Update grammar to reflect correct operator precedence.

ast-generator/src/deserialize.rs

@@ -1,4 +1,4 @@
-use crate::spec::{BooleanChildToBuild, BuildSpec, EnumBuildSpec, EnumRule, EnumRuleChild, EnumRuleChildKind, EnumRuleNodeChild, LeafEnumBuildSpec, LeafEnumRule, LeafStructBuildSpec, LeafStructMember, LeafStructMemberKind, MemberChild, MemberChildToBuild, NodeChildToBuild, ProductionBuildSpec, ProductionKind, ProductionStringFrom, SkipChild, StructBuildSpec, StructChildSpec, VecChild, VecChildToBuild, VecNodeChildToBuild};
+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, ProductionStringFrom, SkipChild, StructBuildSpec, StructChildSpec, VecChild, VecChildToBuild, VecNodeChildToBuild};
 use convert_case::{Case, Casing};
 use yaml_rust2::{Yaml, YamlLoader};
 
@@ -18,8 +18,112 @@ fn unwrap_single_member_hash(hash: &Yaml) -> (String, &Yaml) {
     (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 = match production_yaml["kind"].as_str().unwrap() {
+    let kind = if production_yaml["kind"].is_hash() {
+        let node = production_yaml["kind"]["node"].as_str().unwrap();
+        ProductionKind::Node(node.to_string())
+    } else { 
+        match production_yaml["kind"].as_str().unwrap() {
             "int" => ProductionKind::Int,
             "long" => ProductionKind::Long,
             "double" => ProductionKind::Double,
@@ -28,11 +132,18 @@ fn deserialize_production_spec(rule: &str, production_yaml: &Yaml) -> Production
                 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()),
+                    _ => panic!(
+                        "invalid from: {}",
+                        production_yaml["from"].as_str().unwrap()
+                    ),
                 };
                 ProductionKind::String(from)
-        },
-        _ => panic!("invalid kind: {}", production_yaml["kind"].as_str().unwrap()),
+            }
+            _ => panic!(
+                "invalid kind: {}",
+                production_yaml["kind"].as_str().unwrap()
+            ),
+        }
     };
     ProductionBuildSpec::new(rule, kind)
 }
@@ -46,9 +157,7 @@ fn deserialize_leaf_enum_rules(rules_yaml: &Yaml) -> Vec<Box<LeafEnumRule>> {
         .as_vec()
         .unwrap()
         .iter()
-        .map(|rule_yaml| {
-            deserialize_leaf_enum_rule(rule_yaml)
-        })
+        .map(|rule_yaml| deserialize_leaf_enum_rule(rule_yaml))
         .collect()
 }
 
@@ -63,16 +172,19 @@ fn deserialize_enum_rule_custom_child(rule_props: &Yaml) -> Option<Box<EnumRuleC
             "usize" => EnumRuleChildKind::USize,
             "string" => EnumRuleChildKind::String,
             "boolean" => EnumRuleChildKind::Boolean,
-            _ => panic!("unsupported enum rule kind: {}", rule_props["kind"].as_str().unwrap()),
+            _ => 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)),
-    )))
+    Box::new(EnumRuleChild::new(Box::new(EnumRuleChildKind::Node(
+        EnumRuleNodeChild::new(rule),
+    ))))
 }
 
 fn deserialize_enum_rule(rule_yaml: &Yaml) -> Box<EnumRule> {
@@ -80,7 +192,7 @@ fn deserialize_enum_rule(rule_yaml: &Yaml) -> Box<EnumRule> {
         let (rule, rule_props) = unwrap_single_member_hash(rule_yaml);
         Box::new(EnumRule::new(
             &rule,
-            deserialize_enum_rule_custom_child(rule_props)
+            deserialize_enum_rule_custom_child(rule_props),
         ))
     } else {
         let rule_as_str = rule_yaml.as_str().unwrap();
@@ -164,7 +276,9 @@ fn deserialize_member_child_to_build(
         }
     } else {
         let optional = get_as_bool(&props["optional"]);
-        Box::new(MemberChildToBuild::Node(NodeChildToBuild::new(rule, None, optional)))
+        Box::new(MemberChildToBuild::Node(NodeChildToBuild::new(
+            rule, None, optional,
+        )))
     }
 }
 
@@ -277,9 +391,29 @@ fn deserialize_build_spec(build_spec_name: &str, build_spec: &Yaml) -> BuildSpec
         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(build_spec_name, &build_spec["produce"]))
+        BuildSpec::Production(deserialize_production_spec(
+            build_spec_name,
+            &build_spec["produce"],
+        ))
+    } else if build_spec["polymorphic_type"].is_hash() {
+        BuildSpec::Polymorphic(deserialize_polymorphic_spec(
+            build_spec_name,
+            &build_spec["polymorphic_type"],
+        ))
+    } else if build_spec["polymorphic_build"].is_hash() {
+        BuildSpec::PolymorphicBuild(deserialize_polymorphic_build_build_spec(
+            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"],
+        ))    
     } else {
-        panic!("Expected a node spec for either a struct, leaf_struct, enum, leaf_enum node type, or a production type.");
+        panic!(
+            "Expected a node spec for either a struct, leaf_struct, enum, leaf_enum node type, production, polymorphic type, or polymorphic build type."
+        );
     }
 }
 

