Mono.CSharp.Switch.SwitchGoverningType C# (CSharp) Method

		Expression SwitchGoverningType (ResolveContext ec, Expression expr)
		{
			TypeSpec t = expr.Type;

			if (t == TypeManager.byte_type ||
			    t == TypeManager.sbyte_type ||
			    t == TypeManager.ushort_type ||
			    t == TypeManager.short_type ||
			    t == TypeManager.uint32_type ||
			    t == TypeManager.int32_type ||
			    t == TypeManager.uint64_type ||
			    t == TypeManager.int64_type ||
			    t == TypeManager.char_type ||
			    t == TypeManager.string_type ||
			    t == TypeManager.bool_type ||
			    TypeManager.IsEnumType (t))
				return expr;

			if (allowed_types == null){
				allowed_types = new TypeSpec [] {
					TypeManager.sbyte_type,
					TypeManager.byte_type,
					TypeManager.short_type,
					TypeManager.ushort_type,
					TypeManager.int32_type,
					TypeManager.uint32_type,
					TypeManager.int64_type,
					TypeManager.uint64_type,
					TypeManager.char_type,
					TypeManager.string_type
				};
			}

			//
			// Try to find a *user* defined implicit conversion.
			//
			// If there is no implicit conversion, or if there are multiple
			// conversions, we have to report an error
			//
			Expression converted = null;
			foreach (TypeSpec tt in allowed_types){
				Expression e;
				
				e = Convert.ImplicitUserConversion (ec, expr, tt, loc);
				if (e == null)
					continue;

				//
				// Ignore over-worked ImplicitUserConversions that do
				// an implicit conversion in addition to the user conversion.
				// 
				if (!(e is UserCast))
					continue;

				if (converted != null){
					ec.Report.ExtraInformation (loc, "(Ambiguous implicit user defined conversion in previous ");
					return null;
				}

				converted = e;
			}
			return converted;
		}