Apply the proposed refactoring

crates/ra_hir_def/src/find_path.rs

@@ -11,6 +11,34 @@ use hir_expand::name::{known, Name};
 
 const MAX_PATH_LEN: usize = 15;
 
+impl ModPath {
+    fn starts_with_std(&self) -> bool {
+        self.segments.first().filter(|&first_segment| first_segment == &known::std).is_some()
+    }
+
+    // When std library is present, paths starting with `std::`
+    // should be preferred over paths starting with `core::` and `alloc::`
+    fn should_start_with_std(&self) -> bool {
+        self.segments
+            .first()
+            .filter(|&first_segment| {
+                first_segment == &known::alloc || first_segment == &known::core
+            })
+            .is_some()
+    }
+
+    fn len(&self) -> usize {
+        self.segments.len()
+            + match self.kind {
+                PathKind::Plain => 0,
+                PathKind::Super(i) => i as usize,
+                PathKind::Crate => 1,
+                PathKind::Abs => 0,
+                PathKind::DollarCrate(_) => 1,
+            }
+    }
+}
+
 // FIXME: handle local items
 
 /// Find a path that can be used to refer to a certain item. This can depend on
@@ -102,7 +130,7 @@ fn find_path_inner(
     let mut best_path = None;
     let mut best_path_len = max_len;
     for (module_id, name) in importable_locations {
-        let mut new_path = match find_path_inner(
+        let mut path = match find_path_inner(
             db,
             ItemInNs::Types(ModuleDefId::ModuleId(module_id)),
             from,
@@ -111,51 +139,28 @@ fn find_path_inner(
             None => continue,
             Some(path) => path,
         };
-        new_path.segments.push(name);
+        path.segments.push(name);
 
-        if prefer_new_path(best_path_len, best_path.as_ref(), &new_path) {
-            best_path_len = path_len(&new_path);
-            best_path = Some(new_path);
-        }
+        let new_path =
+            if let Some(best_path) = best_path { select_best_path(best_path, path) } else { path };
+        best_path_len = new_path.len();
+        best_path = Some(new_path);
     }
     best_path
 }
 
-fn prefer_new_path(old_path_len: usize, old_path: Option<&ModPath>, new_path: &ModPath) -> bool {
-    match (old_path.and_then(|mod_path| mod_path.segments.first()), new_path.segments.first()) {
-        (Some(old_path_start), Some(new_path_start))
-            if old_path_start == &known::std && use_std_instead(new_path_start) =>
-        {
-            false
-        }
-        (Some(old_path_start), Some(new_path_start))
-            if new_path_start == &known::std && use_std_instead(old_path_start) =>
-        {
-            true
-        }
-        (None, Some(_)) => true,
-        (Some(_), None) => false,
-        _ => path_len(new_path) < old_path_len,
+fn select_best_path(old_path: ModPath, new_path: ModPath) -> ModPath {
+    if old_path.starts_with_std() && new_path.should_start_with_std() {
+        old_path
+    } else if new_path.starts_with_std() && old_path.should_start_with_std() {
+        new_path
+    } else if new_path.len() < old_path.len() {
+        new_path
+    } else {
+        old_path
     }
 }
 
-// When std library is present, paths starting with `std::`
-// should be preferred over paths starting with `core::` and `alloc::`
-fn use_std_instead(name: &Name) -> bool {
-    name == &known::core || name == &known::alloc
-}
-
-fn path_len(path: &ModPath) -> usize {
-    path.segments.len()
-        + match path.kind {
-            PathKind::Plain => 0,
-            PathKind::Super(i) => i as usize,
-            PathKind::Crate => 1,
-            PathKind::Abs => 0,
-            PathKind::DollarCrate(_) => 1,
-        }
-}
-
 fn find_importable_locations(
     db: &impl DefDatabase,
     item: ItemInNs,