Improve naming of delegate-typed variables.

Author: siegfriedpammer

ICSharpCode.Decompiler.Tests/TestCases/Pretty/DelegateConstruction.cs

@@ -631,21 +631,13 @@ public void M()
 					Action action = delegate {
 						list.Select((int x) => x * 2);
 					};
-#if OPT && ROSLYN
-					Action obj = delegate {
-#else
 					Action action2 = delegate {
-#endif
 						list.Select((int x) => x * 2);
 					};
 					Console.WriteLine();
 					action();
 					Console.WriteLine();
-#if OPT && ROSLYN
-					obj();
-#else
 					action2();
-#endif
 				}
 				catch (Exception)
 				{

ICSharpCode.Decompiler/IL/ILTypeExtensions.cs

@@ -238,6 +238,8 @@ public static IType InferType(this ILInstruction inst, ICompilation? compilation
 						default:
 							return SpecialType.UnknownType;
 					}
+				case ILFunction func when func.DelegateType != null:
+					return func.DelegateType;
 				default:
 					return SpecialType.UnknownType;
 			}