Auto merge of #43505 - eddyb:poly-const-eval-layout-of, r=nikomatsakis

rustc_const_eval: always require Substs and a ParamEnv.

Fixes #43357 by tracking the `Substs` and `ParamEnv` for const-evaluation in generic contexts.

src/librustc/middle/const_val.rs

@@ -14,7 +14,8 @@ pub use rustc_const_math::ConstInt;
 use hir;
 use hir::def::Def;
 use hir::def_id::DefId;
-use ty::{TyCtxt, layout};
+use traits::Reveal;
+use ty::{self, TyCtxt, layout};
 use ty::subst::Substs;
 use util::common::ErrorReported;
 use rustc_const_math::*;
@@ -229,8 +230,9 @@ pub fn eval_length(tcx: TyCtxt,
 {
     let count_expr = &tcx.hir.body(count).value;
     let count_def_id = tcx.hir.body_owner_def_id(count);
-    let substs = Substs::empty();
-    match tcx.at(count_expr.span).const_eval((count_def_id, substs)) {
+    let param_env = ty::ParamEnv::empty(Reveal::UserFacing);
+    let substs = Substs::identity_for_item(tcx.global_tcx(), count_def_id);
+    match tcx.at(count_expr.span).const_eval(param_env.and((count_def_id, substs))) {
         Ok(Integral(Usize(count))) => {
             let val = count.as_u64(tcx.sess.target.uint_type);
             assert_eq!(val as usize as u64, val);

src/librustc/ty/maps.rs

@@ -372,8 +372,8 @@ impl<'tcx> QueryDescription for queries::reachable_set<'tcx> {
 }
 
 impl<'tcx> QueryDescription for queries::const_eval<'tcx> {
-    fn describe(tcx: TyCtxt, (def_id, _): (DefId, &'tcx Substs<'tcx>)) -> String {
-        format!("const-evaluating `{}`", tcx.item_path_str(def_id))
+    fn describe(tcx: TyCtxt, key: ty::ParamEnvAnd<'tcx, (DefId, &'tcx Substs<'tcx>)>) -> String {
+        format!("const-evaluating `{}`", tcx.item_path_str(key.value.0))
     }
 }
 
@@ -935,7 +935,7 @@ define_maps! { <'tcx>
 
     /// Results of evaluating const items or constants embedded in
     /// other items (such as enum variant explicit discriminants).
-    [] const_eval: const_eval_dep_node((DefId, &'tcx Substs<'tcx>))
+    [] const_eval: const_eval_dep_node(ty::ParamEnvAnd<'tcx, (DefId, &'tcx Substs<'tcx>)>)
         -> const_val::EvalResult<'tcx>,
 
     /// Performs the privacy check and computes "access levels".
@@ -1032,8 +1032,9 @@ fn typeck_item_bodies_dep_node<'tcx>(_: CrateNum) -> DepConstructor<'tcx> {
     DepConstructor::TypeckBodiesKrate
 }
 
-fn const_eval_dep_node<'tcx>((def_id, substs): (DefId, &'tcx Substs<'tcx>))
+fn const_eval_dep_node<'tcx>(key: ty::ParamEnvAnd<'tcx, (DefId, &'tcx Substs<'tcx>)>)
                              -> DepConstructor<'tcx> {
+    let (def_id, substs) = key.value;
     DepConstructor::ConstEval { def_id, substs }
 }
 

src/librustc/ty/mod.rs

@@ -1582,14 +1582,15 @@ impl<'a, 'gcx, 'tcx> AdtDef {
     #[inline]
     pub fn discriminants(&'a self, tcx: TyCtxt<'a, 'gcx, 'tcx>)
                          -> impl Iterator<Item=ConstInt> + 'a {
+        let param_env = ParamEnv::empty(traits::Reveal::UserFacing);
         let repr_type = self.repr.discr_type();
         let initial = repr_type.initial_discriminant(tcx.global_tcx());
         let mut prev_discr = None::<ConstInt>;
         self.variants.iter().map(move |v| {
             let mut discr = prev_discr.map_or(initial, |d| d.wrap_incr());
             if let VariantDiscr::Explicit(expr_did) = v.discr {
-                let substs = Substs::empty();
-                match tcx.const_eval((expr_did, substs)) {
+                let substs = Substs::identity_for_item(tcx.global_tcx(), expr_did);
+                match tcx.const_eval(param_env.and((expr_did, substs))) {
                     Ok(ConstVal::Integral(v)) => {
                         discr = v;
                     }
@@ -1617,6 +1618,7 @@ impl<'a, 'gcx, 'tcx> AdtDef {
                                     tcx: TyCtxt<'a, 'gcx, 'tcx>,
                                     variant_index: usize)
                                     -> ConstInt {
+        let param_env = ParamEnv::empty(traits::Reveal::UserFacing);
         let repr_type = self.repr.discr_type();
         let mut explicit_value = repr_type.initial_discriminant(tcx.global_tcx());
         let mut explicit_index = variant_index;
@@ -1627,8 +1629,8 @@ impl<'a, 'gcx, 'tcx> AdtDef {
                     explicit_index -= distance;
                 }
                 ty::VariantDiscr::Explicit(expr_did) => {
-                    let substs = Substs::empty();
-                    match tcx.const_eval((expr_did, substs)) {
+                    let substs = Substs::identity_for_item(tcx.global_tcx(), expr_did);
+                    match tcx.const_eval(param_env.and((expr_did, substs))) {
                         Ok(ConstVal::Integral(v)) => {
                             explicit_value = v;
                             break;

