The Java® Language Specification, Java SE 7 Edition, Fourth Edition

15.12.2.8. Inferring Unresolved Type Arguments

If any of the method’s type arguments were not inferred from the types of the actual arguments, they are now inferred as follows.

• If the method result occurs in a context where it will be subject to assignment conversion (§5.2) to a type S, then let R be the declared result type of the method, and let R’ = R[T₁=B(T₁) ... T_n=B(T_n)], where B(T_i) is the type inferred for T_i in the previous section or T_i if no type was inferred.

If S is a reference type, then let S’ be S. Otherwise, if S is a primitive type, then let S’ be the result of applying boxing conversion (§5.1.7) to S.

Then, a set of initial constraints consisting of:

♦ the constraint S’ >> R’, provided R is not void; and

♦ additional constraints ...