add byte range to main loop and direct the request via callback and define the callback on client side

src/tools/rust-analyzer/crates/load-cargo/src/lib.rs

@@ -591,6 +591,16 @@ impl ProcMacroExpander for Expander {
 
                 Ok(SubResponse::FilePathResult { name })
             }
+            SubRequest::ByteRange { file_id, ast_id, start, end } => {
+                let range = resolve_sub_span(
+                    db,
+                    file_id,
+                    ast_id,
+                    TextRange::new(TextSize::from(start), TextSize::from(end)),
+                );
+
+                Ok(SubResponse::ByteRangeResult { range: range.range.into() })
+            }
         };
         match self.0.expand(
             subtree.view(),

src/tools/rust-analyzer/crates/proc-macro-srv-cli/src/main_loop.rs

@@ -6,7 +6,7 @@ use proc_macro_api::{
     transport::codec::{json::JsonProtocol, postcard::PostcardProtocol},
     version::CURRENT_API_VERSION,
 };
-use std::io::{self, BufRead, Write};
+use std::{io, ops::Range};
 
 use legacy::Message;
 
@@ -240,6 +240,23 @@ impl<C: Codec> proc_macro_srv::ProcMacroClientInterface for ProcMacroClientHandl
             _ => None,
         }
     }
+
+    fn byte_range(
+        &mut self,
+        proc_macro_srv::span::Span { range, anchor, ctx: _ }: proc_macro_srv::span::Span,
+    ) -> Range<usize> {
+        match self.roundtrip(bidirectional::SubRequest::ByteRange {
+            file_id: anchor.file_id.as_u32(),
+            ast_id: anchor.ast_id.into_raw(),
+            start: range.start().into(),
+            end: range.end().into(),
+        }) {
+            Some(bidirectional::BidirectionalMessage::SubResponse(
+                bidirectional::SubResponse::ByteRangeResult { range },
+            )) => range,
+            _ => Range { start: range.start().into(), end: range.end().into() },
+        }
+    }
 }
 
 fn handle_expand_ra<C: Codec>(