From 0a315c56150f97004b556b2ec88cf69c8909cb91 Mon Sep 17 00:00:00 2001
From: Andrew Segavac <andrewseg@gmail.com>
Date: Wed, 20 Aug 2025 22:47:26 -0600
Subject: [PATCH] added withFunction

---
 packages/boringlang/src/types/type_checker.ts | 69 +++++++++++++++++--
 1 file changed, 64 insertions(+), 5 deletions(-)

diff --git a/packages/boringlang/src/types/type_checker.ts b/packages/boringlang/src/types/type_checker.ts
index de786ee..d7b3972 100644
--- a/packages/boringlang/src/types/type_checker.ts
+++ b/packages/boringlang/src/types/type_checker.ts
@@ -1,4 +1,13 @@
-import { functionToType, Module, TypeUsage } from "../parse/ast";
+import {
+  Function,
+  FunctionDeclaration,
+  functionToType,
+  Impl,
+  Module,
+  StructTypeDeclaration,
+  TraitTypeDeclaration,
+  TypeUsage,
+} from "../parse/ast";
 import { TypeSystem } from "./type_system";
 
 interface EnvImpl {
@@ -25,6 +34,27 @@ interface Context {
   environment: Record<string, NamedEntity>;
 }
 
+function typeExists(ctx: Context, type: TypeUsage) {
+  if (type.typeUsage === "NamedTypeUsage") {
+    if (
+      !ctx.environment[type.name.text] ||
+      ctx.environment[type.name.text].namedEntity !== "NamedType"
+    ) {
+      throw Error(`${type.name.text} is not a type.`);
+    }
+  }
+  if (type.typeUsage === "FunctionTypeUsage") {
+    for (const arg of type.arguments) {
+      typeExists(ctx, arg);
+    }
+    typeExists(ctx, type.returnType);
+  }
+}
+
+const deepCopy = <T>(o: T) => {
+  return JSON.parse(JSON.stringify(o)) as T;
+};
+
 class TypeChecker {
   withModule = (module: Module, typeSystem: TypeSystem) => {
     const ctx: Context = {
@@ -94,17 +124,46 @@ class TypeChecker {
     // environment set up, actually recurse.
     for (const item of module.items) {
       if (item.moduleItem === "Function") {
-        // this.withFunction(item, typeSystem);
+        this.withFunction(ctx, item, typeSystem);
       }
       if (item.moduleItem === "Impl") {
-        // this.withImpl(item, typeSystem);
+        this.withImpl(ctx, item, typeSystem);
       }
       if (item.moduleItem === "StructTypeDeclaration") {
-        // this.withImpl(item, typeSystem);
+        this.withStruct(ctx, item, typeSystem);
       }
       if (item.moduleItem === "TraitTypeDeclaration") {
-        // this.withTrait(item, typeSystem);
+        this.withTrait(ctx, item, typeSystem);
       }
     }
   };
+
+  withFunction = (ctx: Context, fn: Function, typeSystem: TypeSystem) => {
+    this.withFunctionDeclaration(ctx, fn.declaration, typeSystem);
+    const fnCtx = deepCopy(ctx);
+    for (const arg of fn.declaration.arguments) {
+      fnCtx.environment[arg.name.text] = {
+        namedEntity: "Variable",
+        type: arg.type,
+      };
+    }
+    // this.withBlock(fnCtx, fn.block, typeSystem);
+    typeSystem.compare({
+      left: fn.declaration.returnType,
+      operation: { operation: "equals" },
+      right: fn.block.type,
+    });
+  };
+
+  withFunctionDeclaration = (ctx: Context, def: FunctionDeclaration, typeSystem: TypeSystem) => {
+    for (const arg of def.arguments) {
+      typeExists(ctx, arg.type);
+    }
+    typeExists(ctx, def.returnType);
+  };
+
+  withImpl = (ctx: Context, impl: Impl, typeSystem: TypeSystem) => {};
+
+  withStruct = (ctx: Context, struct: StructTypeDeclaration, typeSystem: TypeSystem) => {};
+  withTrait = (ctx: Context, trait: TraitTypeDeclaration, typeSystem: TypeSystem) => {};
 }