/**

* @name Comparison of identical values

* @description If the same expression occurs on both sides of a comparison

* operator, the operator is redundant, and probably indicates a mistake.

* @kind problem

* @problem.severity warning

* @id go/comparison-of-identical-expressions

* @tags quality

* reliability

* correctness

* external/cwe/cwe-570

* external/cwe/cwe-571

* @precision very-high

*/

import go

from ComparisonExpr cmp, Expr l

where

l = cmp.getLeftOperand() and

l.getGlobalValueNumber() = cmp.getRightOperand().getGlobalValueNumber() and

// allow floats, where self-comparison may be used for NaN checks

not l.getType().getUnderlyingType() instanceof FloatType and

// allow comparisons of symbolic constants to literal constants; these are often feature flags

not exists(DeclaredConstant decl |

cmp.getAnOperand() = decl.getAReference() and

cmp.getAnOperand() instanceof BasicLit

)

select cmp, "This expression compares an $@ to itself.", cmp.getLeftOperand(), "expression"