From 3f952cdf0e76b3ecf3f5c9c11be13404376a8931 Mon Sep 17 00:00:00 2001
From: rvcas <x@rvcas.dev>
Date: Mon, 14 Nov 2022 14:42:10 -0500
Subject: [PATCH] feat: add new Data type to prelude and allow it to unify with
 any user defined type

---
 crates/lang/src/builtins.rs         | 42 +++++++++++++++++++++--------
 crates/lang/src/tipo/environment.rs | 22 ++++++++++++++-
 2 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/crates/lang/src/builtins.rs b/crates/lang/src/builtins.rs
index f033b917..193aaab2 100644
--- a/crates/lang/src/builtins.rs
+++ b/crates/lang/src/builtins.rs
@@ -13,13 +13,14 @@ use crate::{
     IdGenerator,
 };
 
-const BYTE_ARRAY: &str = "ByteArray";
-const BOOL: &str = "Bool";
-const INT: &str = "Int";
-const LIST: &str = "List";
-const NIL: &str = "Nil";
-const RESULT: &str = "Result";
-const STRING: &str = "String";
+pub const BYTE_ARRAY: &str = "ByteArray";
+pub const BOOL: &str = "Bool";
+pub const INT: &str = "Int";
+pub const DATA: &str = "Data";
+pub const LIST: &str = "List";
+pub const NIL: &str = "Nil";
+pub const RESULT: &str = "Result";
+pub const STRING: &str = "String";
 
 /// Build a prelude that can be injected
 /// into a compiler pipeline
@@ -46,6 +47,18 @@ pub fn prelude(id_gen: &IdGenerator) -> TypeInfo {
         },
     );
 
+    // Data
+    prelude.types.insert(
+        DATA.to_string(),
+        TypeConstructor {
+            parameters: vec![],
+            tipo: data(),
+            location: Span::empty(),
+            module: "".to_string(),
+            public: true,
+        },
+    );
+
     // ByteArray
     prelude.types.insert(
         BYTE_ARRAY.to_string(),
@@ -372,14 +385,12 @@ pub fn from_default_function(
         DefaultFunction::UnIData => None,
         DefaultFunction::UnBData => None,
         DefaultFunction::EqualsData => {
-            let arg = generic_var(id_gen.next());
-
-            let tipo = function(vec![arg.clone(), arg], bool());
+            let tipo = function(vec![data(), data()], bool());
 
             Some((tipo, 1))
         }
         DefaultFunction::SerialiseData => {
-            let tipo = function(vec![generic_var(id_gen.next())], byte_array());
+            let tipo = function(vec![data()], byte_array());
 
             Some((tipo, 1))
         }
@@ -412,6 +423,15 @@ pub fn int() -> Arc<Type> {
     })
 }
 
+pub fn data() -> Arc<Type> {
+    Arc::new(Type::App {
+        public: true,
+        name: DATA.to_string(),
+        module: "".to_string(),
+        args: vec![],
+    })
+}
+
 pub fn byte_array() -> Arc<Type> {
     Arc::new(Type::App {
         args: vec![],
diff --git a/crates/lang/src/tipo/environment.rs b/crates/lang/src/tipo/environment.rs
index a4828c67..27d9bfca 100644
--- a/crates/lang/src/tipo/environment.rs
+++ b/crates/lang/src/tipo/environment.rs
@@ -12,7 +12,7 @@ use crate::{
         RecordConstructor, RecordConstructorArg, Span, TypeAlias, TypedDefinition,
         UnqualifiedImport, UntypedDefinition, Use, PIPE_VARIABLE,
     },
-    builtins::{function, generic_var, unbound_var},
+    builtins::{self, function, generic_var, unbound_var},
     tipo::fields::FieldMap,
     IdGenerator,
 };
@@ -29,6 +29,14 @@ pub struct ScopeResetData {
     local_values: HashMap<String, ValueConstructor>,
 }
 
+const EXCLUDE_DATA_UNIFY: [&str; 5] = [
+    builtins::INT,
+    builtins::BYTE_ARRAY,
+    builtins::STRING,
+    builtins::BOOL,
+    builtins::LIST,
+];
+
 #[derive(Debug)]
 pub struct Environment<'a> {
     /// Accessors defined in the current module
@@ -1099,6 +1107,18 @@ impl<'a> Environment<'a> {
             return Ok(());
         }
 
+        if let (Type::App { name: name1, .. }, Type::App { name: name2, .. }) =
+            (t1.deref(), t2.deref())
+        {
+            if name1 == "Data" && !EXCLUDE_DATA_UNIFY.contains(&name2.as_str()) {
+                return Ok(());
+            }
+
+            if name2 == "Data" && !EXCLUDE_DATA_UNIFY.contains(&name1.as_str()) {
+                return Ok(());
+            }
+        }
+
         // Collapse right hand side type links. Left hand side will be collapsed in the next block.
         if let Type::Var { tipo } = t2.deref() {
             if let TypeVar::Link { tipo } = tipo.borrow().deref() {