Fix/ Statement copying in functions and added loop limit in for loops (#223)

* update visitor.py

replaced deepcopy with shallow copy for function statements

* update visitor.py, test_loop.py

- Added max loop limit in for loop statements
- Added test cases

* update CHANGELOG.md

* Update src/pyqasm/visitor.py

* linting

---------

Co-authored-by: Harshit Gupta <[email protected]>

Author: vinayswamik

CHANGELOG.md

@@ -29,6 +29,7 @@ Types of changes:
 ### Fixed
 - Fixed multiple axes error in circuit visualization of decomposable gates in `draw` method. ([#209](https://github.com/qBraid/pyqasm/pull/210))
 - Fixed depth calculation for decomposable gates by computing depth of each constituent quantum gate.([#211](https://github.com/qBraid/pyqasm/pull/211))
+- Optimized statement copying in `_visit_function_call` with shallow-copy fallback to deepcopy and added `max_loop_iters` loop‐limit check in for loops.([#223](https://github.com/qBraid/pyqasm/pull/223))
 ### Dependencies
 
 ### Other

src/pyqasm/visitor.py

@@ -1924,6 +1924,16 @@ def _visit_forin_loop(self, statement: qasm3_ast.ForInLoop) -> list[qasm3_ast.St
                 span=statement.span,
             )
 
+        # Check if the loop range exceeds the maximum allowed iterations
+        if len(irange) > self._loop_limit:
+            raise_qasm3_error(
+                # pylint: disable-next=line-too-long
+                f"Loop range '{len(irange)-1}' exceeded max allowed '{self._loop_limit}' iterations",
+                err_type=LoopLimitExceededError,
+                error_node=statement,
+                span=statement.span,
+            )
+
         i: Optional[Variable]  # will store iteration Variable to update to loop scope
 
         result = []
@@ -2068,9 +2078,12 @@ def _visit_function_call(
         result = []
         for function_op in subroutine_def.body:
             if isinstance(function_op, qasm3_ast.ReturnStatement):
-                return_statement = copy.deepcopy(function_op)
+                return_statement = copy.copy(function_op)
                 break
-            result.extend(self.visit_statement(copy.deepcopy(function_op)))
+            try:
+                result.extend(self.visit_statement(copy.copy(function_op)))
+            except (TypeError, copy.Error):
+                result.extend(self.visit_statement(copy.deepcopy(function_op)))
 
         return_value = None
         if return_statement:

tests/qasm3/test_loop.py

@@ -20,7 +20,7 @@
 import pytest
 
 from pyqasm.entrypoint import loads
-from pyqasm.exceptions import ValidationError
+from pyqasm.exceptions import LoopLimitExceededError, ValidationError
 from tests.utils import (
     check_single_qubit_gate_op,
     check_single_qubit_rotation_op,
@@ -332,3 +332,38 @@ def test_convert_qasm3_for_loop_unsupported_type(caplog):
 
     assert "Error at line 9, column 16" in caplog.text
     assert 'for bit b in "001"' in caplog.text
+
+
+def test_for_loop_limit_exceeded():
+    """Test that exceeding the loop limit raises LoopLimitExceededError for for loops."""
+    qasm_str = """
+    OPENQASM 3.0;
+    include "stdgates.inc";
+    qubit[4] q;
+    bit[4] c;
+    
+    for int i in [0:1000] {
+        h q[0];
+    }
+    """
+    result = loads(qasm_str)
+    with pytest.raises(LoopLimitExceededError):
+        result.unroll(max_loop_iters=100)
+
+
+def test_for_loop_discrete_set_limit_exceeded():
+    """Test that exceeding the loop limit raises LoopLimitExceededError
+    for for loops with discrete sets."""
+    qasm_str = """
+    OPENQASM 3.0;
+    include "stdgates.inc";
+    qubit[4] q;
+    bit[4] c;
+    
+    for int i in {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15} {
+        h q[0];
+    }
+    """
+    result = loads(qasm_str)
+    with pytest.raises(LoopLimitExceededError):
+        result.unroll(max_loop_iters=10)