ast-generator/src/lib.rs

@@ -2,6 +2,10 @@ pub mod deserialize;
 mod enum_build_fn;
 mod leaf_enum_build_fn;
 mod leaf_struct_build_fn;
+mod polymorphic_build_build_fn;
+mod polymorphic_build_fn;
+mod polymorphic_enum_build_fn;
+mod pretty_print;
 mod production_build_fn;
 mod spec;
 mod struct_build_fn;
@@ -11,6 +15,10 @@ mod util;
 use crate::enum_build_fn::make_enum_build_fn;
 use crate::leaf_enum_build_fn::make_leaf_enum_build_fn;
 use crate::leaf_struct_build_fn::make_leaf_struct_build_fn;
+use crate::polymorphic_build_build_fn::make_polymorphic_build_build_fn;
+use crate::polymorphic_build_fn::make_polymorphic_build_fn;
+use crate::polymorphic_enum_build_fn::make_polymorphic_enum_build_fn;
+use crate::pretty_print::make_pretty_print_impl;
 use crate::production_build_fn::make_production_build_fn;
 use crate::struct_build_fn::make_struct_build_fn;
 use crate::type_gen::make_type;
@@ -38,7 +46,25 @@ fn debug_built_spec(build_spec: &BuildSpec, token_stream: &TokenStream) {
             );
         }
         BuildSpec::Production(production_build_spec) => {
-            println!("Production Spec - rule: {}", production_build_spec.rule())
+            println!("Production Spec - rule: {}", production_build_spec.rule());
+        }
+        BuildSpec::Polymorphic(polymorphic_build_spec) => {
+            println!(
+                "Polymorphic Type Spec - name: {}",
+                polymorphic_build_spec.name()
+            );
+        }
+        BuildSpec::PolymorphicBuild(polymorphic_build_build_spec) => {
+            println!(
+                "Polymorphic Build Spec - name: {}",
+                polymorphic_build_build_spec.name()
+            );
+        }
+        BuildSpec::PolymorphicEnum(polymorphic_enum_build_spec) => {
+            println!(
+                "Polymorphic Enum Spec - name: {}",
+                polymorphic_enum_build_spec.name()
+            );
         }
     }
     println!("{:#?}", token_stream);
@@ -85,9 +111,31 @@ fn generate_build_file(build_specs: &[BuildSpec]) -> AstGeneratedFile {
                 debug_built_spec(build_spec, &stream);
                 stream
             }
+            BuildSpec::Polymorphic(polymorphic_build_spec) => {
+                let stream = make_polymorphic_build_fn(polymorphic_build_spec);
+                debug_built_spec(build_spec, &stream);
+                stream
+            }
+            BuildSpec::PolymorphicBuild(polymorphic_build_build_spec) => {
+                let stream = make_polymorphic_build_build_fn(polymorphic_build_build_spec);
+                debug_built_spec(build_spec, &stream);
+                stream
+            }
+            BuildSpec::PolymorphicEnum(polymorphic_enum_build_spec) => {
+                let stream = make_polymorphic_enum_build_fn(polymorphic_enum_build_spec);
+                debug_built_spec(build_spec, &stream);
+                stream
+            }
         })
         .collect::<Vec<_>>();
     let combined = quote! {
+        //noinspection RsUnusedImport
+        use crate::parser::Rule;
+        //noinspection RsUnusedImport
+        use pest::iterators::Pair;
+        //noinspection RsUnusedImport
+        use crate::ast::node::*;
+
         #(#build_fns)*
     };
     AstGeneratedFile {
@@ -111,9 +159,30 @@ fn generate_node_file(build_specs: &[BuildSpec]) -> AstGeneratedFile {
     }
 }
 
+fn generate_pretty_print_file(build_specs: &[BuildSpec]) -> AstGeneratedFile {
+    let impls = build_specs
+        .iter()
+        .map(|build_spec| {
+            let stream = make_pretty_print_impl(build_spec);
+            debug_built_spec(build_spec, &stream);
+            stream
+        })
+        .collect::<Vec<_>>();
+    
+    let combined = quote! {
+        use crate::ast::node::*;
+        #(#impls)*
+    };
+    AstGeneratedFile {
+        name: String::from("pretty_print.rs"),
+        contents: token_stream_to_string(combined),
+    }
+}
+
 pub fn generate_files(build_specs: &[BuildSpec]) -> Vec<AstGeneratedFile> {
     vec![
         generate_build_file(build_specs),
         generate_node_file(build_specs),
+        generate_pretty_print_file(build_specs),
     ]
 }

ast-generator/src/polymorphic_build_build_fn.rs

@@ -0,0 +1,134 @@
+use convert_case::{Case, Casing};
+use crate::spec::{AlternativeAction, AlternativeBuild, AlternativeBuildChild, AlternativeChild, AlternativeTest, PolymorphicBuildBuildSpec};
+use crate::util::{make_build_fn_name, make_build_pair};
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+
+fn make_build_child(build_child: &AlternativeBuildChild) -> TokenStream {
+    let rule_ident = format_ident!("{}", build_child.rule());
+    let child_ident = format_ident!("{}", build_child.name());
+    let child_build_fn_ident = format_ident!("{}", make_build_fn_name(build_child.rule()));
+
+    quote! {
+        Rule::#rule_ident => {
+            #child_ident = Some(#child_build_fn_ident(inner_pair));
+        }
+    }
+}
+
+fn make_build_action(
+    spec: &PolymorphicBuildBuildSpec,
+    alternative_build: &AlternativeBuild,
+) -> TokenStream {
+    let enum_type_ident = format_ident!("{}", spec.return_type());
+    let enum_variant_ident = format_ident!("{}", alternative_build.enum_variant());
+
+    let child_holders = alternative_build
+        .children()
+        .map(|child| {
+            match child {
+                AlternativeChild::Skip => None,
+                AlternativeChild::Build(build_child) => {
+                    let child_ident = format_ident!("{}", build_child.name());
+                    let child_type_ident = format_ident!("{}", build_child.kind());
+                    Some(quote! {
+                        let mut #child_ident: Option<#child_type_ident> = None
+                    })
+                }
+            }
+        })
+        .filter(Option::is_some)
+        .map(Option::unwrap)
+        .collect::<Vec<_>>();
+
+    let pair_ident = format_ident!("{}", make_build_pair(spec.name()));
+
+    let rule_matchers = alternative_build
+        .children()
+        .map(|child| {
+            match child {
+                AlternativeChild::Skip => None,
+                AlternativeChild::Build(build_child) => {
+                    Some(make_build_child(build_child))
+                }
+            }
+        })
+        .filter(Option::is_some)
+        .map(Option::unwrap)
+        .collect::<Vec<_>>();
+
+    let built_ident = format_ident!("{}", spec.name().to_case(Case::Snake));
+    let inner_type_ident = format_ident!("{}", spec.name());
+    let child_args = alternative_build.children()
+        .map(|child| {
+            match child {
+                AlternativeChild::Skip => None,
+                AlternativeChild::Build(child_build) => {
+                    let child_ident = format_ident!("{}", child_build.name());
+                    Some(quote! {
+                       Box::new(#child_ident.unwrap())
+                    })
+                }
+            }
+        })
+        .filter(Option::is_some)
+        .map(Option::unwrap)
+        .collect::<Vec<_>>();
+    
+    quote! {
+        #(#child_holders;)*
+
+        for inner_pair in #pair_ident.into_inner() {
+            match inner_pair.as_rule() {
+                #(#rule_matchers),*
+                _ => unreachable!()
+            }
+        }
+
+        let #built_ident = #inner_type_ident::new(#(#child_args),*);
+        
+        #enum_type_ident::#enum_variant_ident(#built_ident)
+    }
+}
+
+pub fn make_polymorphic_build_build_fn(spec: &PolymorphicBuildBuildSpec) -> TokenStream {
+    let build_fn_ident = format_ident!("{}", make_build_fn_name(spec.name()));
+    let pair_ident = format_ident!("{}", make_build_pair(spec.name()));
+    let return_type_ident = format_ident!("{}", spec.return_type());
+
+    let alternatives = spec
+        .alternatives()
+        .map(|alternative| {
+            let count_to_match: usize = match alternative.test() {
+                AlternativeTest::NumberOfPairs(count) => count.clone().try_into().unwrap(),
+            };
+            let action = match alternative.action() {
+                AlternativeAction::ReturnBuild(kind) => {
+                    let inner_build_fn_ident = format_ident!("{}", make_build_fn_name(kind));
+                    quote! {
+                        let inner_pair = #pair_ident.into_inner().next().unwrap();
+                        #inner_build_fn_ident(inner_pair)
+                    }
+                }
+                AlternativeAction::Build(alternative_build) => {
+                    make_build_action(spec, alternative_build)
+                }
+            };
+            quote! {
+                #count_to_match => {
+                    #action
+                }
+            }
+        })
+        .collect::<Vec<_>>();
+
+    quote! {
+        fn #build_fn_ident(#pair_ident: Pair<Rule>) -> #return_type_ident {
+            let count = #pair_ident.clone().into_inner().count();
+            match count {
+                #(#alternatives,)*
+                _ => unreachable!()
+            }
+        }
+    }
+}

