Fix for dynamic array operations

slither/tools/mutator/mutators/AOR.py

@@ -2,7 +2,12 @@
 from slither.slithir.operations import Binary, BinaryType
 from slither.tools.mutator.utils.patch import create_patch_with_line
 from slither.tools.mutator.mutators.abstract_mutator import AbstractMutator
+from slither.core.variables.variable import Variable
 from slither.core.expressions.unary_operation import UnaryOperation
+from slither.core.expressions.call_expression import CallExpression
+from slither.core.expressions.member_access import MemberAccess
+from slither.core.expressions.identifier import Identifier
+from slither.core.solidity_types.array_type import ArrayType
 
 arithmetic_operators = [
     BinaryType.ADDITION,
@@ -27,7 +32,39 @@ def _mutate(self) -> Dict:
                     ir_expression = node.expression
                 except:  # pylint: disable=bare-except
                     continue
-                for ir in node.irs:
+
+                # Special cases handling .push and .pop on dynamic arrays.
+                # The IR for these operations has a binary operation due to internal conversion
+                # (see convert_to_push and convert_to_pop in slithir/convert.py)
+                # however it's not present in the source code and should not be mutated.
+                # pylint: disable=too-many-boolean-expressions
+                if (
+                    isinstance(ir_expression, CallExpression)
+                    and isinstance(ir_expression.called, MemberAccess)
+                    and ir_expression.called.member_name == "pop"
+                    and isinstance(ir_expression.called.expression, Identifier)
+                    and isinstance(ir_expression.called.expression.value, Variable)
+                    and isinstance(ir_expression.called.expression.value.type, ArrayType)
+                ):
+                    continue
+
+                # For a .push instruction we skip the last 6 IR operations
+                # because they are fixed based on the internal conversion to the IR
+                # while we need to look at the preceding instructions because
+                # they might contain Binary IR to be mutated.
+                # For example for a.push(3+x) it's correct to mutate 3+x.
+                irs = (
+                    node.irs[:-6]
+                    if isinstance(ir_expression, CallExpression)
+                    and isinstance(ir_expression.called, MemberAccess)
+                    and ir_expression.called.member_name == "push"
+                    and isinstance(ir_expression.called.expression, Identifier)
+                    and isinstance(ir_expression.called.expression.value, Variable)
+                    and isinstance(ir_expression.called.expression.value.type, ArrayType)
+                    else node.irs
+                )
+
+                for ir in irs:
                     if isinstance(ir, Binary) and ir.type in arithmetic_operators:
                         if isinstance(ir_expression, UnaryOperation):
                             continue