make needs_infer specific to inference variables

Notably, excluding ReSkolemized

src/librustc/traits/project.rs

@@ -409,7 +409,7 @@ fn fold_const(&mut self, constant: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tc
         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 @@ fn fold_const(&mut self, constant: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tc
         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 @@ pub fn $method(self, v: $alloc) -> &$lt_tcx $ty {
                 // HACK(eddyb) Depend on flags being accurate to
                 // determine that all contents are in the global tcx.
                 // See comments on Lift for why we can't use that.
-                if !($needs_infer)(&v) {
+                if !($keep_in_local_tcx)(&v) {
                     if !self.is_global() {
                         let v = unsafe {
                             mem::transmute(v)
@@ -2165,7 +2165,7 @@ pub fn $method(self, v: $alloc) -> &$lt_tcx $ty {
 }
 
 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 @@ fn hash<H: Hasher>(&self, s: &mut H) {
             }
         }
 
-        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
+        );)+
     }
 }
 

src/librustc/ty/fold.rs

@@ -91,6 +91,9 @@ fn has_infer_types(&self) -> bool {
     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)
     }

src/librustc/ty/mod.rs

@@ -1476,7 +1476,11 @@ pub fn and<T: TypeFoldable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T> {
             }
 
             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

@@ -1199,7 +1199,6 @@ pub fn type_flags(&self) -> TypeFlags {
             }
             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;
             }

src/librustc_typeck/check/method/probe.rs

@@ -1485,7 +1485,10 @@ fn to_unadjusted_pick(&self) -> Pick<'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 @@ fn tcx(&self) -> TyCtxt<'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 @@ fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
         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);
         }
     }