Merge #2727

2727: Qualify paths in 'add impl members' r=flodiebold a=flodiebold

This makes the 'add impl members' assist qualify paths, so that they should resolve to the same thing as in the definition. To do that, it adds an algorithm that finds a path to refer to any item from any module (if possible), which is actually probably the more important part of this PR :smile: It handles visibility, reexports, renamed crates, prelude etc.; I think the only thing that's missing is support for local items. I'm not sure about the performance, since it takes into account every location where the target item has been `pub use`d, and then recursively goes up the module tree; there's probably potential for optimization by memoizing more, but I think the general shape of the algorithm is necessary to handle every case in Rust's module system.

~The 'find path' part is actually pretty complete, I think; I'm still working on the assist (hence the failing tests).~

Fixes #1943.

Co-authored-by: Florian Diebold <[email protected]>
Co-authored-by: Florian Diebold <[email protected]>

1 files changed, 41 insertions, 1 deletions

diff --git a/crates/ra_hir_def/src/path.rs b/crates/ra_hir_def/src/path.rs
index 82cfa67a9..9f93a5424 100644
--- a/crates/ra_hir_def/src/path.rs
+++ b/crates/ra_hir_def/src/path.rs
@@ -1,7 +1,11 @@
 //! A desugared representation of paths like `crate::foo` or `<Type as Trait>::bar`.
 mod lower;
 
-use std::{iter, sync::Arc};
+use std::{
+    fmt::{self, Display},
+    iter,
+    sync::Arc,
+};
 
 use hir_expand::{
     hygiene::Hygiene,
@@ -248,6 +252,42 @@ impl From<Name> for ModPath {
     }
 }
 
+impl Display for ModPath {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut first_segment = true;
+        let mut add_segment = |s| {
+            if !first_segment {
+                f.write_str("::")?;
+            }
+            first_segment = false;
+            f.write_str(s)?;
+            Ok(())
+        };
+        match self.kind {
+            PathKind::Plain => {}
+            PathKind::Super(n) => {
+                if n == 0 {
+                    add_segment("self")?;
+                }
+                for _ in 0..n {
+                    add_segment("super")?;
+                }
+            }
+            PathKind::Crate => add_segment("crate")?,
+            PathKind::Abs => add_segment("")?,
+            PathKind::DollarCrate(_) => add_segment("$crate")?,
+        }
+        for segment in &self.segments {
+            if !first_segment {
+                f.write_str("::")?;
+            }
+            first_segment = false;
+            write!(f, "{}", segment)?;
+        }
+        Ok(())
+    }
+}
+
 pub use hir_expand::name as __name;
 
 #[macro_export]