step

.vscode/settings.json

@@ -2,5 +2,23 @@
     "chat.tools.terminal.autoApprove": {
         "dune": true,
         "ocamlobjinfo": true
+    },
+    "python.autoComplete.extraPaths": [
+        "${workspaceFolder}/sources/poky/bitbake/lib",
+        "${workspaceFolder}/sources/poky/meta/lib"
+    ],
+    "python.analysis.extraPaths": [
+        "${workspaceFolder}/sources/poky/bitbake/lib",
+        "${workspaceFolder}/sources/poky/meta/lib"
+    ],
+    "files.associations": {
+        "*.smr": "scheme",
+        "*.fnl": "scheme",
+        "*.urn": "scheme",
+        "*.prf": "ini",
+        "*.dhall": "haskell",
+        "bsconfig.json": "jsonc",
+        "*.conf": "bitbake",
+        "*.inc": "bitbake"
     }
 }

bin/main.ml

@@ -37,15 +37,17 @@ let () =
 				exit 1
 		| Ok ast -> ast
 	in
-	(match Spooky.type_check ast with
+	let typed_ast =
-	| Error msg ->
+		match Spooky.type_check ast with
-			prerr_endline ("type error: " ^ msg);
+		| Error msg ->
-			exit 1
+				prerr_endline ("type error: " ^ msg);
-	| Ok () -> ());
+				exit 1
+		| Ok prog -> prog
+	in
 	let generated =
 		match !generator with
-		| Json -> Spooky.generate_json ast
+		| Json -> Spooky.generate_json typed_ast
-		| C -> Spooky.generate_c ast
+		| C -> Spooky.generate_c typed_ast
 	in
 	match !output_path with
 	| Some path ->

examples/modules/math.spooky

@@ -1,3 +1,3 @@
-int add(int a, int b) {
+fn add(a: int, b: int) -> int {
   return a + b;
 }

examples/sample.spooky

@@ -3,18 +3,18 @@ struct Point {
   int y;
 };
 
-int sum_array(int[] arr) {
+fn sum_array(arr: int[]) -> int {
-  int total = 0;
+  let mut total = 0;
   foreach (int n in arr) {
     total = total + n;
   }
   return total;
 }
 
-int main() {
+fn main() -> int {
-  Point p;
+  let p: Point;
-  int[] nums;
+  let nums: int[];
-  int x = 1 + 2 * 3;
+  let mut x = 1 + 2 * 3;
   p.x = x;
   if (x > 0) {
     x = x + p.x;

examples/with_imports.spooky

@@ -1,8 +1,8 @@
 import "modules/types.spooky";
 import "modules/math.spooky";
 
-int main() {
+fn main() -> int {
-  Point p;
+  let p: Point;
   p.x = 1;
   p.y = 2;
   return add(p.x, p.y);

lib/ast.ml

@@ -4,6 +4,8 @@ type typ =
   | TVoid
   | TStruct of string
   | TArray of typ
+  | TComptime of typ        (* #type  — comptime-only *)
+  | TCombo of typ * typ     (* type#type — linked runtime+comptime pair *)
 
 type binop =
   | Add
@@ -34,7 +36,8 @@ type expr =
   | StructGet of expr * string
 
 type stmt =
-  | VarDecl of typ * string * expr option
+  | VarDecl of bool * string * typ option * expr option
+    (* is_mut, name, type_annotation, init *)
   | Expr of expr
   | If of expr * stmt list * stmt list
   | ForEach of typ * string * expr * stmt list
@@ -43,7 +46,7 @@ type stmt =
 
 type func = {
   name : string;
-  params : (typ * string) list;
+  params : (string * typ) list;   (* name, type *)
   ret : typ;
   body : stmt list;
 }
@@ -56,7 +59,8 @@ type struct_def = {
 type top =
   | TopStruct of struct_def
   | TopFunc of func
-  | TopGlobalVar of typ * string * expr option
+  | TopGlobalVar of bool * string * typ option * expr option
+    (* is_mut, name, type_annotation, init *)
 
 type program = top list
 
@@ -67,6 +71,8 @@ let string_of_typ =
     | TVoid -> "void"
     | TStruct n -> "struct " ^ n
     | TArray t -> go t ^ "[]"
+    | TComptime t -> "#" ^ go t
+    | TCombo (t1, t2) -> go t1 ^ "#" ^ go t2
   in
   go
 
