Move the `krate` method to Hir and remove the Krate dep node

[rust.git] / src / librustc / query / mod.rs

diff --git a/src/librustc/query/mod.rs b/src/librustc/query/mod.rs
index deb2d6ac630ac57534958e583400dcbd5e984ab8..82ff7da13aea85fd24ad4bbeab2bf04d405ad9ca 100644 (file)
--- a/src/librustc/query/mod.rs
+++ b/src/librustc/query/mod.rs
@@ -43,6 +43,18 @@ fn describe_as_module(def_id: DefId, tcx: TyCtxt<'_>) -> String {
     }
 
     Other {
+        // Represents crate as a whole (as distinct from the to-level crate module).
+        // If you call `hir_crate` (e.g., indirectly by calling `tcx.hir().krate()`),
+        // we will have to assume that any change means that you need to be recompiled.
+        // This is because the `hir_crate` query gives you access to all other items.
+        // To avoid this fate, do not call `tcx.hir().krate()`; instead,
+        // prefer wrappers like `tcx.visit_all_items_in_krate()`.
+        query hir_crate(key: CrateNum) -> &'tcx Crate<'tcx> {
+            eval_always
+            no_hash
+            desc { "get the crate HIR" }
+        }
+
         /// Records the type of every item.
         query type_of(key: DefId) -> Ty<'tcx> {
             cache_on_disk_if { key.is_local() }
@@ -776,13 +788,47 @@ fn describe_as_module(def_id: DefId, tcx: TyCtxt<'_>) -> String {
     }
 
     Codegen {
+        /// The entire set of monomorphizations the local crate can safely link
+        /// to because they are exported from upstream crates. Do not depend on
+        /// this directly, as its value changes anytime a monomorphization gets
+        /// added or removed in any upstream crate. Instead use the narrower
+        /// `upstream_monomorphizations_for`, `upstream_drop_glue_for`, or, even
+        /// better, `Instance::upstream_monomorphization()`.
         query upstream_monomorphizations(
             k: CrateNum
         ) -> &'tcx DefIdMap<FxHashMap<SubstsRef<'tcx>, CrateNum>> {
             desc { "collecting available upstream monomorphizations `{:?}`", k }
         }
+
+        /// Returns the set of upstream monomorphizations available for the
+        /// generic function identified by the given `def_id`. The query makes
+        /// sure to make a stable selection if the same monomorphization is
+        /// available in multiple upstream crates.
+        ///
+        /// You likely want to call `Instance::upstream_monomorphization()`
+        /// instead of invoking this query directly.
         query upstream_monomorphizations_for(_: DefId)
             -> Option<&'tcx FxHashMap<SubstsRef<'tcx>, CrateNum>> {}
+
+        /// Returns the upstream crate that exports drop-glue for the given
+        /// type (`substs` is expected to be a single-item list containing the
+        /// type one wants drop-glue for).
+        ///
+        /// This is a subset of `upstream_monomorphizations_for` in order to
+        /// increase dep-tracking granularity. Otherwise adding or removing any
+        /// type with drop-glue in any upstream crate would invalidate all
+        /// functions calling drop-glue of an upstream type.
+        ///
+        /// You likely want to call `Instance::upstream_monomorphization()`
+        /// instead of invoking this query directly.
+        ///
+        /// NOTE: This query could easily be extended to also support other
+        ///       common functions that have are large set of monomorphizations
+        ///       (like `Clone::clone` for example).
+        query upstream_drop_glue_for(substs: SubstsRef<'tcx>) -> Option<CrateNum> {
+            desc { "available upstream drop-glue for `{:?}`", substs }
+            no_force
+        }
     }
 
     Other {