Auto merge of #50197 - nikomatsakis:skolemize-out-of-tcx, r=eddyb

move skolemized regions into global tcx

Experimental branch to move skolemized regions into global tcx. This is probably not what we want long term but may be convenient to unblock @sgrif in the short term.

I'd like to do a perf run, though the main concern I guess would be memory usage.

r? @eddyb

Author: bors

src/librustc/traits/project.rs

@@ -409,7 +409,7 @@ impl<'a, 'b, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for AssociatedTypeNormalizer<'a,
         if let ConstVal::Unevaluated(def_id, substs) = constant.val {
             let tcx = self.selcx.tcx().global_tcx();
             if let Some(param_env) = self.tcx().lift_to_global(&self.param_env) {
-                if substs.needs_infer() {
+                if substs.needs_infer() || substs.has_skol() {
                     let identity_substs = Substs::identity_for_item(tcx, def_id);
                     let instance = ty::Instance::resolve(tcx, param_env, def_id, identity_substs);
                     if let Some(instance) = instance {

src/librustc/traits/query/normalize.rs

@@ -196,7 +196,7 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for QueryNormalizer<'cx, 'gcx, 'tcx
         if let ConstVal::Unevaluated(def_id, substs) = constant.val {
             let tcx = self.infcx.tcx.global_tcx();
             if let Some(param_env) = self.tcx().lift_to_global(&self.param_env) {
-                if substs.needs_infer() {
+                if substs.needs_infer() || substs.has_skol() {
                     let identity_substs = Substs::identity_for_item(tcx, def_id);
                     let instance = ty::Instance::resolve(tcx, param_env, def_id, identity_substs);
                     if let Some(instance) = instance {

src/librustc/ty/context.rs

@@ -2119,7 +2119,7 @@ macro_rules! intern_method {
                                             $alloc_method:ident,
                                             $alloc_to_key:expr,
                                             $alloc_to_ret:expr,
-                                            $needs_infer:expr) -> $ty:ty) => {
+                                            $keep_in_local_tcx:expr) -> $ty:ty) => {
         impl<'a, 'gcx, $lt_tcx> TyCtxt<'a, 'gcx, $lt_tcx> {
             pub fn $method(self, v: $alloc) -> &$lt_tcx $ty {
                 {
@@ -2137,7 +2137,7 @@ macro_rules! intern_method {
                 // HACK(eddyb) Depend on flags being accurate to
                 // determine that all contents are in the global tcx.
                 // See comments on Lift for why we can't use that.
-                if !($needs_infer)(&v) {
+                if !($keep_in_local_tcx)(&v) {
                     if !self.is_global() {
                         let v = unsafe {
                             mem::transmute(v)
@@ -2165,7 +2165,7 @@ macro_rules! intern_method {
 }
 
 macro_rules! direct_interners {
-    ($lt_tcx:tt, $($name:ident: $method:ident($needs_infer:expr) -> $ty:ty),+) => {
+    ($lt_tcx:tt, $($name:ident: $method:ident($keep_in_local_tcx:expr) -> $ty:ty),+) => {
         $(impl<$lt_tcx> PartialEq for Interned<$lt_tcx, $ty> {
             fn eq(&self, other: &Self) -> bool {
                 self.0 == other.0
@@ -2180,7 +2180,10 @@ macro_rules! direct_interners {
             }
         }
 
-        intern_method!($lt_tcx, $name: $method($ty, alloc, |x| x, |x| x, $needs_infer) -> $ty);)+
+        intern_method!(
+            $lt_tcx,
+            $name: $method($ty, alloc, |x| x, |x| x, $keep_in_local_tcx) -> $ty
+        );)+
     }
 }
 
@@ -2189,12 +2192,7 @@ pub fn keep_local<'tcx, T: ty::TypeFoldable<'tcx>>(x: &T) -> bool {
 }
 
 direct_interners!('tcx,
-    region: mk_region(|r| {
-        match r {
-            &ty::ReVar(_) | &ty::ReSkolemized(..) => true,
-            _ => false
-        }
-    }) -> RegionKind,
+    region: mk_region(|r: &RegionKind| r.keep_in_local_tcx()) -> RegionKind,
     const_: mk_const(|c: &Const| keep_local(&c.ty) || keep_local(&c.val)) -> Const<'tcx>
 );
 

src/librustc/ty/fold.rs

@@ -91,6 +91,9 @@ pub trait TypeFoldable<'tcx>: fmt::Debug + Clone {
     fn needs_infer(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_TY_INFER | TypeFlags::HAS_RE_INFER)
     }
+    fn has_skol(&self) -> bool {
+        self.has_type_flags(TypeFlags::HAS_RE_SKOL)
+    }
     fn needs_subst(&self) -> bool {
         self.has_type_flags(TypeFlags::NEEDS_SUBST)
     }
@@ -111,15 +114,6 @@ pub trait TypeFoldable<'tcx>: fmt::Debug + Clone {
         self.has_type_flags(TypeFlags::HAS_FREE_REGIONS)
     }
 
