Add simpler entry points to const eval for common usages.

23 files changed, 195 insertions, 253 deletions

diff --git a/src/librustc/mir/interpret/mod.rs b/src/librustc/mir/interpret/mod.rs
index fff876752db..80bac92d003 100644
--- a/src/librustc/mir/interpret/mod.rs
+++ b/src/librustc/mir/interpret/mod.rs
@@ -101,6 +101,7 @@ mod error;
 mod value;
 mod allocation;
 mod pointer;
+mod queries;
 
 pub use self::error::{
     InterpErrorInfo, InterpResult, InterpError, AssertMessage, ConstEvalErr, struct_error,
@@ -116,9 +117,10 @@ pub use self::pointer::{Pointer, PointerArithmetic, CheckInAllocMsg};
 
 use crate::mir;
 use crate::hir::def_id::DefId;
-use crate::ty::{self, TyCtxt, Instance, subst::GenericArgKind};
+use crate::ty::{self, TyCtxt, Instance};
 use crate::ty::codec::TyDecoder;
 use crate::ty::layout::{self, Size};
+use crate::ty::subst::GenericArgKind;
 use std::io;
 use std::fmt;
 use std::num::NonZeroU32;
diff --git a/src/librustc/mir/interpret/queries.rs b/src/librustc/mir/interpret/queries.rs
new file mode 100644
index 00000000000..5fd49a056d2
--- /dev/null
+++ b/src/librustc/mir/interpret/queries.rs
@@ -0,0 +1,89 @@
+use super::{ConstEvalResult, ErrorHandled, GlobalId};
+
+use crate::mir;
+use crate::hir::def_id::DefId;
+use crate::ty::{self, TyCtxt};
+use crate::ty::subst::{InternalSubsts, SubstsRef};
+use syntax_pos::Span;
+
+
+impl<'tcx> TyCtxt<'tcx> {
+
+    /// Evaluates a constant without providing any substitutions. This is useful to evaluate consts
+    /// that can't take any generic arguments like statics, const items or enum discriminants. If a
+    /// generic parameter is used within the constant `ErrorHandled::ToGeneric` will be returned.
+    pub fn const_eval_poly(self, def_id: DefId) -> ConstEvalResult<'tcx> {
+        // In some situations def_id will have substitutions within scope, but they aren't allowed
+        // to be used. So we can't use `Instance::mono`, instead we feed unresolved substitutions
+        // into `const_eval` which will return `ErrorHandled::ToGeneric` if any og them are
+        // encountered.
+        let substs = InternalSubsts::identity_for_item(self, def_id);
+        let instance = ty::Instance::new(def_id, substs);
+        let cid = GlobalId {
+            instance,
+            promoted: None,
+        };
+        let param_env = self.param_env(def_id);
+        self.const_eval_validated(param_env.and(cid))
+    }
+
+    /// Resolves and evaluates a constant.
+    ///
+    /// The constant can be located on a trait like `<A as B>::C`, in which case the given
+    /// substitutions and environment are used to resolve the constant. Alternatively if the
+    /// constant has generic parameters in scope the substitutions are used to evaluate the value of
+    /// the constant. For example in `fn foo<T>() { let _ = [0; bar::<T>()]; }` the repeat count
+    /// constant `bar::<T>()` requires a substitution for `T`, if the substitution for `T` is still
+    /// too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is
+    /// returned.
+    pub fn const_eval_resolve(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        def_id: DefId,
+        substs: SubstsRef<'tcx>,
+        span: Option<Span>
+    ) -> ConstEvalResult<'tcx> {
+        let instance = ty::Instance::resolve(
+            self,
+            param_env,
+            def_id,
+            substs,
+        );
+        if let Some(instance) = instance {
+            self.const_eval_instance(param_env, instance, span)
+        } else {
+            Err(ErrorHandled::TooGeneric)
+        }
+    }
+
+    pub fn const_eval_instance(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        instance: ty::Instance<'tcx>,
+        span: Option<Span>
+    ) -> ConstEvalResult<'tcx> {
+        let cid = GlobalId {
+            instance,
+            promoted: None,
+        };
+        if let Some(span) = span {
+            self.at(span).const_eval_validated(param_env.and(cid))
+        } else {
+            self.const_eval_validated(param_env.and(cid))
+        }
+    }
+
+    /// Evaluate a promoted constant.
+    pub fn const_eval_promoted(
+        self,
+        instance: ty::Instance<'tcx>,
+        promoted: mir::Promoted
+    ) -> ConstEvalResult<'tcx> {
+        let cid = GlobalId {
+            instance,
+            promoted: Some(promoted),
+        };
+        let param_env = ty::ParamEnv::reveal_all();
+        self.const_eval_validated(param_env.and(cid))
+    }
+}
diff --git a/src/librustc/query/mod.rs b/src/librustc/query/mod.rs
index cc02165f605..a9dd856e758 100644
--- a/src/librustc/query/mod.rs
+++ b/src/librustc/query/mod.rs
@@ -448,7 +448,8 @@ rustc_queries! {
         ///
         /// **Do not use this** outside const eval. Const eval uses this to break query cycles
         /// during validation. Please add a comment to every use site explaining why using
-        /// `const_eval` isn't sufficient.
+        /// `const_eval_validated` isn't sufficient. The returned constant also isn't in a suitable
+        /// form to be used outside of const eval.
         query const_eval_raw(key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>)
             -> ConstEvalRawResult<'tcx> {
             no_force
@@ -460,7 +461,13 @@ rustc_queries! {
 