@@ -106,9 +112,11 @@ let indent n = String.make (2 * n) ' '
 let rec string_of_stmt ?(level = 0) st =
   let i = indent level in
   match st with
-  | VarDecl (t, n, None) -> Printf.sprintf "%sVarDecl(%s %s)" i (string_of_typ t) n
+    | VarDecl (mut, n, t_opt, init_opt) ->
-  | VarDecl (t, n, Some e) ->
+      let mut_s = if mut then "mut " else "" in
-      Printf.sprintf "%sVarDecl(%s %s = %s)" i (string_of_typ t) n (string_of_expr e)
+      let t_s = match t_opt with Some t -> ": " ^ string_of_typ t | None -> "" in
+      let init_s = match init_opt with Some e -> " = " ^ string_of_expr e | None -> "" in
+      Printf.sprintf "%sVarDecl(let %s%s%s%s)" i mut_s n t_s init_s
   | Expr e -> Printf.sprintf "%sExpr(%s)" i (string_of_expr e)
   | Return None -> Printf.sprintf "%sReturn" i
   | Return (Some e) -> Printf.sprintf "%sReturn(%s)" i (string_of_expr e)
@@ -134,14 +142,15 @@ let string_of_top = function
       in
       if String.equal fields "" then Printf.sprintf "Struct %s" s.sname
       else Printf.sprintf "Struct %s\n%s" s.sname fields
-  | TopGlobalVar (t, n, init) ->
+  | TopGlobalVar (mut, n, t_opt, init_opt) ->
-      (match init with
+      let mut_s = if mut then "mut " else "" in
-      | None -> Printf.sprintf "GlobalVar(%s %s)" (string_of_typ t) n
+      let t_s = match t_opt with Some t -> ": " ^ string_of_typ t | None -> "" in
-      | Some e -> Printf.sprintf "GlobalVar(%s %s = %s)" (string_of_typ t) n (string_of_expr e))
+      let init_s = match init_opt with Some e -> " = " ^ string_of_expr e | None -> "" in
+      Printf.sprintf "GlobalVar(let %s%s%s%s)" mut_s n t_s init_s
   | TopFunc f ->
       let params =
         f.params
-        |> List.map (fun (t, n) -> Printf.sprintf "%s %s" (string_of_typ t) n)
+        |> List.map (fun (n, t) -> Printf.sprintf "%s: %s" n (string_of_typ t))
         |> String.concat ", "
       in
       let body = String.concat "\n" (List.map (string_of_stmt ~level:1) f.body) in
@@ -155,4 +164,6 @@ let rec equal_typ a b =
   | TInt, TInt | TBool, TBool | TVoid, TVoid -> true
   | TStruct x, TStruct y -> String.equal x y
   | TArray x, TArray y -> equal_typ x y
+  | TComptime x, TComptime y -> equal_typ x y
+  | TCombo (a1, a2), TCombo (b1, b2) -> equal_typ a1 b1 && equal_typ a2 b2
   | _ -> false

lib/ast.mli

@@ -4,6 +4,8 @@ type typ =
   | TVoid
   | TStruct of string
   | TArray of typ
+  | TComptime of typ
+  | TCombo of typ * typ
 
 type binop =
   | Add
@@ -34,7 +36,7 @@ type expr =
   | StructGet of expr * string
 
 type stmt =
-  | VarDecl of typ * string * expr option
+  | VarDecl of bool * string * typ option * expr option
   | Expr of expr
   | If of expr * stmt list * stmt list
   | ForEach of typ * string * expr * stmt list
@@ -43,7 +45,7 @@ type stmt =
 
 type func = {
   name : string;
-  params : (typ * string) list;
+  params : (string * typ) list;
   ret : typ;
   body : stmt list;
 }
@@ -56,7 +58,7 @@ type struct_def = {
 type top =
   | TopStruct of struct_def
   | TopFunc of func
-  | TopGlobalVar of typ * string * expr option
+  | TopGlobalVar of bool * string * typ option * expr option
 
 type program = top list
 

lib/generator_c.ml

@@ -6,6 +6,8 @@ let rec c_type = function
   | TVoid -> "void"
   | TStruct n -> "struct " ^ n
   | TArray t -> c_type t ^ "*"
+  | TComptime t -> c_type t   (* comptime types lower to their runtime equivalent *)
+  | TCombo (t, _) -> c_type t (* combo types use the runtime (left) type in C *)
 
 let rec expr_to_c = function
   | IntLit n -> string_of_int n
@@ -24,8 +26,9 @@ let rec expr_to_c = function
 let indent n = String.make (2 * n) ' '
 
