Struct hir::db::ConstEvalDiscriminantQuery

pub struct ConstEvalDiscriminantQuery;

Implementations

impl ConstEvalDiscriminantQuery

pub fn in_db( self, db: &dyn HirDatabase, ) -> QueryTable<'_, ConstEvalDiscriminantQuery>

Get access to extra methods pertaining to this query. You can also use it to invoke this query.

impl ConstEvalDiscriminantQuery

pub fn in_db_mut( self, db: &mut dyn HirDatabase, ) -> QueryTableMut<'_, ConstEvalDiscriminantQuery>

Like in_db, but gives access to methods for setting the value of an input. Not applicable to derived queries.

Threads, cancellation, and blocking

Mutating the value of a query cannot be done while there are still other queries executing. If you are using your database within a single thread, this is not a problem: you only have &self access to the database, but this method requires &mut self.

However, if you have used snapshot to create other threads, then attempts to set will block the current thread until those snapshots are dropped (usually when those threads complete). This also implies that if you create a snapshot but do not send it to another thread, then invoking set will deadlock.

Before blocking, the thread that is attempting to set will also set a cancellation flag. This will cause any query invocations in other threads to unwind with a Cancelled sentinel value and eventually let the set succeed once all threads have unwound past the ra_salsa invocation.

If your query implementations are performing expensive operations without invoking another query, you can also use the Runtime::unwind_if_cancelled method to check for an ongoing cancellation and bring those operations to a close, thus allowing the set to succeed. Otherwise, long-running computations may lead to “starvation”, meaning that the thread attempting to set has to wait a long, long time. =)

Trait Implementations

impl Debug for ConstEvalDiscriminantQuery

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

Formats the value using the given formatter.

impl Default for ConstEvalDiscriminantQuery

fn default() -> ConstEvalDiscriminantQuery

Returns the “default value” for a type.

impl Query for ConstEvalDiscriminantQuery

type Key = EnumVariantId

Type that you give as a parameter – for queries with zero or more than one input, this will be a tuple.

type Value = Result<i128, ConstEvalError>

What value does the query return?

type Storage = DerivedStorage<ConstEvalDiscriminantQuery>

Internal struct storing the values for the query.

const QUERY_INDEX: u16 = 8u16

A unique index identifying this query within the group.

const QUERY_NAME: &'static str = "const_eval_discriminant"

Name of the query method (e.g., foo)

fn query_storage<'a>( group_storage: &'a <ConstEvalDiscriminantQuery as QueryDb<'_>>::GroupStorage, ) -> &'a Arc<<ConstEvalDiscriminantQuery as Query>::Storage>

Extract storage for this query from the storage for its group.

fn query_storage_mut<'a>( group_storage: &'a <ConstEvalDiscriminantQuery as QueryDb<'_>>::GroupStorage, ) -> &'a Arc<<ConstEvalDiscriminantQuery as Query>::Storage>

Extract storage for this query from the storage for its group.

impl<'d> QueryDb<'d> for ConstEvalDiscriminantQuery

type DynDb = dyn HirDatabase + 'd

Dyn version of the associated trait for this query group.

type Group = HirDatabaseStorage

Associate query group struct.

type GroupStorage = HirDatabaseGroupStorage__

Generated struct that contains storage for all queries in a group.