Introduce TryFromString returning TMaybe

Позволяем писать без неиницилизированных переменных по месту использования.

Вот такую красоту например:

```
if (auto a = TryFromString<T>(str)) {
    что-то делаем с \*a
}
```

1 files changed, 31 insertions, 0 deletions

diff --git a/util/string/cast.h b/util/string/cast.h
index 90e925c194..3d94ecb0de 100644
--- a/util/string/cast.h
+++ b/util/string/cast.h
@@ -2,6 +2,7 @@
 
 #include <util/system/defaults.h>
 #include <util/stream/str.h>
+#include <util/generic/maybe.h>
 #include <util/generic/string.h>
 #include <util/generic/strbuf.h>
 #include <util/generic/typetraits.h>
@@ -270,6 +271,36 @@ inline bool TryFromString(const TUtf16String& s, T& result) {
     return TryFromString<T>(s.data(), s.size(), result);
 }
 
+template <class T, class TChar>
+inline TMaybe<T> TryFromString(TBasicStringBuf<TChar> s) {
+    TMaybe<T> result{NMaybe::TInPlace{}};
+    if (!TryFromString<T>(s, *result)) {
+        result.Clear();
+    }
+
+    return result;
+}
+
+template <class T, class TChar>
+inline TMaybe<T> TryFromString(const TChar* data) {
+    return TryFromString<T>(TBasicStringBuf<TChar>(data));
+}
+
+template <class T>
+inline TMaybe<T> TryFromString(const TString& s) {
+    return TryFromString<T>(TStringBuf(s));
+}
+
+template <class T>
+inline TMaybe<T> TryFromString(const std::string& s) {
+    return TryFromString<T>(TStringBuf(s));
+}
+
+template <class T>
+inline TMaybe<T> TryFromString(const TUtf16String& s) {
+    return TryFromString<T>(TWtringBuf(s));
+}
+
 template <class T, class TStringType>
 inline bool TryFromStringWithDefault(const TStringType& s, T& result, const T& def) {
     return TryFromString<T>(s.data(), s.size(), result, def);