 let rec stmt_to_c ?(level = 1) = function
-  | VarDecl (t, n, None) -> Printf.sprintf "%s%s %s;" (indent level) (c_type t) n
+  | VarDecl (_, n, Some t, None) -> Printf.sprintf "%s%s %s;" (indent level) (c_type t) n
-  | VarDecl (t, n, Some e) -> Printf.sprintf "%s%s %s = %s;" (indent level) (c_type t) n (expr_to_c e)
+  | VarDecl (_, n, Some t, Some e) -> Printf.sprintf "%s%s %s = %s;" (indent level) (c_type t) n (expr_to_c e)
+  | VarDecl (_, n, None, _) -> Printf.sprintf "%s/* unresolved type for %s */" (indent level) n
   | Expr e -> Printf.sprintf "%s%s;" (indent level) (expr_to_c e)
   | Return None -> Printf.sprintf "%sreturn;" (indent level)
   | Return (Some e) -> Printf.sprintf "%sreturn %s;" (indent level) (expr_to_c e)
@@ -64,7 +67,7 @@ let struct_to_c s =
 let func_to_c f =
   let params =
     f.params
-    |> List.map (fun (t, n) -> Printf.sprintf "%s %s" (c_type t) n)
+    |> List.map (fun (n, t) -> Printf.sprintf "%s %s" (c_type t) n)
     |> String.concat ", "
   in
   let body = f.body |> List.map (stmt_to_c ~level:1) |> String.concat "\n" in
@@ -73,10 +76,12 @@ let func_to_c f =
 let top_to_c = function
   | TopStruct s -> struct_to_c s
   | TopFunc f -> func_to_c f
-  | TopGlobalVar (t, n, init) ->
+    | TopGlobalVar (_, n, Some t, init) ->
       (match init with
       | None -> Printf.sprintf "%s %s;" (c_type t) n
       | Some e -> Printf.sprintf "%s %s = %s;" (c_type t) n (expr_to_c e))
+    | TopGlobalVar (_, n, None, _) ->
+      Printf.sprintf "/* unresolved type for global %s */" n
 
 let generate (prog : program) =
   let header = "#include <stdbool.h>\n\n" in

lib/generator_json.ml

@@ -24,6 +24,8 @@ let rec typ_to_json = function
   | TVoid -> obj [ kv "kind" (q "void") ]
   | TStruct name -> obj [ kv "kind" (q "struct"); kv "name" (q name) ]
   | TArray t -> obj [ kv "kind" (q "array"); kv "elem" (typ_to_json t) ]
+  | TComptime t -> obj [ kv "kind" (q "comptime"); kv "inner" (typ_to_json t) ]
+  | TCombo (t1, t2) -> obj [ kv "kind" (q "combo"); kv "runtime" (typ_to_json t1); kv "comptime" (typ_to_json t2) ]
 
 let rec expr_to_json = function
   | IntLit n -> obj [ kv "node" (q "IntLit"); kv "value" (string_of_int n) ]
@@ -45,9 +47,11 @@ let rec expr_to_json = function
       obj [ kv "node" (q "StructGet"); kv "target" (expr_to_json target); kv "field" (q field) ]
 
 let rec stmt_to_json = function
-  | VarDecl (t, n, init) ->
+  | VarDecl (is_mut, n, t_opt, init) ->
       obj
-        [ kv "node" (q "VarDecl"); kv "type" (typ_to_json t); kv "name" (q n);
+        [ kv "node" (q "VarDecl"); kv "mut" (if is_mut then "true" else "false");
+          kv "name" (q n);
+          kv "type" (match t_opt with None -> "null" | Some t -> typ_to_json t);
           kv "init" (match init with None -> "null" | Some e -> expr_to_json e) ]
   | Expr e -> obj [ kv "node" (q "Expr"); kv "expr" (expr_to_json e) ]
   | If (cond, tbranch, ebranch) ->
@@ -77,12 +81,14 @@ let top_to_json = function
           kv "params"
             (arr
                (List.map
-                  (fun (t, n) -> obj [ kv "type" (typ_to_json t); kv "name" (q n) ])
+                  (fun (n, t) -> obj [ kv "name" (q n); kv "type" (typ_to_json t) ])
                   f.params));
           kv "body" (arr (List.map stmt_to_json f.body)) ]
-  | TopGlobalVar (t, n, init) ->
+  | TopGlobalVar (is_mut, n, t_opt, init) ->
       obj
-        [ kv "node" (q "GlobalVar"); kv "type" (typ_to_json t); kv "name" (q n);
+        [ kv "node" (q "GlobalVar"); kv "mut" (if is_mut then "true" else "false");
+          kv "name" (q n);
+          kv "type" (match t_opt with None -> "null" | Some t -> typ_to_json t);
           kv "init" (match init with None -> "null" | Some e -> expr_to_json e) ]
 
 let generate (prog : program) =

lib/lexer.ml

@@ -12,6 +12,9 @@ type token =
   | TReturn
   | TTrue
   | TFalse
+  | TFn
+  | TLet
+  | TMut
   | TIdent of string
   | TIntLit of int
   | TLParen
@@ -39,6 +42,9 @@ type token =
   | TGt
   | TGe
   | TEOF
+  | TArrow
+  | TColon
+  | THash
 
