1 files changed, 341 insertions, 0 deletions

diff --git a/crates/hir_def/src/item_scope.rs b/crates/hir_def/src/item_scope.rs
new file mode 100644
index 000000000..f1e9dfd5b
--- /dev/null
+++ b/crates/hir_def/src/item_scope.rs
@@ -0,0 +1,341 @@
+//! Describes items defined or visible (ie, imported) in a certain scope.
+//! This is shared between modules and blocks.
+
+use std::collections::hash_map::Entry;
+
+use base_db::CrateId;
+use hir_expand::name::Name;
+use once_cell::sync::Lazy;
+use rustc_hash::{FxHashMap, FxHashSet};
+use test_utils::mark;
+
+use crate::{
+    db::DefDatabase, per_ns::PerNs, visibility::Visibility, AdtId, BuiltinType, HasModule, ImplId,
+    LocalModuleId, Lookup, MacroDefId, ModuleDefId, TraitId,
+};
+
+#[derive(Copy, Clone)]
+pub(crate) enum ImportType {
+    Glob,
+    Named,
+}
+
+#[derive(Debug, Default)]
+pub struct PerNsGlobImports {
+    types: FxHashSet<(LocalModuleId, Name)>,
+    values: FxHashSet<(LocalModuleId, Name)>,
+    macros: FxHashSet<(LocalModuleId, Name)>,
+}
+
+#[derive(Debug, Default, PartialEq, Eq)]
+pub struct ItemScope {
+    types: FxHashMap<Name, (ModuleDefId, Visibility)>,
+    values: FxHashMap<Name, (ModuleDefId, Visibility)>,
+    macros: FxHashMap<Name, (MacroDefId, Visibility)>,
+    unresolved: FxHashSet<Name>,
+
+    defs: Vec<ModuleDefId>,
+    impls: Vec<ImplId>,
+    /// Traits imported via `use Trait as _;`.
+    unnamed_trait_imports: FxHashMap<TraitId, Visibility>,
+    /// Macros visible in current module in legacy textual scope
+    ///
+    /// For macros invoked by an unqualified identifier like `bar!()`, `legacy_macros` will be searched in first.
+    /// If it yields no result, then it turns to module scoped `macros`.
+    /// It macros with name qualified with a path like `crate::foo::bar!()`, `legacy_macros` will be skipped,
+    /// and only normal scoped `macros` will be searched in.
+    ///
+    /// Note that this automatically inherit macros defined textually before the definition of module itself.
+    ///
+    /// Module scoped macros will be inserted into `items` instead of here.
+    // FIXME: Macro shadowing in one module is not properly handled. Non-item place macros will
+    // be all resolved to the last one defined if shadowing happens.
+    legacy_macros: FxHashMap<Name, MacroDefId>,
+}
+
+pub(crate) static BUILTIN_SCOPE: Lazy<FxHashMap<Name, PerNs>> = Lazy::new(|| {
+    BuiltinType::ALL
+        .iter()
+        .map(|(name, ty)| (name.clone(), PerNs::types(ty.clone().into(), Visibility::Public)))
+        .collect()
+});
+
+/// Shadow mode for builtin type which can be shadowed by module.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub(crate) enum BuiltinShadowMode {
+    /// Prefer user-defined modules (or other types) over builtins.
+    Module,
+    /// Prefer builtins over user-defined modules (but not other types).
+    Other,
+}
+
+/// Legacy macros can only be accessed through special methods like `get_legacy_macros`.
+/// Other methods will only resolve values, types and module scoped macros only.
