec) => {
+            println!("Spec name: {}", struct_build_spec.name());
         }
     }
-
-    fn new(rule: &str, build: &str) -> Self {
-        Self {
-            rule: rule.to_string(),
-            build: build.to_string(),
-        }
-    }
-}
-
-struct StructBuildSpec {
-    name: String,
-    build: String,
-    children: Vec<ChildSpec>,
-}
-
-#[derive(Debug)]
-struct ChildSpec {
-    name: String,
-    rule: String,
-    vec: bool,
-    skip: bool,
-    build: ChildToBuild,
-}
-
-impl ChildSpec {
-    fn from_child_name(child_name: &str) -> Self {
-        Self {
-            name: child_name.to_string(),
-            rule: child_name.to_case(Case::Pascal),
-            skip: false,
-            vec: false,
-            build: ChildToBuild::TypeRef(child_name.to_case(Case::Pascal)),
-        }
-    }
-
-    fn new(name: &str, rule: &str, vec: bool, skip: bool, build: ChildToBuild) -> Self {
-        Self {
-            name: name.to_string(),
-            rule: rule.to_string(),
-            vec,
-            skip,
-            build,
-        }
-    }
-}
-
-#[derive(Debug)]
-enum ChildToBuild {
-    TypeRef(String),
-    Boolean { on: BuildBooleanOn },
-}
-
-#[derive(Debug)]
-enum BuildBooleanOn {
-    RulePresent,
-}
-
-fn make_enum_type(build_spec: &EnumBuildSpec) -> TokenStream {
-    let children: Vec<TokenStream> = build_spec
-        .rules
-        .iter()
-        .map(|rule| {
-            let member_name_ident = format_ident!("{}", rule.rule);
-            let child_name_ident = format_ident!("{}", rule.build);
-            quote! {
-                #member_name_ident(#child_name_ident)
-            }
-        })
-        .collect();
-    let type_name_ident = format_ident!("{}", build_spec.build);
-    quote! {
-        pub enum #type_name_ident {
-            #(#children),*
-        }
-    }
-}
-
-fn make_child_type_ident(child_spec: &ChildSpec) -> Ident {
-    match &child_spec.build {
-        ChildToBuild::TypeRef(type_name) => format_ident!("{}", type_name),
-        ChildToBuild::Boolean { on: _ } => format_ident!("bool"),
-    }
-}
-
-fn make_child_ident(child_spec: &ChildSpec) -> Ident {
-    format_ident!("{}", child_spec.name)
-}
-
-fn make_struct_type(build_spec: &StructBuildSpec) -> TokenStream {
-    let mut member_names: Vec<Ident> = vec![];
-    let mut annotated_members: Vec<TokenStream> = vec![];
-    let mut accessors: Vec<TokenStream> = vec![];
-
-    for child_spec in build_spec.children.iter() {
-        println!("{:?}", child_spec);
-        if !child_spec.skip {
-            let child_ident = make_child_ident(child_spec);
-            member_names.push(child_ident.clone());
-
-            let child_type_ident = make_child_type_ident(child_spec);
-            let type_annotation = if child_spec.vec {
-                quote! { Vec<#child_type_ident> }
-            } else {
-                quote! { #child_type_ident }
-            };
-            annotated_members.push(quote! {
-                #child_ident: #type_annotation
-            });
-
-            accessors.push(quote! {
-                pub fn #child_ident(&self) -> &#type_annotation {
-                    &self.#child_ident
-                }
-            })
-        }
-    }
-
-    let type_ident = format_ident!("{}", build_spec.build);
-
-    quote! {
-        pub struct #type_ident {
-            #(#annotated_members),*
-        }
-
-        impl #type_ident {
-            pub fn new(#(#annotated_members),*) -> Self {
-                Self {
-                    #(#member_names),*
-                }
-            }
-
-            #(#accessors)*
-        }
-    }
-}
-
-fn make_child_holder(child_spec: &ChildSpec) -> TokenStream {
-    if child_spec.skip {
-        return quote! {};
-    }
-    let child_ident = make_child_ident(child_spec);
-    let child_type_ident = make_child_type_ident(child_spec);
-
-    if child_spec.vec {
-        quote! { let mut #child_ident: Vec<#child_type_ident> = vec![] }
-    } else {
-        match &child_spec.build {
-            ChildToBuild::TypeRef(_) => quote! {
-                let mut #child_ident: Option<#child_type_ident> = None
-            },
-            ChildToBuild::Boolean { on } => match on {
-                BuildBooleanOn::RulePresent => {
