  We introduce a surgery for generalized complex manifolds whose input is a
symplectic 4-manifold containing a symplectic 2-torus with trivial normal
bundle and whose output is a 4-manifold endowed with a generalized complex
structure exhibiting type change along a 2-torus. Performing this surgery on a
K3 surface, we obtain a generalized complex structure on 3 CP^2 # 19
\overline{CP^2}, which has vanishing Seiberg-Witten invariants and hence does
not admit complex or symplectic structure.
