feat: drop none literal in favour of null

congwang-mk · congwang-mk · commit e0ddcd98565e · 2026-05-05T14:25:45.000-07:00
Signed-off-by: Cong Wang &lt;cwang@multikernel.io&gt;
diff --git a/README.md b/README.md
@@ -218,7 +218,7 @@ fn handle_action(action: FilterAction) -> xdp_action {
 // Map lookup and update patterns
 fn lookup_or_create(ip: IpAddress) -> Counter {
     var count = connection_count[ip]
-    if (count != none) {
+    if (count != null) {
         return count  // Entry exists
     } else {
         connection_count[ip] = 1  // Create new entry
diff --git a/SPEC.md b/SPEC.md
@@ -2431,7 +2431,7 @@ fn map_pointer_operations(flow_key: FlowKey) {
     // Map lookup returns pointer to value
     var flow_data = flow_map[flow_key]
     
-    if (flow_data != none) {
+    if (flow_data != null) {
         // Direct modification through pointer
         flow_data->packet_count += 1
         flow_data->byte_count += packet_size
@@ -3016,7 +3016,7 @@ fn packet_filter(ctx: *xdp_md) -> action: xdp_action {
 
 // Userspace functions with named returns
 fn lookup_counter(ip: u32) -> counter_ptr: *u64 {
-    if (counters[ip] == none) {
+    if (counters[ip] == null) {
         counters[ip] = 0
     }
     counter_ptr = &counters[ip]
@@ -3737,7 +3737,7 @@ fn security_filter(ctx: LsmContext) -> i32 {
     var flow_key = extract_flow_key_from_socket(ctx)
         
     // Check global flow statistics for threat detection
-    if (global_flows[flow_key] != none) {
+    if (global_flows[flow_key] != null) {
         var flow_stats = global_flows[flow_key]
         if (flow_stats.is_suspicious()) {
             global_events.submit(EVENT_THREAT_DETECTED { flow_key })
@@ -4029,7 +4029,7 @@ var cache_map : hash<u32, DataCache>(1024)
 @helper
 fn map_lifetime_safety(key: u32) {
     var cache_entry = cache_map[key]
-    if (cache_entry != none) {
+    if (cache_entry != null) {
         // Compiler tracks that cache_entry is valid here
         cache_entry->access_count += 1
         cache_entry->last_access = bpf_ktime_get_ns()
@@ -4085,7 +4085,7 @@ fn kernel_side_processing(ctx: *xdp_md) -> xdp_action {
     
     // Shared memory through maps - safe across contexts
     var shared_buffer = shared_map[0]
-    if (shared_buffer != none) {
+    if (shared_buffer != null) {
         shared_buffer->kernel_processed_count += 1
         memory_copy(packet_data, shared_buffer->data, min(packet_len, 64))
     }
@@ -4100,7 +4100,7 @@ fn userspace_processing() -> i32 {
     
     // ✅ Access through shared maps
     var shared_buffer = shared_map[0]
-    if (shared_buffer != none) {
+    if (shared_buffer != null) {
         shared_buffer->userspace_processed_count += 1
         process_shared_data(shared_buffer->data)
     }
diff --git a/examples/map_operations_demo.ks b/examples/map_operations_demo.ks
@@ -58,7 +58,7 @@ struct ArrayElement {
     
     // Safe concurrent read access - multiple programs can read simultaneously
     var counter = global_counter[key]
-    if (counter != none) {
+    if (counter != null) {
         // High-frequency lookup pattern - will generate optimization suggestions
         for (i in 0..100) {
             var _ = global_counter[key + i]
@@ -89,7 +89,7 @@ fn stats_updater(ctx: *__sk_buff) -> i32 {
     
     // Potential write conflict with other programs
     var stats = shared_stats[ifindex]
-    if (stats == none) {
+    if (stats == null) {
         stats = Statistics {
             packet_count: 0,
             byte_count: 0,
diff --git a/examples/maps_demo.ks b/examples/maps_demo.ks
@@ -84,7 +84,7 @@ fn get_timestamp() -> u64 {
   }
 