-                    quote! { let mut #child_ident: bool = false }
-                }
-            },
-        }
-    }
-}
-
-fn make_struct_build_fn(build_spec: &StructBuildSpec) -> TokenStream {
-    let child_holders = build_spec
-        .children
-        .iter()
-        .map(|child_spec| make_child_holder(child_spec))
-        .collect::<Vec<_>>();
-
-    let build_fn_identifier = format_ident!("build_{}", build_spec.name);
-    let return_type_ident = format_ident!("{}", build_spec.build);
-    quote! {
-        fn #build_fn_identifier() -> #return_type_ident {
-            #(#child_holders);*
-        }
-    }
-}
-
-fn deserialize_yaml_file() -> Vec<BuildSpec> {
-    let docs = YamlLoader::load_from_str(include_str!("../../src/parser/ast.yaml")).unwrap();
-    let doc = &docs[0];
-    let mut build_specs: Vec<BuildSpec> = vec![];
-
-    for (build_spec_name, build_spec) in doc.as_hash().unwrap() {
-        let build_spec_name_pascal = build_spec_name.as_str().unwrap();
-        let children = &build_spec["children"];
-
-        if children.is_array() {
-            let mut child_specs: Vec<ChildSpec> = vec![];
-            for child_spec in children.as_vec().unwrap() {
-                if child_spec.is_hash() {
-                    let as_hash = child_spec.as_hash().unwrap();
-                    let only_pair = as_hash.iter().next().unwrap();
-
-                    let name = only_pair.0.as_str().unwrap();
-                    let props = only_pair.1;
-
-                    let rule = props["rule"].as_str().unwrap();
-
-                    let skip = if !props["skip"].is_badvalue() {
-                        props["skip"].as_bool().unwrap()
-                    } else {
-                        false
-                    };
-
-                    let vec = if !props["vec"].is_badvalue() {
-                        props["vec"].as_bool().unwrap()
-                    } else {
-                        false
-                    };
-
-                    let build = &props["build"];
-                    let child_to_build = if build.is_hash() {
-                        let r#type = build["type"].as_str().unwrap();
-                        let on = build["on"].as_str().unwrap();
-                        if r#type.eq("boolean") && on.eq("rule_present") {
-                            ChildToBuild::Boolean {
-                                on: BuildBooleanOn::RulePresent,
-                            }
-                        } else {
-                            todo!("currently on boolean types are supported")
-                        }
-                    } else {
-                        match build.as_str() {
-                            Some(s) => ChildToBuild::TypeRef(s.to_string()),
-                            None => ChildToBuild::TypeRef(rule.to_string()),
-                        }
-                    };
-
-                    child_specs.push(ChildSpec::new(name, rule, vec, skip, child_to_build))
-                } else {
-                    child_specs.push(ChildSpec::from_child_name(child_spec.as_str().unwrap()));
-                }
-            }
-
-            build_specs.push(BuildSpec::Struct(StructBuildSpec {
-                name: build_spec_name_pascal.to_string(),
-                build: build_spec_name_pascal.to_string(),
-                children: child_specs,
-            }));
-        } else {
-            let rule_specs = &build_spec["rules"];
-            if rule_specs.is_array() {
-                let mut enum_rules: Vec<EnumRule> = vec![];
-                for rule_spec in rule_specs.as_vec().unwrap() {
-                    if rule_spec.is_hash() {
-                        let rule = rule_spec["rule"].as_str().unwrap();
-                        let build = rule_spec["build"].as_str().unwrap();
-                        enum_rules.push(EnumRule::new(rule, build));
-                    } else {
-                        enum_rules.push(EnumRule::from_rule_name(rule_spec.as_str().unwrap()));
-                    }
-                }
-            } else {
-                panic!("either children or rules must be present on the build spec");
-            }
-        }
-    }
-
-    build_specs
+    println!("{:#?}", token_stream);
+    let parsed: File = syn::parse2(token_stream.clone()).unwrap();
+    println!("{}", prettyplease::unparse(&parsed));
