From b92287ec1f87a91e52d568cb690a0c731a1e4814 Mon Sep 17 00:00:00 2001
From: John Doty <john@d0ty.me>
Date: Tue, 16 Jan 2024 19:52:45 -0800
Subject: [PATCH] [fine] Starting to work on generic parameters (yikes)

---
 fine/src/compiler.rs  |  2 ++
 fine/src/semantics.rs | 24 +++++++++++++++++++-----
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/fine/src/compiler.rs b/fine/src/compiler.rs
index 9003796b..e262508b 100644
--- a/fine/src/compiler.rs
+++ b/fine/src/compiler.rs
@@ -478,7 +478,9 @@ fn compile_identifier_expression(c: &mut Compiler, t: TreeRef, tree: &Tree) -> O
                 None => {
                     let tree = &c.syntax[*declaration];
                     compiler_assert_eq!(c, t, tree.kind, TreeKind::FunctionDecl);
+
                     compile_function_declaration(c, t, tree, false)?;
+
                     *c.function_bindings
                         .get(&key)
                         .expect("did not compile the function!")
diff --git a/fine/src/semantics.rs b/fine/src/semantics.rs
index 214f44bd..57a74823 100644
--- a/fine/src/semantics.rs
+++ b/fine/src/semantics.rs
@@ -79,6 +79,8 @@ pub enum Type {
     String,
     Bool,
 
+    TypeArgument(TreeRef, Box<str>), // An un-bound type argument
+
     Function(Vec<Box<Type>>, Box<Type>),
 }
 
@@ -103,9 +105,19 @@ impl Type {
             (Type::Error, _) => true,
             (_, Type::Error) => true,
 
+            (Type::TypeArgument(a_id, ..), Type::TypeArgument(b_id, ..)) => a_id == b_id,
+
             (_, _) => false,
         }
     }
+
+    pub fn is_generic(&self) -> bool {
+        match self {
+            Type::TypeArgument(..) => true,
+            Type::Function(a, b) => a.iter().any(|t| t.is_generic()) || b.is_generic(),
+            _ => false,
+        }
+    }
 }
 
 impl fmt::Debug for Type {
@@ -125,8 +137,9 @@ impl fmt::Display for Type {
             String => write!(f, "string"),
             Bool => write!(f, "bool"),
             MagicPrintGarbage => write!(f, "MagicPrintGarbage"),
+            TypeArgument(_, id) => write!(f, "{id}"),
             Function(args, ret) => {
-                write!(f, "(")?;
+                write!(f, "fun (")?;
                 let mut first = true;
                 for arg in args.iter() {
                     if !first {
@@ -653,7 +666,7 @@ impl<'a> Semantics<'a> {
 
             TreeKind::FunctionDecl => self.type_of_function_decl(tree),
             TreeKind::ReturnType => self.type_of_return_type(tree),
-            TreeKind::Parameter => self.type_of_parameter(tree),
+            TreeKind::Parameter => self.type_of_parameter(t, tree),
 
             _ => self.internal_compiler_error(Some(t), "asking for a nonsense type"),
         };
@@ -1014,13 +1027,14 @@ impl<'a> Semantics<'a> {
         Some(Type::Function(parameter_types, return_type))
     }
 
-    fn type_of_parameter(&self, tree: &Tree) -> Option<Type> {
+    fn type_of_parameter(&self, t: TreeRef, tree: &Tree) -> Option<Type> {
         assert_eq!(tree.kind, TreeKind::Parameter);
         match tree.child_of_kind(self.syntax_tree, TreeKind::TypeExpression) {
             Some(t) => Some(self.type_of(t)),
             None => {
-                self.report_error_tree(tree, "generic parameters not yet supported");
-                Some(Type::Error)
+                // It must be a generic parameter! We'll name this one after the tree where it exists.
+                let name = tree.nth_token(0)?;
+                Some(Type::TypeArgument(t, format!("${}", name.as_str()).into()))
             }
         }
     }