 exception Lex_error of string
 
@@ -65,6 +71,9 @@ let keyword_or_ident s =
   | "return" -> TReturn
   | "true" -> TTrue
   | "false" -> TFalse
+  | "fn" -> TFn
+  | "let" -> TLet
+  | "mut" -> TMut
   | _ -> TIdent s
 
 let lex (src : string) : token list =
@@ -108,6 +117,7 @@ let lex (src : string) : token list =
       | ',' -> loop (i + 1) (TComma :: acc)
       | '.' -> loop (i + 1) (TDot :: acc)
       | '+' -> loop (i + 1) (TPlus :: acc)
+      | '-' when i + 1 < n && src.[i + 1] = '>' -> loop (i + 2) (TArrow :: acc)
       | '-' -> loop (i + 1) (TMinus :: acc)
       | '*' -> loop (i + 1) (TStar :: acc)
       | '%' -> loop (i + 1) (TPercent :: acc)
@@ -122,6 +132,8 @@ let lex (src : string) : token list =
       | '<' -> loop (i + 1) (TLt :: acc)
       | '>' when i + 1 < n && src.[i + 1] = '=' -> loop (i + 2) (TGe :: acc)
       | '>' -> loop (i + 1) (TGt :: acc)
+      | ':' -> loop (i + 1) (TColon :: acc)
+      | '#' -> loop (i + 1) (THash :: acc)
       | c when is_digit c ->
           let tok, j = read_number i (i + 1) in
           loop j (tok :: acc)

lib/lexer.mli

@@ -12,6 +12,9 @@ type token =
   | TReturn
   | TTrue
   | TFalse
+  | TFn
+  | TLet
+  | TMut
   | TIdent of string
   | TIntLit of int
   | TLParen
@@ -39,6 +42,9 @@ type token =
   | TGt
   | TGe
   | TEOF
+  | TArrow
+  | TColon
+  | THash
 
 exception Lex_error of string
 

lib/parser.ml

@@ -56,6 +56,12 @@ let expect st tok =
   | TBoolKw, TBoolKw
   | TVoidKw, TVoidKw
   | TStructKw, TStructKw
+  | TFn, TFn
+  | TLet, TLet
+  | TMut, TMut
+  | TArrow, TArrow
+  | TColon, TColon
+  | THash, THash
   | TEOF, TEOF -> ()
   | _ -> raise (Parse_error "unexpected token")
 
@@ -64,25 +70,9 @@ let expect_ident st =
   | TIdent s -> s
   | _ -> raise (Parse_error "expected identifier")
 
-let starts_builtin_type = function TIntKw | TBoolKw | TVoidKw | TStructKw -> true | _ -> false
+(* Parse a base type (no # prefix or # suffix).
-
+   Handles: int, bool, void, struct Name, TypeName, and [] suffixes. *)
-let rec skip_array_suffixes st j =
+let rec parse_base_type st =
-  match peek_n st j with
-  | TLBracket ->
-      (match peek_n st (j + 1) with
-      | TRBracket -> skip_array_suffixes st (j + 2)
-      | _ -> j)
-  | _ -> j
-
-let looks_like_type_start st =
-  match peek st with
-  | t when starts_builtin_type t -> true
-  | TIdent _ ->
-      let j = skip_array_suffixes st 1 in
-      (match peek_n st j with TIdent _ -> true | _ -> false)
-  | _ -> false
-
-let rec parse_type st =
   let base =
     match consume st with
     | TIntKw -> TInt
@@ -102,6 +92,23 @@ let rec parse_type st =
   in
   arrays base
 
