law: Indian Contract Act, 1872 
  56. Agreement to do impossible act
  An agreement to do an act impossible in itself is void.
  Contract to do act afterwards becoming impossible or unlawful: A
  
  contract to do an act which, after the contract is made, becomes impossible or,
  
  by reason of some event which the promisor could not prevent, unlawful, becomes
  
  void when the act becomes impossible or unlawful.
  Compensation for loss through non-performance of act known to be
  
  impossible or unlawful: Where one person has promised to be something which he
  
  knew or, with reasonable diligence, might have known, and which the promisee
  
  did not know to be impossible or unlawful, such promisor must make compensation
  
  to such promisee for any loss which such promisee sustains through the
  
  non-performance of the promise.
   Illustrations 
  (a) A agrees with B to discover treasure by magic. The agreement
  
  is void.
  (b) A and B contract to marry each other. Before the time fixed
  
  for the marriage, A goes mad. The contract becomes void.
  (c) A contracts to marry B, being already married to C, and
  
  being forbidden by the law to which he is subject to practice polygamy. A must
  
  make compensation to B for the loss caused to her by the non-performance of his
  
  promise.
  (d) A contracts to take in cargo for B at a foreign port. A's
  
  Government afterwards declares war against the country in which the port is
  
  situated. The contract becomes void when war is declared.
  (e) A contracts to act at a theatre for six months in a
  
  consideration of a sum paid in advance by B. On several occasions A is too ill
  
  to act. The contract to act on those occasions becomes void.