ast-generator/src/polymorphic_build_fn.rs

@@ -0,0 +1,18 @@
+use crate::spec::PolymorphicTypeBuildSpec;
+use crate::util::{make_build_fn_name, make_build_pair};
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+
+pub fn make_polymorphic_build_fn(build_spec: &PolymorphicTypeBuildSpec) -> TokenStream {
+    let build_fn_ident = format_ident!("{}", make_build_fn_name(build_spec.name()));
+    let pair_ident = format_ident!("{}", make_build_pair(&build_spec.name()));
+    let return_type_ident = format_ident!("{}", build_spec.name());
+    let inner_build_fn_ident = format_ident!("{}", make_build_fn_name(build_spec.build_kind()));
+
+    quote! {
+        fn #build_fn_ident(#pair_ident: Pair<Rule>) -> #return_type_ident {
+            let inner_pair = #pair_ident.into_inner().next().unwrap();
+            #inner_build_fn_ident(inner_pair)
+        }
+    }
+}

ast-generator/src/polymorphic_enum_build_fn.rs

@@ -0,0 +1,42 @@
+use crate::spec::{PolymorphicEnumBuildSpec, PolymorphicEnumRule};
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+use crate::util::{make_build_fn_name, make_build_pair};
+
+pub fn make_polymorphic_enum_build_fn(spec: &PolymorphicEnumBuildSpec) -> TokenStream {
+    let build_fn_ident = format_ident!("{}", make_build_fn_name(spec.name()));
+    let pair_ident = format_ident!("{}", make_build_pair(spec.name()));
+    let return_type_ident = format_ident!("{}", spec.return_type());
+    
+    let match_arms = spec.rules()
+        .map(|rule| {
+            match rule {
+                PolymorphicEnumRule::Wrap(name_and_kind) => {
+                    let rule_ident = format_ident!("{}", name_and_kind.name());
+                    let enum_variant_ident = format_ident!("{}", name_and_kind.kind());
+                    let rule_build_fn = format_ident!("{}", make_build_fn_name(name_and_kind.name()));
+                    quote! {
+                        Rule::#rule_ident => #return_type_ident::#enum_variant_ident(#rule_build_fn(inner_pair))
+                    }
+                },
+                PolymorphicEnumRule::ReturnBuild(name_and_kind) => {
+                    let rule_ident = format_ident!("{}", name_and_kind.name());
+                    let rule_build_fn = format_ident!("{}", make_build_fn_name(name_and_kind.kind()));
+                    quote! {
+                        Rule::#rule_ident => #rule_build_fn(inner_pair)
+                    }
+                }
+            }
+        })
+        .collect::<Vec<_>>();
+    
+    quote! {
+        fn #build_fn_ident(#pair_ident: Pair<Rule>) -> #return_type_ident {
+            let inner_pair = #pair_ident.into_inner().next().unwrap();
+            match inner_pair.as_rule() {
+                #(#match_arms,)*
+                _ => unreachable!()
+            }
+        }
+    }
+}