+(* Parse a full type, including comptime forms:
+     #type        -> TComptime type
+     type         -> type
+     type#type    -> TCombo (runtime_type, comptime_type) *)
+and parse_type st =
+  match peek st with
+  | THash ->
+      expect st THash;
+      TComptime (parse_base_type st)
+  | _ ->
+      let t = parse_base_type st in
+      (match peek st with
+      | THash ->
+          expect st THash;
+          TCombo (t, parse_base_type st)
+      | _ -> t)
+
 let rec parse_program st =
   let rec loop acc =
     match peek st with
@@ -115,62 +122,66 @@ and parse_top st =
   | TStructKw ->
       expect st TStructKw;
       let sname = expect_ident st in
-      (match peek st with
+      expect st TLBrace;
-      | TLBrace ->
+      let rec fields acc =
-          expect st TLBrace;
+        match peek st with
-          let rec fields acc =
+        | TRBrace -> List.rev acc
-            match peek st with
+        | _ ->
-            | TRBrace -> List.rev acc
+            let t = parse_base_type st in
-            | _ ->
+            let n = expect_ident st in
-                let t = parse_type st in
+            expect st TSemicolon;
-                let n = expect_ident st in
+            fields ((t, n) :: acc)
-                expect st TSemicolon;
+      in
-                fields ((t, n) :: acc)
+      let fs = fields [] in
-          in
+      expect st TRBrace;
-          let fs = fields [] in
+      expect st TSemicolon;
-          expect st TRBrace;
+      TopStruct { sname; fields = fs }
-          expect st TSemicolon;
+  | TFn ->
-          TopStruct { sname; fields = fs }
+      expect st TFn;
-      | _ ->
+      let name = expect_ident st in
-          let ty = TStruct sname in
-          parse_top_after_type st ty)
-  | _ ->
-      if not (looks_like_type_start st) then raise (Parse_error "expected top-level declaration");
-      let ty = parse_type st in
-      parse_top_after_type st ty
-
-and parse_top_after_type st ty =
-  let name = expect_ident st in
-  match peek st with
-  | TLParen ->
       expect st TLParen;
       let params = parse_params st in
       expect st TRParen;
+      expect st TArrow;
+      let ret = parse_type st in
       let body = parse_stmt_as_block st in
-      TopFunc { name; params; ret = ty; body }
+      TopFunc { name; params; ret; body }
-  | _ ->
+  | TLet ->
-      let init =
+      expect st TLet;
+      let is_mut =
         match peek st with
-        | TAssign ->
+        | TMut ->
-            expect st TAssign;
+            expect st TMut;
-            Some (parse_expr st)
+            true
+        | _ -> false
+      in
+      let name = expect_ident st in
+      let t_annot =
+        match peek st with
+        | TColon ->
+            expect st TColon;
+            Some (parse_type st)
         | _ -> None
       in
+      expect st TAssign;
+      let e = parse_expr st in
       expect st TSemicolon;
-      TopGlobalVar (ty, name, init)
+      TopGlobalVar (is_mut, name, t_annot, Some e)
+  | _ -> raise (Parse_error "expected top-level declaration (struct, fn, or let)")
 
 and parse_params st =
   match peek st with
   | TRParen -> []
   | _ ->
       let rec loop acc =
-        let t = parse_type st in
         let n = expect_ident st in
+        expect st TColon;
+        let t = parse_type st in
         match peek st with
         | TComma ->
             expect st TComma;
-            loop ((t, n) :: acc)
+            loop ((n, t) :: acc)
-        | _ -> List.rev ((t, n) :: acc)
+        | _ -> List.rev ((n, t) :: acc)
       in
       loop []
 
@@ -229,9 +240,23 @@ and parse_stmt st =
       in
       expect st TSemicolon;
       Return v
-  | _ when looks_like_type_start st ->
+  | TLet ->
-      let ty = parse_type st in
+      expect st TLet;
+      let is_mut =
+        match peek st with
+        | TMut ->
+            expect st TMut;
+            true
+        | _ -> false
+      in
       let n = expect_ident st in
+      let t_annot =
+        match peek st with
+        | TColon ->
+            expect st TColon;
+            Some (parse_type st)
+        | _ -> None
+      in
       let init =
         match peek st with
         | TAssign ->
@@ -240,7 +265,7 @@ and parse_stmt st =
         | _ -> None
       in
       expect st TSemicolon;
-      VarDecl (ty, n, init)
+      VarDecl (is_mut, n, t_annot, init)
   | _ ->
       let e = parse_expr st in
       expect st TSemicolon;

lib/spooky.ml

@@ -23,7 +23,7 @@ let parse_and_type_check src =
   | Error e -> Error e
   | Ok prog ->
       (match type_check prog with
-      | Ok () -> Ok prog
+      | Ok annotated -> Ok annotated
       | Error e -> Error ("type error: " ^ e))
 
 let parse_and_type_check_file path =
@@ -31,7 +31,7 @@ let parse_and_type_check_file path =
   | Error e -> Error e
   | Ok prog ->
       (match type_check prog with
-      | Ok () -> Ok prog
+      | Ok annotated -> Ok annotated
       | Error e -> Error ("type error: " ^ e))
 
 let generate_json = Generator_json.generate

lib/spooky.mli

@@ -12,7 +12,7 @@ val parse_string : string -> (program, string) result
 val load_source_with_imports : string -> (string, string) result
 val parse_file : string -> (program, string) result
 val string_of_program : program -> string
-val type_check : program -> (unit, string) result
+val type_check : program -> (program, string) result
 val parse_and_type_check : string -> (program, string) result
 val parse_and_type_check_file : string -> (program, string) result
 val generate_json : program -> string

lib/typechecker.ml

@@ -12,7 +12,7 @@ type func_sig = {
 type tc_ctx = {
   structs : (typ StringMap.t) StringMap.t;
   funcs : func_sig StringMap.t;
-  globals : typ StringMap.t;
+  globals : (typ * bool) StringMap.t;
 }
 