+impl ItemScope {
+    pub fn entries<'a>(&'a self) -> impl Iterator<Item = (&'a Name, PerNs)> + 'a {
+        // FIXME: shadowing
+        let keys: FxHashSet<_> = self
+            .types
+            .keys()
+            .chain(self.values.keys())
+            .chain(self.macros.keys())
+            .chain(self.unresolved.iter())
+            .collect();
+
+        keys.into_iter().map(move |name| (name, self.get(name)))
+    }
+
+    pub fn declarations(&self) -> impl Iterator<Item = ModuleDefId> + '_ {
+        self.defs.iter().copied()
+    }
+
+    pub fn impls(&self) -> impl Iterator<Item = ImplId> + ExactSizeIterator + '_ {
+        self.impls.iter().copied()
+    }
+
+    pub fn visibility_of(&self, def: ModuleDefId) -> Option<Visibility> {
+        self.name_of(ItemInNs::Types(def))
+            .or_else(|| self.name_of(ItemInNs::Values(def)))
+            .map(|(_, v)| v)
+    }
+
+    /// Iterate over all module scoped macros
+    pub(crate) fn macros<'a>(&'a self) -> impl Iterator<Item = (&'a Name, MacroDefId)> + 'a {
+        self.entries().filter_map(|(name, def)| def.take_macros().map(|macro_| (name, macro_)))
+    }
+
+    /// Iterate over all legacy textual scoped macros visible at the end of the module
+    pub(crate) fn legacy_macros<'a>(&'a self) -> impl Iterator<Item = (&'a Name, MacroDefId)> + 'a {
+        self.legacy_macros.iter().map(|(name, def)| (name, *def))
+    }
+
+    /// Get a name from current module scope, legacy macros are not included
+    pub(crate) fn get(&self, name: &Name) -> PerNs {
+        PerNs {
+            types: self.types.get(name).copied(),
+            values: self.values.get(name).copied(),
+            macros: self.macros.get(name).copied(),
+        }
+    }
+
+    pub(crate) fn name_of(&self, item: ItemInNs) -> Option<(&Name, Visibility)> {
+        for (name, per_ns) in self.entries() {
+            if let Some(vis) = item.match_with(per_ns) {
+                return Some((name, vis));
+            }
+        }
+        None
+    }
+
+    pub(crate) fn traits<'a>(&'a self) -> impl Iterator<Item = TraitId> + 'a {
+        self.types
+            .values()
+            .filter_map(|(def, _)| match def {
+                ModuleDefId::TraitId(t) => Some(*t),
+                _ => None,
+            })
+            .chain(self.unnamed_trait_imports.keys().copied())
+    }
+
+    pub(crate) fn define_def(&mut self, def: ModuleDefId) {
+        self.defs.push(def)
+    }
+
+    pub(crate) fn get_legacy_macro(&self, name: &Name) -> Option<MacroDefId> {
+        self.legacy_macros.get(name).copied()
+    }
+
+    pub(crate) fn define_impl(&mut self, imp: ImplId) {
+        self.impls.push(imp)
+    }
+
+    pub(crate) fn define_legacy_macro(&mut self, name: Name, mac: MacroDefId) {
+        self.legacy_macros.insert(name, mac);
+    }
+
+    pub(crate) fn unnamed_trait_vis(&self, tr: TraitId) -> Option<Visibility> {
+        self.unnamed_trait_imports.get(&tr).copied()
+    }
+
+    pub(crate) fn push_unnamed_trait(&mut self, tr: TraitId, vis: Visibility) {
+        self.unnamed_trait_imports.insert(tr, vis);
+    }
+
+    pub(crate) fn push_res(&mut self, name: Name, def: PerNs) -> bool {
+        let mut changed = false;
+
+        if let Some(types) = def.types {
+            self.types.entry(name.clone()).or_insert_with(|| {
+                changed = true;
+                types
+            });
+        }
+        if let Some(values) = def.values {
+            self.values.entry(name.clone()).or_insert_with(|| {
+                changed = true;
+                values
+            });
+        }
+        if let Some(macros) = def.macros {
+            self.macros.entry(name.clone()).or_insert_with(|| {
+                changed = true;
+                macros
+            });
+        }
+
+        if def.is_none() {
+            if self.unresolved.insert(name) {
+                changed = true;
+            }
+        }
+
+        changed
+    }
+
+    pub(crate) fn push_res_with_import(
+        &mut self,
+        glob_imports: &mut PerNsGlobImports,
+        lookup: (LocalModuleId, Name),
+        def: PerNs,
+        def_import_type: ImportType,
+    ) -> bool {
+        let mut changed = false;
+
+        macro_rules! check_changed {
+            (
+                $changed:ident,
+                ( $this:ident / $def:ident ) . $field:ident,
+                $glob_imports:ident [ $lookup:ident ],
+                $def_import_type:ident
+            ) => {{
+                let existing = $this.$field.entry($lookup.1.clone());
+                match (existing, $def.$field) {
+                    (Entry::Vacant(entry), Some(_)) => {
+                        match $def_import_type {
+                            ImportType::Glob => {
+                                $glob_imports.$field.insert($lookup.clone());
+                            }
+                            ImportType::Named => {
