Add parent scope information to nr error type

Parent's name makes information clearer when a segment is missing.

gcc/rust/ChangeLog:

	* resolve/rust-forever-stack.h (class ResolutionError):
	* resolve/rust-forever-stack.hxx:
	* resolve/rust-late-name-resolver-2.0.cc (Late::visit):
	* resolve/rust-name-resolution-context.h:

Signed-off-by: Pierre-Emmanuel Patry <[email protected]>

Author: P-E-P

gcc/rust/resolve/rust-forever-stack.h

@@ -545,19 +545,33 @@ class ForeverStackStore
 
 class ResolutionError
 {
+  std::string name;
   location_t offending_location;
   std::vector<Identifier> suggestions;
-
-  ResolutionError (location_t loc, std::vector<Identifier> suggestions)
-    : offending_location (loc), suggestions (suggestions)
+  // Parent scope for name resolution "X not found in Y"
+  tl::optional<std::string> parent;
+
+  ResolutionError (std::string name, location_t loc,
+		   std::vector<Identifier> suggestions,
+		   tl::optional<std::string> parent)
+    : name (name), offending_location (loc), suggestions (suggestions),
+      parent (parent)
   {}
 
 public:
-  static ResolutionError make_error (location_t loc,
-				     std::vector<Identifier> suggestions = {})
+  static ResolutionError make_error (std::string name, location_t loc,
+				     std::vector<Identifier> suggestions = {},
+				     tl::optional<std::string> parent
+				     = tl::nullopt)
   {
-    return ResolutionError (loc, suggestions);
+    return ResolutionError (name, loc, suggestions, parent);
   }
+
+  const std::string &get_name () const { return name; }
+
+  location_t get_offending_location () { return offending_location; }
+
+  tl::optional<std::string> get_parent () { return parent; }
 };
 
 template <Namespace N> class ForeverStack

gcc/rust/resolve/rust-forever-stack.hxx

@@ -442,7 +442,7 @@ ForeverStack<N>::find_starting_point (
 				     !is_start (iterator, segments)
 				       && is_self_or_crate))
 	return tl::make_unexpected (
-	  ResolutionError::make_error (seg.get_locus ()));
+	  ResolutionError::make_error (seg.as_string (), seg.get_locus ()));
 
       if (seg.is_crate_path_seg ())
 	{
@@ -468,7 +468,8 @@ ForeverStack<N>::find_starting_point (
 		seg.get_locus (), ErrorCode::E0433,
 		"too many leading %<super%> keywords");
 	      return tl::make_unexpected (
-		ResolutionError::make_error (seg.get_locus ()));
+		ResolutionError::make_error (seg.as_string (),
+					     seg.get_locus ()));
 	    }
 
 	  starting_point
@@ -522,7 +523,7 @@ ForeverStack<N>::resolve_segments (
 				       || seg.is_super_path_seg ()
 				       || seg.is_lower_self_seg ()))
 	return tl::make_unexpected (
-	  ResolutionError::make_error (seg.get_locus ()));
+	  ResolutionError::make_error (seg.as_string (), seg.get_locus ()));
 
       tl::optional<typename ForeverStack<N>::Node &> child = tl::nullopt;
 
@@ -576,7 +577,8 @@ ForeverStack<N>::resolve_segments (
 		  insert_segment_resolution (outer_seg,
 					     rib_lookup->get_node_id ());
 		  return tl::make_unexpected (
-		    ResolutionError::make_error (seg.get_locus ()));
+		    ResolutionError::make_error (seg.as_string (),
+						 seg.get_locus ()));
 		}
 	    }
 
@@ -592,7 +594,8 @@ ForeverStack<N>::resolve_segments (
 	      || current_node->is_prelude ())
 	    {
 	      return tl::make_unexpected (
-		ResolutionError::make_error (seg.get_locus ()));
+		ResolutionError::make_error (seg.as_string (),
+					     seg.get_locus ()));
 	    }
 
 	  current_node = &current_node->parent.value ();
@@ -680,7 +683,8 @@ ForeverStack<N>::resolve_path (
 	return res.value ();
       else
 	return tl::make_unexpected (
-	  ResolutionError::make_error (unwrapped.get_locus ()));
+	  ResolutionError::make_error (unwrapped.as_string (),
+				       unwrapped.get_locus ()));
     }
 
   std::reference_wrapper<Node> starting_point = cursor ();
@@ -698,13 +702,13 @@ ForeverStack<N>::resolve_path (
 	  [this, &segments, &insert_segment_resolution] (Node &final_node)
 	    -> tl::expected<Rib::Definition, ResolutionError> {
 	    auto &seg = unwrap_type_segment (segments.back ());
+
+	    std::string seg_name = seg.as_string ();
 	    //
 	    // leave resolution within impl blocks to type checker
 	    if (final_node.rib.kind == Rib::Kind::TraitOrImpl)
 	      return tl::make_unexpected (
-		ResolutionError::make_error (seg.get_locus ()));
-
-	    std::string seg_name = seg.as_string ();
+		ResolutionError::make_error (seg_name, seg.get_locus ()));
 
 	    // assuming this can't be a lang item segment
 	    tl::optional<Rib::Definition> res
@@ -721,7 +725,7 @@ ForeverStack<N>::resolve_path (
 	      return res.value ();
 	    else
 	      return tl::make_unexpected (
-		ResolutionError::make_error (seg.get_locus ()));
+		ResolutionError::make_error (seg_name, seg.get_locus ()));
 	  });
   cleanup_current ();
   return res;

gcc/rust/resolve/rust-late-name-resolver-2.0.cc

@@ -545,10 +545,27 @@ Late::visit (AST::Visibility &vis)
 {
   if (vis.has_path ())
     {
-      if (auto resolved
-	  = ctx.resolve_path (vis.get_path_unchecked (), Namespace::Types))
+      auto resolved
+	= ctx.resolve_path (vis.get_path_unchecked (), Namespace::Types);
+      if (resolved)
 	ctx.map_usage (Usage (vis.get_path_unchecked ().get_node_id ()),
 		       Definition (resolved->get_node_id ()));
+      else if (resolved.error ().kind == PathResolutionError::Kind::RESOLVE)
+	{
+	  auto error = resolved.error ().get_error_unchecked ();
+	  if (auto parent = error.get_parent ())
+	    rust_error_at (error.get_offending_location (), ErrorCode::E0433,
+			   "Could not resolve %qs in %qs",
+			   error.get_name ().c_str (),
+			   parent.value ().c_str ());
+	  else
+	    rust_error_at (error.get_offending_location (), ErrorCode::E0433,
+			   "Could not resolve %qs", error.get_name ().c_str ());
+	}
+      else
+	{
+	  rust_unreachable ();
+	}
     }
 }
 

gcc/rust/resolve/rust-name-resolution-context.h

@@ -229,6 +229,8 @@ class PathResolutionError
   PathResolutionError (ResolutionError error)
     : error (error), kind (Kind::RESOLVE)
   {}
+
+  ResolutionError get_error_unchecked () { return error.value (); }
 };
 // Now our resolver, which keeps track of all the `ForeverStack`s we could want
 class NameResolutionContext