Mono.CSharp.Parameter.ResolveDefaultExpression C# (CSharp) Method

		Expression ResolveDefaultExpression (ResolveContext rc)
		{
			default_expr = default_expr.Resolve (rc);
			if (default_expr == null)
				return null;

			if (!(default_expr is Constant || default_expr is DefaultValueExpression || (default_expr is New && ((New)default_expr).IsDefaultStruct))) {
				rc.Compiler.Report.Error (1736, default_expr.Location,
					"The expression being assigned to optional parameter `{0}' must be a constant or default value",
					Name);

				return null;
			}

			if (default_expr.Type == parameter_type)
				return default_expr;

			var res = Convert.ImplicitConversionStandard (rc, default_expr, parameter_type, default_expr.Location);
			if (res != null) {
				if (TypeManager.IsNullableType (parameter_type) && res is Nullable.Wrap) {
					Nullable.Wrap wrap = (Nullable.Wrap) res;
					res = wrap.Child;
					if (!(res is Constant)) {
						rc.Compiler.Report.Error (1770, default_expr.Location,
							"The expression being assigned to nullable optional parameter `{0}' must be default value",
							Name);
						return null;
					}
				}

				if (!default_expr.IsNull && TypeManager.IsReferenceType (parameter_type) && parameter_type != TypeManager.string_type) {
					rc.Compiler.Report.Error (1763, default_expr.Location,
						"Optional parameter `{0}' of type `{1}' can only be initialized with `null'",
						Name, GetSignatureForError ());

					return null;
				}

				return res;
			}

			rc.Compiler.Report.Error (1750, Location,
				"Optional parameter expression of type `{0}' cannot be converted to parameter type `{1}'",
				TypeManager.CSharpName (default_expr.Type), GetSignatureForError ());

			return null;
		}