fix(import_granularity): do not merge aliases

Author: sivizius

Diff for: src/imports.rs

@@ -817,9 +817,18 @@ fn merge_use_trees_inner(trees: &mut Vec<UseTree>, use_tree: UseTree, merge_by:
             // tree `use_tree` should be merge.
             // In other cases `similarity` won't be used, so set it to `0` as a dummy value.
             let similarity = if merge_by == SharedPrefix::One {
+                let tree_depth = tree.path.len();
+
+                // Only merge prefixes, not leaves,
+                //   e.g. `foo::i` with `foo::i as j`.
+                let max_depth = (tree_depth == use_tree.path.len())
+                    .then_some(tree_depth - 1)
+                    .unwrap_or(usize::MAX);
+
                 tree.path
                     .iter()
                     .zip(&use_tree.path)
+                    .take(max_depth)
                     .take_while(|(a, b)| a.equal_except_alias(b))
                     .count()
             } else {

Diff for: tests/source/5131_one.rs

@@ -13,3 +13,4 @@ use bar::d::e;
 use bar::d::e as e2;
 use qux::h;
 use qux::i;
+use qux::i as j;

Diff for: tests/target/5131_one.rs

@@ -4,9 +4,9 @@ pub use foo::{x, x as x2, y};
 use {
     bar::{
         a,
-        b::{self, f, g},
+        b::{self, f, f as f2, g},
         c,
         d::{e, e as e2},
     },
-    qux::{h, i},
+    qux::{h, i, i as j},
 };