Auto merge of #45916 - eddyb:even-mirer-0, r=nikomatsakis

rustc_mir: hardcode pass list internally and remove premature pluggability.

Fixes #41712 by moving the MIR pass lists from `rustc_driver` to `rustc_mir`.
The application of the passes is done with the `rustc_mir::transform::run_passes` macro, which is public, as are all the passes AFAIK, and can be used to apply MIR passes outside of `rustc_mir`.

With the ability to override query providers through the `rustc_driver` (orthogonal to, and not included in this PR), custom drivers will be able to substitute the entire pass list if they want to.
**EDIT**: the aforementioned ability is added by #45944.

r? @nikomatsakis

src/librustc/hir/map/mod.rs

@@ -448,6 +448,28 @@ impl<'hir> Map<'hir> {
         })
     }
 
+    pub fn body_owner_kind(&self, id: NodeId) -> BodyOwnerKind {
+        // Handle constants in enum discriminants, types, and repeat expressions.
+        let def_id = self.local_def_id(id);
+        let def_key = self.def_key(def_id);
+        if def_key.disambiguated_data.data == DefPathData::Initializer {
+            return BodyOwnerKind::Const;
+        }
+
+        match self.get(id) {
+            NodeItem(&Item { node: ItemConst(..), .. }) |
+            NodeTraitItem(&TraitItem { node: TraitItemKind::Const(..), .. }) |
+            NodeImplItem(&ImplItem { node: ImplItemKind::Const(..), .. }) => {
+                BodyOwnerKind::Const
+            }
+            NodeItem(&Item { node: ItemStatic(_, m, _), .. }) => {
+                BodyOwnerKind::Static(m)
+            }
+            // Default to function if it's not a constant or static.
+            _ => BodyOwnerKind::Fn
+        }
+    }
+
     pub fn ty_param_owner(&self, id: NodeId) -> NodeId {
         match self.get(id) {
             NodeItem(&Item { node: ItemTrait(..), .. }) => id,

src/librustc/hir/mod.rs

@@ -1028,6 +1028,18 @@ impl Body {
     }
 }
 
+#[derive(Copy, Clone, Debug)]
+pub enum BodyOwnerKind {
+    /// Functions and methods.
+    Fn,
+
+    /// Constants and associated constants.
+    Const,
+
+    /// Initializer of a `static` item.
+    Static(Mutability),
+}
+
 /// An expression
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash)]
 pub struct Expr {

src/librustc/middle/region.rs

@@ -31,7 +31,6 @@ use hir;
 use hir::def_id::DefId;
 use hir::intravisit::{self, Visitor, NestedVisitorMap};
 use hir::{Block, Arm, Pat, PatKind, Stmt, Expr, Local};
-use mir::transform::MirSource;
 use rustc_data_structures::indexed_vec::Idx;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher,
                                            StableHasherResult};
@@ -1298,7 +1297,7 @@ impl<'a, 'tcx> Visitor<'tcx> for RegionResolutionVisitor<'a, 'tcx> {
 
         // The body of the every fn is a root scope.
         self.cx.parent = self.cx.var_parent;
-        if let MirSource::Fn(_) = MirSource::from_node(self.tcx, owner_id) {
+        if let hir::BodyOwnerKind::Fn = self.tcx.hir.body_owner_kind(owner_id) {
             self.visit_expr(&body.value);
         } else {
             // Only functions have an outer terminating (drop) scope, while

src/librustc/mir/mod.rs

@@ -41,7 +41,6 @@ use syntax_pos::Span;
 mod cache;
 pub mod tcx;
 pub mod visit;
-pub mod transform;
 pub mod traversal;
 
 /// Types for locals

src/librustc/ty/context.rs

@@ -31,7 +31,6 @@ use middle::lang_items;
 use middle::resolve_lifetime::{self, ObjectLifetimeDefault};
 use middle::stability;
 use mir::Mir;
-use mir::transform::Passes;
 use ty::subst::{Kind, Substs};
 use ty::ReprOptions;
 use traits;
@@ -882,8 +881,6 @@ pub struct GlobalCtxt<'tcx> {
 
     pub maps: maps::Maps<'tcx>,
 
-    pub mir_passes: Rc<Passes>,
-
     // Records the free variables refrenced by every closure
     // expression. Do not track deps for this, just recompute it from
     // scratch every time.
@@ -1055,7 +1052,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                                   cstore: &'tcx CrateStore,
                                   local_providers: ty::maps::Providers<'tcx>,
                                   extern_providers: ty::maps::Providers<'tcx>,
-                                  mir_passes: Rc<Passes>,
                                   arenas: &'tcx GlobalArenas<'tcx>,
                                   arena: &'tcx DroplessArena,
                                   resolutions: ty::Resolutions,
@@ -1172,7 +1168,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             hir,
             def_path_hash_to_def_id,
             maps: maps::Maps::new(providers),
-            mir_passes,
             rcache: RefCell::new(FxHashMap()),
             selection_cache: traits::SelectionCache::new(),
             evaluation_cache: traits::EvaluationCache::new(),

src/librustc/ty/maps/keys.rs

@@ -11,7 +11,6 @@
 //! Defines the set of legal keys that can be used in queries.
 
 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE, DefIndex};
-use mir::transform::{MirSuite, MirPassIndex};
 use ty::{self, Ty, TyCtxt};
 use ty::subst::Substs;
 use ty::fast_reject::SimplifiedType;
@@ -116,24 +115,6 @@ impl<'tcx> Key for (DefId, &'tcx Substs<'tcx>) {
     }
 }
 
-impl Key for (MirSuite, DefId) {
-    fn map_crate(&self) -> CrateNum {
-        self.1.map_crate()
-    }
-    fn default_span(&self, tcx: TyCtxt) -> Span {
-        self.1.default_span(tcx)
-    }
-}
-
-impl Key for (MirSuite, MirPassIndex, DefId) {
-    fn map_crate(&self) -> CrateNum {
-        self.2.map_crate()
-    }
-    fn default_span(&self, tcx: TyCtxt) -> Span {
-        self.2.default_span(tcx)
-    }
-}
-
 impl<'tcx> Key for (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>) {
     fn map_crate(&self) -> CrateNum {
         self.1.def_id().krate