Simplify logic in the case we aren't tracing

Author: Adam Hrbac

graalpython/com.oracle.graal.python.test/src/com/oracle/graal/python/test/runtime/TracingTests.java

@@ -52,6 +52,17 @@ public void ensureBytecode() {
         Assume.assumeTrue(PythonTests.usingBytecodeCompiler());
     }
 
+    @Test
+    public void traceInExistingScopeWithOnlyReturn() {
+        String source = "import sys\n" +
+                        "def trace(fr, ev, arg): print(fr.f_lineno, ev); return trace\n" +
+                        "def fun():\n" +
+                        "  sys._getframe().f_trace = trace\n" +
+                        "  sys.settrace(lambda:None)\n" +
+                        "fun()";
+        PythonTests.assertPrints("5 return\n", source);
+    }
+
     @Test
     public void traceCall() {
         String source = "import sys\n" +

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/bytecode/PBytecodeRootNode.java

@@ -1119,8 +1119,7 @@ private Object bytecodeLoop(VirtualFrame virtualFrame, Frame localFrame, Bytecod
                             initialBci == 0 ? getFirstLineno() : (mutableData.pastLine = bciToLine(initialBci)), false);
         }
 
-        mutableData.returnLine = mutableData.pastLine;
-        mutableData.pastBci = initialBci;
+        mutableData.returnLine = -1;
 
         int oparg = 0;
         while (true) {