Add params validation for basic gates

CHANGELOG.md

@@ -50,7 +50,23 @@ barrier q3[0];
 ```
 
 ### Improved / Modified
+- Improved the error messages for the parameter mismatch errors in basic quantum gates ([#169](https://github.com/qBraid/pyqasm/issues/169)). Following error is raised on parameter count mismatch - 
 
+```python
+In [1]: import pyqasm
+   ...: 
+   ...: qasm = """
+   ...: OPENQASM 3;
+   ...: include "stdgates.inc";
+   ...: qubit[2] q;
+   ...: rx(0.5, 1) q[1];
+   ...: """
+   ...: program = pyqasm.loads(qasm)
+   ...: program.validate()
+
+......
+ValidationError: Expected 1 parameter for gate 'rx', but got 2  
+```
 ### Deprecated
 
 ### Removed

src/pyqasm/maps/gates.py

@@ -1091,6 +1091,39 @@ def two_qubit_gate_op(
     "c4x": c4x_gate,
 }
 
+PARAMS_OP_SET = {
+    1: {
+        "rx",
+        "ry",
+        "rz",
+        "phaseshift",
+        "p",
+        "gpi",
+        "gpi2",
+        "xx",
+        "rxx",
+        "yy",
+        "ryy",
+        "zz",
+        "rzz",
+        "xy",
+        "pswap",
+        "cp",
+        "cu1",
+        "crx",
+        "cry",
+        "crz",
+        "cphaseshift",
+        "cp10",
+        "cphaseshift01",
+        "cp01",
+        "cp00",
+        "cphaseshift00",
+    },
+    2: {"xx_plus_yy", "u2", "U2"},
+    3: {"ms", "cu3", "u", "U", "u3", "U3"},
+    4: {"cu"},
+}
 BASIS_GATE_MAP = {
     # default basis set is the gate set of the stdgates.inc library file
     BasisSet.DEFAULT: {
@@ -1116,6 +1149,25 @@ def two_qubit_gate_op(
 }
 
 
+def map_qasm_op_num_params(op_name: str) -> int:
+    """
+    Map a basic QASM operation to the number of parameters it takes.
+
+    Args:
+        op_name (str): The QASM operation name.
+
+    Returns:
+        int: The number of parameters the operation takes.
+
+    Raises:
+        ValidationError: If the QASM operation is unsupported or undeclared.
+    """
+    for num_params, op_set in PARAMS_OP_SET.items():
+        if op_name in op_set:
+            return num_params
+    return 0
+
+
 def map_qasm_op_to_callable(op_name: str) -> tuple[Callable, int]:
     """
     Map a QASM operation to a callable.

src/pyqasm/visitor.py

@@ -36,6 +36,7 @@
 from pyqasm.maps.gates import (
     map_qasm_ctrl_op_to_callable,
     map_qasm_inv_op_to_callable,
+    map_qasm_op_num_params,
     map_qasm_op_to_callable,
 )
 from pyqasm.subroutines import Qasm3SubroutineProcessor
@@ -769,14 +770,21 @@ def _visit_basic_gate_operation(  # pylint: disable=too-many-locals
             qasm_func, op_qubit_count, inverse_action = map_qasm_inv_op_to_callable(
                 operation.name.name
             )
-
         op_parameters = []
+        actual_num_params = map_qasm_op_num_params(operation.name.name)
 
         if len(operation.arguments) > 0:  # parametric gate
             op_parameters = self._get_op_parameters(operation)
             if inverse_action == InversionOp.INVERT_ROTATION:
                 op_parameters = [-1 * param for param in op_parameters]
 
+        if len(op_parameters) != actual_num_params:
+            raise_qasm3_error(
+                f"Expected {op_qubit_count} parameter{'s' if op_qubit_count > 1 else ''}"
+                f" for gate '{operation.name.name}', but got {len(op_parameters)}",
+                span=operation.span,
+            )
+
         result = []
         unrolled_targets = self._unroll_multiple_target_qubits(operation, op_qubit_count)
         unrolled_gate_function = partial(qasm_func, *op_parameters)

tests/qasm3/resources/gates.py

@@ -340,7 +340,7 @@ def test_fixture():
         """,
         "Unsupported / undeclared QASM operation: custom_gate",
     ),
-    "parameter_mismatch": (
+    "parameter_mismatch_1": (
         """
         OPENQASM 3;
         include "stdgates.inc";
@@ -355,6 +355,20 @@ def test_fixture():
         """,
         "Parameter count mismatch for gate custom_gate: expected 2 arguments, but got 1 instead.",
     ),
+    "parameter_mismatch_2": (
+        """
+        OPENQASM 3;
+        include "stdgates.inc";
+
+        qubit[2] q;
+
+        rx(0.5) q[1];
+
+        // too many parameters
+        rz(0.5, 0.0) q[0];
+        """,
+        "Expected 1 parameter for gate 'rz', but got 2",
+    ),
     "qubit_mismatch": (
         """
         OPENQASM 3;