What causes "Unable to convert fix: {:#}" in denoland/deno?

Save the file and re-request the quick fix once edits settle, so the server's snapshot matches the editor.

Unable to convert fix: {:#}

Error message

Unable to convert fix: {:#}

What it means

While computing quick-fix code actions for a diagnostic, every tsc fix action is converted into an LSP code action via collector.add_ts_fix_action; this error wraps a conversion failure for one of them. The usual root cause is mapping a tsc text span to an LSP range through the module's line index — for example a span that no longer fits the document after unsynchronized edits — but any converter error surfaces here and aborts the whole code action request.

Source

Thrown at cli/lsp/ts_server.rs:406

                lsp_warn!(
                  "Unable to get code fixes from TypeScript: {:#}",
                  err
                );
              }
              vec![]
            });
          for fix_action in fix_actions {
            if token.is_cancelled() {
              return Err(anyhow!("request cancelled"));
            }
            collector
              .add_ts_fix_action(
                &fix_action,
                diagnostic,
                module,
                language_server,
              )
              .map_err(|err| anyhow!("Unable to convert fix: {:#}", err))?;
            if collector.is_fix_all_action(
              &fix_action,
              diagnostic,
              &file_diagnostics,
            ) {
              collector.add_ts_fix_all_action(&fix_action, module, diagnostic);
            }
          }
        }

        let mut actions = collector
          .into_code_actions(has_deno_code_actions)
          .map(lsp::CodeActionOrCommand::CodeAction)
          .collect::<Vec<_>>();

        let only = context
          .only
          .as_ref()

View on GitHub (pinned to 9ad36f7a2c)

Solutions

Save the file and re-request the quick fix once edits settle, so the server's snapshot matches the editor.
Run "Deno: Restart Language Server" if the error persists for a specific file.
Update the Deno CLI and extension — conversion bugs against particular tsc fix shapes get patched.
Inspect the wrapped error after the colon in the Deno Language Server output to identify which fix failed.

Defensive patterns

Strategy: fallback

Try / catch

// If quick-fix conversion fails, degrade gracefully: keep the editor's
// built-in actions instead of failing the whole code action request.
async function codeActionsSafe(client, params) {
  try {
    return await client.sendRequest('textDocument/codeAction', params);
  } catch (err) {
    if (String(err?.message).includes('Unable to convert fix')) {
      console.warn('quick fixes unavailable:', err.message);
      return [];
    }
    throw err;
  }
}

Prevention

Save the file before invoking Quick Fix so the server snapshot matches the editor
Avoid auto-fix-on-save racing concurrent edits
Restart the language server when one file's quick fixes keep failing, and update Deno

When it happens

Trigger: A codeActions request for a diagnostic that has tsc fixes available, where converting one fix action fails — commonly immediately after edits while the client's document version and the server snapshot disagree, or for fixes spanning files not present in the snapshot.

Common situations: Invoking Quick Fix while still typing; editor auto-fix-on-save racing concurrent edits; older Deno versions with span-conversion bugs against specific fix shapes.

Related errors

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/baee47dc788a02ae. Report an issue: GitHub.