1 files changed, 217 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/mir/interpret/queries.rs b/compiler/rustc_middle/src/mir/interpret/queries.rs
new file mode 100644
index 000000000..786927e2d
--- /dev/null
+++ b/compiler/rustc_middle/src/mir/interpret/queries.rs
@@ -0,0 +1,217 @@
+use super::{ErrorHandled, EvalToConstValueResult, EvalToValTreeResult, GlobalId};
+
+use crate::mir;
+use crate::ty::subst::InternalSubsts;
+use crate::ty::visit::TypeVisitable;
+use crate::ty::{self, query::TyCtxtAt, query::TyCtxtEnsure, TyCtxt};
+use rustc_hir::def_id::DefId;
+use rustc_span::{Span, DUMMY_SP};
+
+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.
+    #[instrument(skip(self), level = "debug")]
+    pub fn const_eval_poly(self, def_id: DefId) -> EvalToConstValueResult<'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 of 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).with_reveal_all_normalized(self);
+        self.const_eval_global_id(param_env, cid, None)
+    }
+    /// 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.
+    #[instrument(level = "debug", skip(self))]
+    pub fn const_eval_resolve(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        ct: ty::Unevaluated<'tcx>,
+        span: Option<Span>,
+    ) -> EvalToConstValueResult<'tcx> {
+        // Cannot resolve `Unevaluated` constants that contain inference
+        // variables. We reject those here since `resolve_opt_const_arg`
+        // would fail otherwise.
+        //
+        // When trying to evaluate constants containing inference variables,
+        // use `Infcx::const_eval_resolve` instead.
+        if ct.substs.has_infer_types_or_consts() {
+            bug!("did not expect inference variables here");
+        }
+
+        match ty::Instance::resolve_opt_const_arg(self, param_env, ct.def, ct.substs) {
+            Ok(Some(instance)) => {
+                let cid = GlobalId { instance, promoted: ct.promoted };
+                self.const_eval_global_id(param_env, cid, span)
+            }
+            Ok(None) => Err(ErrorHandled::TooGeneric),
+            Err(error_reported) => Err(ErrorHandled::Reported(error_reported)),
+        }
+    }
+
+    #[instrument(level = "debug", skip(self))]
+    pub fn const_eval_resolve_for_typeck(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        ct: ty::Unevaluated<'tcx>,
+        span: Option<Span>,
+    ) -> EvalToValTreeResult<'tcx> {
+        // Cannot resolve `Unevaluated` constants that contain inference
+        // variables. We reject those here since `resolve_opt_const_arg`
+        // would fail otherwise.
+        //
+        // When trying to evaluate constants containing inference variables,
+        // use `Infcx::const_eval_resolve` instead.
+        if ct.substs.has_infer_types_or_consts() {
+            bug!("did not expect inference variables here");
+        }
+
+        match ty::Instance::resolve_opt_const_arg(self, param_env, ct.def, ct.substs) {
+            Ok(Some(instance)) => {
+                let cid = GlobalId { instance, promoted: ct.promoted };
+                self.const_eval_global_id_for_typeck(param_env, cid, span)
+            }
+            Ok(None) => Err(ErrorHandled::TooGeneric),
+            Err(error_reported) => Err(ErrorHandled::Reported(error_reported)),
+        }
+    }
+
+    pub fn const_eval_instance(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        instance: ty::Instance<'tcx>,
+        span: Option<Span>,
+    ) -> EvalToConstValueResult<'tcx> {
+        self.const_eval_global_id(param_env, GlobalId { instance, promoted: None }, span)
+    }
+
+    /// Evaluate a constant to a `ConstValue`.
+    #[instrument(skip(self), level = "debug")]
+    pub fn const_eval_global_id(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        cid: GlobalId<'tcx>,
+        span: Option<Span>,
+    ) -> EvalToConstValueResult<'tcx> {
+        let param_env = param_env.with_const();
+        // Const-eval shouldn't depend on lifetimes at all, so we can erase them, which should
+        // improve caching of queries.
+        let inputs = self.erase_regions(param_env.and(cid));
+        if let Some(span) = span {
+            self.at(span).eval_to_const_value_raw(inputs)
+        } else {
+            self.eval_to_const_value_raw(inputs)
+        }
+    }
+
+    /// Evaluate a constant to a type-level constant.
