1 files changed, 155 insertions, 0 deletions

diff --git a/crates/ra_hir_def/src/item_scope.rs b/crates/ra_hir_def/src/item_scope.rs
new file mode 100644
index 000000000..9e082c5f7
--- /dev/null
+++ b/crates/ra_hir_def/src/item_scope.rs
@@ -0,0 +1,155 @@
+//! Describes items defined or visible (ie, imported) in a certain scope.
+//! This is shared between modules and blocks.
+
+use hir_expand::name::Name;
+use once_cell::sync::Lazy;
+use rustc_hash::FxHashMap;
+
+use crate::{per_ns::PerNs, BuiltinType, ImplId, MacroDefId, ModuleDefId, TraitId};
+
+#[derive(Debug, Default, PartialEq, Eq)]
+pub struct ItemScope {
+    items: FxHashMap<Name, Resolution>,
+    impls: Vec<ImplId>,
+    /// 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>,
+}
+
+static BUILTIN_SCOPE: Lazy<FxHashMap<Name, Resolution>> = Lazy::new(|| {
+    BuiltinType::ALL
+        .iter()
+        .map(|(name, ty)| {
+            (name.clone(), Resolution { def: PerNs::types(ty.clone().into()), import: false })
+        })
+        .collect()
+});
+
+/// Shadow mode for builtin type which can be shadowed by module.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub(crate) enum BuiltinShadowMode {
+    // Prefer Module
+    Module,
+    // Prefer 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, &'a Resolution)> + 'a {
+        //FIXME: shadowing
+        self.items.iter().chain(BUILTIN_SCOPE.iter())
+    }
+
+    pub fn declarations(&self) -> impl Iterator<Item = ModuleDefId> + '_ {
+        self.entries()
+            .filter_map(|(_name, res)| if !res.import { Some(res.def) } else { None })
+            .flat_map(|per_ns| {
+                per_ns.take_types().into_iter().chain(per_ns.take_values().into_iter())
+            })
+    }
+
+    pub fn impls(&self) -> impl Iterator<Item = ImplId> + ExactSizeIterator + '_ {
+        self.impls.iter().copied()
+    }
+
+    /// Iterate over all module scoped macros
+    pub(crate) fn macros<'a>(&'a self) -> impl Iterator<Item = (&'a Name, MacroDefId)> + 'a {
+        self.items
+            .iter()
+            .filter_map(|(name, res)| res.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, shadow: BuiltinShadowMode) -> Option<&Resolution> {
+        match shadow {
+            BuiltinShadowMode::Module => self.items.get(name).or_else(|| BUILTIN_SCOPE.get(name)),
+            BuiltinShadowMode::Other => {
+                let item = self.items.get(name);
+                if let Some(res) = item {
+                    if let Some(ModuleDefId::ModuleId(_)) = res.def.take_types() {
+                        return BUILTIN_SCOPE.get(name).or(item);
+                    }
+                }
+
+                item.or_else(|| BUILTIN_SCOPE.get(name))
+            }
+        }
+    }
+
+    pub(crate) fn traits<'a>(&'a self) -> impl Iterator<Item = TraitId> + 'a {
+        self.items.values().filter_map(|r| match r.def.take_types() {
+            Some(ModuleDefId::TraitId(t)) => Some(t),
+            _ => None,
+        })
+    }
+
+    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 push_res(&mut self, name: Name, res: &Resolution, import: bool) -> bool {
+        let mut changed = false;
+        let existing = self.items.entry(name.clone()).or_default();
+
+        if existing.def.types.is_none() && res.def.types.is_some() {
+            existing.def.types = res.def.types;
+            existing.import = import || res.import;
+            changed = true;
+        }
+        if existing.def.values.is_none() && res.def.values.is_some() {
+            existing.def.values = res.def.values;
+            existing.import = import || res.import;
+            changed = true;
+        }
+        if existing.def.macros.is_none() && res.def.macros.is_some() {
+            existing.def.macros = res.def.macros;
+            existing.import = import || res.import;
+            changed = true;
+        }
+
+        if existing.def.is_none() && res.def.is_none() && !existing.import && res.import {
+            existing.import = res.import;
+        }
+        changed
+    }
+
+    pub(crate) fn collect_resolutions(&self) -> Vec<(Name, Resolution)> {
+        self.items.iter().map(|(name, res)| (name.clone(), res.clone())).collect()
+    }
+
+    pub(crate) fn collect_legacy_macros(&self) -> FxHashMap<Name, MacroDefId> {
+        self.legacy_macros.clone()
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Default)]
+pub struct Resolution {
+    /// None for unresolved
+    pub def: PerNs,
+    pub(crate) import: bool,
+}