   // Log repeated connections
-  if (recent_connections[src_ip] != none) {
+  if (recent_connections[src_ip] != null) {
     event_log[0] = 1
   }
   
diff --git a/examples/object_allocation.ks b/examples/object_allocation.ks
@@ -21,7 +21,7 @@ var conn_tracker : hash<u32, *ConnStats>(1024)
     // Look up existing connection stats
     var stats = conn_tracker[src_ip]
     
-    if (stats == none) {
+    if (stats == null) {
         // First packet from this IP - allocate new stats object
         stats = new ConnStats()
         if (stats == null) {
diff --git a/examples/rate_limiter.ks b/examples/rate_limiter.ks
@@ -21,7 +21,7 @@ config network {
   var src_ip = 0x7F000001 // Placeholder IP (127.0.0.1)
     
   // Update the count
-  if (packet_counts[src_ip] != none) {
+  if (packet_counts[src_ip] != null) {
     packet_counts[src_ip] += 1
   } else {
     packet_counts[src_ip] = 0
diff --git a/examples/ringbuf_demo.ks b/examples/ringbuf_demo.ks
@@ -44,7 +44,7 @@ fn get_timestamp() -> u64 {
 @xdp fn network_monitor(ctx: *xdp_md) -> xdp_action {
   var key: u32 = 0
   var stat = stats[key]
-  if (stat == none) {
+  if (stat == null) {
     var init_stat = Stats { events_submitted: 0, events_dropped: 0, buffer_full_count: 0 }
     stats[key] = init_stat
     stat = stats[key]
diff --git a/examples/safety_demo.ks b/examples/safety_demo.ks
@@ -110,7 +110,7 @@ fn array_validation_demo(ctx: *xdp_md) -> xdp_action {
   // Safe map access
   var key: u32 = 1
   var count = packet_stats[key]
-  if (count != none) {
+  if (count != null) {
     packet_stats[key] = count + 1
   } else {
     packet_stats[key] = 1
diff --git a/examples/test_error_handling.ks b/examples/test_error_handling.ks
@@ -22,7 +22,7 @@ fn process_key(key: u32) -> u32 {
     try {
         // Check if key exists (expected absence - use null)
         var value = test_map[key]
-        if (value == none) {
+        if (value == null) {
             // Key doesn't exist - create default value (expected pattern)
             var default_value = 42
             test_map[key] = default_value
diff --git a/examples/types_demo.ks b/examples/types_demo.ks
@@ -64,7 +64,7 @@ fn extract_packet_info(ctx: *xdp_md) -> *PacketInfo {
 fn get_filter_action(info: PacketInfo) -> FilterAction {
   // Look up in the filter map
   var action = packet_filter[info]
-  if (action != none) {
+  if (action != null) {
     return action
   } else {
     return FILTER_ACTION_ALLOW
@@ -86,7 +86,7 @@ fn protocol_from_u8(proto_num: u8) -> Protocol {
 fn update_stats(info: PacketInfo) {
   // Update connection count
   var current_count = connection_count[info.src_ip]
-  if (current_count != none) {
+  if (current_count != null) {
     connection_count[info.src_ip] = current_count + 1
   } else {
     connection_count[info.src_ip] = 1
@@ -95,7 +95,7 @@ fn update_stats(info: PacketInfo) {
   // Update protocol stats
   var proto = protocol_from_u8(info.protocol)
   var stats = protocol_stats[proto]
-  if (stats != none) {
+  if (stats != null) {
     protocol_stats[proto] = stats + 1
   } else {
     protocol_stats[proto] = 1
@@ -107,7 +107,7 @@ fn update_stats(info: PacketInfo) {
   // Extract packet information
   var packet_info = extract_packet_info(ctx)
   
-  if (packet_info != none) {
+  if (packet_info != null) {
     // Update statistics
     update_stats(*packet_info)
     
diff --git a/src/ast.ml b/src/ast.ml
@@ -81,8 +81,6 @@ type bpf_type =
   (* Ring buffer reference type - represents a ring buffer for dispatch *)
   | RingbufRef of bpf_type (* value type *)
   | Ringbuf of bpf_type * int (* value_type, size - ring buffer object *)
-  (* None type - represents missing/absent values *)
-  | NoneType
   (* Null type - represents null pointers, compatible with any pointer type *)
   | Null
 