 }
 
 pub fn test_dump() -> String {
-    let build_specs = deserialize_yaml_file();
+    let build_specs = deserialize::deserialize_yaml_spec(include_str!("../../src/parser/ast.yaml"));
     let mut streams: Vec<TokenStream> = vec![];
 
     for build_spec in &build_specs {
-        match build_spec {
-            BuildSpec::Enum(enum_spec) => {
-                streams.push(make_enum_type(enum_spec));
-            }
-            BuildSpec::Struct(struct_spec) => {
-                streams.push(make_struct_type(struct_spec));
-            }
-        }
+        let type_stream = make_type(build_spec);
+        debug_built_spec(build_spec, &type_stream);
+        streams.push(type_stream);
     }
 
     for build_spec in &build_specs {
         match build_spec {
             BuildSpec::Enum(_) => {}
             BuildSpec::Struct(struct_spec) => {
-                streams.push(make_struct_type(struct_spec));
+                let struct_build_fn_stream = make_struct_build_fn(struct_spec);
+                debug_built_spec(build_spec, &struct_build_fn_stream);
+                streams.push(struct_build_fn_stream);
             }
         }
     }
@@ -312,7 +49,6 @@ pub fn test_dump() -> String {
     let combined = quote! {
         #(#streams)*
     };
-
-    let syntax_tree = syn::parse2(combined).unwrap();
-    prettyplease::unparse(&syntax_tree)
+    let file: File = syn::parse2(combined).unwrap();
+    prettyplease::unparse(&file)
 }
diff --git a/ast-generator/src/spec.rs b/ast-generator/src/spec.rs
new file mode 100644
index 0000000..c6bddb4
--- /dev/null
+++ b/ast-generator/src/spec.rs
@@ -0,0 +1,328 @@
+use crate::build_fn_gen::make_build_fn_name;
+use convert_case::{Case, Casing};
+
+pub enum BuildSpec {
+    Enum(EnumBuildSpec),
+    Struct(StructBuildSpec),
+}
+
+pub struct EnumBuildSpec {
+    name: String,
+    build: String,
+    rules: Vec<EnumRule>,
+}
+
+impl EnumBuildSpec {
+    pub fn from_name(name: &str, rules: Vec<EnumRule>) -> Self {
+        EnumBuildSpec {
+            name: name.to_string(),
+            build: name.to_string(),
+            rules,
+        }
+    }
+
+    /// The top-level key for the build spec in the yaml file.
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// The enum type to be built, in Pascal case.
+    pub fn build(&self) -> &str {
+        &self.build
+    }
+
+    /// The individual rule specs.
+    pub fn rules(&self) -> &[EnumRule] {
+        &self.rules
+    }
+}
+
+pub struct EnumRule {
+    rule: String,
+    build: String,
+    with: String,
+}
+
+impl EnumRule {
+    pub fn from_rule(rule: &str) -> Self {
+        Self {
+            rule: rule.to_string(),
+            build: rule.to_string(),
+            with: make_build_fn_name(rule),
+        }
+    }
+
+    pub fn new(rule: &str, build: &str, with: &str) -> Self {
+        Self {
+            rule: rule.to_string(),
+            build: build.to_string(),
+            with: with.to_string(),
+        }
+    }
+
+    /// The enum rule to match, in Pascal case.
+    pub fn rule(&self) -> &str {
+        &self.rule
+    }
+
+    /// The type to build, in Pascal case.
+    pub fn build(&self) -> &str {
+        &self.build
+    }
+
+    /// The build-fn name, in snake case.
+    pub fn with(&self) -> &str {
+        &self.with
+    }
+}
+
+pub struct StructBuildSpec {
+    name: String,
+    build: String,
+    var_name: String,
+    with: String,
+    children: Vec<ChildSpec>,
+}
+
+impl StructBuildSpec {
+    pub fn from_name(name: &str, child_specs: Vec<ChildSpec>) -> Self {
+        Self {
+            name: name.to_string(),
+            build: name.to_string(),
+            var_name: name.to_case(Case::Snake),
+            with: make_build_fn_name(name),
+            children: child_specs,
+        }
+    }
+
+    /// The top-level name of this build spec.
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// The type to be built, in Pascal case.
+    pub fn build(&self) -> &str {
+        &self.build
+    }
+
+    /// The name of the variable to be built, in snake case.
+    pub fn var_name(&self) -> &str {
+        &self.var_name
+    }
+
+    /// The build-fn name, in snake case.
+    pub fn with(&self) -> &str {
+        &self.with
+    }
+
+    /// The children for this build spec.