ast-generator/src/pretty_print.rs

@@ -0,0 +1,256 @@
+use crate::spec::{
+    AlternativeChild, BuildSpec, EnumBuildSpec, EnumRuleChildKind, LeafEnumBuildSpec,
+    LeafStructBuildSpec, LeafStructMemberKind, MemberChildToBuild, PolymorphicBuildBuildSpec,
+    PolymorphicEnumBuildSpec, PolymorphicTypeBuildSpec, ProductionBuildSpec, StructBuildSpec,
+    StructChildSpec, VecChildToBuild,
+};
+use convert_case::{Case, Casing};
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+
+fn make_production_p2_impl(_spec: &ProductionBuildSpec) -> TokenStream {
+    quote! {}
+}
+
+fn make_polymorphic_enum_p2_impl(_spec: &PolymorphicEnumBuildSpec) -> TokenStream {
+    quote! {}
+}
+
+fn make_polymorphic_build_p2_impl(spec: &PolymorphicBuildBuildSpec) -> TokenStream {
+    let (_, build) = spec.primary_alternative();
+    let type_ident = format_ident!("{}", spec.name());
+    let name_str = spec.name();
+
+    let child_statements = build
+        .children()
+        .map(|child| match child {
+            AlternativeChild::Skip => None,
+            AlternativeChild::Build(build) => {
+                let child_ident = format_ident!("{}", build.name());
+                Some(quote! {
+                    self.#child_ident().pretty_print(writer)?
+                })
+            }
+        })
+        .filter(Option::is_some)
+        .map(Option::unwrap)
+        .collect::<Vec<TokenStream>>();
+
+    quote! {
+        impl PrettyPrint for #type_ident {
+            fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
+                writer.writeln_indented(#name_str);
+                writer.increase_indent();
+                #(#child_statements;)*
+                writer.decrease_indent();
+                Ok(())
+            }
+        }
+    }
+}
+
+fn make_polymorphic_type_p2_impl(spec: &PolymorphicTypeBuildSpec) -> TokenStream {
+    let type_ident = format_ident!("{}", spec.name());
+    let child_matchers = spec
+        .enum_members()
+        .map(|member| {
+            let enum_member_ident = format_ident!("{}", member.name());
+            let inner_name = format_ident!("{}", member.inner_kind().to_case(Case::Snake));
+            quote! {
+                #type_ident::#enum_member_ident(#inner_name) => #inner_name.pretty_print(writer)
+            }
+        })
+        .collect::<Vec<_>>();
+
+    quote! {
+        impl PrettyPrint for #type_ident {
+            fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
+                match self {
+                    #(#child_matchers,)*
+                }
+            }
+        }
+    }
+}
+
+fn make_leaf_enum_p2_impl(spec: &LeafEnumBuildSpec) -> TokenStream {
+    let type_ident = format_ident!("{}", spec.build());
+    let child_matchers = spec
+        .rules()
+        .map(|rule| {
+            let enum_variant_ident = format_ident!("{}", rule.rule());
+            let name_str = rule.rule();
+            quote! {
+                #type_ident::#enum_variant_ident => writer.writeln_indented(#name_str)
+            }
+        })
+        .collect::<Vec<_>>();
+
+    quote! {
+        impl PrettyPrint for #type_ident {
+            fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
+                match self {
+                    #(#child_matchers,)*
+                }
+            }
+        }
+    }
+}
+
+fn make_enum_p2_impl(spec: &EnumBuildSpec) -> TokenStream {
+    let type_ident = format_ident!("{}", spec.build());
+    let type_str = spec.build();
+
+    let child_matchers = spec
+        .rules()
+        .map(|rule| {
+            let enum_variant_ident = format_ident!("{}", rule.rule());
+            if let Some(child) = rule.child() {
+                match child.kind() {
+                    EnumRuleChildKind::Node(node_child) => {
+                        let child_name_ident =
+                            format_ident!("{}", node_child.build().to_case(Case::Snake));
+                        Some(quote! {
+                            #type_ident::#enum_variant_ident(#child_name_ident) => {
+                                #child_name_ident.pretty_print(writer)?;
+                            }
+                        })
+                    }
+                    _ => None,
+                }
+            } else {
+                let variant_str = rule.rule();
+                Some(quote! {
+                    #type_ident::#enum_variant_ident => writer.writeln_indented(#variant_str)?
+                })
+            }
+        })
+        .filter(Option::is_some)
+        .map(Option::unwrap)
+        .collect::<Vec<_>>();
+
+    quote! {
+        impl PrettyPrint for #type_ident {
+            fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
+                writer.writeln_indented(#type_str)?;
+                writer.increase_indent();
+                match self {
+                    #(#child_matchers,)*
+                    _ => {}
+                }
+                writer.decrease_indent();
+                Ok(())
+            }
+        }
+    }
+}
+
+fn make_leaf_struct_p2_impl(leaf_struct_build_spec: &LeafStructBuildSpec) -> TokenStream {
+    let type_ident = format_ident!("{}", leaf_struct_build_spec.build());
+    let member_formatters = leaf_struct_build_spec
+        .members()
+        .map(|member| match member.kind() {
+            LeafStructMemberKind::String => Some("{}"),
+        })
+        .filter(Option::is_some)
+        .map(Option::unwrap)
+        .collect::<Vec<_>>()
+        .join(", ");
+
+    let format_string = format!("{}({})", leaf_struct_build_spec.build(), member_formatters);
+
+    let members = leaf_struct_build_spec
+        .members()
+        .map(|member| {
+            let member_ident = format_ident!("{}", member.name());
+            quote! {
+                self.#member_ident()
+            }
+        })
+        .collect::<Vec<_>>();
+
+    quote! {
+        impl PrettyPrint for #type_ident {
+            fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
+                writer.writeln_indented(&format!(#format_string, #(#members),*))
+            }
+        }
+    }
+}
+
+fn make_struct_p2_impl(struct_build_spec: &StructBuildSpec) -> TokenStream {
+    let child_print_statements = struct_build_spec
+        .children()
+        .map(|child| match child {
+            StructChildSpec::SkipChild(_) => None,
+            StructChildSpec::VecChild(vec_child) => match vec_child.build() {
+                VecChildToBuild::Node(_) => {
+                    let child_ident = format_ident!("{}", vec_child.name());
+                    Some(quote! {
+                        for child in self.#child_ident() {
+                            child.pretty_print(writer)?;
+                        }
+                    })
+                }
+                VecChildToBuild::String => None,
+            },
+            StructChildSpec::MemberChild(member_child) => match member_child.build() {
+                MemberChildToBuild::Node(node_member_child) => {
+                    let child_ident = format_ident!("{}", member_child.name());
+                    if node_member_child.optional() {
+                        Some(quote! {
+                            if let Some(child) = self.#child_ident() {
+                                child.pretty_print(writer)?;
+                            }
+                        })
+                    } else {
+                        Some(quote! {
+                            self.#child_ident().pretty_print(writer)?;
+                        })
+                    }
+                }
+                MemberChildToBuild::Boolean(boolean_member_child) => {
+                    let format_string = format!("{}({})", boolean_member_child.name(), "{}");
+                    let child_ident = format_ident!("{}", boolean_member_child.name());
+                    Some(quote! {
+                        writer.writeln_indented(&format!(#format_string, self.#child_ident()))?;
+                    })
+                }
+            },
+        })
+        .filter(Option::is_some)
+        .map(Option::unwrap)
+        .collect::<Vec<_>>();
+
+    let type_ident = format_ident!("{}", struct_build_spec.build());
+    let type_string = struct_build_spec.build();
+
+    quote! {
+        impl PrettyPrint for #type_ident {
+            fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
+                writer.writeln_indented(#type_string)?;
+                writer.increase_indent();
+                #(#child_print_statements)*
+                writer.decrease_indent();
+                Ok(())
+            }
+        }
+    }
+}
+
+pub fn make_pretty_print_impl(build_spec: &BuildSpec) -> TokenStream {
+    match build_spec {
+        BuildSpec::Struct(struct_spec) => make_struct_p2_impl(struct_spec),
+        BuildSpec::LeafStruct(leaf_struct) => make_leaf_struct_p2_impl(leaf_struct),
+        BuildSpec::Enum(enum_spec) => make_enum_p2_impl(enum_spec),
+        BuildSpec::LeafEnum(leaf_enum) => make_leaf_enum_p2_impl(leaf_enum),
+        BuildSpec::Polymorphic(polymorphic) => make_polymorphic_type_p2_impl(polymorphic),
+        BuildSpec::PolymorphicBuild(polymorphic_build) => {
+            make_polymorphic_build_p2_impl(polymorphic_build)
+        }
+        BuildSpec::PolymorphicEnum(polymorphic_enum) => {
+            make_polymorphic_enum_p2_impl(polymorphic_enum)
+        }
+        BuildSpec::Production(production) => make_production_p2_impl(production),
+    }
+}

ast-generator/src/production_build_fn.rs

@@ -11,6 +11,7 @@ pub fn make_production_build_fn(production_build_spec: &ProductionBuildSpec) ->
         ProductionKind::Double => format_ident!("f64"),
         ProductionKind::String(_) => format_ident!("String"),
         ProductionKind::Boolean => format_ident!("bool"),
+        ProductionKind::Node(node_type) => format_ident!("{}", node_type),
     };
     let pair_ident = format_ident!("{}", make_build_pair(production_build_spec.rule()));
 
