The pipeline is finally reasonably clean

src/pipeline/dealias/alias_cache.rs

@@ -0,0 +1,59 @@
+use std::slice;
+
+use chumsky::primitive::Container;
+use hashbrown::HashMap;
+
+use crate::representations::project::{ProjectMod, ItemKind, ProjectEntry};
+use crate::tree::ModMember;
+use crate::utils::{pushed, unwrap_or};
+use crate::{ProjectTree, VName, Tok, NameLike};
+
+use super::walk_with_links::{walk_with_links, Target};
+
+pub struct AliasCache {
+  data: HashMap<Vec<Tok<String>>, Option<Vec<Tok<String>>>>,
+}
+impl AliasCache {
+  pub fn new() -> Self {
+    Self { data: HashMap::new() }
+  }
+
+  /// Finds the absolute nsname corresponding to the given name in the given
+  /// context, if it's imported. If the name is defined locally, returns None
+  /// to avoid allocating several vectors for every local variable.
+  pub fn resolv_name<'a>(
+    &'a mut self,
+    root: &ProjectMod<VName>,
+    location: &[Tok<String>],
+    name: Tok<String>
+  ) -> Option<&'a [Tok<String>]> {
+    let full_path = pushed(location, name);
+    if let Some(result) = self.data.get(&full_path) {
+      return result.as_deref();
+    }
+    let (ent, finalp) = walk_with_links(root, location.iter().cloned())
+      .expect("This path should be valid");
+    let m = unwrap_or!{ent => Target::Mod; panic!("Must be a module")};
+    let result = m.extra.imports_from.get(&name).map(|next| {
+      self.resolv_name(root, &next, name).unwrap_or(&next)
+    });
+    self.data.insert(full_path, result.map(|s| s.to_vec()));
+    return result;
+  }
+
+  /// Find the absolute target of a 
+  pub fn resolv_vec<'a>(
+    &'a mut self,
+    root: &ProjectMod<VName>,
+    modname: &[Tok<String>],
+    vname: &[Tok<String>],
+  ) -> Option<&'a [Tok<String>]> {
+    let (name, ns) = vname.split_last().expect("name cannot be empty");
+    if ns.is_empty() {
+      self.resolv_name(modname, name)
+    } else {
+      let origin = self.resolv_vec(modname, ns)?;
+      self.resolv_name(origin, name)
+    }
+  }
+}