c++ MAINTENANCE use bool return type (#1255)

diff --git a/swig/cpp/src/Tree_Data.hpp b/swig/cpp/src/Tree_Data.hpp
index 03042f6..0f4d405 100644
--- a/swig/cpp/src/Tree_Data.hpp
+++ b/swig/cpp/src/Tree_Data.hpp
@@ -58,7 +58,7 @@
     /** get bit variable from [lyd_val](@ref lyd_val)*/
     std::vector<S_Type_Bit> bit();
     /** get bln variable from [lyd_val](@ref lyd_val)*/
-    int8_t bln() {return LY_TYPE_BOOL == value_type ? value.bln : throw "wrong type";};
+    bool bln() {return LY_TYPE_BOOL == value_type ? value.bln : throw "wrong type";};
     /** get dec64 variable from [lyd_val](@ref lyd_val)*/
     Decimal64 dec64() {return LY_TYPE_DEC64 == value_type ? Decimal64{ value.dec64, type->info.dec64.dig } : throw "wrong type";};
     /** get enm variable from [lyd_val](@ref lyd_val)*/