Struct rslint_core::groups::errors::UseIsnan

pub struct UseIsnan {
    pub enforce_for_switch_case: bool,
    pub enforce_for_index_of: bool,
}

Disallow incorrect comparisons against NaN.

NaN is a special Number value used to represent "not a number" results in calculations. This value is specified in the IEEE Standard for Binary Floating-Point-Arithmetic.

In JavaScript, NaN is unique, it is not equal to anything, including itself! therefore any comparisons to it will either always yield true or false. Therefore you should use isNaN(/* num */) instead to test if a value is NaN. This rule is aimed at removing this footgun.

Invalid Code Examples

if (foo == NaN) {
    // unreachable
}

if (NaN != NaN) {
    // always runs
}

Correct Code Examples

if (isNaN(foo)) {
    /* */
}

if (!isNaN(foo)) {
    /* */
}

Fields

enforce_for_switch_case: bool

Switch statements use === internally to match an expression, therefore switch (NaN) and case NaN will never match. This rule disables uses like that which are always incorrect (true by default)

enforce_for_index_of: bool

Index functions like indexOf and lastIndexOf use === internally, therefore matching them against NaN will always yield -1. This option disallows using indexOf(NaN) and lastIndexOf(NaN) (false by default)

Implementations

impl UseIsnan

pub fn new() -> Self

Trait Implementations

impl Clone for UseIsnan

fn clone(&self) -> UseIsnan

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl CstRule for UseIsnan

fn check_node(&self, node: &SyntaxNode, ctx: &mut RuleCtx) -> Option<()>

Check an individual node in the syntax tree. You can use the match_ast macro to make matching a node to an ast node easier. The reason this uses nodes and not a visitor is because nodes are more flexible, converting them to an AST node has zero cost and you can easily traverse surrounding nodes. Defaults to doing nothing.

fn check_token(&self, token: &SyntaxToken, ctx: &mut RuleCtx) -> Option<()>

Check an individual token in the syntax tree. Defaults to doing nothing.

fn check_root(&self, root: &SyntaxNode, ctx: &mut RuleCtx) -> Option<()>

Check the root of the tree one time. This method is guaranteed to only be called once. The root's kind will be either SCRIPT or MODULE. Defaults to doing nothing.

impl Debug for UseIsnan

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for UseIsnan

fn default() -> Self

Returns the "default value" for a type.

impl<'de> Deserialize<'de> for UseIsnan where
    UseIsnan: Default, 

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error> where
    __D: Deserializer<'de>, 

Deserialize this value from the given Serde deserializer.

impl Rule for UseIsnan

fn name(&self) -> &'static str

A unique, kebab-case name for the rule.

fn group(&self) -> &'static str

The name of the group this rule belongs to.

fn docs(&self) -> &'static str

Optional docs for the rule, an empty string by default

impl Serialize for UseIsnan

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error> where
    __S: Serializer, 

Serialize this value into the given Serde serializer.