2 files changed, 119 insertions, 106 deletions

diff --git a/crates/ra_hir_def/src/path.rs b/crates/ra_hir_def/src/path.rs
index e547b2f03..ec9d13e82 100644
--- a/crates/ra_hir_def/src/path.rs
+++ b/crates/ra_hir_def/src/path.rs
@@ -1,4 +1,5 @@
 //! A desugared representation of paths like `crate::foo` or `<Type as Trait>::bar`.
+mod lower_use;
 
 use std::{iter, sync::Arc};
 
@@ -9,7 +10,7 @@ use hir_expand::{
 };
 use ra_db::CrateId;
 use ra_syntax::{
-    ast::{self, NameOwner, TypeAscriptionOwner},
+    ast::{self, TypeAscriptionOwner},
     AstNode,
 };
 
@@ -28,8 +29,7 @@ pub struct PathSegment {
 }
 
 /// Generic arguments to a path segment (e.g. the `i32` in `Option<i32>`). This
-/// can (in the future) also include bindings of associated types, like in
-/// `Iterator<Item = Foo>`.
+/// also includes bindings of associated types, like in `Iterator<Item = Foo>`.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct GenericArgs {
     pub args: Vec<GenericArg>,
@@ -72,7 +72,7 @@ impl Path {
         mut cb: impl FnMut(Path, &ast::UseTree, bool, Option<Name>),
     ) {
         if let Some(tree) = item_src.value.use_tree() {
-            expand_use_tree(None, tree, hygiene, &mut cb);
+            lower_use::lower_use_tree(None, tree, hygiene, &mut cb);
         }
     }
 
@@ -296,108 +296,6 @@ impl From<Name> for Path {
     }
 }
 
-fn expand_use_tree(
-    prefix: Option<Path>,
-    tree: ast::UseTree,
-    hygiene: &Hygiene,
-    cb: &mut dyn FnMut(Path, &ast::UseTree, bool, Option<Name>),
-) {
-    if let Some(use_tree_list) = tree.use_tree_list() {
-        let prefix = match tree.path() {
-            // E.g. use something::{{{inner}}};
-            None => prefix,
-            // E.g. `use something::{inner}` (prefix is `None`, path is `something`)
-            // or `use something::{path::{inner::{innerer}}}` (prefix is `something::path`, path is `inner`)
-            Some(path) => match convert_path(prefix, path, hygiene) {
-                Some(it) => Some(it),
-                None => return, // FIXME: report errors somewhere
-            },
-        };
-        for child_tree in use_tree_list.use_trees() {
-            expand_use_tree(prefix.clone(), child_tree, hygiene, cb);
-        }
-    } else {
-        let alias = tree.alias().and_then(|a| a.name()).map(|a| a.as_name());
-        if let Some(ast_path) = tree.path() {
-            // Handle self in a path.
-            // E.g. `use something::{self, <...>}`
-            if ast_path.qualifier().is_none() {
-                if let Some(segment) = ast_path.segment() {
-                    if segment.kind() == Some(ast::PathSegmentKind::SelfKw) {
-                        if let Some(prefix) = prefix {
-                            cb(prefix, &tree, false, alias);
-                            return;
-                        }
-                    }
-                }
-            }
-            if let Some(path) = convert_path(prefix, ast_path, hygiene) {
-                let is_glob = tree.has_star();
-                cb(path, &tree, is_glob, alias)
-            }
-            // FIXME: report errors somewhere
-            // We get here if we do
-        }
-    }
-}
-
-fn convert_path(prefix: Option<Path>, path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
-    let prefix = if let Some(qual) = path.qualifier() {
-        Some(convert_path(prefix, qual, hygiene)?)
-    } else {
-        prefix
-    };
-
-    let segment = path.segment()?;
-    let res = match segment.kind()? {
-        ast::PathSegmentKind::Name(name_ref) => {
-            match hygiene.name_ref_to_name(name_ref) {
-                Either::Left(name) => {
-                    // no type args in use
-                    let mut res = prefix.unwrap_or_else(|| Path {
-                        kind: PathKind::Plain,
-                        segments: Vec::with_capacity(1),
-                    });
-                    res.segments.push(PathSegment {
-                        name,
-                        args_and_bindings: None, // no type args in use
-                    });
-                    res
-                }
-                Either::Right(crate_id) => {
-                    return Some(Path::from_simple_segments(
-                        PathKind::DollarCrate(crate_id),
-                        iter::empty(),
-                    ))
-                }
-            }
-        }
-        ast::PathSegmentKind::CrateKw => {
-            if prefix.is_some() {
-                return None;
-            }
-            Path::from_simple_segments(PathKind::Crate, iter::empty())
-        }
-        ast::PathSegmentKind::SelfKw => {
-            if prefix.is_some() {
-                return None;
-            }
-            Path::from_simple_segments(PathKind::Self_, iter::empty())
-        }
-        ast::PathSegmentKind::SuperKw => {
-            if prefix.is_some() {
-                return None;
-            }
-            Path::from_simple_segments(PathKind::Super, iter::empty())
-        }
-        ast::PathSegmentKind::Type { .. } => {
-            // not allowed in imports
-            return None;
-        }
-    };
-    Some(res)
-}
-
 pub mod known {
     use hir_expand::name;
 