@@ -77,6 +78,13 @@ pub fn make_production_build_fn(production_build_spec: &ProductionBuildSpec) ->
         ProductionKind::Boolean => quote! {
             #pair_ident.as_str().parse::<bool>().unwrap()
         },
+        ProductionKind::Node(node_type) => {
+            let build_fn_ident = format_ident!("{}", make_build_fn_name(node_type));
+            quote! {
+                let inner_pair = #pair_ident.into_inner().next().unwrap();
+                #build_fn_ident(inner_pair)
+            }
+        }
     };
 
     quote! {

ast-generator/src/spec.rs

@@ -4,6 +4,9 @@ pub enum BuildSpec {
     Struct(StructBuildSpec),
     LeafStruct(LeafStructBuildSpec),
     Production(ProductionBuildSpec),
+    Polymorphic(PolymorphicTypeBuildSpec),
+    PolymorphicBuild(PolymorphicBuildBuildSpec),
+    PolymorphicEnum(PolymorphicEnumBuildSpec),
 }
 
 // Enum build spec
@@ -34,14 +37,14 @@ impl EnumBuildSpec {
 
 pub struct EnumRule {
     rule: String,
-    child: Option<Box<EnumRuleChild>>
+    child: Option<Box<EnumRuleChild>>,
 }
 
 impl EnumRule {
     pub fn new(rule: &str, child: Option<Box<EnumRuleChild>>) -> Self {
         Self {
             rule: rule.to_string(),
-            child
+            child,
         }
     }
 
@@ -60,7 +63,7 @@ impl EnumRule {
 }
 
 pub struct EnumRuleChild {
-    kind: Box<EnumRuleChildKind>
+    kind: Box<EnumRuleChildKind>,
 }
 
 impl EnumRuleChild {
@@ -80,11 +83,11 @@ pub enum EnumRuleChildKind {
     Double,
     USize,
     String,
-    Boolean
+    Boolean,
 }
 
 pub struct EnumRuleNodeChild {
-    build: String
+    build: String,
 }
 
 impl EnumRuleNodeChild {
@@ -110,7 +113,7 @@ impl LeafEnumBuildSpec {
     pub fn new(build: &str, rules: Vec<Box<LeafEnumRule>>) -> Self {
         Self {
             build: build.to_string(),
-            rules
+            rules,
         }
     }
 
@@ -150,7 +153,7 @@ impl StructBuildSpec {
     pub fn new(build: &str, children: Vec<Box<StructChildSpec>>) -> Self {
         Self {
             build: build.to_string(),
-            children
+            children,
         }
     }
 
@@ -229,7 +232,7 @@ impl VecChild {
 #[derive(Debug)]
 pub enum VecChildToBuild {
     Node(VecNodeChildToBuild),
-    String
+    String,
 }
 
 #[derive(Debug)]
@@ -239,7 +242,9 @@ pub struct VecNodeChildToBuild {
 
 impl VecNodeChildToBuild {
     pub fn new(build: &str) -> Self {
-        Self { build: build.to_string() }
+        Self {
+            build: build.to_string(),
+        }
     }
 
     /// The type to build, in Pascal case.
@@ -294,11 +299,7 @@ pub struct NodeChildToBuild {
 }
 
 impl NodeChildToBuild {
-    pub fn new(
-        build: &str,
-        or_else: Option<String>,
-        optional: bool,
-    ) -> Self {
+    pub fn new(build: &str, or_else: Option<String>, optional: bool) -> Self {
         Self {
             build: build.to_string(),
             or_else,
@@ -324,13 +325,13 @@ impl NodeChildToBuild {
 
 #[derive(Debug)]
 pub struct BooleanChildToBuild {
-    name: String
+    name: String,
 }
 
 impl BooleanChildToBuild {
     pub fn new(name: &str) -> Self {
         Self {
-            name: name.to_string()
+            name: name.to_string(),
         }
     }
 
@@ -416,10 +417,256 @@ pub enum ProductionKind {
     Long,
     Double,
     String(ProductionStringFrom),
-    Boolean
+    Boolean,
+    Node(String),
 }
 
 pub enum ProductionStringFrom {
     StringInner,
-    WholePair
+    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
+    }
 }

ast-generator/src/type_gen.rs

@@ -1,11 +1,116 @@
 use crate::spec::{
-    BooleanChildToBuild, BuildSpec, EnumBuildSpec, EnumRuleChildKind, LeafEnumBuildSpec,
-    LeafStructBuildSpec, LeafStructMemberKind, MemberChildToBuild, NodeChildToBuild,
+    AlternativeAction, AlternativeChild, BooleanChildToBuild, BuildSpec, EnumBuildSpec,
+    EnumRuleChildKind, LeafEnumBuildSpec, LeafStructBuildSpec, LeafStructMemberKind,
+    MemberChildToBuild, NodeChildToBuild, PolymorphicBuildBuildSpec, PolymorphicTypeBuildSpec,
     StructBuildSpec, StructChildSpec, VecChild, VecChildToBuild,
 };
 use proc_macro2::{Ident, TokenStream};
 use quote::{format_ident, quote};
 