 let fail_type msg = raise (Type_error msg)
@@ -31,36 +31,21 @@ let rec validate_type (structs : (typ StringMap.t) StringMap.t) (allow_void : bo
       if equal_typ t TVoid then fail_type "array element type cannot be void";
       validate_type structs false t
   | TInt | TBool -> ()
-
+  | TComptime t -> validate_type structs false t
-let collect_ctx (prog : program) : tc_ctx =
+  | TCombo (t1, t2) ->
-  let rec collect tops structs funcs globals =
+      validate_type structs false t1;
-    match tops with
+      validate_type structs false t2
-    | [] -> { structs; funcs; globals }
-    | TopStruct s :: tl ->
-        if StringMap.mem s.sname structs then fail_type ("duplicate struct: " ^ s.sname);
-        let fields =
-          List.fold_left
-            (fun acc (t, n) ->
-              if StringMap.mem n acc then fail_type ("duplicate field " ^ n ^ " in struct " ^ s.sname);
-              StringMap.add n t acc)
-            StringMap.empty s.fields
-        in
-        collect tl (StringMap.add s.sname fields structs) funcs globals
-    | TopFunc f :: tl ->
-        if StringMap.mem f.name funcs then fail_type ("duplicate function: " ^ f.name);
-        let sig_ = { fparams = List.map fst f.params; fret = f.ret } in
-        collect tl structs (StringMap.add f.name sig_ funcs) globals
-    | TopGlobalVar (t, n, _) :: tl ->
-        if StringMap.mem n globals then fail_type ("duplicate global variable: " ^ n);
-        collect tl structs funcs (StringMap.add n t globals)
-  in
-  collect prog StringMap.empty StringMap.empty StringMap.empty
 
 let lookup_var env x =
   match StringMap.find_opt x env with
-  | Some t -> t
+  | Some (t, _) -> t
   | None -> fail_type ("unknown variable: " ^ x)
 
+let is_var_mutable env x =
+  match StringMap.find_opt x env with
+  | Some (_, m) -> m
+  | None -> false
+
 let lookup_struct_field ctx sname fname =
   match StringMap.find_opt sname ctx.structs with
   | None -> fail_type ("unknown struct: " ^ sname)
@@ -99,11 +84,20 @@ let rec infer_expr ctx env = function
           if not (equal_typ ta tb) then fail_type "equality operands must have same type";
           TBool)
   | Assign (lhs, rhs) ->
-      (match lhs with Var _ | ArrayGet _ | StructGet _ -> () | _ -> fail_type "left side of assignment is not assignable");
+      (match lhs with
-      let tl = infer_expr ctx env lhs in
+       | Var x ->
-      let tr = infer_expr ctx env rhs in
+           if not (is_var_mutable env x) then
-      expect_type tr tl;
+             fail_type ("cannot assign to immutable variable: " ^ x);
-      tl
+           let tl = lookup_var env x in
+           let tr = infer_expr ctx env rhs in
+           expect_type tr tl;
+           tl
+       | ArrayGet _ | StructGet _ ->
+           let tl = infer_expr ctx env lhs in
+           let tr = infer_expr ctx env rhs in
+           expect_type tr tl;
+           tl
+       | _ -> fail_type "left side of assignment is not assignable")
   | ArrayGet (arr, idx) ->
       expect_type (infer_expr ctx env idx) TInt;
       (match infer_expr ctx env arr with
@@ -131,11 +125,57 @@ let rec infer_expr ctx env = function
       List.iter2 (fun arg pty -> expect_type (infer_expr ctx env arg) pty) args sig_.fparams;
       sig_.fret
 
