rust/crates/ra_hir/src/nameres.rs

//! Name resolution algorithm. The end result of the algorithm is an `ItemMap`:
//! a map which maps each module to its scope: the set of items visible in the
//! module. That is, we only resolve imports here, name resolution of item
//! bodies will be done in a separate step.
//!
//! Like Rustc, we use an interactive per-crate algorithm: we start with scopes
//! containing only directly defined items, and then iteratively resolve
//! imports.
//!
//! To make this work nicely in the IDE scenario, we place `InputModuleItems`
//! in between raw syntax and name resolution. `InputModuleItems` are computed
//! using only the module's syntax, and it is all directly defined items plus
//! imports. The plan is to make `InputModuleItems` independent of local
//! modifications (that is, typing inside a function should not change IMIs),
//! so that the results of name resolution can be preserved unless the module
//! structure itself is modified.
pub(crate) mod lower;

use crate::nameres::lower::*;

use std::sync::Arc;

use rustc_hash::{FxHashMap, FxHashSet};
use ra_db::SourceRootId;

use crate::{
    DefId, DefLoc, DefKind,
    Path, PathKind,
    HirDatabase, Crate,
    Name,
    module_tree::{ModuleId, ModuleTree},
};

/// `ItemMap` is the result of name resolution. It contains, for each
/// module, the set of visible items.
// FIXME: currenty we compute item map per source-root. We should do it per crate instead.
#[derive(Default, Debug, PartialEq, Eq)]
pub struct ItemMap {
    pub per_module: FxHashMap<ModuleId, ModuleScope>,
}

#[derive(Debug, Default, PartialEq, Eq, Clone)]
pub struct ModuleScope {
    items: FxHashMap<Name, Resolution>,
}

impl ModuleScope {
    pub fn entries<'a>(&'a self) -> impl Iterator<Item = (&'a Name, &'a Resolution)> + 'a {
        self.items.iter()
    }
    pub fn get(&self, name: &Name) -> Option<&Resolution> {
        self.items.get(name)
    }
}

/// `Resolution` is basically `DefId` atm, but it should account for stuff like
/// multiple namespaces, ambiguity and errors.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Resolution {
    /// None for unresolved
    pub def_id: PerNs<DefId>,
    /// ident by which this is imported into local scope.
    pub import: Option<ImportId>,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum Namespace {
    Types,
    Values,
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct PerNs<T> {
    pub types: Option<T>,
    pub values: Option<T>,
}

impl<T> PerNs<T> {
    pub fn none() -> PerNs<T> {
        PerNs {
            types: None,
            values: None,
        }
    }

    pub fn values(t: T) -> PerNs<T> {
        PerNs {
            types: None,
            values: Some(t),
        }
    }

    pub fn types(t: T) -> PerNs<T> {
        PerNs {
            types: Some(t),
            values: None,
        }
    }

    pub fn both(types: T, values: T) -> PerNs<T> {
        PerNs {
            types: Some(types),
            values: Some(values),
        }
    }

    pub fn is_none(&self) -> bool {
        self.types.is_none() && self.values.is_none()
    }

    pub fn take(self, namespace: Namespace) -> Option<T> {
        match namespace {
            Namespace::Types => self.types,
            Namespace::Values => self.values,
        }
    }

    pub fn take_types(self) -> Option<T> {
        self.take(Namespace::Types)
    }

    pub fn take_values(self) -> Option<T> {
        self.take(Namespace::Values)
    }

    pub fn get(&self, namespace: Namespace) -> Option<&T> {
        self.as_ref().take(namespace)
    }

    pub fn as_ref(&self) -> PerNs<&T> {
        PerNs {
            types: self.types.as_ref(),
            values: self.values.as_ref(),
        }
    }

    pub fn and_then<U>(self, f: impl Fn(T) -> Option<U>) -> PerNs<U> {
        PerNs {
            types: self.types.and_then(&f),
            values: self.values.and_then(&f),
        }
    }

    pub fn map<U>(self, f: impl Fn(T) -> U) -> PerNs<U> {
        PerNs {
            types: self.types.map(&f),
            values: self.values.map(&f),
        }
    }
}

pub(crate) struct Resolver<'a, DB> {
    db: &'a DB,
    input: &'a FxHashMap<ModuleId, Arc<LoweredModule>>,
    source_root: SourceRootId,
    module_tree: Arc<ModuleTree>,
    processed_imports: FxHashSet<(ModuleId, ImportId)>,
    result: ItemMap,
}

impl<'a, DB> Resolver<'a, DB>
where
    DB: HirDatabase,
{
    pub(crate) fn new(
        db: &'a DB,
        input: &'a FxHashMap<ModuleId, Arc<LoweredModule>>,
        source_root: SourceRootId,
        module_tree: Arc<ModuleTree>,
    ) -> Resolver<'a, DB> {
        Resolver {
            db,
            input,
            source_root,
            module_tree,
            processed_imports: FxHashSet::default(),
            result: ItemMap::default(),
        }
    }

    pub(crate) fn resolve(mut self) -> ItemMap {
        for (&module_id, items) in self.input.iter() {
            self.populate_module(module_id, Arc::clone(items));
        }

        loop {
            let processed_imports_count = self.processed_imports.len();
            for &module_id in self.input.keys() {
                self.db.check_canceled();
                self.resolve_imports(module_id);
            }
            if processed_imports_count == self.processed_imports.len() {
                // no new imports resolved
                break;
            }
        }
        self.result
    }

    fn populate_module(&mut self, module_id: ModuleId, input: Arc<LoweredModule>) {
        let mut module_items = ModuleScope::default();

