TypeInference failure for copysign

Correction: copysign fails to be resolved regardless of datatypes, I think. The following code raises a RuntimeError: unable to resolve function 'copysign' with 2 given arguments:

import pyopencl as cl
import pyopencl.array as cla
import loopy as lp

ctx = cl.create_some_context()
queue = cl.CommandQueue(ctx)

n = 2

knl = lp.make_kernel(
    "{ [i]: 0<=i<n }",
    "out[i] = copysign(a[i], b[i])",
    [
        lp.GlobalArg('a', dtype='float64'),
        lp.GlobalArg('b', dtype='float64'),
        ...
    ],
    fixed_parameters=dict(n=n),

    lang_version=(2018, 2))

a = cla.zeros(queue, (n,), 'float64') + 1
b = cla.zeros(queue, (n,), 'float64') + 1

evt, (out,) = knl(queue, a=a, b=b)

Still happy to quickly fix this, but I'm not familiar with loopy's function mangling so direction would be appreciated!

Original text:

Datatype inference in LoopKernel.mangle_function fails when parsing copysign(1, x) for float-type x. The OpenCL spec requires both arguments to have the same type, but here the type of 1 is inferred to be integer (and sadly 1. as a float32).

For context, this is coming from here, but without knowing the type of the second argument to copysign I don't see how it could be fixed there. Maybe if one argument is constant, mangle_function should match its dtype to the other argument? If a proper fix is clear, I can throw together a patch (ASAP).