Error handling of RERAISE is strange

Bug report

There's a strange pattern used in RERAISE opcode:

Lines 1174 to 1189 in 4767a6e

    
           tier1 inst(RERAISE, (values[oparg], exc_st -- values[oparg])) { 
        
               PyObject *exc = PyStackRef_AsPyObjectBorrow(exc_st); 
        
               assert(oparg >= 0 && oparg <= 2); 
        
               if (oparg) { 
        
                   PyObject *lasti = PyStackRef_AsPyObjectBorrow(values[0]); 
        
                   if (PyLong_Check(lasti)) { 
        
                       frame->instr_ptr = _PyCode_CODE(_PyFrame_GetCode(frame)) + PyLong_AsLong(lasti); 
        
                       assert(!_PyErr_Occurred(tstate)); 
        
                   } 
        
                   else { 
        
                       assert(PyLong_Check(lasti)); 
        
                       _PyErr_SetString(tstate, PyExc_SystemError, "lasti is not an int"); 
        
                       ERROR_NO_POP(); 
        
                   } 
        
               }

Especially these lines:

cpython/Python/bytecodes.c

Lines 1180 to 1187 in 4767a6e

    
           if (PyLong_Check(lasti)) { 
        
               frame->instr_ptr = _PyCode_CODE(_PyFrame_GetCode(frame)) + PyLong_AsLong(lasti); 
        
               assert(!_PyErr_Occurred(tstate)); 
        
           } 
        
           else { 
        
               assert(PyLong_Check(lasti)); 
        
               _PyErr_SetString(tstate, PyExc_SystemError, "lasti is not an int"); 
        
               ERROR_NO_POP();

It looks like the assert call is not needed here:

In debug builds it will always crash, since PyLong_Check(lasti) will always be false
In non-debug builds it will set SystemError as it should be (at least, I think so). That's the only line that matches r'assert\(.*\);\n\s+_PyErr'

I have a PR ready.

Linked PRs

gh-122759: Remove assert from RERAISE error handling #122760

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	tier1 inst(RERAISE, (values[oparg], exc_st -- values[oparg])) {
	PyObject *exc = PyStackRef_AsPyObjectBorrow(exc_st);

	assert(oparg >= 0 && oparg <= 2);
	if (oparg) {
	PyObject *lasti = PyStackRef_AsPyObjectBorrow(values[0]);
	if (PyLong_Check(lasti)) {
	frame->instr_ptr = _PyCode_CODE(_PyFrame_GetCode(frame)) + PyLong_AsLong(lasti);
	assert(!_PyErr_Occurred(tstate));
	}
	else {
	assert(PyLong_Check(lasti));
	_PyErr_SetString(tstate, PyExc_SystemError, "lasti is not an int");
	ERROR_NO_POP();
	}
	}

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Error handling of RERAISE is strange #122759

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Error handling of `RERAISE` is strange #122759