1 files changed, 40 insertions, 1 deletions

diff --git a/crates/ra_lsp_server/src/conv.rs b/crates/ra_lsp_server/src/conv.rs
index 759e5e914..08a656569 100644
--- a/crates/ra_lsp_server/src/conv.rs
+++ b/crates/ra_lsp_server/src/conv.rs
@@ -190,9 +190,13 @@ impl TryConvWith for SourceChange {
             None => None,
             Some(pos) => {
                 let line_index = world.analysis().file_line_index(pos.file_id);
+                let edits = self.source_file_edits.iter().find(|it| it.file_id == pos.file_id)
+                    .map(|it| it.edits.as_slice()).unwrap_or(&[]);
+                let line_col = translate_offset_with_edit(&*line_index, pos.offset, edits);
+                let position = Position::new(line_col.line as u64, u32::from(line_col.col) as u64);
                 Some(TextDocumentPositionParams {
                     text_document: TextDocumentIdentifier::new(pos.file_id.try_conv_with(world)?),
-                    position: pos.offset.conv_with(&line_index),
+                    position,
                 })
             }
         };
@@ -207,6 +211,41 @@ impl TryConvWith for SourceChange {
     }
 }
 
+// HACK: we should translate offset to line/column using linde_index *with edits applied*.
+// A naive version of this function would be to apply `edits` to the original text,
+// construct a new line index and use that, but it would be slow.
+//
+// Writing fast & correct version is issue #105, let's use a quick hack in the meantime
+fn translate_offset_with_edit(
+    pre_edit_index: &LineIndex,
+    offset: TextUnit,
+    edits: &[AtomEdit],
+) -> LineCol {
+    let fallback = pre_edit_index.line_col(offset);
+    let edit = match edits.first() {
+        None => return fallback,
+        Some(edit) => edit
+    };
+    let end_offset = edit.delete.start() + TextUnit::of_str(&edit.insert);
+    if !(edit.delete.start() <= offset && offset <= end_offset) {
+        return fallback
+    }
+    let rel_offset = offset - edit.delete.start();
+    let in_edit_line_col = LineIndex::new(&edit.insert).line_col(rel_offset);
+    let edit_line_col = pre_edit_index.line_col(edit.delete.start());
+    if in_edit_line_col.line == 0 {
+        LineCol {
+            line: edit_line_col.line,
+            col: edit_line_col.col + in_edit_line_col.col,
+        }
+    } else {
+        LineCol {
+            line: edit_line_col.line + in_edit_line_col.line,
+            col: in_edit_line_col.col,
+        }
+    }
+}
+
 impl TryConvWith for SourceFileEdit {
     type Ctx = ServerWorld;
     type Output = TextDocumentEdit;