1 files changed, 171 insertions, 0 deletions

diff --git a/crates/hir_def/src/visibility.rs b/crates/hir_def/src/visibility.rs
new file mode 100644
index 000000000..e6e0853a3
--- /dev/null
+++ b/crates/hir_def/src/visibility.rs
@@ -0,0 +1,171 @@
+//! Defines hir-level representation of visibility (e.g. `pub` and `pub(crate)`).
+
+use hir_expand::{hygiene::Hygiene, InFile};
+use syntax::ast;
+
+use crate::{
+    db::DefDatabase,
+    nameres::CrateDefMap,
+    path::{ModPath, PathKind},
+    ModuleId,
+};
+
+/// Visibility of an item, not yet resolved.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum RawVisibility {
+    /// `pub(in module)`, `pub(crate)` or `pub(super)`. Also private, which is
+    /// equivalent to `pub(self)`.
+    Module(ModPath),
+    /// `pub`.
+    Public,
+}
+
+impl RawVisibility {
+    pub(crate) const fn private() -> RawVisibility {
+        let path = ModPath { kind: PathKind::Super(0), segments: Vec::new() };
+        RawVisibility::Module(path)
+    }
+
+    pub(crate) fn from_ast(
+        db: &dyn DefDatabase,
+        node: InFile<Option<ast::Visibility>>,
+    ) -> RawVisibility {
+        Self::from_ast_with_hygiene(node.value, &Hygiene::new(db.upcast(), node.file_id))
+    }
+
+    pub(crate) fn from_ast_with_hygiene(
+        node: Option<ast::Visibility>,
+        hygiene: &Hygiene,
+    ) -> RawVisibility {
+        Self::from_ast_with_hygiene_and_default(node, RawVisibility::private(), hygiene)
+    }
+
+    pub(crate) fn from_ast_with_hygiene_and_default(
+        node: Option<ast::Visibility>,
+        default: RawVisibility,
+        hygiene: &Hygiene,
+    ) -> RawVisibility {
+        let node = match node {
+            None => return default,
+            Some(node) => node,
+        };
+        match node.kind() {
+            ast::VisibilityKind::In(path) => {
+                let path = ModPath::from_src(path, hygiene);
+                let path = match path {
+                    None => return RawVisibility::private(),
+                    Some(path) => path,
+                };
+                RawVisibility::Module(path)
+            }
+            ast::VisibilityKind::PubCrate => {
+                let path = ModPath { kind: PathKind::Crate, segments: Vec::new() };
+                RawVisibility::Module(path)
+            }
+            ast::VisibilityKind::PubSuper => {
+                let path = ModPath { kind: PathKind::Super(1), segments: Vec::new() };
+                RawVisibility::Module(path)
+            }
+            ast::VisibilityKind::PubSelf => {
+                let path = ModPath { kind: PathKind::Plain, segments: Vec::new() };
+                RawVisibility::Module(path)
+            }
+            ast::VisibilityKind::Pub => RawVisibility::Public,
+        }
+    }
+
+    pub fn resolve(
+        &self,
+        db: &dyn DefDatabase,
+        resolver: &crate::resolver::Resolver,
+    ) -> Visibility {
+        // we fall back to public visibility (i.e. fail open) if the path can't be resolved
+        resolver.resolve_visibility(db, self).unwrap_or(Visibility::Public)
+    }
+}
+
+/// Visibility of an item, with the path resolved.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum Visibility {
+    /// Visibility is restricted to a certain module.
+    Module(ModuleId),
+    /// Visibility is unrestricted.
+    Public,
+}
+
+impl Visibility {
+    pub fn is_visible_from(self, db: &dyn DefDatabase, from_module: ModuleId) -> bool {
+        let to_module = match self {
+            Visibility::Module(m) => m,
+            Visibility::Public => return true,
+        };
+        // if they're not in the same crate, it can't be visible
+        if from_module.krate != to_module.krate {
+            return false;
+        }
+        let def_map = db.crate_def_map(from_module.krate);
+        self.is_visible_from_def_map(&def_map, from_module.local_id)
+    }
+
+    pub(crate) fn is_visible_from_other_crate(self) -> bool {
+        match self {
+            Visibility::Module(_) => false,
+            Visibility::Public => true,
+        }
+    }
+
+    pub(crate) fn is_visible_from_def_map(
+        self,
+        def_map: &CrateDefMap,
+        from_module: crate::LocalModuleId,
+    ) -> bool {
+        let to_module = match self {
+            Visibility::Module(m) => m,
+            Visibility::Public => return true,
+        };
+        // from_module needs to be a descendant of to_module
+        let mut ancestors = std::iter::successors(Some(from_module), |m| {
+            let parent_id = def_map[*m].parent?;
+            Some(parent_id)
+        });
+        ancestors.any(|m| m == to_module.local_id)
+    }
+
+    /// Returns the most permissive visibility of `self` and `other`.
+    ///
+    /// If there is no subset relation between `self` and `other`, returns `None` (ie. they're only
+    /// visible in unrelated modules).
+    pub(crate) fn max(self, other: Visibility, def_map: &CrateDefMap) -> Option<Visibility> {
+        match (self, other) {
+            (Visibility::Module(_), Visibility::Public)
+            | (Visibility::Public, Visibility::Module(_))
+            | (Visibility::Public, Visibility::Public) => Some(Visibility::Public),
+            (Visibility::Module(mod_a), Visibility::Module(mod_b)) => {
+                if mod_a.krate != mod_b.krate {
+                    return None;
+                }
+
+                let mut a_ancestors = std::iter::successors(Some(mod_a.local_id), |m| {
+                    let parent_id = def_map[*m].parent?;
+                    Some(parent_id)
+                });
+                let mut b_ancestors = std::iter::successors(Some(mod_b.local_id), |m| {
+                    let parent_id = def_map[*m].parent?;
+                    Some(parent_id)
+                });
+
+                if a_ancestors.any(|m| m == mod_b.local_id) {
+                    // B is above A
+                    return Some(Visibility::Module(mod_b));
+                }
+
+                if b_ancestors.any(|m| m == mod_a.local_id) {
+                    // A is above B
+                    return Some(Visibility::Module(mod_a));
+                }
+
+                None
+            }
+        }
+    }
+}