@@ -187,7 +185,6 @@ type literal =
   | BoolLit of bool
   | ArrayLit of array_init_style   (* Enhanced array initialization *)
   | NullLit
-  | NoneLit
 
 (** Array initialization styles *)
 and array_init_style =
@@ -716,7 +713,6 @@ let rec string_of_bpf_type = function
   | ProgramHandle -> "ProgramHandle"
   | RingbufRef value_type -> Printf.sprintf "ringbuf_ref<%s>" (string_of_bpf_type value_type)
   | Ringbuf (value_type, size) -> Printf.sprintf "ringbuf<%s>(%d)" (string_of_bpf_type value_type) size
-  | NoneType -> "none"
   | Null -> "null"
 
 let rec string_of_literal = function
@@ -732,7 +728,6 @@ let rec string_of_literal = function
       Printf.sprintf "[%s]" (String.concat ", " (List.map string_of_literal literals))
   | ArrayLit (ZeroArray) -> "[]"
   | NullLit -> "null"
-  | NoneLit -> "none"
 
 let string_of_binary_op = function
   | Add -> "+"
diff --git a/src/ebpf_c_codegen.ml b/src/ebpf_c_codegen.ml
@@ -1230,8 +1230,7 @@ let rec generate_c_value ?(auto_deref_map_access=false) ctx ir_val =
   | IRLiteral (BoolLit b) -> if b then "1" else "0"
   | IRLiteral (CharLit c) -> sprintf "'%c'" c
   | IRLiteral (NullLit) -> "NULL"
-  | IRLiteral (NoneLit) -> "0"
-  | IRLiteral (StringLit s) -> 
+  | IRLiteral (StringLit s) ->
       (* Generate string literal as struct initialization *)
       (match ir_val.val_type with
        | IRStr size ->
@@ -1263,7 +1262,6 @@ let rec generate_c_value ?(auto_deref_map_access=false) ctx ir_val =
              | Ast.CharLit c -> sprintf "'%c'" c
              | Ast.StringLit s -> sprintf "\"%s\"" (escape_c_string s)
              | Ast.NullLit -> "NULL"
-             | Ast.NoneLit -> "0"
              | Ast.ArrayLit _ -> "{0}"  (* Nested arrays simplified *)
            in
            "{" ^ fill_str ^ "}"
@@ -1275,7 +1273,6 @@ let rec generate_c_value ?(auto_deref_map_access=false) ctx ir_val =
              | Ast.CharLit c -> sprintf "'%c'" c
              | Ast.StringLit s -> sprintf "\"%s\"" (escape_c_string s)
              | Ast.NullLit -> "NULL"
-             | Ast.NoneLit -> "0"
              | Ast.ArrayLit _ -> "{0}"  (* Nested arrays simplified *)
            ) elements in
            if List.length elements = 0 then
@@ -1433,15 +1430,13 @@ let generate_c_expression ctx ir_expr =
            let index_str = generate_c_value ctx right in
            sprintf "%s.data[%s]" array_str index_str
        | _ ->
-           (* Check for absence-literal comparisons first.
-              Both `none` and `null` count as absence literals here; the
-              codegen emits a pointer presence check against the underlying
-              lookup pointer (or against the value directly when it is
-              already a pointer). This is what makes `if (var x = map[k])`
-              and `entry != null` produce correct C without an extra
-              dereference. *)
+           (* `null` comparisons against a map-access lower to a presence
+              check against the underlying lookup pointer (or against the
+              value directly when it is already a pointer), so
+              `if (var x = map[k])` and `entry != null` produce correct C
+              without an extra dereference. *)
            let is_absence_lit = function
-             | IRLiteral (Ast.NoneLit) | IRLiteral (Ast.NullLit) -> true
+             | IRLiteral (Ast.NullLit) -> true
              | _ -> false
            in
            (match left.value_desc, op, right.value_desc with
diff --git a/src/evaluator.ml b/src/evaluator.ml
@@ -37,7 +37,6 @@ type runtime_value =
   | ContextValue of string * (string * runtime_value) list
   | NullValue  (* Simple null value representation *)
   | UnitValue
-  | None  (* Sentinel value for map lookup failures and missing values *)
 
