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/**

* @name Useless null check

* @description Checking whether an expression is null when that expression cannot

* possibly be null is useless.

* @kind problem

* @problem.severity warning

* @precision very-high

* @id java/useless-null-check

* @tags quality

* maintainability

* useless-code

* external/cwe/cwe-561

*/

import java

import semmle.code.java.dataflow.NullGuards

import semmle.code.java.controlflow.Guards

from Expr guard, Expr e, Expr reason, string msg

where

guardSuggestsExprMaybeNull(guard, e) and

e = clearlyNotNullExpr(reason) and

(

if reason = directNullGuard(_, _, _)

then msg = "This check is useless. $@ cannot be null at this check, since it is guarded by $@."

else

if reason != e

then

msg = "This check is useless. $@ cannot be null at this check, since $@ always is non-null."

else msg = "This check is useless, since $@ always is non-null."

)

select guard, msg, e, e.toString(), reason, reason.toString()