nac3core/artiq: raise dedicated UnwrapNoneError

not to confuse with option none, and the None token is parsed as a special ast::constant instead of an ast::name so the handling is invalid

nac3artiq/demo/embedding_map.py

@@ -16,7 +16,8 @@ class EmbeddingMap:
                                           "CacheError",
                                           "SPIError",
                                           "0:ZeroDivisionError",
-                                          "0:IndexError"])
+                                          "0:IndexError",
+                                          "0:UnwrapNoneError"])
 
     def preallocate_runtime_exception_names(self, names):
         for i, name in enumerate(names):

nac3artiq/demo/min_artiq.py

@@ -11,7 +11,7 @@ from embedding_map import EmbeddingMap
 
 __all__ = [
     "Kernel", "KernelInvariant", "virtual",
-    "Option", "Some", "none",
+    "Option", "Some", "none", "UnwrapNoneError",
     "round64", "floor64", "ceil64",
     "extern", "kernel", "portable", "nac3",
     "rpc", "ms", "us", "ns",
@@ -47,7 +47,7 @@ class Option(Generic[T]):
     
     def unwrap(self):
         if self.is_none():
-            raise ValueError("unwrap on none")
+            raise UnwrapNoneError()
         return self._nac3_option
 
     def __repr__(self) -> str:
@@ -274,5 +274,10 @@ class KernelContextManager:
     def __exit__(self):
         pass
 
+@nac3
+class UnwrapNoneError(Exception):
+    """raised when unwrapping a none value"""
+    artiq_builtin = True
+
 parallel = KernelContextManager()
 sequential = KernelContextManager()

nac3core/src/codegen/expr.rs

@@ -1319,8 +1319,8 @@ pub fn gen_expr<'ctx, 'a, G: CodeGenerator>(
                             ctx.make_assert(
                                 generator,
                                 not_null,
-                                "0:ValueError",
-                                "unwrap on none",
+                                "0:UnwrapNoneError",
+                                "",
                                 [None, None, None],
                                 expr.location,
                             );

nac3core/src/toplevel/builtins.rs

@@ -105,7 +105,8 @@ pub fn get_builtins(primitives: &mut (PrimitiveStore, Unifier)) -> BuiltinInfo {
         ("__param2__".into(), int64, true),
     ];
 
-    // for Option, is_some and is_none share the same type
+    // for Option, is_some and is_none share the same type: () -> bool,
+    // and they are methods under the same class `Option`
     let (is_some_ty, unwrap_ty, (option_ty_var, option_ty_var_id)) =
         if let TypeEnum::TObj { fields, params, .. } =
             primitives.1.get_ty(primitives.0.option).as_ref()