C# Language Specification

Input types

If E is a method group or implicitly typed anonymous function and T is a delegate type or expression tree type then all the parameter types of T are input types of E with type T.

4. Output types

If E is a method group or an anonymous function and T is a delegate type or expression tree type then the return type of T is an output type of E with type T.

5. Dependence

An unfixed type variable X_i depends directly on an unfixed type variable X_j if for some argument E_k with type T_k X_j occurs in an input type of E_k with type T_k and X_i occurs in an output type of E_k with type T_k.

X_j depends on X_i if X_j depends directly on X_i or if X_i depends directly on X_k and X_k depends on X_j. Thus “depends on” is the transitive but not reflexive closure of “depends directly on”.

6. Output type inferences

An output type inference is made from an expression E to a type T in the following way:

• 
  If E is an anonymous function with inferred return type U (§7.5.2.12) and T is a delegate type or expression tree type with return type T_b, then a lower-bound inference (§7.5.2.9) is made from U to T_b.
  
• 
  Otherwise, if E is a method group and T is a delegate type or expression tree type with parameter types T₁…T_k and return type T_b, and overload resolution of E with the types T₁…T_k yields a single method with return type U, then a lower-bound inference is made from U to T_b.
  
• 
  Otherwise, if E is an expression with type U, then a lower-bound inference is made from U to T.
  
• 
  Otherwise, no inferences are made.
  

7. Explicit parameter type inferences

An explicit parameter type inference is made from an expression E to a type T in the following way:

• 
  If E is an explicitly typed anonymous function with parameter types U₁…U_k and T is a delegate type or expression tree type with parameter types V₁…V_k then for each U_i an exact inference (§7.5.2.8) is made from U_i to the corresponding V_i.
  

8.