A Step-indexed Semantic Model of Types for the Call-by-Name Lambda   Calculus
  Step-indexed semantic models of types were proposed as an alternative to purely syntactic safety proofs using subject-reduction. Building upon the work by Appel and others, we introduce a generalized step-indexed model for the call-by-name lambda calculus. We also show how to prove type safety of general recursion in our call-by-name model. 
Benedikt Meurer
cs.PL