Auto merge of #111026 - compiler-errors:only-typeck-root, r=cjgillot

Only cache typeck results if it's the typeck root

context: https://rust-lang.zulipchat.com/#narrow/stream/241847-t-compiler.2Fwg-incr-comp/topic/incr_comp_query_cache_promotion.20taking.20forever

Basically, typeck children just copy the typeck results of their typeck root item, so caching their results means copying the same typeck results for each child item.

r? `@ghost`

Author: bors

Diff for: compiler/rustc_middle/src/query/mod.rs

@@ -875,7 +875,7 @@ rustc_queries! {
 
     query typeck(key: LocalDefId) -> &'tcx ty::TypeckResults<'tcx> {
         desc { |tcx| "type-checking `{}`", tcx.def_path_str(key) }
-        cache_on_disk_if { true }
+        cache_on_disk_if(tcx) { !tcx.is_typeck_child(key.to_def_id()) }
     }
     query diagnostic_only_typeck(key: LocalDefId) -> &'tcx ty::TypeckResults<'tcx> {
         desc { |tcx| "type-checking `{}`", tcx.def_path_str(key) }