fix[cartesian]: Fix @gtscript.function inlining in while loops (#…

…1669)

## Description

When calling a `@gtscript.function` from a `while` loop the
`CallInliner` responsible of inlining statements in `gtir` is missing a
`visit_While` leading to ejection of those statements to the first AST
that is parsed properly

## Requirements

- [x] All fixes and/or new features come with corresponding tests.

---------

Co-authored-by: Florian Deconinck <[email protected]>

src/gt4py/cartesian/frontend/gtscript_frontend.py

@@ -398,6 +398,10 @@ def visit_Assert(self, node: ast.Assert):
         # Assertions are removed in the AssertionChecker later.
         return node
 
+    def visit_While(self, node: ast.While):
+        node.body = self._process_stmts(node.body)
+        return node
+
     def visit_Assign(self, node: ast.Assign):
         if (
             isinstance(node.value, ast.Call)

tests/cartesian_tests/integration_tests/multi_feature_tests/test_code_generation.py

@@ -716,3 +716,28 @@ def test(out: Field[np.float64], inp: GlobalTable[F64_VEC4]):
     out = gt_storage.zeros(backend=backend, shape=(2, 2, 2), dtype=np.float64)
     test(out, inp)
     assert (out[:] == 42).all()
+
+
+@pytest.mark.parametrize("backend", ALL_BACKENDS)
+def test_function_inline_in_while(backend):
+    @gtscript.function
+    def add_42(v):
+        return v + 42
+
+    @gtscript.stencil(backend=backend)
+    def test(
+        in_field: Field[np.float64],
+        out_field: Field[np.float64],
+    ):
+        with computation(PARALLEL), interval(...):
+            count = 1
+            while count < 10:
+                sa = add_42(out_field)
+                out_field = in_field + sa
+                count = count + 1
+
+    domain = (5, 5, 2)
+    in_arr = gt_storage.ones(backend=backend, shape=domain, dtype=np.float64)
+    out_arr = gt_storage.ones(backend=backend, shape=domain, dtype=np.float64)
+    test(in_arr, out_arr)
+    assert (out_arr[:, :, :] == 388.0).all()