Use correct toolchain channel when generating builtin type doc links

src/tools/rust-analyzer/crates/ide/src/doc_links.rs

@@ -487,19 +487,23 @@ fn get_doc_base_urls(
     let system_doc = sysroot
         .map(|sysroot| format!("file:///{sysroot}/share/doc/rust/html/"))
         .and_then(|it| Url::parse(&it).ok());
+    let krate = def.krate(db);
+    let channel = krate
+        .and_then(|krate| db.toolchain_channel(krate.into()))
+        .unwrap_or(ReleaseChannel::Nightly)
+        .as_str();
 
     // special case base url of `BuiltinType` to core
     // https://github.com/rust-lang/rust-analyzer/issues/12250
     if let Definition::BuiltinType(..) = def {
-        let web_link = Url::parse("https://doc.rust-lang.org/nightly/core/").ok();
+        let web_link = Url::parse(&format!("https://doc.rust-lang.org/{channel}/core/")).ok();
         let system_link = system_doc.and_then(|it| it.join("core/").ok());
         return (web_link, system_link);
     };
 
-    let Some(krate) = def.krate(db) else { return Default::default() };
+    let Some(krate) = krate else { return Default::default() };
     let Some(display_name) = krate.display_name(db) else { return Default::default() };
     let crate_data = &db.crate_graph()[krate.into()];
-    let channel = db.toolchain_channel(krate.into()).unwrap_or(ReleaseChannel::Nightly).as_str();
 
     let (web_base, local_base) = match &crate_data.origin {
         // std and co do not specify `html_root_url` any longer so we gotta handwrite this ourself.