+    #[instrument(skip(self), level = "debug")]
+    pub fn const_eval_global_id_for_typeck(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        cid: GlobalId<'tcx>,
+        span: Option<Span>,
+    ) -> EvalToValTreeResult<'tcx> {
+        let param_env = param_env.with_const();
+        debug!(?param_env);
+        // Const-eval shouldn't depend on lifetimes at all, so we can erase them, which should
+        // improve caching of queries.
+        let inputs = self.erase_regions(param_env.and(cid));
+        debug!(?inputs);
+        if let Some(span) = span {
+            self.at(span).eval_to_valtree(inputs)
+        } else {
+            self.eval_to_valtree(inputs)
+        }
+    }
+
+    /// Evaluate a static's initializer, returning the allocation of the initializer's memory.
+    #[inline(always)]
+    pub fn eval_static_initializer(
+        self,
+        def_id: DefId,
+    ) -> Result<mir::ConstAllocation<'tcx>, ErrorHandled> {
+        self.at(DUMMY_SP).eval_static_initializer(def_id)
+    }
+}
+
+impl<'tcx> TyCtxtAt<'tcx> {
+    /// Evaluate a static's initializer, returning the allocation of the initializer's memory.
+    pub fn eval_static_initializer(
+        self,
+        def_id: DefId,
+    ) -> Result<mir::ConstAllocation<'tcx>, ErrorHandled> {
+        trace!("eval_static_initializer: Need to compute {:?}", def_id);
+        assert!(self.is_static(def_id));
+        let instance = ty::Instance::mono(*self, def_id);
+        let gid = GlobalId { instance, promoted: None };
+        self.eval_to_allocation(gid, ty::ParamEnv::reveal_all())
+    }
+
+    /// Evaluate anything constant-like, returning the allocation of the final memory.
+    fn eval_to_allocation(
+        self,
+        gid: GlobalId<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+    ) -> Result<mir::ConstAllocation<'tcx>, ErrorHandled> {
+        let param_env = param_env.with_const();
+        trace!("eval_to_allocation: Need to compute {:?}", gid);
+        let raw_const = self.eval_to_allocation_raw(param_env.and(gid))?;
+        Ok(self.global_alloc(raw_const.alloc_id).unwrap_memory())
+    }
+}
+
+impl<'tcx> TyCtxtEnsure<'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.
+    #[instrument(skip(self), level = "debug")]
+    pub fn const_eval_poly(self, def_id: DefId) {
+        // 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 of them are
+        // encountered.
+        let substs = InternalSubsts::identity_for_item(self.tcx, def_id);
+        let instance = ty::Instance::new(def_id, substs);
+        let cid = GlobalId { instance, promoted: None };
+        let param_env =
+            self.tcx.param_env(def_id).with_reveal_all_normalized(self.tcx).with_const();
+        // Const-eval shouldn't depend on lifetimes at all, so we can erase them, which should
+        // improve caching of queries.
+        let inputs = self.tcx.erase_regions(param_env.and(cid));
+        self.eval_to_const_value_raw(inputs)
+    }
+
+    /// Evaluate a static's initializer, returning the allocation of the initializer's memory.
+    pub fn eval_static_initializer(self, def_id: DefId) {
+        trace!("eval_static_initializer: Need to compute {:?}", def_id);
+        assert!(self.tcx.is_static(def_id));
+        let instance = ty::Instance::mono(self.tcx, def_id);
+        let gid = GlobalId { instance, promoted: None };
+        let param_env = ty::ParamEnv::reveal_all().with_const();
+        trace!("eval_to_allocation: Need to compute {:?}", gid);
+        self.eval_to_allocation_raw(param_env.and(gid))
+    }
+}
+
+impl<'tcx> TyCtxt<'tcx> {
+    /// Destructure a mir constant ADT or array into its variant index and its field values.
+    /// Panics if the destructuring fails, use `try_destructure_mir_constant` for fallible version.
+    pub fn destructure_mir_constant(
+        self,
+        param_env: ty::ParamEnv<'tcx>,
+        constant: mir::ConstantKind<'tcx>,
+    ) -> mir::DestructuredMirConstant<'tcx> {
+        self.try_destructure_mir_constant(param_env.and(constant)).unwrap()
+    }
+}