Details are on the PR, but in summary, I believe that the ability to pass a Complex as the abs argument is the expected behaviour (given other methods on Complex also accept Complex value as long as they are real, in the sense they have a zero imaginary part). However Complex.polar with a single argument creates the new Complex without first extracting the real part of the argument, so Complex.polar(1+0.0i).real => (1+0i)
The propose fix simply ensures that the single argument case is handled in the same way as the 2 argument case, so Complex.polar(1+0.0i).real => 1
Complex.polar accepts Complex values as arguments for the polar form as long
as the value of the complex has no imaginary part (ie it is 'real'). In f_complex_polar this is handled by extracting the real part of the arguments.
However in the case polar is called with only a single argument, the absolute
value (abs), then the Complex is created without applying a check on the type
of abs, meaning it is possible to create a Complex where the real part is itself
an instance of a Complex. This change removes the short circuit for the single
argument case meaning the real part extraction is performed correctly
(by f_complex_polar).
Also adds an example to spec/ruby/core/complex/polar_spec.rb to check that
the real part of a complex argument is correctly extracted and used in the
resulting Complex real and imaginary parts.
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