         /// Results of evaluating const items or constants embedded in
         /// other items (such as enum variant explicit discriminants).
-        query const_eval(key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>)
+        ///
+        /// In contrast to `const_eval_raw` this performs some validation on the constant, and
+        /// returns a proper constant that is usable by the rest of the compiler.
+        ///
+        /// **Do not use this** directly, use one of the following wrappers: `tcx.const_eval_poly`,
+        /// `tcx.const_eval_resolve`, `tcx.const_eval_instance`, or `tcx.const_eval_promoted`.
+        query const_eval_validated(key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>)
             -> ConstEvalResult<'tcx> {
             no_force
             desc { |tcx|
diff --git a/src/librustc/traits/fulfill.rs b/src/librustc/traits/fulfill.rs
index 27731990d2b..3fd2415c83c 100644
--- a/src/librustc/traits/fulfill.rs
+++ b/src/librustc/traits/fulfill.rs
@@ -1,5 +1,4 @@
 use crate::infer::{InferCtxt, ShallowResolver};
-use crate::mir::interpret::{GlobalId, ErrorHandled};
 use crate::ty::{self, Ty, TypeFoldable, ToPolyTraitRef};
 use crate::ty::error::ExpectedFound;
 use rustc_data_structures::obligation_forest::{DoCompleted, Error, ForestObligation};
@@ -501,27 +500,13 @@ impl<'a, 'b, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'b, 'tcx> {
                         ProcessResult::Unchanged
                 } else {
                     if !substs.has_local_value() {
-                        let instance = ty::Instance::resolve(
-                            self.selcx.tcx(),
-                            obligation.param_env,
-                            def_id,
-                            substs,
-                        );
-                        if let Some(instance) = instance {
-                            let cid = GlobalId {
-                                instance,
-                                promoted: None,
-                            };
-                            match self.selcx.tcx().at(obligation.cause.span)
-                                                    .const_eval(obligation.param_env.and(cid)) {
-                                Ok(_) => ProcessResult::Changed(vec![]),
-                                Err(err) => ProcessResult::Error(
-                                    CodeSelectionError(ConstEvalFailure(err)))
-                            }
-                        } else {
-                            ProcessResult::Error(CodeSelectionError(
-                                ConstEvalFailure(ErrorHandled::TooGeneric)
-                            ))
+                        match self.selcx.tcx().const_eval_resolve(obligation.param_env,
+                                                                  def_id,
+                                                                  substs,
+                                                                  Some(obligation.cause.span)) {
+                            Ok(_) => ProcessResult::Changed(vec![]),
+                            Err(err) => ProcessResult::Error(
+                                CodeSelectionError(ConstEvalFailure(err)))
                         }
                     } else {
                         pending_obligation.stalled_on =
diff --git a/src/librustc/traits/select.rs b/src/librustc/traits/select.rs
index 94a77c553e5..8d04c832f26 100644
--- a/src/librustc/traits/select.rs
+++ b/src/librustc/traits/select.rs
@@ -33,7 +33,6 @@ use crate::dep_graph::{DepKind, DepNodeIndex};
 use crate::hir::def_id::DefId;
 use crate::infer::{CombinedSnapshot, InferCtxt, InferOk, PlaceholderMap, TypeFreshener};
 use crate::middle::lang_items;
-use crate::mir::interpret::GlobalId;
 use crate::ty::fast_reject;
 use crate::ty::relate::TypeRelation;
 use crate::ty::subst::{Subst, SubstsRef};
@@ -820,22 +819,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             }
 
