query-ify const_field

Cargo.lock

@@ -2703,7 +2703,6 @@ dependencies = [
  "rustc-demangle 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_data_structures 0.0.0",
  "rustc_metadata 0.0.0",
- "rustc_mir 0.0.0",
  "rustc_target 0.0.0",
  "syntax 0.0.0",
  "syntax_pos 0.0.0",

src/librustc/dep_graph/dep_node.rs

@@ -49,6 +49,7 @@
 //! user of the `DepNode` API of having to know how to compute the expected
 //! fingerprint for a given set of node parameters.
 
+use crate::mir;
 use crate::mir::interpret::GlobalId;
 use crate::hir::def_id::{CrateNum, DefId, DefIndex, CRATE_DEF_INDEX};
 use crate::hir::map::DefPathHash;

src/librustc/query/mod.rs

@@ -4,6 +4,7 @@ use crate::ty::{self, ParamEnvAnd, Ty, TyCtxt};
 use crate::ty::subst::SubstsRef;
 use crate::dep_graph::SerializedDepNodeIndex;
 use crate::hir::def_id::{CrateNum, DefId, DefIndex};
+use crate::mir;
 use crate::mir::interpret::GlobalId;
 use crate::traits;
 use crate::traits::query::{
@@ -431,6 +432,15 @@ rustc_queries! {
                 tcx.queries.on_disk_cache.try_load_query_result(tcx, id).map(Ok)
             }
         }
+
+        /// Extracts a field of a (variant of a) const.
+        query const_field(
+            key: ty::ParamEnvAnd<'tcx, (&'tcx ty::Const<'tcx>, mir::Field)>
+        ) -> &'tcx ty::Const<'tcx> {
+            eval_always
+            no_force
+            desc { "extract field of const" }
+        }
     }
 
     TypeChecking {

src/librustc/ty/print/mod.rs

@@ -7,9 +7,10 @@ use rustc_data_structures::fx::FxHashSet;
 
 // `pretty` is a separate module only for organization.
 mod pretty;
-pub mod obsolete;
 pub use self::pretty::*;
 
+pub mod obsolete;
+
 pub trait Print<'gcx, 'tcx, P> {
     type Output;
     type Error;

src/librustc/ty/query/keys.rs

@@ -127,6 +127,15 @@ impl<'tcx> Key for (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>) {
     }
 }
 
+impl<'tcx> Key for (&'tcx ty::Const<'tcx>, mir::Field) {
+    fn query_crate(&self) -> CrateNum {
+        LOCAL_CRATE
+    }
+    fn default_span(&self, _: TyCtxt<'_, '_, '_>) -> Span {
+        DUMMY_SP
+    }
+}
+
 impl<'tcx> Key for ty::PolyTraitRef<'tcx>{
     fn query_crate(&self) -> CrateNum {
         self.def_id().krate

src/librustc_codegen_ssa/mir/constant.rs

@@ -1,5 +1,4 @@
 use rustc::mir::interpret::ErrorHandled;
-use rustc_mir::const_eval::const_field;
 use rustc::mir;
 use rustc_data_structures::indexed_vec::Idx;
 use rustc::ty::{self, Ty};
@@ -46,12 +45,8 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     _ => bug!("invalid simd shuffle type: {}", c.ty),
                 };
                 let values: Vec<_> = (0..fields).map(|field| {
-                    let field = const_field(
-                        bx.tcx(),
-                        ty::ParamEnv::reveal_all(),
-                        None,
-                        mir::Field::new(field as usize),
-                        c,
+                    let field = bx.tcx().const_field(
+                        ty::ParamEnv::reveal_all().and((&c, mir::Field::new(field as usize)))
                     );
                     if let Some(prim) = field.val.try_to_scalar() {
                         let layout = bx.layout_of(field_ty);

src/librustc_mir/const_eval.rs

@@ -470,7 +470,7 @@ impl<'a, 'mir, 'tcx> interpret::Machine<'a, 'mir, 'tcx>
     }
 }
 
-/// Projects to a field of a (variant of a) const.
+/// Extracts a field of a (variant of a) const.
 // this function uses `unwrap` copiously, because an already validated constant must have valid
 // fields and can thus never fail outside of compiler bugs
 pub fn const_field<'a, 'tcx>(

src/librustc_mir/hair/pattern/mod.rs

@@ -5,7 +5,7 @@ mod check_match;
 
 pub(crate) use self::check_match::check_match;
 
-use crate::const_eval::{const_field, const_variant_index};
+use crate::const_eval::const_variant_index;
 
 use crate::hair::util::UserAnnotatedTyHelpers;
 use crate::hair::constant::*;
@@ -949,7 +949,9 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
         debug!("const_to_pat: cv={:#?} id={:?}", cv, id);
         let adt_subpattern = |i, variant_opt| {
             let field = Field::new(i);
-            let val = const_field(self.tcx, self.param_env, variant_opt, field, cv);
+            let val = crate::const_eval::const_field(
+                self.tcx, self.param_env, variant_opt, field, cv
+            );
             self.const_to_pat(instance, val, id, span)
         };
         let adt_subpatterns = |n, variant_opt| {

src/librustc_mir/lib.rs

@@ -63,6 +63,10 @@ pub fn provide(providers: &mut Providers<'_>) {
     providers.const_eval = const_eval::const_eval_provider;
     providers.const_eval_raw = const_eval::const_eval_raw_provider;
     providers.check_match = hair::pattern::check_match;
+    providers.const_field = |tcx, param_env_and_value| {
+        let (param_env, (value, field)) = param_env_and_value.into_parts();
+        const_eval::const_field(tcx, param_env, None, field, value)
+    };
 }
 
 __build_diagnostic_array! { librustc_mir, DIAGNOSTICS }