1 files changed, 95 insertions, 0 deletions

diff --git a/crates/hir_def/src/per_ns.rs b/crates/hir_def/src/per_ns.rs
new file mode 100644
index 000000000..74665c588
--- /dev/null
+++ b/crates/hir_def/src/per_ns.rs
@@ -0,0 +1,95 @@
+//! In rust, it is possible to have a value, a type and a macro with the same
+//! name without conflicts.
+//!
+//! `PerNs` (per namespace) captures this.
+
+use hir_expand::MacroDefId;
+
+use crate::{item_scope::ItemInNs, visibility::Visibility, ModuleDefId};
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub struct PerNs {
+    pub types: Option<(ModuleDefId, Visibility)>,
+    pub values: Option<(ModuleDefId, Visibility)>,
+    pub macros: Option<(MacroDefId, Visibility)>,
+}
+
+impl Default for PerNs {
+    fn default() -> Self {
+        PerNs { types: None, values: None, macros: None }
+    }
+}
+
+impl PerNs {
+    pub fn none() -> PerNs {
+        PerNs { types: None, values: None, macros: None }
+    }
+
+    pub fn values(t: ModuleDefId, v: Visibility) -> PerNs {
+        PerNs { types: None, values: Some((t, v)), macros: None }
+    }
+
+    pub fn types(t: ModuleDefId, v: Visibility) -> PerNs {
+        PerNs { types: Some((t, v)), values: None, macros: None }
+    }
+
+    pub fn both(types: ModuleDefId, values: ModuleDefId, v: Visibility) -> PerNs {
+        PerNs { types: Some((types, v)), values: Some((values, v)), macros: None }
+    }
+
+    pub fn macros(macro_: MacroDefId, v: Visibility) -> PerNs {
+        PerNs { types: None, values: None, macros: Some((macro_, v)) }
+    }
+
+    pub fn is_none(&self) -> bool {
+        self.types.is_none() && self.values.is_none() && self.macros.is_none()
+    }
+
+    pub fn take_types(self) -> Option<ModuleDefId> {
+        self.types.map(|it| it.0)
+    }
+
+    pub fn take_types_vis(self) -> Option<(ModuleDefId, Visibility)> {
+        self.types
+    }
+
+    pub fn take_values(self) -> Option<ModuleDefId> {
+        self.values.map(|it| it.0)
+    }
+
+    pub fn take_macros(self) -> Option<MacroDefId> {
+        self.macros.map(|it| it.0)
+    }
+
+    pub fn filter_visibility(self, mut f: impl FnMut(Visibility) -> bool) -> PerNs {
+        PerNs {
+            types: self.types.filter(|(_, v)| f(*v)),
+            values: self.values.filter(|(_, v)| f(*v)),
+            macros: self.macros.filter(|(_, v)| f(*v)),
+        }
+    }
+
+    pub fn with_visibility(self, vis: Visibility) -> PerNs {
+        PerNs {
+            types: self.types.map(|(it, _)| (it, vis)),
+            values: self.values.map(|(it, _)| (it, vis)),
+            macros: self.macros.map(|(it, _)| (it, vis)),
+        }
+    }
+
+    pub fn or(self, other: PerNs) -> PerNs {
+        PerNs {
+            types: self.types.or(other.types),
+            values: self.values.or(other.values),
+            macros: self.macros.or(other.macros),
+        }
+    }
+
+    pub fn iter_items(self) -> impl Iterator<Item = ItemInNs> {
+        self.types
+            .map(|it| ItemInNs::Types(it.0))
+            .into_iter()
+            .chain(self.values.map(|it| ItemInNs::Values(it.0)).into_iter())
+            .chain(self.macros.map(|it| ItemInNs::Macros(it.0)).into_iter())
+    }
+}