             ty::Predicate::ConstEvaluatable(def_id, substs) => {
-                let tcx = self.tcx();
                 if !(obligation.param_env, substs).has_local_value() {
-                    let param_env = obligation.param_env;
-                    let instance =
-                        ty::Instance::resolve(tcx, param_env, def_id, substs);
-                    if let Some(instance) = instance {
-                        let cid = GlobalId {
-                            instance,
-                            promoted: None,
-                        };
-                        match self.tcx().const_eval(param_env.and(cid)) {
-                            Ok(_) => Ok(EvaluatedToOk),
-                            Err(_) => Ok(EvaluatedToErr),
-                        }
-                    } else {
-                        Ok(EvaluatedToErr)
+                    match self.tcx().const_eval_resolve(obligation.param_env,
+                                                        def_id,
+                                                        substs,
+                                                        None) {
+                        Ok(_) => Ok(EvaluatedToOk),
+                        Err(_) => Ok(EvaluatedToErr),
                     }
                 } else {
                     // Inference variables still left in param_env or substs.
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 15bbfa7860f..c60d4a46935 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -19,7 +19,7 @@ use crate::middle::cstore::CrateStoreDyn;
 use crate::middle::lang_items::{FnTraitLangItem, FnMutTraitLangItem, FnOnceTraitLangItem};
 use crate::middle::resolve_lifetime::ObjectLifetimeDefault;
 use crate::mir::ReadOnlyBodyAndCache;
-use crate::mir::interpret::{GlobalId, ErrorHandled};
+use crate::mir::interpret::ErrorHandled;
 use crate::mir::GeneratorLayout;
 use crate::session::CrateDisambiguator;
 use crate::traits::{self, Reveal};
@@ -2344,13 +2344,7 @@ impl<'tcx> AdtDef {
     pub fn eval_explicit_discr(&self, tcx: TyCtxt<'tcx>, expr_did: DefId) -> Option<Discr<'tcx>> {
         let param_env = tcx.param_env(expr_did);
         let repr_type = self.repr.discr_type();
-        let substs = InternalSubsts::identity_for_item(tcx, expr_did);
-        let instance = ty::Instance::new(expr_did, substs);
-        let cid = GlobalId {
-            instance,
-            promoted: None
-        };
-        match tcx.const_eval(param_env.and(cid)) {
+        match tcx.const_eval_poly(expr_did) {
             Ok(val) => {
                 // FIXME: Find the right type and use it instead of `val.ty` here
                 if let Some(b) = val.try_eval_bits(tcx, param_env, val.ty) {
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index 6cb0d1e9946..1e08c36ca50 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -15,7 +15,7 @@ use crate::ty::{self, AdtDef, Discr, DefIdTree, TypeFlags, Ty, TyCtxt, TypeFolda
 use crate::ty::{List, TyS, ParamEnvAnd, ParamEnv};
 use crate::ty::layout::VariantIdx;
 use crate::util::captures::Captures;
-use crate::mir::interpret::{Scalar, GlobalId};
+use crate::mir::interpret::Scalar;
 
 use polonius_engine::Atom;
 use rustc_index::vec::Idx;
@@ -2340,13 +2340,9 @@ impl<'tcx> Const<'tcx> {
 
             let (param_env, substs) = param_env_and_substs.into_parts();
 
-            // try to resolve e.g. associated constants to their definition on an impl
-            let instance = ty::Instance::resolve(tcx, param_env, did, substs)?;
-            let gid = GlobalId {
-                instance,
-                promoted: None,
-            };
-            tcx.const_eval(param_env.and(gid)).ok()
+            // try to resolve e.g. associated constants to their definition on an impl, and then
+            // evaluate the const.
+            tcx.const_eval_resolve(param_env, did, substs, None).ok()
         };
 
         match self.val {
diff --git a/src/librustc_codegen_llvm/consts.rs b/src/librustc_codegen_llvm/consts.rs
index 11a105c1828..c048321e383 100644
--- a/src/librustc_codegen_llvm/consts.rs
+++ b/src/librustc_codegen_llvm/consts.rs
@@ -8,7 +8,7 @@ use crate::value::Value;
 use libc::c_uint;
 use rustc::hir::def_id::DefId;
 use rustc::mir::interpret::{ConstValue, Allocation, read_target_uint,
-    Pointer, ErrorHandled, GlobalId};
+    Pointer, ErrorHandled};
 use rustc::mir::mono::MonoItem;
 use rustc::hir::Node;
 use rustc_target::abi::HasDataLayout;
@@ -81,13 +81,7 @@ pub fn codegen_static_initializer(
     cx: &CodegenCx<'ll, 'tcx>,
     def_id: DefId,
 ) -> Result<(&'ll Value, &'tcx Allocation), ErrorHandled> {
-    let instance = ty::Instance::mono(cx.tcx, def_id);
-    let cid = GlobalId {
-        instance,
-        promoted: None,
-    };
-    let param_env = ty::ParamEnv::reveal_all();
-    let static_ = cx.tcx.const_eval(param_env.and(cid))?;
+    let static_ = cx.tcx.const_eval_poly(def_id)?;
 