+let collect_ctx (prog : program) : tc_ctx =
+  let rec collect tops structs funcs globals =
+    match tops with
+    | [] -> { structs; funcs; globals }
+    | TopStruct s :: tl ->
+        if StringMap.mem s.sname structs then fail_type ("duplicate struct: " ^ s.sname);
+        let fields =
+          List.fold_left
+            (fun acc (t, n) ->
+              if StringMap.mem n acc then fail_type ("duplicate field " ^ n ^ " in struct " ^ s.sname);
+              StringMap.add n t acc)
+            StringMap.empty s.fields
+        in
+        collect tl (StringMap.add s.sname fields structs) funcs globals
+    | TopFunc f :: tl ->
+        if StringMap.mem f.name funcs then fail_type ("duplicate function: " ^ f.name);
+        let sig_ = { fparams = List.map snd f.params; fret = f.ret } in
+        collect tl structs (StringMap.add f.name sig_ funcs) globals
+    | TopGlobalVar (is_mut, n, t_annot, init_e) :: tl ->
+        if StringMap.mem n globals then fail_type ("duplicate global variable: " ^ n);
+        let partial_ctx = { structs; funcs; globals } in
+        let t = match t_annot with
+          | Some t -> t
+          | None ->
+              (match init_e with
+              | Some e -> infer_expr partial_ctx globals e
+              | None ->
+                  fail_type ("global variable '" ^ n ^ "' requires a type annotation or initializer"))
+        in
+        collect tl structs funcs (StringMap.add n (t, is_mut) globals)
+  in
+  collect prog StringMap.empty StringMap.empty StringMap.empty
+
 let rec check_stmt ctx ret env = function
-  | VarDecl (t, n, init) ->
+  | VarDecl (is_mut, n, t_annot, init) ->
-      validate_type ctx.structs false t;
+      let t = match (t_annot, init) with
-      (match init with None -> () | Some e -> expect_type (infer_expr ctx env e) t);
+        | (Some t, Some e) ->
-      StringMap.add n t env
+            validate_type ctx.structs false t;
+            expect_type (infer_expr ctx env e) t;
+            t
+        | (Some t, None) ->
+            validate_type ctx.structs false t;
+            t
+        | (None, Some e) ->
+            let t = infer_expr ctx env e in
+            validate_type ctx.structs false t;
+            t
+        | (None, None) ->
+            fail_type ("cannot determine type of '" ^ n ^ "': no type annotation and no initializer")
+      in
+      StringMap.add n (t, is_mut) env
   | Expr e ->
       ignore (infer_expr ctx env e);
       env
@@ -149,7 +189,7 @@ let rec check_stmt ctx ret env = function
       (match infer_expr ctx env iterable with
       | TArray elem_t -> expect_type elem_t it_t
       | t -> fail_type ("foreach expects array iterable, got " ^ string_of_typ t));
-      let env' = StringMap.add it_name it_t env in
+      let env' = StringMap.add it_name (it_t, false) env in
       ignore (check_block ctx ret env' body);
       env
   | Return None ->
@@ -172,7 +212,7 @@ let rec has_return_stmt = function
 
 let check_program (prog : program) =
   let ctx = collect_ctx prog in
-  StringMap.iter (fun _ t -> validate_type ctx.structs false t) ctx.globals;
+  StringMap.iter (fun _ (t, _) -> validate_type ctx.structs false t) ctx.globals;
   StringMap.iter
     (fun _ sig_ ->
       List.iter (validate_type ctx.structs false) sig_.fparams;
@@ -182,18 +222,21 @@ let check_program (prog : program) =
     (function
       | TopStruct s ->
           List.iter (fun (t, _) -> validate_type ctx.structs false t) s.fields
-      | TopGlobalVar (t, _, init) ->
+      | TopGlobalVar (_, n, t_annot, init) ->
+          let t = match t_annot with
+            | Some t -> t
+            | None -> fst (StringMap.find n ctx.globals)
+          in
           validate_type ctx.structs false t;
-          let env = ctx.globals in
+          (match init with None -> () | Some e -> expect_type (infer_expr ctx ctx.globals e) t)
-          (match init with None -> () | Some e -> expect_type (infer_expr ctx env e) t)
       | TopFunc f ->
           let env_with_globals = ctx.globals in
           let env =
             List.fold_left
-              (fun acc (t, n) ->
+              (fun acc (n, t) ->
                 validate_type ctx.structs false t;
                 if StringMap.mem n acc then fail_type ("duplicate parameter name: " ^ n);
-                StringMap.add n t acc)
+                StringMap.add n (t, false) acc)
               env_with_globals f.params
           in
           ignore (check_block ctx f.ret env f.body);
@@ -201,8 +244,59 @@ let check_program (prog : program) =
             fail_type ("non-void function " ^ f.name ^ " must return a value"))
     prog
 
-let type_check (prog : program) =
+(* Annotation pass: fills in inferred types so generators always get fully-typed ASTs. *)
+let rec annotate_stmts ctx env stmts =
+  List.fold_left_map (annotate_stmt ctx) env stmts
+
+and annotate_stmt ctx env stmt =
+  match stmt with
+  | VarDecl (is_mut, n, t_annot, init) ->
+      let t = match (t_annot, init) with
+        | (Some t, _) -> t
+        | (None, Some e) -> infer_expr ctx env e
+        | (None, None) -> TVoid (* unreachable after successful check_program *)
+      in
+      let env' = StringMap.add n (t, is_mut) env in
+      (env', VarDecl (is_mut, n, Some t, init))
+  | If (cond, tbranch, ebranch) ->
+      let (_, tbranch') = annotate_stmts ctx env tbranch in
+      let (_, ebranch') = annotate_stmts ctx env ebranch in
+      (env, If (cond, tbranch', ebranch'))
+  | ForEach (it_t, it_name, iterable, body) ->
+      let env' = StringMap.add it_name (it_t, false) env in
+      let (_, body') = annotate_stmts ctx env' body in
+      (env, ForEach (it_t, it_name, iterable, body'))
+  | Block stmts ->
+      let (_, stmts') = annotate_stmts ctx env stmts in
+      (env, Block stmts')
+  | other -> (env, other)
+
+let annotate_top ctx = function
+  | TopFunc f ->
+      let env =
+        List.fold_left
+          (fun acc (n, t) -> StringMap.add n (t, false) acc)
+          ctx.globals f.params
+      in
+      let (_, body') = annotate_stmts ctx env f.body in
+      TopFunc { f with body = body' }
+  | TopGlobalVar (is_mut, n, t_annot, init) ->
+      let t = match t_annot with
+        | Some t -> t
+        | None ->
+            (match init with
+            | Some e -> infer_expr ctx ctx.globals e
+            | None -> TVoid)
+      in
+      TopGlobalVar (is_mut, n, Some t, init)
+  | other -> other
+
+let annotate_program prog =
+  let ctx = collect_ctx prog in
+  List.map (annotate_top ctx) prog
+
+let type_check (prog : program) : (program, string) result =
   try
     check_program prog;
-    Ok ()
+    Ok (annotate_program prog)
   with Type_error msg -> Error msg