+fn make_polymorphic_build_type(build_spec: &PolymorphicBuildBuildSpec) -> TokenStream {
+    let alternative_action = build_spec
+        .alternatives()
+        .find(|alternative| {
+            if let AlternativeAction::Build(_) = alternative.action() {
+                true
+            } else {
+                false
+            }
+        })
+        .unwrap();
+
+    let alternative_build =
+        if let AlternativeAction::Build(alternative_build) = alternative_action.action() {
+            alternative_build
+        } else {
+            unreachable!()
+        };
+
+    let annotated_members = alternative_build
+        .children()
+        .map(|child| match child {
+            AlternativeChild::Skip => None,
+            AlternativeChild::Build(build_child) => {
+                let child_name_ident = format_ident!("{}", build_child.name());
+                let type_ident = format_ident!("{}", build_child.kind());
+                Some(quote! {
+                    #child_name_ident: Box<#type_ident>
+                })
+            }
+        })
+        .filter(Option::is_some)
+        .map(Option::unwrap)
+        .collect::<Vec<_>>();
+
+    let initializers = alternative_build
+        .children()
+        .map(|child| match child {
+            AlternativeChild::Skip => None,
+            AlternativeChild::Build(build_child) => Some(format_ident!("{}", build_child.name())),
+        })
+        .filter(Option::is_some)
+        .map(Option::unwrap)
+        .collect::<Vec<_>>();
+
+    let accessors = alternative_build
+        .children()
+        .map(|child| match child {
+            AlternativeChild::Skip => None,
+            AlternativeChild::Build(build_child) => {
+                let child_ident = format_ident!("{}", build_child.name());
+                let child_ident_mut = format_ident!("{}_mut", build_child.name());
+                let child_type_ident = format_ident!("{}", build_child.kind());
+                Some(quote! {
+                    pub fn #child_ident(&self) -> &#child_type_ident {
+                        &self.#child_ident
+                    }
+
+                    pub fn #child_ident_mut(&mut self) -> &mut #child_type_ident {
+                        &mut self.#child_ident
+                    }
+                })
+            }
+        })
+        .collect::<Vec<_>>();
+
+    let type_ident = format_ident!("{}", build_spec.name());
+
+    quote! {
+        pub struct #type_ident {
+            #(#annotated_members),*
+        }
+
+        impl #type_ident {
+            pub fn new(#(#annotated_members),*) -> Self {
+                Self {
+                    #(#initializers),*
+                }
+            }
+
+            #(#accessors)*
+        }
+    }
+}
+
+fn make_polymorphic_type_type(build_spec: &PolymorphicTypeBuildSpec) -> TokenStream {
+    let members = build_spec
+        .enum_members()
+        .map(|enum_member| {
+            let member_ident = format_ident!("{}", enum_member.name());
+            let inner_type_ident = format_ident!("{}", enum_member.inner_kind());
+            quote! {
+                #member_ident(#inner_type_ident)
+            }
+        })
+        .collect::<Vec<_>>();
+    let type_name_ident = format_ident!("{}", build_spec.name());
+    quote! {
+        pub enum #type_name_ident {
+            #(#members),*
+        }
+    }
+}
+
 fn make_enum_type(build_spec: &EnumBuildSpec) -> TokenStream {
     let children: Vec<TokenStream> = build_spec
         .rules()
@@ -348,5 +453,12 @@ pub fn make_type(build_spec: &BuildSpec) -> Option<TokenStream> {
             Some(make_leaf_struct_type(leaf_struct_build_spec))
         }
         BuildSpec::Production(_) => None,
+        BuildSpec::Polymorphic(polymorphic_build_spec) => {
+            Some(make_polymorphic_type_type(polymorphic_build_spec))
+        }
+        BuildSpec::PolymorphicBuild(polymorphic_build_build_spec) => {
+            Some(make_polymorphic_build_type(polymorphic_build_build_spec))
+        }
+        BuildSpec::PolymorphicEnum(_) => None,
     }
 }

examples/forty_two.dm

@@ -0,0 +1,3 @@
+fn main()
+    println 42
+end

examples/worlds.dm

@@ -0,0 +1,19 @@
+class World(pub name: String, pub color: String) end
+
+fn getWorlds() -> List<World> = [
+    World('Mercury', 'Red'),
+    World('Earth', 'Blue'),
+    World('Jupiter', 'Orange')
+]
+
+fn findWorldByColor(worlds: List<World>, color: String) -> String
+    worlds.find { it.color == color }
+        .map { it.name }
+        .expect "No world has the given color ${color}"
+end
+
+fn main()
+    let worlds = getWorlds()
+    let blueWorld = findWorldByColor(worlds, 'Blue')
+    println "Hello, ${blueWorld}!"
+end

src/ast/mod.rs

@@ -45,15 +45,15 @@ pub mod node {
 }
 
 pub mod build {
-    //noinspection RsUnusedImport
-    use crate::parser::Rule;
-    //noinspection RsUnusedImport
-    use pest::iterators::Pair;
-    //noinspection RsUnusedImport
-    use crate::ast::node::*;
+    use pest::iterators::Pairs;
 
     include!(concat!(env!("OUT_DIR"), "/src/ast/build.rs"));
     
+    pub fn build_ast(parsed_pairs: &mut Pairs<Rule>) -> Box<CompilationUnit> {
+        let compilation_unit_pair = parsed_pairs.next().unwrap();
+        Box::new(build_compilation_unit(compilation_unit_pair))
+    }
+
     #[cfg(test)]
     mod build_tests {
         use super::*;
@@ -102,5 +102,42 @@ pub mod build {
             assert_eq!(backtick_string.inners().count(), 2);
             assert_eq!(backtick_string.expressions().count(), 1);
         }
+
+        #[test]
+        fn d_string_expression_simple() {
+            let pair = parse(Rule::DStringExpression, "${thing}");
+            let d_string_expression = build_d_string_expression(pair);
+        }
+
+        #[test]
+        fn d_string_inner() {
+            let pair = parse(Rule::DStringInner, "Hello!");
+            let d_string_inner = build_d_string_inner(pair);
+            assert_eq!("Hello!", d_string_inner);
+        }
+
+        #[test]
+        fn d_string_mixed() {
+            let pair = parse(Rule::DString, "\"Hello, ${world}!\"");
+            let d_string = build_d_string(pair);
+            assert_eq!(d_string.inners().count(), 2);
+            assert_eq!(d_string.expressions().count(), 1);
+        }
+
+        #[test]
+        fn expression_simple_call() {
+            let pair = parse(Rule::Expression, "hello(42)");
+            let expression = build_expression(pair);
         }
     }
+}
+
+pub mod pretty_print {
+    use crate::util::indent_writer::IndentWriter;
+
+    pub trait PrettyPrint {
+        fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()>;
+    }
+    
+    include!(concat!(env!("OUT_DIR"), "/src/ast/pretty_print.rs"));
+}

src/bin/dmc/main.rs

@@ -1,58 +1,55 @@
 // mod name_analysis;
-// mod p3;
+mod p3;
 // mod unparse;
-//
-// use std::path::PathBuf;
-//
+
+use std::path::PathBuf;
+
 // use crate::name_analysis::name_analysis;
-// use crate::p3::pretty_print_parse;
+use crate::p3::pretty_print_parse;
 // use crate::unparse::unparse;
-// use clap::{Parser, Subcommand};
-//
-// #[derive(Debug, Parser)]
-// #[command(name = "dmc")]
-// #[command(about = "Deimos Compiler", long_about = None)]
-// struct Cli {
-//     #[command(subcommand)]
-//     command: Commands,
-// }
-//
-// #[derive(Debug, Subcommand)]
-// enum Commands {
-//     #[command(arg_required_else_help = true)]
-//     Unparse {
-//         paths: Vec<PathBuf>,
-//     },
-//     P3 {
-//         paths: Vec<PathBuf>,
-//     },
-//     NameAnalysis {
-//         paths: Vec<PathBuf>,
-//     },
-// }
-//
-// fn main() {
-//     let args = Cli::parse();
-//     match args.command {
+use clap::{Parser, Subcommand};
+
+#[derive(Debug, Parser)]
+#[command(name = "dmc")]
+#[command(about = "Deimos Compiler", long_about = None)]
+struct Cli {
+    #[command(subcommand)]
+    command: Commands,
+}
+
+#[derive(Debug, Subcommand)]
+enum Commands {
+    #[command(arg_required_else_help = true)]
+    Unparse {
+        paths: Vec<PathBuf>,
+    },
+    P3 {
+        paths: Vec<PathBuf>,
+    },
+    NameAnalysis {
+        paths: Vec<PathBuf>,
+    },
+}
+
+fn main() {
+    let args = Cli::parse();
+    match args.command {
         // Commands::Unparse { paths } => {
         //     for path in paths {
         //         unparse(&path);
         //     }
         // }
-//         Commands::P3 { paths } => {
-//             for path in paths {
-//                 pretty_print_parse(&path)
-//             }
-//         }
+        Commands::P3 { paths } => {
+            for path in paths {
+                pretty_print_parse(&path)
+            }
+        }
         // Commands::NameAnalysis { paths } => {
         //     let result = name_analysis(&paths);
         //     if let Err(e) = result {
         //         eprintln!("{}", e)
         //     }
         // }
-//     }
-// }
-
-fn main() {
-    panic!("TODO")
+        _ => todo!()
+    }
 }

