Remove -Z incremental-queries.

Because it uses `parse_bool` and defaults to true, it is actually
impossible to set it to false. And it hasn't been experimental for some
time now.

src/librustc/ty/query/plumbing.rs

@@ -615,9 +615,7 @@ impl<'tcx> TyCtxt<'tcx> {
         debug_assert!(self.dep_graph.is_green(dep_node));
 
         // First we try to load the result from the on-disk cache.
-        let result = if Q::cache_on_disk(self, key.clone(), None)
-            && self.sess.opts.debugging_opts.incremental_queries
-        {
+        let result = if Q::cache_on_disk(self, key.clone(), None) {
             let prof_timer = self.prof.incr_cache_loading();
             let result = Q::try_load_from_disk(self, prev_dep_node_index);
             prof_timer.finish_with_query_invocation_id(dep_node_index.into());

src/librustc_incremental/persist/load.rs

@@ -195,7 +195,7 @@ pub fn load_dep_graph(sess: &Session) -> DepGraphFuture {
 }
 
 pub fn load_query_result_cache(sess: &Session) -> OnDiskCache<'_> {
-    if sess.opts.incremental.is_none() || !sess.opts.debugging_opts.incremental_queries {
+    if sess.opts.incremental.is_none() {
         return OnDiskCache::new_empty(sess.source_map());
     }
 

src/librustc_incremental/persist/save.rs

@@ -31,11 +31,9 @@ pub fn save_dep_graph(tcx: TyCtxt<'_>) {
 
         join(
             move || {
-                if tcx.sess.opts.debugging_opts.incremental_queries {
-                    sess.time("incr_comp_persist_result_cache", || {
-                        save_in(sess, query_cache_path, |e| encode_query_cache(tcx, e));
-                    });
-                }
+                sess.time("incr_comp_persist_result_cache", || {
+                    save_in(sess, query_cache_path, |e| encode_query_cache(tcx, e));
+                });
             },
             || {
                 sess.time("incr_comp_persist_dep_graph", || {

src/librustc_session/options.rs

@@ -791,8 +791,6 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "print tasks that execute and the color their dep node gets (requires debug build)"),
     incremental: Option<String> = (None, parse_opt_string, [UNTRACKED],
         "enable incremental compilation (experimental)"),
-    incremental_queries: bool = (true, parse_bool, [UNTRACKED],
-        "enable incremental compilation support for queries (experimental)"),
     incremental_info: bool = (false, parse_bool, [UNTRACKED],
         "print high-level information about incremental reuse (or the lack thereof)"),
     incremental_dump_hash: bool = (false, parse_bool, [UNTRACKED],

src/tools/compiletest/src/runtest.rs

@@ -1852,7 +1852,6 @@ impl<'test> TestCx<'test> {
             if let Some(ref incremental_dir) = self.props.incremental_dir {
                 rustc.args(&["-C", &format!("incremental={}", incremental_dir.display())]);
                 rustc.args(&["-Z", "incremental-verify-ich"]);
-                rustc.args(&["-Z", "incremental-queries"]);
             }
 
             if self.config.mode == CodegenUnits {