lib/typechecker.mli

@@ -1 +1 @@
-val type_check : Ast.program -> (unit, string) result
+val type_check : Ast.program -> (Ast.program, string) result

test/test_spooky.ml

@@ -4,18 +4,18 @@ struct Item {
 	int value;
 };
 
-int fold(int[] xs) {
+fn fold(xs: int[]) -> int {
-	int total = 0;
+	let mut total: int = 0;
 	foreach (int x in xs) {
 		total = total + x;
 	}
 	return total;
 }
 
-int main() {
+fn main() -> int {
-	int[] xs;
+	let xs: int[];
-	Item it;
+	let it: Item;
-	int y = 2 + 3 * 4;
+	let mut y = 2 + 3 * 4;
 	it.value = y;
 	if (y >= 0) {
 		y = fold(xs);
@@ -28,14 +28,52 @@ int main() {
 
 let invalid_program =
 	{|
-int main() {
+fn main() -> int {
-	bool flag = true;
+	let flag = true;
-	int x = 1;
+	let mut x = 1;
 	x = flag;
 	return x;
 }
 |}
 
+let combo_valid_program =
+	{|
+fn get_value() -> int#int {
+	let x = 1;
+	return x;
+}
+
+fn do_work(v: int#int) -> int {
+	return 0;
+}
+
+fn main() -> int {
+	let x = get_value();
+	return do_work(x);
+}
+|}
+
+let combo_invalid_program =
+	{|
+fn get_value() -> int {
+	return 1;
+}
+
+fn get_comptime() -> #int {
+	return 2;
+}
+
+fn do_work(v: int#int) -> int {
+	return 0;
+}
+
+fn main() -> int {
+	let x = get_value();
+	let y = get_comptime();
+	return do_work(x);
+}
+|}
+
 let test_valid_program () =
 	match Spooky.parse_and_type_check valid_program with
 	| Ok _ -> ()
@@ -46,6 +84,16 @@ let test_invalid_program () =
 	| Ok _ -> failwith "expected type error, but got success"
 	| Error _ -> ()
 
+let test_combo_valid_program () =
+	match Spooky.parse_and_type_check combo_valid_program with
+	| Ok _ -> ()
+	| Error msg -> failwith ("expected valid combo program, got: " ^ msg)
+
+let test_combo_invalid_program () =
+	match Spooky.parse_and_type_check combo_invalid_program with
+	| Ok _ -> failwith "expected combo type error, but got success"
+	| Error _ -> ()
+
 let write_file path content =
 	let oc = open_out_bin path in
 	Fun.protect ~finally:(fun () -> close_out oc) (fun () -> output_string oc content)
@@ -65,9 +113,9 @@ let test_imports () =
 		~finally:cleanup
 		(fun () ->
 			write_file (Filename.concat modules_dir "math.spooky")
-				"int add(int a, int b) { return a + b; }\n";
+				"fn add(a: int, b: int) -> int { return a + b; }\n";
 			write_file (Filename.concat base "main.spooky")
-				"import \"modules/math.spooky\";\nint main() { return add(1, 2); }\n";
+				"import \"modules/math.spooky\";\nfn main() -> int { return add(1, 2); }\n";
 			match Spooky.parse_and_type_check_file (Filename.concat base "main.spooky") with
 			| Ok _ -> ()
 			| Error msg -> failwith ("expected valid import program, got: " ^ msg))
@@ -75,5 +123,7 @@ let test_imports () =
 let () =
 	test_valid_program ();
 	test_invalid_program ();
+	test_combo_valid_program ();
+	test_combo_invalid_program ();
 	test_imports ();
 	print_endline "All parser/type-check tests passed."