diff --git a/crates/ra_hir_def/src/path/lower_use.rs b/crates/ra_hir_def/src/path/lower_use.rs
new file mode 100644
index 000000000..e2e1f716d
--- /dev/null
+++ b/crates/ra_hir_def/src/path/lower_use.rs
@@ -0,0 +1,115 @@
+//! Lowers a single complex use like `use foo::{bar, baz};` into a list of paths like
+//! `foo::bar`, `foo::baz`;
+
+use std::iter;
+
+use either::Either;
+use hir_expand::{
+    hygiene::Hygiene,
+    name::{AsName, Name},
+};
+use ra_syntax::ast::{self, NameOwner};
+
+use crate::path::{Path, PathKind, PathSegment};
+
+pub(crate) fn lower_use_tree(
+    prefix: Option<Path>,
+    tree: ast::UseTree,
+    hygiene: &Hygiene,
+    cb: &mut dyn FnMut(Path, &ast::UseTree, bool, Option<Name>),
+) {
+    if let Some(use_tree_list) = tree.use_tree_list() {
+        let prefix = match tree.path() {
+            // E.g. use something::{{{inner}}};
+            None => prefix,
+            // E.g. `use something::{inner}` (prefix is `None`, path is `something`)
+            // or `use something::{path::{inner::{innerer}}}` (prefix is `something::path`, path is `inner`)
+            Some(path) => match convert_path(prefix, path, hygiene) {
+                Some(it) => Some(it),
+                None => return, // FIXME: report errors somewhere
+            },
+        };
+        for child_tree in use_tree_list.use_trees() {
+            lower_use_tree(prefix.clone(), child_tree, hygiene, cb);
+        }
+    } else {
+        let alias = tree.alias().and_then(|a| a.name()).map(|a| a.as_name());
+        if let Some(ast_path) = tree.path() {
+            // Handle self in a path.
+            // E.g. `use something::{self, <...>}`
+            if ast_path.qualifier().is_none() {
+                if let Some(segment) = ast_path.segment() {
+                    if segment.kind() == Some(ast::PathSegmentKind::SelfKw) {
+                        if let Some(prefix) = prefix {
+                            cb(prefix, &tree, false, alias);
+                            return;
+                        }
+                    }
+                }
+            }
+            if let Some(path) = convert_path(prefix, ast_path, hygiene) {
+                let is_glob = tree.has_star();
+                cb(path, &tree, is_glob, alias)
+            }
+            // FIXME: report errors somewhere
+            // We get here if we do
+        }
+    }
+}
+
+fn convert_path(prefix: Option<Path>, path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
+    let prefix = if let Some(qual) = path.qualifier() {
+        Some(convert_path(prefix, qual, hygiene)?)
+    } else {
+        prefix
+    };
+
+    let segment = path.segment()?;
+    let res = match segment.kind()? {
+        ast::PathSegmentKind::Name(name_ref) => {
+            match hygiene.name_ref_to_name(name_ref) {
+                Either::Left(name) => {
+                    // no type args in use
+                    let mut res = prefix.unwrap_or_else(|| Path {
+                        kind: PathKind::Plain,
+                        segments: Vec::with_capacity(1),
+                    });
+                    res.segments.push(PathSegment {
+                        name,
+                        args_and_bindings: None, // no type args in use
+                    });
+                    res
+                }
+                Either::Right(crate_id) => {
+                    return Some(Path::from_simple_segments(
+                        PathKind::DollarCrate(crate_id),
+                        iter::empty(),
+                    ))
+                }
+            }
+        }
+        ast::PathSegmentKind::CrateKw => {
+            if prefix.is_some() {
+                return None;
+            }
+            Path::from_simple_segments(PathKind::Crate, iter::empty())
+        }
+        ast::PathSegmentKind::SelfKw => {
+            if prefix.is_some() {
+                return None;
+            }
+            Path::from_simple_segments(PathKind::Self_, iter::empty())
+        }
+        ast::PathSegmentKind::SuperKw => {
+            if prefix.is_some() {
+                return None;
+            }
+            Path::from_simple_segments(PathKind::Super, iter::empty())
+        }
+        ast::PathSegmentKind::Type { .. } => {
+            // not allowed in imports
+            return None;
+        }
+    };
+    Some(res)
+}