src/bin/dmc/p3.rs

@@ -10,8 +10,7 @@ pub fn pretty_print_parse(path: &PathBuf) {
     let parse_result = DeimosParser::parse(Rule::CompilationUnit, &src);
     match parse_result {
         Ok(mut pairs) => {
-            let compilation_unit_pair = pairs.next().unwrap();
-            let compilation_unit = build_ast(&path.display().to_string(), 0, compilation_unit_pair);
+            let compilation_unit = build_ast(&mut pairs);
             let mut indent_writer = IndentWriter::new(0, "  ", Box::new(std::io::stdout()));
             compilation_unit
                 .pretty_print(&mut indent_writer)

src/parser/ast.yaml

@@ -291,6 +291,9 @@ Class:
     - class_level_declarations:
         rule: ClassLevelDeclaration
         vec: true
+    - end_kw:
+        rule: End
+        skip: true
 
 # Function constructs
 Function:
@@ -305,6 +308,8 @@ Function:
         skip: true
     - generics:
         rule: GenericParameters
+        build:
+          or_else_default: true
     - identifier
     - parameters
     - return_type:
@@ -564,53 +569,153 @@ ForStatement:
 
 # Expressions
 Expression:
-  children:
-    - ternary_expression
+  polymorphic_type:
+    enum_members:
+      - Ternary:
+          inner:
+            kind: TernaryExpression
+      - Or:
+          inner:
+            kind: OrExpression
+      - And:
+          inner:
+            kind: AndExpression
+      - Comparison:
+          inner:
+            kind: ComparisonExpression
+      - Shift:
+          inner:
+            kind: ShiftExpression
+      - Additive:
+          inner:
+            kind: AdditiveExpression
+      - Multiplicative:
+          inner:
+            kind: MultiplicativeExpression
+      - Prefix:
+          inner:
+            kind: PrefixExpression
+      - Suffix:
+          inner:
+            kind: SuffixExpression
+      - Literal:
+          inner:
+            kind: Literal
+      - Fqn:
+          inner:
+            kind: FullyQualifiedName
+      - Closure:
+          inner:
+            kind: Closure
+      - List:
+          inner:
+            kind: ListExpression
+    build:
+      kind: TernaryExpression
 TernaryExpression:
+  polymorphic_build:
+    return_type: Expression
+    alternatives:
+      - test:
+          number_of_pairs: 1
+        action:
+          return_build:
+            kind: OrExpression
+      - test:
+          number_of_pairs: 3
+        action:
+          build:
+            enum_variant: Ternary
             children:
-    - or_expression
-    - ternary_alternatives:
-        optional: true
-TernaryAlternatives:
-  children:
-    - ternary_true_alternative
-    - ternary_false_alternative
+              - test:
+                  kind: Expression
+                  rule: OrExpression
+              - on_true:
+                  kind: Expression
+                  rule: TernaryTrueAlternative
+              - on_false:
+                  kind: Expression
+                  rule: TernaryFalseAlternative
 TernaryTrueAlternative:
-  children:
-    - expression
+  produce:
+    kind:
+      node: Expression
 TernaryFalseAlternative:
-  children:
-    - expression
+  produce:
+    kind:
+      node: Expression
 OrExpression:
+  polymorphic_build:
+    return_type: Expression
+    alternatives:
+      - test:
+          number_of_pairs: 1
+        action:
+          return_build:
+            kind: AndExpression
+      - test:
+          number_of_pairs: 3
+        action:
+          build:
+            enum_variant: Or
             children:
               - left:
+                  kind: Expression
                   rule: AndExpression
               - or_sym:
                   rule: Or
                   skip: true
               - right:
+                  kind: Expression
                   rule: Expression
-         optional: true
 AndExpression:
+  polymorphic_build:
+    return_type: Expression
+    alternatives:
+      - test:
+          number_of_pairs: 1
+        action:
+          return_build:
+            kind: ComparisonExpression
+      - test:
+          number_of_pairs: 3
+        action:
+          build:
+            enum_variant: And
             children:
               - left:
+                  kind: Expression
                   rule: ComparisonExpression
               - and_sym:
                   rule: And
                   skip: true
               - right:
+                  kind: Expression
                   rule: Expression
-        optional: true
 ComparisonExpression:
+  polymorphic_build:
+    return_type: Expression
+    alternatives:
+      - test:
+          number_of_pairs: 1
+        action:
+          return_build:
+            kind: ShiftExpression
+      - test:
+          number_of_pairs: 3
+        action:
+          build:
+            enum_variant: Comparison
             children:
               - left:
+                  kind: Expression
                   rule: ShiftExpression
               - operator:
+                  kind: ComparisonOperator
                   rule: ComparisonOperator
-        optional: true
               - right:
+                  kind: Expression
                   rule: Expression
-        optional: true
 ComparisonOperator:
   leaf_rules:
     - Greater
@@ -620,64 +725,144 @@ ComparisonOperator:
     - EqualTo
     - NotEqualTo
 ShiftExpression:
+  polymorphic_build:
+    return_type: Expression
+    alternatives:
+      - test:
+          number_of_pairs: 1
+        action:
+          return_build:
+            kind: AdditiveExpression
+      - test:
+          number_of_pairs: 3
+        action:
+          build:
+            enum_variant: Shift
             children:
               - left:
+                  kind: Expression
                   rule: AdditiveExpression
               - operator:
+                  kind: ShiftOperator
                   rule: ShiftOperator
-        optional: true
               - right:
+                  kind: Expression
                   rule: Expression
-        optional: true
 ShiftOperator:
   leaf_rules:
     - LeftShift
     - RightShift
 AdditiveExpression:
+  polymorphic_build:
+    return_type: Expression
+    alternatives:
+      - test:
+          number_of_pairs: 1
+        action:
+          return_build:
+            kind: MultiplicativeExpression
+      - test:
+          number_of_pairs: 3
+        action:
+          build:
+            enum_variant: Additive
             children:
               - left:
+                  kind: Expression
                   rule: MultiplicativeExpression
               - operator:
+                  kind: AdditiveOperator
                   rule: AdditiveOperator
-        optional: true
               - right:
+                  kind: Expression
                   rule: Expression
-        optional: true
 AdditiveOperator:
   leaf_rules:
     - Add
     - Subtract
 MultiplicativeExpression:
+  polymorphic_build:
+    return_type: Expression
+    alternatives:
+      - test:
+          number_of_pairs: 1
+        action:
+          return_build:
+            kind: PrefixExpression
+      - test:
+          number_of_pairs: 3
+        action:
+          build:
+            enum_variant: Multiplicative
             children:
               - left:
+                  kind: Expression
                   rule: PrefixExpression
               - operator:
+                  kind: MultiplicativeOperator
                   rule: MultiplicativeOperator
-        optional: true
               - right:
+                  kind: Expression
                   rule: Expression
-        optional: true
 MultiplicativeOperator:
   leaf_rules:
     - Multiply
     - Divide
     - Modulo
 PrefixExpression:
+  polymorphic_build:
+    return_type: Expression
+    alternatives:
+      - test:
+          number_of_pairs: 1
+        action:
+          return_build:
+            kind: SuffixExpression
+      - test:
+          number_of_pairs: 2
+        action:
+          build:
+            enum_variant: Prefix
+            children:
+              - prefix_operators:
+                  kind: PrefixOperators
+                  rule: PrefixOperators
+              - right:
+                  kind: Expression
+                  rule: SuffixExpression
+PrefixOperators:
   children:
     - operators:
         rule: PrefixOperator
         vec: true
-    - right:
-        rule: SuffixExpression
 PrefixOperator:
   leaf_rules:
     - Spread
     - Not
     - Negative
 SuffixExpression:
+  polymorphic_build:
+    return_type: Expression
+    alternatives:
+      - test:
+          number_of_pairs: 1
+        action:
+          return_build:
+            kind: PrimaryExpression
+      - test:
+          number_of_pairs: 2
+        action:
+          build:
+            enum_variant: Suffix
             children:
               - left:
+                  kind: Expression
                   rule: PrimaryExpression
+              - suffix_operators:
+                  kind: SuffixOperators
+                  rule: SuffixOperators
+SuffixOperators:
+  children:
     - operators:
         rule: SuffixOperator
         vec: true
@@ -697,11 +882,27 @@ ObjectIndex:
   children:
     - expression
 PrimaryExpression:
+  polymorphic_enum:
+    return_type: Expression
     rules:
-    - Literal
-    - FullyQualifiedName
-    - Closure
-    - ParenthesizedExpression
+      - Literal:
+          wrap:
+            enum_variant: Literal
+      - FullyQualifiedName:
+          wrap:
+            enum_variant: Fqn
+      - Closure:
+          wrap:
+            enum_variant: Closure
+      - ListExpression:
+          wrap:
+            enum_variant: List
+      - ParenthesizedExpression:
+          return_build:
+            kind: Expression
+ListExpression:
+  children:
+    - expression_list
 ParenthesizedExpression:
   children:
     - expression

