Function isNarrowingBinaryExpression

internal/binder/binder.go:2666–2684

(expr *ast.BinaryExpression)

}

func isNarrowingBinaryExpression(expr *ast.BinaryExpression) bool {
	switch expr.OperatorToken.Kind {
	case ast.KindEqualsToken, ast.KindBarBarEqualsToken, ast.KindAmpersandAmpersandEqualsToken, ast.KindQuestionQuestionEqualsToken:
		return containsNarrowableReference(expr.Left)
	case ast.KindEqualsEqualsToken, ast.KindExclamationEqualsToken, ast.KindEqualsEqualsEqualsToken, ast.KindExclamationEqualsEqualsToken:
		left := ast.SkipParentheses(expr.Left)
		right := ast.SkipParentheses(expr.Right)
		return isNarrowableOperand(left) || isNarrowableOperand(right) ||
			isNarrowingTypeOfOperands(right, left) || isNarrowingTypeOfOperands(left, right) ||
			(ast.IsBooleanLiteral(right) && isNarrowingExpression(left) || ast.IsBooleanLiteral(left) && isNarrowingExpression(right))
	case ast.KindInstanceOfKeyword:
		return isNarrowableOperand(expr.Left)
	case ast.KindInKeyword:
		return isNarrowingExpression(expr.Right)
	case ast.KindCommaToken:
		return isNarrowingExpression(expr.Right)
	}
	return false
}

func isNarrowableOperand(expr *ast.Node) bool {
	switch expr.Kind {