refactored iroha::expected::Result

[MBoldyrev]

Signed-off-by: Mikhail Boldyrev miboldyrev@gmail.com

Description of the Change

Finally I got too tired of typing the arguments of iroha::expected::Result::match functions. Looking at its signature and docstring comment, I saw that the first matcher is for the value case, and the second - for the error. But this deduction did not happen, because both were just passed to some sort of apply_visitor, which does not care of visitors' positions. So I made a change before the visitor application, forcing the first visitor to accept value type, and the second - error type.

Benefits

saves some hair on your head. just see this:

-        auto block = getBlock(i);
-        block.match(
-            [&result](
-                expected::Value<std::unique_ptr<shared_model::interface::Block>>
-                    &v) { result.emplace_back(std::move(v.value)); },
-            [this](const expected::Error<std::string> &e) {
-              log_->error(e.error);
-            });
+        getBlock(i).match(
+            [&result](auto &&v) { result.emplace_back(std::move(v.value)); },
+            [this](const auto &e) { log_->error(e.error); });

Possible Drawbacks

Usage Examples or Tests [optional]

just use auto type in matchers. don't forget about matched Result const- and ref-qualifiers: for example, if it is an rvalue (most common case), use either auto && or const auto & argument type in your machers.

Alternate Designs [optional]