     let alloc = match static_.val {
         ty::ConstKind::Value(ConstValue::ByRef {
diff --git a/src/librustc_codegen_llvm/intrinsic.rs b/src/librustc_codegen_llvm/intrinsic.rs
index 900f2d2defc..da776757fdf 100644
--- a/src/librustc_codegen_llvm/intrinsic.rs
+++ b/src/librustc_codegen_llvm/intrinsic.rs
@@ -14,7 +14,6 @@ use rustc_codegen_ssa::glue;
 use rustc_codegen_ssa::base::{to_immediate, wants_msvc_seh, compare_simd_types};
 use rustc::ty::{self, Ty};
 use rustc::ty::layout::{self, FnAbiExt, LayoutOf, HasTyCtxt, Primitive};
-use rustc::mir::interpret::GlobalId;
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
 use rustc::hir;
 use rustc_target::abi::HasDataLayout;
@@ -202,11 +201,9 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
             "needs_drop" |
             "type_id" |
             "type_name" => {
-                let gid = GlobalId {
-                    instance,
-                    promoted: None,
-                };
-                let ty_name = self.tcx.const_eval(ty::ParamEnv::reveal_all().and(gid)).unwrap();
+                let ty_name = self.tcx
+                    .const_eval_instance(ty::ParamEnv::reveal_all(), instance, None)
+                    .unwrap();
                 OperandRef::from_const(self, ty_name).immediate_or_packed_pair(self)
             }
             "init" => {
diff --git a/src/librustc_codegen_ssa/mir/block.rs b/src/librustc_codegen_ssa/mir/block.rs
index dabd097b000..a532c23a6e0 100644
--- a/src/librustc_codegen_ssa/mir/block.rs
+++ b/src/librustc_codegen_ssa/mir/block.rs
@@ -638,12 +638,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                 projection: &[],
                             } = place.as_ref()
                             {
-                                let param_env = ty::ParamEnv::reveal_all();
-                                let cid = mir::interpret::GlobalId {
-                                    instance: self.instance,
-                                    promoted: Some(promoted),
-                                };
-                                let c = bx.tcx().const_eval(param_env.and(cid));
+                                let c = bx.tcx().const_eval_promoted(self.instance, promoted);
                                 let (llval, ty) = self.simd_shuffle_indices(
                                     &bx,
                                     terminator.source_info.span,
diff --git a/src/librustc_codegen_ssa/mir/constant.rs b/src/librustc_codegen_ssa/mir/constant.rs
index fb8f504d04b..fc17e2c0c71 100644
--- a/src/librustc_codegen_ssa/mir/constant.rs
+++ b/src/librustc_codegen_ssa/mir/constant.rs
@@ -43,17 +43,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         match constant.literal.val {
             ty::ConstKind::Unevaluated(def_id, substs) => {
                 let substs = self.monomorphize(&substs);
-                let instance = ty::Instance::resolve(
-                    self.cx.tcx(), ty::ParamEnv::reveal_all(), def_id, substs,
-                ).unwrap();
-                let cid = mir::interpret::GlobalId {
-                    instance,
-                    promoted: None,
-                };
-                self.cx.tcx().const_eval(ty::ParamEnv::reveal_all().and(cid)).map_err(|err| {
-                    self.cx.tcx().sess.span_err(constant.span, "erroneous constant encountered");
-                    err
-                })
+                self.cx.tcx()
+                    .const_eval_resolve(ty::ParamEnv::reveal_all(), def_id, substs, None)
+                    .map_err(|err| {
+                        self.cx.tcx().sess.span_err(
+                            constant.span,
+                            "erroneous constant encountered");
+                        err
+                    })
             },
             _ => Ok(self.monomorphize(&constant.literal)),
         }
diff --git a/src/librustc_codegen_ssa/mir/place.rs b/src/librustc_codegen_ssa/mir/place.rs
index 5e13cabced0..1132f9b2f03 100644
--- a/src/librustc_codegen_ssa/mir/place.rs
+++ b/src/librustc_codegen_ssa/mir/place.rs
@@ -473,14 +473,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 }),
                 projection: [],
             } => {
-                let param_env = ty::ParamEnv::reveal_all();
                 let instance = Instance::new(*def_id, self.monomorphize(substs));
-                let cid = mir::interpret::GlobalId {
-                    instance: instance,
-                    promoted: Some(*promoted),
-                };
                 let layout = cx.layout_of(self.monomorphize(&ty));
-                match bx.tcx().const_eval(param_env.and(cid)) {
+                match bx.tcx().const_eval_promoted(instance, *promoted) {
                     Ok(val) => match val.val {
                         ty::ConstKind::Value(mir::interpret::ConstValue::ByRef {
                             alloc, offset
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 10b00d35d9b..b46e8a8438f 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -1134,19 +1134,9 @@ declare_lint_pass!(
 
 fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
     let def_id = cx.tcx.hir().body_owner_def_id(body_id);
-    let param_env = if cx.tcx.is_static(def_id) {
-        // Use the same param_env as `codegen_static_initializer`, to reuse the cache.
-        ty::ParamEnv::reveal_all()
-    } else {
-        cx.tcx.param_env(def_id)
-    };
-    let cid = ::rustc::mir::interpret::GlobalId {
-        instance: ty::Instance::mono(cx.tcx, def_id),
-        promoted: None
-    };
     // trigger the query once for all constants since that will already report the errors
     // FIXME: Use ensure here
-    let _ = cx.tcx.const_eval(param_env.and(cid));
+    let _ = cx.tcx.const_eval_poly(def_id);
 }
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
diff --git a/src/librustc_mir/const_eval.rs b/src/librustc_mir/const_eval.rs
index b219fec31dc..a2f066bee08 100644
--- a/src/librustc_mir/const_eval.rs
+++ b/src/librustc_mir/const_eval.rs
@@ -652,7 +652,7 @@ fn validate_and_turn_into_const<'tcx>(
     })
 }
 
-pub fn const_eval_provider<'tcx>(
+pub fn const_eval_validated_provider<'tcx>(
     tcx: TyCtxt<'tcx>,
     key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>,
 ) -> ::rustc::mir::interpret::ConstEvalResult<'tcx> {
@@ -660,7 +660,7 @@ pub fn const_eval_provider<'tcx>(
     if key.param_env.reveal == Reveal::All {
         let mut key = key.clone();
         key.param_env.reveal = Reveal::UserFacing;
-        match tcx.const_eval(key) {
+        match tcx.const_eval_validated(key) {
             // try again with reveal all as requested
             Err(ErrorHandled::TooGeneric) => {
                 // Promoteds should never be "too generic" when getting evaluated.
diff --git a/src/librustc_mir/hair/cx/expr.rs b/src/librustc_mir/hair/cx/expr.rs
index 8c852854be1..f116f7d14da 100644
--- a/src/librustc_mir/hair/cx/expr.rs
+++ b/src/librustc_mir/hair/cx/expr.rs
@@ -5,7 +5,7 @@ use crate::hair::cx::to_ref::ToRef;
 use crate::hair::util::UserAnnotatedTyHelpers;
 use rustc_index::vec::Idx;
 use rustc::hir::def::{CtorOf, Res, DefKind, CtorKind};
-use rustc::mir::interpret::{GlobalId, ErrorHandled, Scalar};
+use rustc::mir::interpret::{ErrorHandled, Scalar};
 use rustc::ty::{self, AdtKind, Ty};
 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, AutoBorrowMutability, PointerCast};
 use rustc::ty::subst::{InternalSubsts, SubstsRef};
@@ -514,21 +514,15 @@ fn make_mirror_unadjusted<'a, 'tcx>(
         hir::ExprKind::Repeat(ref v, ref count) => {
             let def_id = cx.tcx.hir().local_def_id(count.hir_id);
             let substs = InternalSubsts::identity_for_item(cx.tcx, def_id);
-            let instance = ty::Instance::resolve(
-                cx.tcx,
-                cx.param_env,
-                def_id,
-                substs,
-            ).unwrap();
-            let global_id = GlobalId {
-                instance,
-                promoted: None
-            };
             let span = cx.tcx.def_span(def_id);
-            let count = match cx.tcx.at(span).const_eval(cx.param_env.and(global_id)) {
+            let count = match cx.tcx.const_eval_resolve(cx.param_env,
+                                                        def_id,
+                                                        substs,
+                                                        Some(span)) {
                 Ok(cv) => cv.eval_usize(cx.tcx, cx.param_env),
                 Err(ErrorHandled::Reported) => 0,
                 Err(ErrorHandled::TooGeneric) => {
+                    let span = cx.tcx.def_span(def_id);
                     cx.tcx.sess.span_err(span, "array lengths can't depend on generic parameters");
                     0
                 },
diff --git a/src/librustc_mir/hair/pattern/mod.rs b/src/librustc_mir/hair/pattern/mod.rs
index 0086c3b0e10..e12f0322564 100644
--- a/src/librustc_mir/hair/pattern/mod.rs
+++ b/src/librustc_mir/hair/pattern/mod.rs
@@ -11,7 +11,7 @@ use crate::hair::constant::*;
 
