QuakeSynthesizer cannot handle std::vector<char> argument type

[1tnguyen]

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Describe the bug

When there is a kernel argument of type std::vector<char>, QuakeSynthesizer couldn't perform the synthesis. This affects the hardware backends and remote backends (nvqc).

Steps to reproduce the bug

#include <cudaq.h>
void f(const std::vector<char>& k) __qpu__ {
  cudaq::qubit q;
  for (int i = 0; i < k.size(); ++i)
    rx(1.0*k[i], q);
}

int main() {
  std::vector<char> x { 1, 2};  
  auto counts = cudaq::sample(f, x);
  counts.dump();
  return 0;
}

Run with:

nvq++ --target quantinuum --emulate test.cpp
./a.out

Error:

loc("test.cpp":2:1): error: 'func.func' op synthesis failed for vector<integral-type>.
loc("test.cpp":2:1): error: argument(s) still in use after synthesis.
terminate called after throwing an instance of 'std::runtime_error'
  what():  Could not successfully apply quake-synth.
Aborted (core dumped)

Expected behavior

Successful synthesis.

Is this a regression? If it is, put the last known working version (or commit) here.

Not a regression

Environment

• CUDA Quantum version: main
• Python version: 3.10
• C++ compiler: gcc-12
• Operating system: Ubuntu22.04

Suggestions

No response

[schweitzpgi]

FWIW, this isn't really a valid kernel signature. The vector must be pass by value according to the spec.

void f(const std::vector<char>& k) __qpu__ { // error