-    fn is_normalized_for_trans(&self) -> bool {
-        !self.has_type_flags(TypeFlags::HAS_RE_INFER |
-                             TypeFlags::HAS_FREE_REGIONS |
-                             TypeFlags::HAS_TY_INFER |
-                             TypeFlags::HAS_PARAMS |
-                             TypeFlags::HAS_NORMALIZABLE_PROJECTION |
-                             TypeFlags::HAS_TY_ERR |
-                             TypeFlags::HAS_SELF)
-    }
     /// Indicates whether this value references only 'global'
     /// types/lifetimes that are the same regardless of what fn we are
     /// in. This is used for caching. Errs on the side of returning

src/librustc/ty/mod.rs

@@ -1476,7 +1476,11 @@ impl<'tcx> ParamEnv<'tcx> {
             }
 
             Reveal::All => {
-                if value.needs_infer() || value.has_param_types() || value.has_self_ty() {
+                if value.has_skol()
+                    || value.needs_infer()
+                    || value.has_param_types()
+                    || value.has_self_ty()
+                {
                     ParamEnvAnd {
                         param_env: self,
                         value,

src/librustc/ty/sty.rs

@@ -1171,13 +1171,6 @@ impl RegionKind {
         }
     }
 
-    pub fn needs_infer(&self) -> bool {
-        match *self {
-            ty::ReVar(..) | ty::ReSkolemized(..) => true,
-            _ => false
-        }
-    }
-
     pub fn escapes_depth(&self, depth: u32) -> bool {
         match *self {
             ty::ReLateBound(debruijn, _) => debruijn.depth > depth,
@@ -1195,20 +1188,29 @@ impl RegionKind {
         }
     }
 
+    pub fn keep_in_local_tcx(&self) -> bool {
+        if let ty::ReVar(..) = self {
+            true
+        } else {
+            false
+        }
+    }
+
     pub fn type_flags(&self) -> TypeFlags {
         let mut flags = TypeFlags::empty();
 
+        if self.keep_in_local_tcx() {
+            flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
+        }
+
         match *self {
             ty::ReVar(..) => {
                 flags = flags | TypeFlags::HAS_FREE_REGIONS;
                 flags = flags | TypeFlags::HAS_RE_INFER;
-                flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
             }
             ty::ReSkolemized(..) => {
                 flags = flags | TypeFlags::HAS_FREE_REGIONS;
-                flags = flags | TypeFlags::HAS_RE_INFER;
                 flags = flags | TypeFlags::HAS_RE_SKOL;
-                flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
             }
             ty::ReLateBound(..) => { }
             ty::ReEarlyBound(..) => {

src/librustc_typeck/check/method/probe.rs

@@ -1485,7 +1485,10 @@ impl<'tcx> Candidate<'tcx> {
                     // inference variables or other artifacts. This
                     // means they are safe to put into the
                     // `WhereClausePick`.
-                    assert!(!trait_ref.skip_binder().substs.needs_infer());
+                    assert!(
+                        !trait_ref.skip_binder().substs.needs_infer()
+                            && !trait_ref.skip_binder().substs.has_skol()
+                    );
 
                     WhereClausePick(trait_ref.clone())
                 }

src/librustc_typeck/check/writeback.rs

@@ -107,7 +107,7 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
 
     fn write_ty_to_tables(&mut self, hir_id: hir::HirId, ty: Ty<'gcx>) {
         debug!("write_ty_to_tables({:?}, {:?})", hir_id, ty);
-        assert!(!ty.needs_infer());
+        assert!(!ty.needs_infer() && !ty.has_skol());
         self.tables.node_types_mut().insert(hir_id, ty);
     }
 
@@ -431,7 +431,7 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
         if let Some(substs) = self.fcx.tables.borrow().node_substs_opt(hir_id) {
             let substs = self.resolve(&substs, &span);
             debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
-            assert!(!substs.needs_infer());
+            assert!(!substs.needs_infer() && !substs.has_skol());
             self.tables.node_substs_mut().insert(hir_id, substs);
         }
     }