be strict on restoration of thread state after leaving an indirect call

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/ExecutionContext.java

@@ -409,7 +409,9 @@ private static IndirectCallState enter(VirtualFrame frame, PythonThreadState pyt
         public static void exit(VirtualFrame frame, PythonLanguage language, PythonContext context, Object savedState) {
             if (savedState != null && frame != null && context != null) {
                 exit(frame, context.getThreadState(language), savedState);
+                return;
             }
+            assert savedState == null : "tried to exit an indirect call with state, but without frame/context";
         }
 
         public static void exit(VirtualFrame frame, PNodeWithRaiseAndIndirectCall indirectCallNode, Object savedState) {
@@ -418,24 +420,28 @@ public static void exit(VirtualFrame frame, PNodeWithRaiseAndIndirectCall indire
                 if (context != null) {
                     PythonLanguage language = indirectCallNode.getLanguage();
                     exit(frame, context.getThreadState(language), savedState);
+                    return;
                 }
             }
+            assert savedState == null : "tried to exit an indirect call with state, but without frame/context";
         }
 
         /**
          * @see #exit(VirtualFrame, PythonLanguage, PythonContext, Object)
          */
         public static void exit(VirtualFrame frame, PythonThreadState pythonThreadState, Object savedState) {
-            if (frame == null || savedState == null) {
+            if (frame == null) {
+                assert savedState == null : "tried to exit an indirect call with state, but without frame";
+                return;
+            }
+            if (savedState == null) {
                 return;
             }
             IndirectCallState state = (IndirectCallState) savedState;
             if (state.info != null) {
                 pythonThreadState.popTopFrameInfo();
             }
-            if (state.curExc != null) {
-                pythonThreadState.setCaughtException(state.curExc);
-            }
+            pythonThreadState.setCaughtException(state.curExc);
         }
     }