+    pub fn children(&self) -> &[ChildSpec] {
+        &self.children
+    }
+}
+
+pub enum ChildSpec {
+    SkipChild(SkipChild),
+    VecChild(VecChild),
+    SingleChild(SingleChild),
+}
+
+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: VecChildToBuild,
+}
+
+impl VecChild {
+    pub fn new(name: &str, rule: &str, build: 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 {
+    Type(VecTypeChildToBuild),
+}
+
+#[derive(Debug)]
+pub struct VecTypeChildToBuild {
+    build: String,
+    var_name: String,
+    with: String,
+}
+
+impl VecTypeChildToBuild {
+    pub fn new(build: &str, var_name: &str, with: &str) -> Self {
+        Self {
+            build: build.to_string(),
+            var_name: var_name.to_string(),
+            with: with.to_string(),
+        }
+    }
+
+    /// The type to build, in Pascal case.
+    pub fn build(&self) -> &str {
+        &self.build
+    }
+
+    /// The name of the variable to build, in snake case.
+    pub fn var_name(&self) -> &str {
+        &self.var_name
+    }
+
+    /// The build-fn name.
+    pub fn with(&self) -> &str {
+        &self.with
+    }
+}
+
+#[derive(Debug)]
+pub struct SingleChild {
+    name: String,
+    rule: String,
+    build: SingleChildToBuild,
+}
+
+impl SingleChild {
+    pub fn from_name_snake(name: &str) -> Self {
+        Self {
+            name: name.to_string(),
+            rule: name.to_case(Case::Pascal),
+            build: SingleChildToBuild::Type(SingleTypeChildToBuild::from_build_or_rule(
+                &name.to_case(Case::Pascal),
+            )),
+        }
+    }
+
+    pub fn new(name: &str, rule: &str, build: SingleChildToBuild) -> 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) -> &SingleChildToBuild {
+        &self.build
+    }
+}
+
+#[derive(Debug)]
+pub enum SingleChildToBuild {
+    Type(SingleTypeChildToBuild),
+    Boolean(SingleBooleanChildToBuild),
+}
+
+#[derive(Debug)]
+pub struct SingleTypeChildToBuild {
+    build: String,
+    var_name: String,
+    with: String,
+}
+
+impl SingleTypeChildToBuild {
+    pub fn from_build_or_rule(build_or_rule: &str) -> 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),
+        }
+    }
+
+    /// The type to build, in Pascal case.
+    pub fn build(&self) -> &str {
+        &self.build
+    }
+
+    /// The variable name to build, in snake case.
+    pub fn var_name(&self) -> &str {
+        &self.var_name
+    }
+
+    /// The build-fn name.
+    pub fn with(&self) -> &str {
+        &self.with
+    }
+}
+
+#[derive(Debug)]
+pub struct SingleBooleanChildToBuild {
+    var_name: String,
+    on: BuildBooleanOn,
+}
+
+impl SingleBooleanChildToBuild {
+    pub fn new(var_name: &str, on: BuildBooleanOn) -> Self {
+        Self {
+            var_name: var_name.to_string(),
+            on,
+        }
+    }
+
+    pub fn var_name(&self) -> &str {
+        &self.var_name
+    }
+
+    pub fn on(&self) -> &BuildBooleanOn {
+        &self.on
+    }
+}
+
+#[derive(Debug)]
+pub enum BuildBooleanOn {
+    RulePresent,
+}
diff --git a/ast-generator/src/type_gen.rs b/ast-generator/src/type_gen.rs
new file mode 100644
index 0000000..4c60280
--- /dev/null
+++ b/ast-generator/src/type_gen.rs
@@ -0,0 +1,152 @@
+use crate::spec::{
+    BuildSpec, ChildSpec, EnumBuildSpec, SingleBooleanChildToBuild, SingleChildToBuild,
+    SingleTypeChildToBuild, StructBuildSpec, VecChild, VecChildToBuild,
+};
+use proc_macro2::{Ident, TokenStream};
+use quote::{format_ident, quote};
+
+fn make_enum_type(build_spec: &EnumBuildSpec) -> TokenStream {
+    let children: Vec<TokenStream> = build_spec
+        .rules()
+        .iter()
+        .map(|rule| {
+            let member_name_ident = format_ident!("{}", rule.rule());
+            let child_name_ident = format_ident!("{}", rule.build());
+            quote! {
+                #member_name_ident(#child_name_ident)
+            }
+        })
+        .collect();
+    let type_name_ident = format_ident!("{}", build_spec.build());
+    quote! {
+        pub enum #type_name_ident {
+            #(#children),*
+        }
+    }