        // Populate extern crates prelude
        {
            let root_id = module_id.crate_root(&self.module_tree);
            let file_id = root_id.source(&self.module_tree).file_id;
            let crate_graph = self.db.crate_graph();
            if let Some(crate_id) = crate_graph.crate_id_for_crate_root(file_id.as_original_file())
            {
                let krate = Crate::new(crate_id);
                for dep in krate.dependencies(self.db) {
                    if let Some(module) = dep.krate.root_module(self.db) {
                        let def_id = module.def_id;
                        self.add_module_item(
                            &mut module_items,
                            dep.name.clone(),
                            PerNs::types(def_id),
                        );
                    }
                }
            };
        }
        for (import_id, import_data) in input.imports.iter() {
            if let Some(segment) = import_data.path.segments.iter().last() {
                if !import_data.is_glob {
                    module_items.items.insert(
                        segment.name.clone(),
                        Resolution {
                            def_id: PerNs::none(),
                            import: Some(import_id),
                        },
                    );
                }
            }
        }
        // Populate explicitly declared items, except modules
        for (name, &def_id) in input.declarations.iter() {
            let resolution = Resolution {
                def_id,
                import: None,
            };
            module_items.items.insert(name.clone(), resolution);
        }

        // Populate modules
        for (name, module_id) in module_id.children(&self.module_tree) {
            let def_loc = DefLoc {
                kind: DefKind::Module,
                source_root_id: self.source_root,
                module_id,
                source_item_id: module_id.source(&self.module_tree),
            };
            let def_id = def_loc.id(self.db);
            self.add_module_item(&mut module_items, name, PerNs::types(def_id));
        }

        self.result.per_module.insert(module_id, module_items);
    }

    fn add_module_item(&self, module_items: &mut ModuleScope, name: Name, def_id: PerNs<DefId>) {
        let resolution = Resolution {
            def_id,
            import: None,
        };
        module_items.items.insert(name, resolution);
    }

    fn resolve_imports(&mut self, module_id: ModuleId) {
        for (import_id, import_data) in self.input[&module_id].imports.iter() {
            if self.processed_imports.contains(&(module_id, import_id)) {
                // already done
                continue;
            }
            if self.resolve_import(module_id, import_id, import_data) {
                log::debug!("import {:?} resolved (or definite error)", import_id);
                self.processed_imports.insert((module_id, import_id));
            }
        }
    }

    fn resolve_import(
        &mut self,
        module_id: ModuleId,
        import_id: ImportId,
        import: &ImportData,
    ) -> bool {
        log::debug!("resolving import: {:?}", import);
        if import.is_glob {
            return false;
        };

        let mut curr: ModuleId = match import.path.kind {
            PathKind::Plain | PathKind::Self_ => module_id,
            PathKind::Super => {
                match module_id.parent(&self.module_tree) {
                    Some(it) => it,
                    None => {
                        // TODO: error
                        log::debug!("super path in root module");
                        return true; // this can't suddenly resolve if we just resolve some other imports
                    }
                }
            }
            PathKind::Crate => module_id.crate_root(&self.module_tree),
            PathKind::Abs => {
                // TODO: absolute use is not supported for now
                return false;
            }
        };

        for (i, segment) in import.path.segments.iter().enumerate() {
            let is_last = i == import.path.segments.len() - 1;

            let def_id = match self.result.per_module[&curr].items.get(&segment.name) {
                Some(res) if !res.def_id.is_none() => res.def_id,
                _ => {
                    log::debug!("path segment {:?} not found", segment.name);
                    return false;
                }
            };

            if !is_last {
                let type_def_id = if let Some(d) = def_id.take(Namespace::Types) {
                    d
                } else {
                    log::debug!(
                        "path segment {:?} resolved to value only, but is not last",
                        segment.name
                    );
                    return false;
                };
                curr = match type_def_id.loc(self.db) {
                    DefLoc {
                        kind: DefKind::Module,
                        module_id: target_module_id,
                        source_root_id,
                        ..
                    } => {
                        if source_root_id == self.source_root {
                            target_module_id
                        } else {
                            let module = crate::code_model_api::Module::new(type_def_id);
                            let path = Path {
                                segments: import.path.segments[i + 1..].iter().cloned().collect(),
                                kind: PathKind::Crate,
                            };
                            log::debug!("resolving {:?} in other source root", path);
                            let def_id = module.resolve_path(self.db, &path);
                            if !def_id.is_none() {
                                let last_segment = path.segments.last().unwrap();
                                self.update(module_id, |items| {
                                    let res = Resolution {
                                        def_id,
                                        import: Some(import_id),
                                    };
                                    items.items.insert(last_segment.name.clone(), res);
                                });
                                log::debug!(
                                    "resolved import {:?} ({:?}) cross-source root to {:?}",
                                    last_segment.name,
                                    import,
                                    def_id.map(|did| did.loc(self.db))
                                );
                                return true;
                            } else {
                                log::debug!("rest of path did not resolve in other source root");
                                return true;
                            }
                        }
                    }
                    _ => {
                        log::debug!(
                            "path segment {:?} resolved to non-module {:?}, but is not last",
                            segment.name,
                            type_def_id.loc(self.db)
                        );
                        return true; // this resolved to a non-module, so the path won't ever resolve
                    }
                }
            } else {
                log::debug!(
                    "resolved import {:?} ({:?}) within source root to {:?}",
                    segment.name,
                    import,
                    def_id.map(|did| did.loc(self.db))
                );
                self.update(module_id, |items| {
                    let res = Resolution {
                        def_id,
                        import: Some(import_id),
                    };
                    items.items.insert(segment.name.clone(), res);
                })
            }
        }
        true
    }

    fn update(&mut self, module_id: ModuleId, f: impl FnOnce(&mut ModuleScope)) {
        let module_items = self.result.per_module.get_mut(&module_id).unwrap();
        f(module_items)
    }
}

#[cfg(test)]
mod tests;