fix: missing validation on events

also update expected exception on some struct failures now that we're
using a common helper function

tests/functional/syntax/test_ann_assign.py

@@ -3,6 +3,7 @@
 
 from vyper import compiler
 from vyper.exceptions import (
+    InstantiationException,
     InvalidAttribute,
     TypeMismatch,
     UndeclaredDefinition,
@@ -73,7 +74,7 @@ def foo() -> int128:
 def foo() -> int128:
     s: S = S(a=1)
     """,
-        VariableDeclarationException,
+        InstantiationException,
     ),
     (
         """

tests/functional/syntax/test_structs.py

@@ -32,7 +32,8 @@ def foo():
     """,
         UnknownAttribute,
     ),
-    """
+    (
+        """
 struct A:
     x: int128
     y: int128
@@ -41,6 +42,8 @@ def foo():
 def foo():
     self.a = A(x=1)
     """,
+        InstantiationException,
+    ),
     """
 struct A:
     x: int128
@@ -61,7 +64,8 @@ def foo():
 def foo():
     self.a = A(self.b)
     """,
-    """
+    (
+        """
 struct A:
     x: int128
     y: int128
@@ -70,6 +74,8 @@ def foo():
 def foo():
     self.a = A({x: 1})
     """,
+        InstantiationException,
+    ),
     """
 struct C:
     c: int128

vyper/semantics/types/user.py

@@ -7,6 +7,7 @@
 from vyper.exceptions import (
     EventDeclarationException,
     FlagDeclarationException,
+    InstantiationException,
     NamespaceCollision,
     StructureException,
     UnfoldableNode,
@@ -284,6 +285,13 @@ def from_EventDef(cls, base_node: vy_ast.EventDef) -> "EventT":
     def _ctor_call_return(self, node: vy_ast.Call) -> None:
         # validate keyword arguments if provided
         if len(node.keywords) > 0:
+            if len(node.args) > 0:
+                raise InstantiationException(
+                    "Event instantiation requires either all keyword arguments "
+                    "or all positional arguments",
+                    node,
+                )
+
             return validate_kwargs(node, self.arguments.copy(), self.typeclass)
 
         # warn about positional argument depreciation