 use rustc::mir::{Field, BorrowKind, Mutability};
 use rustc::mir::{UserTypeProjection};
-use rustc::mir::interpret::{GlobalId, ConstValue, get_slice_bytes, sign_extend};
+use rustc::mir::interpret::{ConstValue, ErrorHandled, get_slice_bytes, sign_extend};
 use rustc::ty::{self, Region, TyCtxt, AdtDef, Ty, UserType, DefIdTree};
 use rustc::ty::{CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations};
 use rustc::ty::subst::{SubstsRef, GenericArg};
@@ -854,57 +854,37 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         let kind = match res {
             Res::Def(DefKind::Const, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
                 let substs = self.tables.node_substs(id);
-                match ty::Instance::resolve(
-                    self.tcx,
-                    self.param_env,
-                    def_id,
-                    substs,
-                ) {
-                    Some(instance) => {
-                        let cid = GlobalId {
-                            instance,
-                            promoted: None,
-                        };
-                        match self.tcx.at(span).const_eval(self.param_env.and(cid)) {
-                            Ok(value) => {
-                                let pattern = self.const_to_pat(value, id, span);
-                                if !is_associated_const {
-                                    return pattern;
-                                }
+                match self.tcx.const_eval_resolve(self.param_env, def_id, substs, Some(span)) {
+                    Ok(value) => {
+                        let pattern = self.const_to_pat(value, id, span);
+                        if !is_associated_const {
+                            return pattern;
+                        }
 
-                                let user_provided_types = self.tables().user_provided_types();
-                                return if let Some(u_ty) = user_provided_types.get(id) {
-                                    let user_ty = PatTyProj::from_user_type(*u_ty);
-                                    Pat {
-                                        span,
-                                        kind: Box::new(
-                                            PatKind::AscribeUserType {
-                                                subpattern: pattern,
-                                                ascription: Ascription {
-                                                    /// Note that use `Contravariant` here. See the
-                                                    /// `variance` field documentation for details.
-                                                    variance: ty::Variance::Contravariant,
-                                                    user_ty,
-                                                    user_ty_span: span,
-                                                },
-                                            }
-                                        ),
-                                        ty: value.ty,
+                        let user_provided_types = self.tables().user_provided_types();
+                        return if let Some(u_ty) = user_provided_types.get(id) {
+                            let user_ty = PatTyProj::from_user_type(*u_ty);
+                            Pat {
+                                span,
+                                kind: Box::new(
+                                    PatKind::AscribeUserType {
+                                        subpattern: pattern,
+                                        ascription: Ascription {
+                                            /// Note that use `Contravariant` here. See the
+                                            /// `variance` field documentation for details.
+                                            variance: ty::Variance::Contravariant,
+                                            user_ty,
+                                            user_ty_span: span,
+                                        },
                                     }
-                                } else {
-                                    pattern
-                                }
-                            },
-                            Err(_) => {
-                                self.tcx.sess.span_err(
-                                    span,
-                                    "could not evaluate constant pattern",
-                                );
-                                PatKind::Wild
+                                ),
+                                ty: value.ty,
                             }
+                        } else {
+                            pattern
                         }
                     },
-                    None => {
+                    Err(ErrorHandled::TooGeneric) => {
                         self.errors.push(if is_associated_const {
                             PatternError::AssocConstInPattern(span)
                         } else {
@@ -912,6 +892,13 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                         });
                         PatKind::Wild
                     },
+                    Err(_) => {
+                        self.tcx.sess.span_err(
+                            span,
+                            "could not evaluate constant pattern",
+                        );
+                        PatKind::Wild
+                    }
                 }
             }
             _ => self.lower_variant_or_leaf(res, id, span, ty, vec![]),
diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs
index 67f0aed243d..46782ef0a80 100644
--- a/src/librustc_mir/interpret/intrinsics.rs
+++ b/src/librustc_mir/interpret/intrinsics.rs
@@ -11,7 +11,7 @@ use rustc::hir::def_id::DefId;
 use rustc::ty::TyCtxt;
 use rustc::mir::{
     self, BinOp,
-    interpret::{InterpResult, Scalar, GlobalId, ConstValue}
+    interpret::{InterpResult, Scalar, ConstValue}
 };
 
