Type check augmented assignments to primitives (facebookincubator#148)

Summary:
fix for facebookincubator#147

reject mixing incompatible types in augmented assignments in order to bring type checking in line with binops

Pull Request resolved: facebookincubator#148

Reviewed By: alexmalyshev

Differential Revision: D116791481

Pulled By: yoney

fbshipit-source-id: 2356f8d50089416e51d00f9073676256567b6569

Author: robertmorelli

cinderx/PythonLib/cinderx/compiler/static/type_binder.py

@@ -833,7 +833,12 @@ def visitAnnAssign(self, node: AnnAssign) -> None:
     def visitAugAssign(self, node: AugAssign) -> None:
         self.visit(node.target)
         target_type = self.get_type(node.target).inexact()
-        self.visit(node.value, target_type)
+        if isinstance(target_type, CInstance):
+            self.visitExpectedType(
+                node.value, target_type, target_type.binop_error("{1}", "{0}", node.op)
+            )
+        else:
+            self.visit(node.value, target_type)
         self.set_type(node, target_type)
 
     @contextmanager

cinderx/PythonLib/test_cinderx/test_compiler/test_static/test_augassign.py

@@ -45,6 +45,37 @@ def a(i: int) -> int:
             self.assertInBytecode(a, "PRIMITIVE_BINARY_OP", 0)
             self.assertEqual(a(3), 5)
 
+    def test_primitive_int_dynamic_rhs(self) -> None:
+        codestr = """
+        from __static__ import int64
+
+        class C:
+            def __init__(self) -> None:
+                self.total: int64 = 0
+
+            def add_values(self, values: dict[str, int]) -> None:
+                for _, value in values.items():
+                    self.total += value
+        """
+        self.type_error(codestr, r"cannot add int64 and dynamic", at="value")
+
+    def test_primitive_int_dynamic_rhs_explicit_cast(self) -> None:
+        codestr = """
+        from __static__ import box, int64
+
+        class C:
+            def __init__(self) -> None:
+                self.total: int64 = 0
+
+            def add_values(self, values: dict[str, int]) -> int:
+                for _, value in values.items():
+                    self.total += int64(value)
+                return box(self.total)
+        """
+        with self.in_module(codestr) as mod:
+            instance = mod.C()
+            self.assertEqual(instance.add_values({"a": 2, "b": 3}), 5)
+
     def test_inexact(self) -> None:
         codestr = """
         def something():