+}
+
+fn handle_vec_child(
+    vec_child: &VecChild,
+    member_names: &mut Vec<Ident>,
+    annotated_members: &mut Vec<TokenStream>,
+    accessors: &mut Vec<TokenStream>,
+) {
+    let (child_ident, child_type_ident) = match vec_child.build() {
+        VecChildToBuild::Type(vec_type_child) => (
+            format_ident!("{}", vec_type_child.var_name()),
+            format_ident!("{}", vec_type_child.build()),
+        ),
+    };
+
+    member_names.push(child_ident.clone());
+    annotated_members.push(quote! {
+        #child_ident: Vec<#child_type_ident>
+    });
+    accessors.push(quote! {
+        pub fn #child_ident(&self) -> &[#child_type_ident] {
+            &self.#child_ident
+        }
+    });
+}
+
+fn handle_single_type_child(
+    single_type_child: &SingleTypeChildToBuild,
+    member_names: &mut Vec<Ident>,
+    annotated_members: &mut Vec<TokenStream>,
+    accessors: &mut Vec<TokenStream>,
+) {
+    let child_ident = format_ident!("{}", single_type_child.var_name());
+    let child_type_ident = format_ident!("{}", single_type_child.build());
+    member_names.push(child_ident.clone());
+    annotated_members.push(quote! {
+        #child_ident: #child_type_ident
+    });
+    accessors.push(quote! {
+        pub fn #child_ident(&self) -> &#child_type_ident {
+            &self.#child_ident
+        }
+    });
+}
+
+fn handle_single_boolean_child(
+    single_boolean_child: &SingleBooleanChildToBuild,
+    member_names: &mut Vec<Ident>,
+    annotated_members: &mut Vec<TokenStream>,
+    accessors: &mut Vec<TokenStream>,
+) {
+    let child_ident = format_ident!("{}", single_boolean_child.var_name());
+    member_names.push(child_ident.clone());
+    annotated_members.push(quote! {
+        #child_ident: bool
+    });
+    accessors.push(quote! {
+        pub fn #child_ident(&self) -> bool {
+            self.#child_ident
+        }
+    })
+}
+
+fn make_struct_type(build_spec: &StructBuildSpec) -> TokenStream {
+    let mut member_names: Vec<Ident> = vec![];
+    let mut annotated_members: Vec<TokenStream> = vec![];
+    let mut accessors: Vec<TokenStream> = vec![];
+
+    for child_spec in build_spec.children().iter() {
+        match child_spec {
+            ChildSpec::SkipChild(_) => {}
+            ChildSpec::VecChild(vec_child) => {
+                handle_vec_child(
+                    vec_child,
+                    &mut member_names,
+                    &mut annotated_members,
+                    &mut accessors,
+                );
+            }
+            ChildSpec::SingleChild(single_child) => {
+                match single_child.build() {
+                    SingleChildToBuild::Type(single_type_child) => {
+                        handle_single_type_child(
+                            single_type_child,
+                            &mut member_names,
+                            &mut annotated_members,
+                            &mut accessors,
+                        );
+                    }
+                    SingleChildToBuild::Boolean(single_boolean_child) => {
+                        handle_single_boolean_child(
+                            single_boolean_child,
+                            &mut member_names,
+                            &mut annotated_members,
+                            &mut accessors,
+                        );
+                    }
+                };
+            }
+        }
+    }
+
+    let type_ident = format_ident!("{}", build_spec.build());
+
+    quote! {
+        pub struct #type_ident {
+            #(#annotated_members),*
+        }
+
+        impl #type_ident {
+            pub fn new(#(#annotated_members),*) -> Self {
+                Self {
+                    #(#member_names),*
+                }
+            }
+
+            #(#accessors)*
+        }
+    }
+}
+
+pub fn make_type(build_spec: &BuildSpec) -> TokenStream {
+    match build_spec {
+        BuildSpec::Enum(enum_build_spec) => make_enum_type(enum_build_spec),
+        BuildSpec::Struct(struct_build_spec) => make_struct_type(struct_build_spec),
+    }
+}