 use super::{
@@ -123,11 +123,9 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             sym::size_of |
             sym::type_id |
             sym::type_name => {
-                let gid = GlobalId {
-                    instance,
-                    promoted: None,
-                };
-                let val = self.tcx.const_eval(self.param_env.and(gid))?;
+                let val = self.tcx.const_eval_instance(self.param_env,
+                                                       instance,
+                                                       Some(self.tcx.span))?;
                 let val = self.eval_const_to_op(val, None)?;
                 self.copy_op(val, dest)?;
             }
diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs
index 42fbfeca3f0..70ea3745b4d 100644
--- a/src/librustc_mir/interpret/place.rs
+++ b/src/librustc_mir/interpret/place.rs
@@ -619,11 +619,6 @@ where
                 let ty = place_static.ty;
                 assert!(!ty.needs_subst());
                 let layout = self.layout_of(ty)?;
-                let instance = ty::Instance::mono(*self.tcx, place_static.def_id);
-                let cid = GlobalId {
-                    instance,
-                    promoted: None
-                };
                 // Just create a lazy reference, so we can support recursive statics.
                 // tcx takes care of assigning every static one and only one unique AllocId.
                 // When the data here is ever actually used, memory will notice,
@@ -639,7 +634,7 @@ where
                 // Notice that statics have *two* AllocIds: the lazy one, and the resolved
                 // one.  Here we make sure that the interpreted program never sees the
                 // resolved ID.  Also see the doc comment of `Memory::get_static_alloc`.
-                let alloc_id = self.tcx.alloc_map.lock().create_static_alloc(cid.instance.def_id());
+                let alloc_id = self.tcx.alloc_map.lock().create_static_alloc(place_static.def_id);
                 let ptr = self.tag_static_base_pointer(Pointer::from(alloc_id));
                 MPlaceTy::from_aligned_ptr(ptr, layout)
             }
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index f6b3c5b8e5e..cf54530317c 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -56,7 +56,7 @@ pub fn provide(providers: &mut Providers<'_>) {
     shim::provide(providers);
     transform::provide(providers);
     monomorphize::partitioning::provide(providers);
-    providers.const_eval = const_eval::const_eval_provider;
+    providers.const_eval_validated = const_eval::const_eval_validated_provider;
     providers.const_eval_raw = const_eval::const_eval_raw_provider;
     providers.check_match = hair::pattern::check_match;
     providers.const_caller_location = const_eval::const_caller_location;
diff --git a/src/librustc_mir/monomorphize/collector.rs b/src/librustc_mir/monomorphize/collector.rs
index 93a76712b28..ab95c795c43 100644
--- a/src/librustc_mir/monomorphize/collector.rs
+++ b/src/librustc_mir/monomorphize/collector.rs
@@ -189,7 +189,7 @@ use rustc::session::config::EntryFnType;
 use rustc::mir::{self, Location, PlaceBase, Static, StaticKind};
 use rustc::mir::visit::Visitor as MirVisitor;
 use rustc::mir::mono::{MonoItem, InstantiationMode};
-use rustc::mir::interpret::{Scalar, GlobalId, GlobalAlloc, ErrorHandled};
+use rustc::mir::interpret::{Scalar, GlobalAlloc, ErrorHandled};
 use rustc::util::nodemap::{FxHashSet, FxHashMap, DefIdMap};
 use rustc::util::common::time;
 
@@ -379,13 +379,7 @@ fn collect_items_rec<'tcx>(
 
             recursion_depth_reset = None;
 
-            let cid = GlobalId {
-                instance,
-                promoted: None,
-            };
-            let param_env = ty::ParamEnv::reveal_all();
-
-            if let Ok(val) = tcx.const_eval(param_env.and(cid)) {
+            if let Ok(val) = tcx.const_eval_poly(def_id) {
                 collect_const(tcx, val, InternalSubsts::empty(), &mut neighbors);
             }
         }
@@ -681,12 +675,8 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
                 def_id,
                 ..
             }) => {
-                let param_env = ty::ParamEnv::reveal_all();
-                let cid = GlobalId {
-                    instance: Instance::new(*def_id, substs.subst(self.tcx, self.param_substs)),
-                    promoted: Some(*promoted),
-                };
-                match self.tcx.const_eval(param_env.and(cid)) {
+                let instance = Instance::new(*def_id, substs.subst(self.tcx, self.param_substs));
+                match self.tcx.const_eval_promoted(instance, *promoted) {
                     Ok(val) => collect_const(self.tcx, val, substs, self.output),
                     Err(ErrorHandled::Reported) => {},
                     Err(ErrorHandled::TooGeneric) => {
@@ -1041,14 +1031,7 @@ impl ItemLikeVisitor<'v> for RootCollector<'_, 'v> {
                 // but even just declaring them must collect the items they refer to
                 let def_id = self.tcx.hir().local_def_id(item.hir_id);
 
-                let instance = Instance::mono(self.tcx, def_id);
-                let cid = GlobalId {
-                    instance,
-                    promoted: None,
-                };
-                let param_env = ty::ParamEnv::reveal_all();
-
-                if let Ok(val) = self.tcx.const_eval(param_env.and(cid)) {
+                if let Ok(val) = self.tcx.const_eval_poly(def_id) {
                     collect_const(self.tcx, val, InternalSubsts::empty(), &mut self.output);
                 }
             }
@@ -1288,16 +1271,7 @@ fn collect_const<'tcx>(
             }
         }
         ty::ConstKind::Unevaluated(def_id, substs) => {
-            let instance = ty::Instance::resolve(tcx,
-                                                param_env,
-                                                def_id,
-                                                substs).unwrap();
-
-            let cid = GlobalId {
-                instance,
-                promoted: None,
-            };
-            match tcx.const_eval(param_env.and(cid)) {
+            match tcx.const_eval_resolve(param_env, def_id, substs, None) {
                 Ok(val) => collect_const(tcx, val, param_substs, output),
                 Err(ErrorHandled::Reported) => {},
                 Err(ErrorHandled::TooGeneric) => span_bug!(
diff --git a/src/librustc_typeck/check/expr.rs b/src/librustc_typeck/check/expr.rs
index 19441be87b9..b287b39cb99 100644
--- a/src/librustc_typeck/check/expr.rs
+++ b/src/librustc_typeck/check/expr.rs
@@ -31,7 +31,6 @@ use rustc::hir::ptr::P;
 use rustc::infer;
 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc::middle::lang_items;
-use rustc::mir::interpret::GlobalId;
 use rustc::ty;
 use rustc::ty::adjustment::{
     Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability,
@@ -39,7 +38,6 @@ use rustc::ty::adjustment::{
 use rustc::ty::{AdtKind, Visibility};
 use rustc::ty::Ty;
 use rustc::ty::TypeFoldable;
-use rustc::ty::subst::InternalSubsts;
 use rustc::traits::{self, ObligationCauseCode};
 
