Suppress exceptions correctly in with blocks

batavia/VirtualMachine.js

@@ -1638,6 +1638,10 @@ VirtualMachine.prototype.byte_END_FINALLY = function() {
     var exc_type = this.pop()
     if (exc_type === builtins.None) {
         why = null
+    } else if (exc_type === 'silenced') {
+        var block = this.pop_block() // should be except-handler
+        this.unwind_block(block)
+        return null
     } else {
         value = this.pop()
         if (value instanceof builtins.BaseException.$pyclass) {
@@ -1748,7 +1752,7 @@ VirtualMachine.prototype.byte_WITH_CLEANUP = function() {
     }
     var ret = callables.call_function(exit_func, [exc, val, tb]) // XXX this arg list is incorrect for first 2 cases
     //TODO: silence error if necessary
-    if (!exc instanceof types.NoneType && ret) { // XXX
+    if (!(exc instanceof types.NoneType) && ret) { // XXX
         this.push('silenced')
     }
 }

tests/structures/test_with.py

@@ -42,3 +42,18 @@ def __exit__(self, exc, val, tb):
             except Exception as e:
                 print(type(e), e)
         """)
+
+    def test_suppress_exception(self):
+        self.assertCodeExecution("""
+            class mgr:
+                def __enter__(self):
+                    pass
+                def __exit__(self, exc, val, tb):
+                    print('supress')
+                    return True
+
+            with mgr():
+                raise KeyError(42)
+                print('raised')
+            print('done')
+        """)