From 2c37bced66a89451386f8ecc37de55d96394bcd7 Mon Sep 17 00:00:00 2001
From: Andrew Segavac <andrew@eunomia.io>
Date: Sat, 25 Sep 2021 12:40:49 -0600
Subject: [PATCH] added interpereter support for traits

---
 examples/main.bl   | 13 ++-----
 src/interpreter.rs | 84 +++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 75 insertions(+), 22 deletions(-)

diff --git a/examples/main.bl b/examples/main.bl
index ce03029..ec2c4bb 100644
--- a/examples/main.bl
+++ b/examples/main.bl
@@ -28,11 +28,6 @@ fn unit_function() {
   let a: i64 = 4;
 }
 
-fn main(): i64 {
-    add(4, subtract(5, 2))
-}
-
-
 fn returns_user(): User {
     return User{
         id: 4,
@@ -74,11 +69,9 @@ fn if_expression(): i64 {
 }
 
 fn main(): i64 {
-  if (false) {
-    add(4, 4)
-  } else {
-    61
-  }
+    let a = User{id: 4};
+    let b = a.instance_method();
+    b
 }
 
 type TestTrait trait {
diff --git a/src/interpreter.rs b/src/interpreter.rs
index 8c92b2c..2f1265f 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -29,11 +29,17 @@ pub struct StructValue {
 type BuiltinFunction = fn(Vec<Value>) -> Value;
 
 #[derive(Debug, Clone)]
-pub enum Function {
+pub enum FunctionRef {
     User(ast::Function),
     Builtin(BuiltinFunction),
 }
 
+#[derive(Debug, Clone)]
+pub struct Function {
+    pub partial: Vec<Value>,
+    pub ref_: FunctionRef,
+}
+
 #[derive(Debug, Clone)]
 pub enum Value {
     Numeric(NumericValue),
@@ -89,7 +95,12 @@ impl Context {
                 ast::ModuleItem::Function(function) => {
                     ctx.environment.insert(
                         function.declaration.name.name.value.to_string(),
-                        NamedEntity::Variable(Value::Function(Function::User(function.clone()))),
+                        NamedEntity::Variable(Value::Function(
+                            Function{
+                                partial: vec!(),
+                                ref_: FunctionRef::User(function.clone()),
+                            }
+                        )),
                     );
                 }
                 ast::ModuleItem::Impl(impl_) => {
@@ -214,7 +225,12 @@ impl TreeWalkInterpreter {
         let mut ctx = Context::from_module(module);
 
         let main = match &ctx.environment["main"] {
-            NamedEntity::Variable(Value::Function(Function::User(func))) => func.clone(),
+            NamedEntity::Variable(Value::Function(func)) => {
+                match &func.ref_ {
+                    FunctionRef::User(ref_) => ref_.clone(),
+                    _ => panic!("main should be a user defined function"),
+                }
+            },
             _ => panic!("main should be a user defined function"),
         };
 
@@ -362,15 +378,25 @@ impl TreeWalkInterpreter {
                     argument_values.push(argument_value);
                 }
                 match &source {
-                    Value::Function(Function::User(user_function)) => {
-                        let mut fn_ctx = ctx.new_env();
-                        for (i, function_arg) in user_function.declaration.arguments.iter().enumerate() {
-                            fn_ctx.set_variable(function_arg.name.name.value.to_string(), &argument_values[i].clone());
+                    Value::Function(function) => {
+                        match &function.ref_ {
+                            FunctionRef::User(user_function) => {
+                                let mut fn_ctx = ctx.new_env();
+                                let mut i = 0;
+                                for partial_arg in &function.partial {
+                                    fn_ctx.set_variable(user_function.declaration.arguments[i].name.name.value.to_string(), &partial_arg.clone());
+                                    i = i + 1;
+                                }
+                                for argument_value in &argument_values {
+                                    fn_ctx.set_variable(user_function.declaration.arguments[i].name.name.value.to_string(), &argument_value.clone());
+                                }
+                                return ExpressionResult::Value(self.with_function(&mut fn_ctx, user_function));
+                            }
+                            FunctionRef::Builtin(builtin_function) => {
+                                let all_values = function.partial.iter().map(|val| {val.clone()}).chain(argument_values.into_iter()).collect();
+                                return ExpressionResult::Value(builtin_function(all_values));
+                            }
                         }
-                        return ExpressionResult::Value(self.with_function(&mut fn_ctx, user_function));
-                    }
-                    Value::Function(Function::Builtin(builtin_function)) => {
-                        return ExpressionResult::Value(builtin_function(argument_values));
                     }
                     _ => panic!("type error: function call source must be a function"),
                 }
@@ -414,7 +440,41 @@ impl TreeWalkInterpreter {
                 match &source {
                     Value::Struct(struct_) => {
                         let s = struct_.lock().unwrap();
-                        return ExpressionResult::Value(s.fields[&struct_getter.attribute.name.value].clone());
+                        if s.fields.contains_key(&struct_getter.attribute.name.value) {
+                            return ExpressionResult::Value(s.fields[&struct_getter.attribute.name.value].clone());
+                        }
+                        for module_item in &ctx.current_module.items {
+                            match module_item {
+                                ast::ModuleItem::Impl(impl_) => {
+                                    if impl_.struct_name.name.value == s.source.name.name.value {
+                                        for method in &impl_.functions {
+                                            if method.declaration.name.name.value == struct_getter.attribute.name.value {
+                                                // if first type matches, partial apply self
+                                                if method.declaration.arguments.len() > 0 {
+                                                    match &method.declaration.arguments[0].type_ {
+                                                        ast::TypeUsage::Named(arg_named) => {
+                                                            if arg_named.name.name.value == s.source.name.name.value {
+                                                                return ExpressionResult::Value(Value::Function(Function{
+                                                                    partial: vec!(source.clone()),
+                                                                    ref_: FunctionRef::User(method.clone()),
+                                                                }));
+                                                            }
+                                                        }
+                                                        _ => {},
+                                                    }
+                                                }
+                                                return ExpressionResult::Value(Value::Function(Function{
+                                                    partial: vec!(),
+                                                    ref_: FunctionRef::User(method.clone()),
+                                                }));
+                                            }
+                                        }
+                                    }
+                                }
+                                _ => {}
+                            }
+                        }
+                        panic!("TypeError: Method not found");
                     }
                     _ => {
                         panic!("TypeError: struct getter used with non-struct");