Fix for nested subroutines and if statements in subroutines (#53)

* Fix for nested subroutines and if statements in subroutines

* Also autodeclare

Author: PhilReinhold

oqpy/subroutines.py

@@ -97,6 +97,8 @@ def wrapper(
         for input_val in inputs.values():
             inner_prog._mark_var_declared(input_val)
         output = func(inner_prog, **inputs)
+        inner_prog.autodeclare()
+        inner_prog._state.finalize_if_clause()
         body = inner_prog._state.body
         if isinstance(output, OQPyExpression):
             return_type = output.type
@@ -115,6 +117,9 @@ def wrapper(
             raise ValueError(
                 "Output type of subroutine {name} was neither oqpy expression nor None."
             )
+        program.defcals.update(inner_prog.defcals)
+        program.subroutines.update(inner_prog.subroutines)
+        program.externs.update(inner_prog.externs)
         stmt = ast.SubroutineDefinition(
             identifier,
             arguments=arguments,

tests/test_directives.py

@@ -1999,3 +1999,41 @@ def test_io_declaration():
     ).strip()
     assert prog.to_qasm() == expected
     _check_respects_type_hints(prog)
+
+
+def test_nested_subroutines():
+    @oqpy.subroutine
+    def f(prog: oqpy.Program) -> oqpy.IntVar:
+        i = oqpy.IntVar(name="i", init_expression=1)
+        with oqpy.If(prog, i == 1):
+            prog.increment(i, 1)
+        return i
+
+    @oqpy.subroutine
+    def g(prog: oqpy.Program) -> oqpy.IntVar:
+        return f(prog)
+
+
+    prog = oqpy.Program()
+    x = oqpy.IntVar(name="x")
+    prog.set(x, g(prog))
+
+    expected = textwrap.dedent(
+        """
+        OPENQASM 3.0;
+        def f() -> int[32] {
+            int[32] i = 1;
+            if (i == 1) {
+                i += 1;
+            }
+            return i;
+        }
+        def g() -> int[32] {
+            return f();
+        }
+        int[32] x;
+        x = g();
+        """
+    ).strip()
+
+    assert prog.to_qasm() == expected