+                                $glob_imports.$field.remove(&$lookup);
+                            }
+                        }
+
+                        if let Some(fld) = $def.$field {
+                            entry.insert(fld);
+                        }
+                        $changed = true;
+                    }
+                    (Entry::Occupied(mut entry), Some(_))
+                        if $glob_imports.$field.contains(&$lookup)
+                            && matches!($def_import_type, ImportType::Named) =>
+                    {
+                        mark::hit!(import_shadowed);
+                        $glob_imports.$field.remove(&$lookup);
+                        if let Some(fld) = $def.$field {
+                            entry.insert(fld);
+                        }
+                        $changed = true;
+                    }
+                    _ => {}
+                }
+            }};
+        }
+
+        check_changed!(changed, (self / def).types, glob_imports[lookup], def_import_type);
+        check_changed!(changed, (self / def).values, glob_imports[lookup], def_import_type);
+        check_changed!(changed, (self / def).macros, glob_imports[lookup], def_import_type);
+
+        if def.is_none() {
+            if self.unresolved.insert(lookup.1) {
+                changed = true;
+            }
+        }
+
+        changed
+    }
+
+    pub(crate) fn resolutions<'a>(&'a self) -> impl Iterator<Item = (Option<Name>, PerNs)> + 'a {
+        self.entries().map(|(name, res)| (Some(name.clone()), res)).chain(
+            self.unnamed_trait_imports
+                .iter()
+                .map(|(tr, vis)| (None, PerNs::types(ModuleDefId::TraitId(*tr), *vis))),
+        )
+    }
+
+    pub(crate) fn collect_legacy_macros(&self) -> FxHashMap<Name, MacroDefId> {
+        self.legacy_macros.clone()
+    }
+}
+
+impl PerNs {
+    pub(crate) fn from_def(def: ModuleDefId, v: Visibility, has_constructor: bool) -> PerNs {
+        match def {
+            ModuleDefId::ModuleId(_) => PerNs::types(def, v),
+            ModuleDefId::FunctionId(_) => PerNs::values(def, v),
+            ModuleDefId::AdtId(adt) => match adt {
+                AdtId::UnionId(_) => PerNs::types(def, v),
+                AdtId::EnumId(_) => PerNs::types(def, v),
+                AdtId::StructId(_) => {
+                    if has_constructor {
+                        PerNs::both(def, def, v)
+                    } else {
+                        PerNs::types(def, v)
+                    }
+                }
+            },
+            ModuleDefId::EnumVariantId(_) => PerNs::both(def, def, v),
+            ModuleDefId::ConstId(_) | ModuleDefId::StaticId(_) => PerNs::values(def, v),
+            ModuleDefId::TraitId(_) => PerNs::types(def, v),
+            ModuleDefId::TypeAliasId(_) => PerNs::types(def, v),
+            ModuleDefId::BuiltinType(_) => PerNs::types(def, v),
+        }
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
+pub enum ItemInNs {
+    Types(ModuleDefId),
+    Values(ModuleDefId),
+    Macros(MacroDefId),
+}
+
+impl ItemInNs {
+    fn match_with(self, per_ns: PerNs) -> Option<Visibility> {
+        match self {
+            ItemInNs::Types(def) => {
+                per_ns.types.filter(|(other_def, _)| *other_def == def).map(|(_, vis)| vis)
+            }
+            ItemInNs::Values(def) => {
+                per_ns.values.filter(|(other_def, _)| *other_def == def).map(|(_, vis)| vis)
+            }
+            ItemInNs::Macros(def) => {
+                per_ns.macros.filter(|(other_def, _)| *other_def == def).map(|(_, vis)| vis)
+            }
+        }
+    }
+
+    pub fn as_module_def_id(self) -> Option<ModuleDefId> {
+        match self {
+            ItemInNs::Types(id) | ItemInNs::Values(id) => Some(id),
+            ItemInNs::Macros(_) => None,
+        }
+    }
+
+    /// Returns the crate defining this item (or `None` if `self` is built-in).
+    pub fn krate(&self, db: &dyn DefDatabase) -> Option<CrateId> {
+        Some(match self {
+            ItemInNs::Types(did) | ItemInNs::Values(did) => match did {
+                ModuleDefId::ModuleId(id) => id.krate,
+                ModuleDefId::FunctionId(id) => id.lookup(db).module(db).krate,
+                ModuleDefId::AdtId(id) => id.module(db).krate,
+                ModuleDefId::EnumVariantId(id) => id.parent.lookup(db).container.module(db).krate,
+                ModuleDefId::ConstId(id) => id.lookup(db).container.module(db).krate,
+                ModuleDefId::StaticId(id) => id.lookup(db).container.module(db).krate,
+                ModuleDefId::TraitId(id) => id.lookup(db).container.module(db).krate,
+                ModuleDefId::TypeAliasId(id) => id.lookup(db).module(db).krate,
+                ModuleDefId::BuiltinType(_) => return None,
+            },
+            ItemInNs::Macros(id) => return id.krate,
+        })
+    }
+}