src/parser/deimos.pest

@@ -596,40 +596,52 @@ Expression = {
 
 TernaryExpression = {
       OrExpression
-    ~ ( TernaryAlternatives )?
+    ~ TernaryRhs*
 }
 
-TernaryAlternatives = {
+TernaryRhs = {
       TernaryTrueAlternative
     ~ TernaryFalseAlternative
 }
 
 TernaryTrueAlternative = {
       "?"
-    ~ Expression
+    ~ OrExpression
 }
 
 TernaryFalseAlternative = {
       ":"
-    ~ Expression
+    ~ OrExpression
 }
 
 OrExpression = {
       AndExpression
-    ~ ( Or ~ Expression )?
+    ~ OrRhs*
+}
+
+OrRhs = {
+      Or 
+    ~ AndExpression
 }
 
 AndExpression = {
       ComparisonExpression
-    ~ ( And ~ Expression )?
+    ~ AndRhs*
+}
+
+AndRhs = {
+      And
+    ~ ComparisonExpression
 }
 
 ComparisonExpression = {
       ShiftExpression
-    ~ (
+    ~ ComparisonRhs*
+}
+
+ComparisonRhs = {
       ComparisonOperator
     ~ Expression
-      )?
 }
 
 ComparisonOperator = {
@@ -643,10 +655,12 @@ ComparisonOperator = {
 
 ShiftExpression = {
       AdditiveExpression
-    ~ (
+    ~ ShiftRhs*
+}
+
+ShiftRhs = {
       ShiftOperator
-        ~ Expression
-      )?
+    ~ AdditiveExpression
 }
 
 ShiftOperator = {
@@ -656,10 +670,12 @@ ShiftOperator = {
 
 AdditiveExpression = {
       MultiplicativeExpression
-    ~ (
+    ~ AdditiveRhs*
+}
+
+AdditiveRhs = {
       AdditiveOperator
-        ~ Expression
-      )?
+    ~ MultiplicativeExpression
 }
 
 AdditiveOperator = {
@@ -669,10 +685,12 @@ AdditiveOperator = {
 
 MultiplicativeExpression = {
       PrefixExpression
-    ~ (
+    ~ MultiplicativeRhs*
+}
+
+MultiplicativeRhs = {
       MultiplicativeOperator
-        ~ Expression
-      )?
+    ~ PrefixExpression
 }
 
 MultiplicativeOperator = {
@@ -682,10 +700,14 @@ MultiplicativeOperator = {
 }
 
 PrefixExpression = {
-      PrefixOperator*
+      PrefixOperators?
     ~ SuffixExpression
 }
 
+PrefixOperators = {
+      PrefixOperator+
+}
+
 PrefixOperator = {
       Spread
     | Not
@@ -694,7 +716,11 @@ PrefixOperator = {
 
 SuffixExpression = {
       PrimaryExpression
-    ~ SuffixOperator*
+    ~ SuffixOperators?
+}
+
+SuffixOperators = {
+      SuffixOperator+
 }
 
 SuffixOperator = {
@@ -720,9 +746,16 @@ PrimaryExpression = {
       Literal
     | FullyQualifiedName
     | Closure
+    | ListExpression
     | ParenthesizedExpression
 }
 
+ListExpression = {
+      "["
+    ~ ExpressionList?
+    ~ "]"
+}
+
 ParenthesizedExpression = {
       "("
     ~ Expression