make debugging of transient failure a bit easier

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/function/PFunction.java

@@ -72,6 +72,7 @@ public PFunction(String name, String qualname, String enclosingClassName, PCode
         super(PythonBuiltinClassType.PFunction, PythonBuiltinClassType.PFunction.newInstance());
         this.name = name;
         this.qualname = qualname;
+        assert code != null;
         this.code = code;
         this.enclosingClassName = enclosingClassName;
         this.globals = globals;
@@ -146,6 +147,7 @@ public PCode getCode() {
 
     public void setCode(PCode code) {
         codeStableAssumption.invalidate("code changed for function " + getName());
+        assert code != null : "code cannot be null";
         this.code = code;
     }
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/builtins/FunctionNodes.java

@@ -206,7 +206,8 @@ public static GetFunctionCodeNode create() {
     @GenerateUncached
     public abstract static class GetSignatureNode extends PNodeWithContext {
         private static Signature doFunctionInternal(GetFunctionCodeNode getFunctionCodeNode, PFunction function) {
-            return getFunctionCodeNode.execute(function).getSignature();
+            PCode code = getFunctionCodeNode.execute(function);
+            return code.getSignature();
         }
 
         public abstract Signature execute(Object function);