Support raising exceptions without call

Author: adrian17

tests/snippets/try_exceptions.py

@@ -8,6 +8,19 @@
     # print(ex.__traceback__)
     # print(type(ex.__traceback__))
 
+try:
+    raise ZeroDivisionError
+except ZeroDivisionError as ex:
+    pass
+
+class E(Exception):
+    def __init__(self):
+        asdf
+
+try:
+    raise E
+except NameError as ex:
+    pass
 
 l = []
 try:

vm/src/frame.rs

@@ -515,6 +515,12 @@ impl Frame {
                 if objtype::isinstance(&exception, &vm.ctx.exceptions.base_exception_type) {
                     info!("Exception raised: {:?}", exception);
                     Err(exception)
+                } else if objtype::isinstance(&exception, &vm.ctx.type_type())
+                    && objtype::issubclass(&exception, &vm.ctx.exceptions.base_exception_type)
+                {
+                    let exception = vm.new_empty_exception(exception)?;
+                    info!("Exception raised: {:?}", exception);
+                    Err(exception)
                 } else {
                     let msg = format!(
                         "Can only raise BaseException derived types, not {}",

vm/src/vm.rs

@@ -107,7 +107,17 @@ impl VirtualMachine {
         self.ctx.new_dict()
     }
 
+    pub fn new_empty_exception(&mut self, exc_type: PyObjectRef) -> PyResult {
+        info!("New exception created: no msg");
+        let args = PyFuncArgs {
+            args: vec![],
+            kwargs: vec![],
+        };
+        self.invoke(exc_type, args)
+    }
+
     pub fn new_exception(&mut self, exc_type: PyObjectRef, msg: String) -> PyObjectRef {
+        // TODO: exc_type may be user-defined exception, so we should return PyResult
         // TODO: maybe there is a clearer way to create an instance:
         info!("New exception created: {}", msg);
         let pymsg = self.new_str(msg);