Make impl_wf_check incremental

src/librustc/dep_graph/dep_node.rs

@@ -479,6 +479,7 @@ define_dep_nodes!( <'tcx>
     [] CheckModPrivacy(DefId),
     [] CheckModIntrinsics(DefId),
     [] CheckModLiveness(DefId),
+    [] CheckModImplWf(DefId),
     [] CollectModItemTypes(DefId),
 
     [] Reachability,

src/librustc/ty/query/config.rs

@@ -136,6 +136,15 @@ impl<'tcx> QueryDescription<'tcx> for queries::check_mod_liveness<'tcx> {
     }
 }
 
+impl<'tcx> QueryDescription<'tcx> for queries::check_mod_impl_wf<'tcx> {
+    fn describe(
+        tcx: TyCtxt<'_, '_, '_>,
+        key: DefId,
+    ) -> Cow<'static, str> {
+        format!("checking that impls are well-formed in {}", key.describe_as_module(tcx)).into()
+    }
+}
+
 impl<'tcx> QueryDescription<'tcx> for queries::collect_mod_item_types<'tcx> {
     fn describe(
         tcx: TyCtxt<'_, '_, '_>,

src/librustc/ty/query/mod.rs

@@ -270,6 +270,8 @@ define_queries! { <'tcx>
 
         [] fn check_mod_liveness: CheckModLiveness(DefId) -> (),
 
+        [] fn check_mod_impl_wf: CheckModImplWf(DefId) -> (),
+
         [] fn collect_mod_item_types: CollectModItemTypes(DefId) -> (),
 
         /// Caches CoerceUnsized kinds for impls on custom types.

src/librustc/ty/query/plumbing.rs

@@ -1260,6 +1260,7 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
         DepKind::CheckModPrivacy => { force!(check_mod_privacy, def_id!()); }
         DepKind::CheckModIntrinsics => { force!(check_mod_intrinsics, def_id!()); }
         DepKind::CheckModLiveness => { force!(check_mod_liveness, def_id!()); }
+        DepKind::CheckModImplWf => { force!(check_mod_impl_wf, def_id!()); }
         DepKind::CollectModItemTypes => { force!(collect_mod_item_types, def_id!()); }
         DepKind::Reachability => { force!(reachable_set, LOCAL_CRATE); }
         DepKind::MirKeys => { force!(mir_keys, LOCAL_CRATE); }

src/librustc_typeck/impl_wf_check.rs

@@ -13,6 +13,7 @@ use rustc::hir;
 use rustc::hir::itemlikevisit::ItemLikeVisitor;
 use rustc::hir::def_id::DefId;
 use rustc::ty::{self, TyCtxt};
+use rustc::ty::query::Providers;
 use rustc::util::nodemap::{FxHashMap, FxHashSet};
 use std::collections::hash_map::Entry::{Occupied, Vacant};
 
@@ -52,7 +53,23 @@ pub fn impl_wf_check<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
     // We will tag this as part of the WF check -- logically, it is,
     // but it's one that we must perform earlier than the rest of
     // WfCheck.
-    tcx.hir().krate().visit_all_item_likes(&mut ImplWfCheck { tcx });
+    for &module in tcx.hir().krate().modules.keys() {
+        tcx.ensure().check_mod_impl_wf(tcx.hir().local_def_id(module));
+    }
+}
+
+fn check_mod_impl_wf<'tcx>(tcx: TyCtxt<'_, 'tcx, 'tcx>, module_def_id: DefId) {
+    tcx.hir().visit_item_likes_in_module(
+        module_def_id,
+        &mut ImplWfCheck { tcx }
+    );
+}
+
+pub fn provide(providers: &mut Providers<'_>) {
+    *providers = Providers {
+        check_mod_impl_wf,
+        ..*providers
+    };
 }
 
 struct ImplWfCheck<'a, 'tcx: 'a> {

src/librustc_typeck/lib.rs

@@ -318,6 +318,7 @@ pub fn provide(providers: &mut Providers) {
     check::provide(providers);
     variance::provide(providers);
     outlives::provide(providers);
+    impl_wf_check::provide(providers);
 }
 
 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>)