 use rustc_error_codes::*;
@@ -1023,20 +1021,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let count = if self.const_param_def_id(count).is_some() {
             Ok(self.to_const(count, tcx.type_of(count_def_id)))
         } else {
-            let param_env = ty::ParamEnv::empty();
-            let substs = InternalSubsts::identity_for_item(tcx, count_def_id);
-            let instance = ty::Instance::resolve(
-                tcx,
-                param_env,
-                count_def_id,
-                substs,
-            ).unwrap();
-            let global_id = GlobalId {
-                instance,
-                promoted: None
-            };
-
-            tcx.const_eval(param_env.and(global_id))
+            tcx.const_eval_poly(count_def_id)
         };
 
         let uty = match expected {
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index 09771bb7625..84f5847ddd3 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -106,7 +106,7 @@ use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc::infer::error_reporting::TypeAnnotationNeeded::E0282;
 use rustc::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
 use rustc::middle::region;
-use rustc::mir::interpret::{ConstValue, GlobalId};
+use rustc::mir::interpret::ConstValue;
 use rustc::traits::{self, ObligationCause, ObligationCauseCode, TraitEngine};
 use rustc::ty::{
     self, AdtKind, CanonicalUserType, Ty, TyCtxt, Const, GenericParamDefKind,
@@ -1836,13 +1836,7 @@ fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span)
     // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
     // the consumer's responsibility to ensure all bytes that have been read
     // have defined values.
-    let instance = ty::Instance::mono(tcx, id);
-    let cid = GlobalId {
-        instance,
-        promoted: None
-    };
-    let param_env = ty::ParamEnv::reveal_all();
-    if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
+    if let Ok(static_) = tcx.const_eval_poly(id) {
         let alloc = if let ty::ConstKind::Value(ConstValue::ByRef { alloc, .. }) = static_.val {
             alloc
         } else {
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index e5f684cbca8..7eb1370c342 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -15,7 +15,6 @@ use rustc::infer::region_constraints::{RegionConstraintData, Constraint};
 use rustc::middle::resolve_lifetime as rl;
 use rustc::middle::lang_items;
 use rustc::middle::stability;
-use rustc::mir::interpret::GlobalId;
 use rustc::hir;
 use rustc::hir::def::{CtorKind, DefKind, Res};
 use rustc::hir::def_id::{CrateNum, DefId, CRATE_DEF_INDEX};
@@ -1334,13 +1333,7 @@ impl Clean<Type> for hir::Ty {
             TyKind::Slice(ref ty) => Slice(box ty.clean(cx)),
             TyKind::Array(ref ty, ref length) => {
                 let def_id = cx.tcx.hir().local_def_id(length.hir_id);
-                let param_env = cx.tcx.param_env(def_id);
-                let substs = InternalSubsts::identity_for_item(cx.tcx, def_id);
-                let cid = GlobalId {
-                    instance: ty::Instance::new(def_id, substs),
-                    promoted: None
-                };
-                let length = match cx.tcx.const_eval(param_env.and(cid)) {
+                let length = match cx.tcx.const_eval_poly(def_id) {
                     Ok(length) => print_const(cx, length),
                     Err(_) => cx.sess()
                                 .source_map()
@@ -1534,16 +1527,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
             ty::Slice(ty) => Slice(box ty.clean(cx)),
             ty::Array(ty, n) => {
                 let mut n = cx.tcx.lift(&n).expect("array lift failed");
-                if let ty::ConstKind::Unevaluated(def_id, substs) = n.val {
-                    let param_env = cx.tcx.param_env(def_id);
-                    let cid = GlobalId {
-                        instance: ty::Instance::new(def_id, substs),
-                        promoted: None
-                    };
-                    if let Ok(new_n) = cx.tcx.const_eval(param_env.and(cid)) {
-                        n = new_n;
-                    }
-                };
+                n = n.eval(cx.tcx, ty::ParamEnv::reveal_all());
                 let n = print_const(cx, n);
                 Array(box ty.clean(cx), n)
             }