 (** Additional exceptions that depend on runtime_value *)
 exception Return_value of runtime_value
@@ -54,7 +53,6 @@ let rec runtime_values_equal v1 v2 =
   | EnumValue (name1, val1), EnumValue (name2, val2) -> name1 = name2 && val1 = val2
   | NullValue, NullValue -> true
   | UnitValue, UnitValue -> true
-  | None, None -> true
   | PointerValue addr1, PointerValue addr2 -> addr1 = addr2
   | MapHandle name1, MapHandle name2 -> name1 = name2
   | ArrayValue arr1, ArrayValue arr2 -> 
@@ -326,7 +324,6 @@ let rec string_of_runtime_value = function
           name ^ " = " ^ string_of_runtime_value value) fields))
   | NullValue -> "null"
   | UnitValue -> "()"
-  | None -> "none"
 
 (** Convert literal to runtime value *)
 let runtime_value_of_literal = function
@@ -335,7 +332,6 @@ let runtime_value_of_literal = function
   | CharLit c -> CharValue c
   | BoolLit b -> BoolValue b
   | NullLit -> NullValue  (* null is represented as simple null value *)
-  | NoneLit -> None      (* none is represented as none sentinel value *)
   | ArrayLit _literals -> 
       (* TODO: Implement array literal evaluation *)
       failwith "Array literal evaluation not implemented yet"
@@ -359,7 +355,6 @@ let is_truthy_value rv =
   | ContextValue (_, _) -> true                   (* context values are always truthy *)
   | NullValue -> false                            (* null is always falsy *)
   | UnitValue -> false                            (* unit value is falsy *)
-  | None -> false                                 (* none is always falsy *)
   | ArrayValue _ -> failwith "Arrays cannot be used in boolean context"
   | StructValue _ -> failwith "Structs cannot be used in boolean context"
 
@@ -405,15 +400,7 @@ let eval_binary_op left_val op right_val pos =
   | Ne, NullValue, _ -> BoolValue true
   | Eq, _, NullValue -> BoolValue false
   | Ne, _, NullValue -> BoolValue true
-  
-  (* None comparisons *)
-  | Eq, None, None -> BoolValue true
-  | Ne, None, None -> BoolValue false
-  | Eq, None, _ -> BoolValue false
-  | Ne, None, _ -> BoolValue true
-  | Eq, _, None -> BoolValue false
-  | Ne, _, None -> BoolValue true
-  
+
   (* Logical operations *)
   | And, BoolValue l, BoolValue r -> BoolValue (l && r)
   | Or, BoolValue l, BoolValue r -> BoolValue (l || r)
@@ -575,8 +562,8 @@ and eval_array_access ctx arr_expr idx_expr pos =
        (try
           Hashtbl.find map_store key_str
         with Not_found ->
-          (* For map access, return sentinel value for missing keys *)
-          None)
+          (* For map access, missing keys evaluate to null *)
+          NullValue)
    | _ ->
        (* Regular array access *)
        let arr_val = eval_expression ctx arr_expr in
diff --git a/src/ir.ml b/src/ir.ml
@@ -729,7 +729,6 @@ let rec ast_type_to_ir_type = function
   | ProgramHandle -> IRI32 (* Program handles are represented as file descriptors (i32) in IR to support error codes *)
   | Ringbuf (value_type, size) -> IRRingbuf (ast_type_to_ir_type value_type, size) (* Ring buffer object *)
   | RingbufRef _ -> IRU32 (* Ring buffer references are represented as pointers/handles (u32) in IR *)
-  | NoneType -> IRU32  (* None type represented as u32 sentinel value in IR *)
   | Null -> IRPointer (IRU32, {min_size = Some 0; max_size = Some 0; alignment = 1; nullable = true})  (* Null is represented as a nullable pointer in IR *)
 
