ExistsInsteadOfCast.ql

/**
 * @name Using exists instead of a cast
 * @description TODO
 * @kind problem
 * @problem.severity warning
 * @id ql/exists-instead-of-cast
 * @precision high
 */

import ql

from Exists ex, ComparisonFormula comp, AstNode operand, AstNode formula
where
  count(ex.getArgument(_)) = 1 and
  exists(ex.getRange()) and
  exists(ex.getFormula()) and
  comp = ex.getRange() and
  comp.getOperator() = "=" and
  comp.getAnOperand().(VarAccess).getDeclaration() = ex.getArgument(0) and
  not operand.(VarAccess).getDeclaration() = ex.getArgument(0) and
  operand = comp.getAnOperand() and
  count(VarAccess access | access.getDeclaration() = ex.getArgument(0)) = 2 and
  formula = ex.getFormula()
select ex, "This exists can be simplfied to a cast of $@ to " + ex.getArgument(0).getType().getName() + ".", operand, "the operand"