src/librustc/ty/structural_impls.rs

@@ -398,7 +398,7 @@ macro_rules! CopyImpls {
     }
 }
 
-CopyImpls! { (), hir::Unsafety, abi::Abi }
+CopyImpls! { (), hir::Unsafety, abi::Abi, hir::def_id::DefId }
 
 impl<'tcx, T:TypeFoldable<'tcx>, U:TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> (T, U) {

src/librustc_const_eval/check_match.rs

@@ -21,6 +21,7 @@ use rustc::middle::mem_categorization::{cmt};
 use rustc::middle::region::RegionMaps;
 use rustc::session::Session;
 use rustc::ty::{self, Ty, TyCtxt};
+use rustc::ty::subst::Substs;
 use rustc::lint;
 use rustc_errors::{Diagnostic, Level, DiagnosticBuilder};
 
@@ -51,7 +52,8 @@ impl<'a, 'tcx> Visitor<'tcx> for OuterVisitor<'a, 'tcx> {
             tcx: self.tcx,
             tables: self.tcx.body_tables(b),
             region_maps: &self.tcx.region_maps(def_id),
-            param_env: self.tcx.param_env(def_id)
+            param_env: self.tcx.param_env(def_id),
+            identity_substs: Substs::identity_for_item(self.tcx, def_id),
         }.visit_body(self.tcx.hir.body(b));
     }
 }
@@ -69,6 +71,7 @@ struct MatchVisitor<'a, 'tcx: 'a> {
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
     tables: &'a ty::TypeckTables<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
+    identity_substs: &'tcx Substs<'tcx>,
     region_maps: &'a RegionMaps,
 }
 
@@ -110,7 +113,7 @@ impl<'a, 'tcx> Visitor<'tcx> for MatchVisitor<'a, 'tcx> {
     }
 }
 
-impl<'a, 'gcx, 'tcx> PatternContext<'a, 'gcx, 'tcx> {
+impl<'a, 'tcx> PatternContext<'a, 'tcx> {
     fn report_inlining_errors(&self, pat_span: Span) {
         for error in &self.errors {
             match *error {
@@ -162,7 +165,9 @@ impl<'a, 'tcx> MatchVisitor<'a, 'tcx> {
 
             let inlined_arms : Vec<(Vec<_>, _)> = arms.iter().map(|arm| (
                 arm.pats.iter().map(|pat| {
-                    let mut patcx = PatternContext::new(self.tcx, self.tables);
+                    let mut patcx = PatternContext::new(self.tcx,
+                                                        self.param_env.and(self.identity_substs),
+                                                        self.tables);
                     let pattern = expand_pattern(cx, patcx.lower_pattern(&pat));
                     if !patcx.errors.is_empty() {
                         patcx.report_inlining_errors(pat.span);
@@ -229,7 +234,9 @@ impl<'a, 'tcx> MatchVisitor<'a, 'tcx> {
     fn check_irrefutable(&self, pat: &Pat, origin: &str) {
         let module = self.tcx.hir.get_module_parent(pat.id);
         MatchCheckCtxt::create_and_enter(self.tcx, module, |ref mut cx| {
-            let mut patcx = PatternContext::new(self.tcx, self.tables);
+            let mut patcx = PatternContext::new(self.tcx,
+                                                self.param_env.and(self.identity_substs),
+                                                self.tables);
             let pattern = patcx.lower_pattern(pat);
             let pattern_ty = pattern.ty;
             let pats : Matrix = vec![vec![