TOPIC:

I have below statement which gives warning as follows:
if jObject.Get('available') = 'true' then
unit1.pas(77,33) Note: Call to subroutine "operator :=(const source:ShortString):Variant;" marked as inline is not inlined

Can anyone please explain what I am doing wrong and what it actually will be?

I think this hint can be ignored. (It is not a warning, but a hint)

It means, that a routine that was marked as inline was not compiled inline into the assembly code, but instead a call to the routine was compiled.
Routines can be marked as inline. This tells the compiler: "Please unroll the code in place to speed it up and dont call it".

However quite often the compiler decides not to unroll, because it is not possible or the compiler thinks it would be inefficient.
This hint is quite common and has no influence to the functionality, but only influence to speed and size of the code.