From 8cc1ed81dfd9e6eeb50d3621e0c862e9d3b4fe92 Mon Sep 17 00:00:00 2001
From: yukang <moorekang@gmail.com>
Date: Mon, 1 Jul 2024 13:05:23 +0800
Subject: [PATCH] Fix import suggestion error when failed not from starting

---
 compiler/rustc_resolve/src/diagnostics.rs     | 12 +++++++++-
 .../ui/imports/suggest-import-issue-120074.rs | 11 +++++++++
 .../suggest-import-issue-120074.stderr        | 23 +++++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/imports/suggest-import-issue-120074.rs
 create mode 100644 tests/ui/imports/suggest-import-issue-120074.stderr

diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 263daa11ec316..50a4e03d233a7 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -1987,10 +1987,20 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             candidates
                 .sort_by_cached_key(|c| (c.path.segments.len(), pprust::path_to_string(&c.path)));
             if let Some(candidate) = candidates.get(0) {
+                let path = {
+                    // remove the possible common prefix of the path
+                    let start_index = (0..failed_segment_idx)
+                        .find(|&i| path[i].ident != candidate.path.segments[i].ident)
+                        .unwrap_or_default();
+                    let segments = (start_index..=failed_segment_idx)
+                        .map(|s| candidate.path.segments[s].clone())
+                        .collect();
+                    Path { segments, span: Span::default(), tokens: None }
+                };
                 (
                     String::from("unresolved import"),
                     Some((
-                        vec![(ident.span, pprust::path_to_string(&candidate.path))],
+                        vec![(ident.span, pprust::path_to_string(&path))],
                         String::from("a similar path exists"),
                         Applicability::MaybeIncorrect,
                     )),
diff --git a/tests/ui/imports/suggest-import-issue-120074.rs b/tests/ui/imports/suggest-import-issue-120074.rs
new file mode 100644
index 0000000000000..a798e9eeeb809
--- /dev/null
+++ b/tests/ui/imports/suggest-import-issue-120074.rs
@@ -0,0 +1,11 @@
+pub mod foo {
+    pub mod bar {
+        pub fn do_the_thing() -> usize {
+            42
+        }
+    }
+}
+
+fn main() {
+    println!("Hello, {}!", crate::bar::do_the_thing); //~ ERROR failed to resolve: unresolved import
+}
diff --git a/tests/ui/imports/suggest-import-issue-120074.stderr b/tests/ui/imports/suggest-import-issue-120074.stderr
new file mode 100644
index 0000000000000..c1dff93bbdbff
--- /dev/null
+++ b/tests/ui/imports/suggest-import-issue-120074.stderr
@@ -0,0 +1,23 @@
+error[E0433]: failed to resolve: unresolved import
+  --> $DIR/suggest-import-issue-120074.rs:10:35
+   |
+LL |     println!("Hello, {}!", crate::bar::do_the_thing);
+   |                                   ^^^ unresolved import
+   |
+help: a similar path exists
+   |
+LL |     println!("Hello, {}!", crate::foo::bar::do_the_thing);
+   |                                   ~~~~~~~~
+help: consider importing this module
+   |
+LL + use foo::bar;
+   |
+help: if you import `bar`, refer to it directly
+   |
+LL -     println!("Hello, {}!", crate::bar::do_the_thing);
+LL +     println!("Hello, {}!", bar::do_the_thing);
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0433`.