_sage_getargspec_cython fails to parse -Infinity

[jdemeyer]

sage: from sage.misc.sageinspect import _sage_getargspec_cython
sage: _sage_getargspec_cython("def foo(x=-Infinity):\n    pass")
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-20-70637b2db91d> in <module>()
----> 1 _sage_getargspec_cython("def foo(x=-Infinity):\n    pass")

/usr/local/src/sage-git/local/lib/python2.7/site-packages/sage/misc/sageinspect.pyc in _sage_getargspec_cython(source)
   1121         keywords = '**'+keywords
   1122     return _sage_getargspec_from_ast('def dummy('+''.join(py_units)
-> 1123                                      +varargs+keywords+'): pass')
   1124 
   1125 def sage_getfile(obj):

/usr/local/src/sage-git/local/lib/python2.7/site-packages/sage/misc/sageinspect.pyc in _sage_getargspec_from_ast(source)
    913     visitor = SageArgSpecVisitor()
    914     args = [visitor.visit(a) for a in ast_args.args]
--> 915     defaults = [visitor.visit(d) for d in ast_args.defaults]
    916 
    917     return inspect.ArgSpec(args, ast_args.vararg, ast_args.kwarg,

/usr/local/src/sage-git/local/lib/python/ast.pyc in visit(self, node)
    239         method = 'visit_' + node.__class__.__name__
    240         visitor = getattr(self, method, self.generic_visit)
--> 241         return visitor(node)
    242 
    243     def generic_visit(self, node):

/usr/local/src/sage-git/local/lib/python2.7/site-packages/sage/misc/sageinspect.pyc in visit_UnaryOp(self, node)
    679             return self.visit(node.operand)
    680         if op == 'USub':
--> 681             return -self.visit(node.operand)
    682 
    683 def _grep_first_pair_of_parentheses(s):

TypeError: bad operand type for unary -: 'str'

CC: @simon-king-jena

Component: documentation

Stopgaps: #19100

Issue created by migration from https://trac.sagemath.org/ticket/18192

[jdemeyer]

comment:1

Any clue what to do with this? Ideally, we should just get the complete argument as a string (say, a default argument which is 2*(Infinity+1)). Is there a way to do this?

[jdemeyer]

Stopgaps: #19100