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package rule
import (
"github.com/mgechev/revive/lint"
"go/ast"
"go/token"
)
// ConstantLogicalExprRule warns on constant logical expressions.
type ConstantLogicalExprRule struct{}
// Apply applies the rule to given file.
func (r *ConstantLogicalExprRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
var failures []lint.Failure
onFailure := func(failure lint.Failure) {
failures = append(failures, failure)
}
astFile := file.AST
w := &lintConstantLogicalExpr{astFile, onFailure}
ast.Walk(w, astFile)
return failures
}
// Name returns the rule name.
func (r *ConstantLogicalExprRule) Name() string {
return "constant-logical-expr"
}
type lintConstantLogicalExpr struct {
file *ast.File
onFailure func(lint.Failure)
}
func (w *lintConstantLogicalExpr) Visit(node ast.Node) ast.Visitor {
switch n := node.(type) {
case *ast.BinaryExpr:
if !w.isOperatorWithLogicalResult(n.Op) {
return w
}
if gofmt(n.X) != gofmt(n.Y) { // check if subexpressions are the same
return w
}
if n.Op == token.EQL {
w.newFailure(n, "expression always evaluates to true")
return w
}
if w.isInequalityOperator(n.Op) {
w.newFailure(n, "expression always evaluates to false")
return w
}
w.newFailure(n, "left and right hand-side sub-expressions are the same")
}
return w
}
func (w *lintConstantLogicalExpr) isOperatorWithLogicalResult(t token.Token) bool {
switch t {
case token.LAND, token.LOR, token.EQL, token.LSS, token.GTR, token.NEQ, token.LEQ, token.GEQ:
return true
}
return false
}
func (w *lintConstantLogicalExpr) isInequalityOperator(t token.Token) bool {
switch t {
case token.LSS, token.GTR, token.NEQ, token.LEQ, token.GEQ:
return true
}
return false
}
func (w lintConstantLogicalExpr) newFailure(node ast.Node, msg string) {
w.onFailure(lint.Failure{
Confidence: 1,
Node: node,
Category: "logic",
Failure: msg,
})
}
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