MB-37956: makeCollectionID/makeScopeID should use gsl::narrow<>

We currently use narrow_cast<> to cast a ManifestUid to a ScopeID or
CollectionID. But this doesn't throw if the value can't be fitted into
narrower value. So we should use gsl::narrow<> which will throw if the
value can't be fitted into the narrow value.

gsl::narrow will cast to ScopeIDType and CollectionIDType first as this
gives us the benefit of also throwing if the conversion can't be
done. Then creating a ScopeID and CollectionID object (We perform the
gsl::narrow<> to the underlying type first so that we don't need to
implement extra operators that gsl::narrow requires). Any narrowing
exceptions throw will be caught and re-thrown as an
std::invalid_argument() exception.

This issue was found as gsl::narrow_cast<> is marked noexcept in
gsl-lite 0.38.1. Which caused us to crash due to ScopeID and
CollectionID throwing in the constructor.

Change-Id: Ie220f3d80c851d1b78d39916898f2c5e8aef7e87
Reviewed-on: http://review.couchbase.org/c/kv_engine/+/154775
Reviewed-by: Dave Rigby <daver@couchbase.com>
Tested-by: Build Bot <build@couchbase.com>

engines/ep/src/collections/collections_types.h

@@ -107,7 +107,12 @@ static inline ManifestUid makeUid(const std::string& uid) {
  */
 static inline CollectionID makeCollectionID(const char* uid) {
     // CollectionID is 8 characters max and smaller than a ManifestUid
-    return gsl::narrow_cast<CollectionID>(makeUid(uid, 8));
+    try {
+        return gsl::narrow<CollectionIDType>(makeUid(uid, 8));
+    } catch (const gsl::narrowing_error& e) {
+        throw std::invalid_argument("Cannot narrow uid:'" + std::string(uid) +
+                                    "' to a CollectionID");
+    }
 }
 
 /**
@@ -127,11 +132,16 @@ static inline CollectionID makeCollectionID(const std::string& uid) {
  * A valid CollectionID is a std::string where each character satisfies
  * std::isxdigit and can be converted to a CollectionID by std::strtoul
  * @param uid C-string uid
- * @return std::invalid_argument if uid is invalid
+ * @throws std::invalid_argument if uid is invalid
  */
 static inline ScopeID makeScopeID(const char* uid) {
-    // ScopeId is 8 characters max and smaller than a ManifestUid
-    return gsl::narrow_cast<ScopeID>(makeUid(uid, 8));
+    try {
+        // ScopeId is 8 characters max and smaller than a ManifestUid
+        return gsl::narrow<ScopeIDType>(makeUid(uid, 8));
+    } catch (const gsl::narrowing_error& e) {
+        throw std::invalid_argument("Cannot narrow uid:'" + std::string(uid) +
+                                    "' to a ScopeID");
+    }
 }
 
 /**