Add i64 type in external gate arguments

[TheGupta2012]

Follow up for #201

Summary of changes

• By default, all args in external gates were considered as double which resulted in discrepancy in the function call by pyqir
• Adds the i64 type in the external gate arguments to account for int arguments

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[Sola85]

Do I see correctly that this would create new function definitions depending on the type of the arguments? I.e.

rz(1) q[0];
rz(1.1) q[0];

would result in two definitions of the rz gate (when marked as external)?
I'm wondering whether this can have unintended consequences for people using the generated qir...

I think the best fix for #201 in particular would be to make pyqir allow implicit casts from int to double.

The more general problem might be that qbraid-qir currently does not know the intended types of external gate arguments and therefore the best it can do is guess... Meaning that there will always be edge-cases that are not handled properly (given the unavailablilty of "correct" argument types).

[TheGupta2012]

You're correct @Sola85, this fix would generate different definitions of the external gates depending on the actual arguments. We have currently fixed the parameters for all gates to be FloatLiterals when they are unrolled and thus we were using the double type in the function definitions.

Another bug which I now see is that -

rz(1) q[0];
rz(1.1) q[0];

would result in an error as rz(1.1) q[0]; will refer to the cached definition with the integer argument!

I think I'm with you where pyqir should allow implicit casts from int to double. If you wanna open an issue in pyqir, go for it otherwise I can open it later today