 (* Helper function that preserves type aliases when converting AST types to IR types *)
diff --git a/src/ir_generator.ml b/src/ir_generator.ml
@@ -234,11 +234,10 @@ let lower_literal lit pos =
     | StringLit s -> IRStr (max 1 (String.length s))  (* String literals get IRStr type *)
     | CharLit _ -> IRChar
     | BoolLit _ -> IRBool
-    | NullLit -> 
+    | NullLit ->
         let bounds = make_bounds_info ~nullable:true () in
         IRPointer (IRU32, bounds)  (* null literal as nullable pointer to u32 *)
-    | NoneLit -> IRU32  (* none literal as sentinel u32 value *)
-    | ArrayLit init_style -> 
+    | ArrayLit init_style ->
         (* Handle enhanced array literal lowering *)
         (match init_style with
          | ZeroArray ->
@@ -251,10 +250,9 @@ let lower_literal lit pos =
                | BoolLit _ -> IRBool
                | CharLit _ -> IRChar
                | StringLit _ -> IRPointer (IRU8, make_bounds_info ~nullable:false ())
-               | NullLit -> 
+               | NullLit ->
                    let bounds = make_bounds_info ~nullable:true () in
                    IRPointer (IRU32, bounds)
-               | NoneLit -> IRU32  (* none literal as sentinel u32 value *)
                | ArrayLit _ -> IRU32  (* Nested arrays default to u32 *)
              in
              IRArray (element_ir_type, 0, make_bounds_info ())  (* Size resolved during type unification *)
@@ -271,10 +269,9 @@ let lower_literal lit pos =
                  | CharLit _ -> IRChar
                  | StringLit _ -> IRPointer (IRU8, make_bounds_info ~nullable:false ())
                  | ArrayLit _ -> IRU32  (* Nested arrays default to u32 *)
-                 | NullLit -> 
+                 | NullLit ->
                      let bounds = make_bounds_info ~nullable:true () in
                      IRPointer (IRU32, bounds)
-                 | NoneLit -> IRU32  (* none literal as sentinel u32 value *)
                in
                let bounds_info = make_bounds_info ~min_size:element_count ~max_size:element_count () in
                IRArray (element_ir_type, element_count, bounds_info))
@@ -314,7 +311,6 @@ let literal_to_ir_type = function
   | CharLit _ -> IRChar
   | StringLit _ -> IRPointer (IRU8, make_bounds_info ~nullable:false ())
   | NullLit -> IRPointer (IRU32, make_bounds_info ~nullable:true ())
-  | NoneLit -> IRU32
   | ArrayLit _ -> IRU32  (* Default for arrays *)
 
 (** Unified AST to IR type conversion for basic types *)
diff --git a/src/lexer.mll b/src/lexer.mll
@@ -122,7 +122,6 @@
     | "true" -> BOOL_LIT true
     | "false" -> BOOL_LIT false
     | "null" -> NULL
-    | "none" -> NONE
     | id -> IDENTIFIER id
 }
 
diff --git a/src/parser.mly b/src/parser.mly
@@ -46,7 +46,7 @@
 %token <string> STRING IDENTIFIER
 %token <char> CHAR_LIT
 %token <bool> BOOL_LIT
-%token NULL NONE
+%token NULL
 
 /* Keywords */
 %token FN EXTERN INCLUDE PIN TYPE STRUCT ENUM IMPL
@@ -516,7 +516,6 @@ literal:
   | CHAR_LIT { CharLit $1 }
   | BOOL_LIT { BoolLit $1 }
   | NULL { NullLit }
-  | NONE { NoneLit }
   | LBRACKET array_init_expr RBRACKET { ArrayLit $2 }
 
 array_init_expr:
diff --git a/src/type_checker.ml b/src/type_checker.ml
diff --git a/src/userspace_codegen.ml b/src/userspace_codegen.ml
diff --git a/tests/test_enum.ml b/tests/test_enum.ml
diff --git a/tests/test_map_integration.ml b/tests/test_map_integration.ml
diff --git a/tests/test_map_operations.ml b/tests/test_map_operations.ml
diff --git a/tests/test_truthy_falsy.ml b/tests/test_truthy_falsy.ml
diff --git a/tests/test_type_checker.ml b/tests/test_type_checker.ml

Original file line number	Diff line number	Diff line change
`@@ -84,7 +84,7 @@ fn get_timestamp() -> u64 {`
`84`	`84`	`}`
`85`	`85`
`86`	`86`	`// Log repeated connections`
`87`		`- if (recent_connections[src_ip] != none) {`
	`87`	`+ if (recent_connections[src_ip] != null) {`
`88`	`88`	`event_log[0] = 1`
`89`	`89`	`}`
`90`	`90`