Move rustc_query_system::query::dep_graph to rustc_middle.

Most of the files within the `dep_graph` module can be moved wholesale
into `rustc_middle`. But two of them (`mod.rs` and `dep_node.rs`) have
the same name as existing files in `rustc_middle`, so for those I just
copied the contents into the existing files.

The commit also moves `QueryContext` and `incremental_verify_ich*`
because they are tightly intertwined with the dep graph code. And a
couple of error structs moved as well.

Author: nnethercote

Cargo.lock

@@ -4093,7 +4093,6 @@ dependencies = [
  "rustc_passes",
  "rustc_privacy",
  "rustc_query_impl",
- "rustc_query_system",
  "rustc_resolve",
  "rustc_session",
  "rustc_span",
@@ -4519,13 +4518,11 @@ dependencies = [
  "rustc_errors",
  "rustc_feature",
  "rustc_hir",
- "rustc_index",
  "rustc_macros",
  "rustc_serialize",
  "rustc_session",
  "rustc_span",
  "smallvec",
- "tracing",
 ]
 
 [[package]]

compiler/rustc_interface/Cargo.toml

@@ -35,7 +35,6 @@ rustc_parse = { path = "../rustc_parse" }
 rustc_passes = { path = "../rustc_passes" }
 rustc_privacy = { path = "../rustc_privacy" }
 rustc_query_impl = { path = "../rustc_query_impl" }
-rustc_query_system = { path = "../rustc_query_system" }
 rustc_resolve = { path = "../rustc_resolve" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }

compiler/rustc_interface/src/callbacks.rs

@@ -12,11 +12,10 @@
 use std::fmt;
 
 use rustc_errors::{DiagInner, TRACK_DIAGNOSTIC};
-use rustc_middle::dep_graph::{DepNodeExt, TaskDepsRef};
+use rustc_middle::dep_graph::dep_node::default_dep_kind_debug;
+use rustc_middle::dep_graph::{DepContext, DepKind, DepNode, DepNodeExt, TaskDepsRef};
 use rustc_middle::ty::tls;
 use rustc_query_impl::QueryCtxt;
-use rustc_query_system::dep_graph::dep_node::default_dep_kind_debug;
-use rustc_query_system::dep_graph::{DepContext, DepKind, DepNode};
 
 fn track_span_parent(def_id: rustc_span::def_id::LocalDefId) {
     tls::with_context_opt(|icx| {
@@ -107,9 +106,9 @@ pub fn dep_node_debug(node: DepNode, f: &mut std::fmt::Formatter<'_>) -> std::fm
 pub fn setup_callbacks() {
     rustc_span::SPAN_TRACK.swap(&(track_span_parent as fn(_)));
     rustc_hir::def_id::DEF_ID_DEBUG.swap(&(def_id_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
-    rustc_query_system::dep_graph::dep_node::DEP_KIND_DEBUG
+    rustc_middle::dep_graph::dep_node::DEP_KIND_DEBUG
         .swap(&(dep_kind_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
-    rustc_query_system::dep_graph::dep_node::DEP_NODE_DEBUG
+    rustc_middle::dep_graph::dep_node::DEP_NODE_DEBUG
         .swap(&(dep_node_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
     TRACK_DIAGNOSTIC.swap(&(track_diagnostic as _));
 }