Turn debugger_visualizers from feed- into regular query.

compiler/rustc_middle/src/hir/map/mod.rs

@@ -1165,6 +1165,11 @@ pub(super) fn crate_hash(tcx: TyCtxt<'_>, _: LocalCrate) -> Svh {
 
     source_file_names.sort_unstable();
 
+    // We have to take care of debugger visualizers explicitly. The HIR (and
+    // thus `hir_body_hash`) contains the #[debugger_visualizer] attributes but
+    // these attributes only store the file path to the visualizer file, not
+    // their content. Yet that content is exported into crate metadata, so any
+    // changes to it need to be reflected in the crate hash.
     let debugger_visualizers: Vec<_> = tcx
         .debugger_visualizers(LOCAL_CRATE)
         .iter()

compiler/rustc_middle/src/query/mod.rs

@@ -1790,13 +1790,18 @@ rustc_queries! {
         desc { "looking at the source for a crate" }
         separate_provide_extern
     }
+
     /// Returns the debugger visualizers defined for this crate.
+    /// NOTE: This query has to be marked `eval_always` because it reads data
+    ///       directly from disk that is not tracked anywhere else. I.e. it
+    ///       represents a genuine input to the query system.
     query debugger_visualizers(_: CrateNum) -> &'tcx Vec<rustc_span::DebuggerVisualizerFile> {
         arena_cache
         desc { "looking up the debugger visualizers for this crate" }
         separate_provide_extern
-        feedable
+        eval_always
     }
+
     query postorder_cnums(_: ()) -> &'tcx [CrateNum] {
         eval_always
         desc { "generating a postorder list of CrateNums" }