Newtype for InstanceOfArg semi-traversable tuple

Author: eggyal

compiler/rustc_middle/src/query/keys.rs

@@ -335,6 +335,14 @@ impl<'tcx> Key for (DefId, GenericArgsRef<'tcx>) {
     }
 }
 
+impl<'tcx> Key for ty::InstanceOfArg<'tcx> {
+    type CacheSelector = DefaultCacheSelector<Self>;
+
+    fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
+        self.0.default_span(tcx)
+    }
+}
+
 impl<'tcx> Key for (ty::UnevaluatedConst<'tcx>, ty::UnevaluatedConst<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 

compiler/rustc_middle/src/query/mod.rs

@@ -2103,7 +2103,7 @@ rustc_queries! {
     ///    from `Ok(None)` to avoid misleading diagnostics when an error
     ///    has already been/will be emitted, for the original cause
     query resolve_instance(
-        key: ty::ParamEnvAnd<'tcx, (DefId, GenericArgsRef<'tcx>)>
+        key: ty::ParamEnvAnd<'tcx, ty::InstanceOfArg<'tcx>>
     ) -> Result<Option<ty::Instance<'tcx>>, ErrorGuaranteed> {
         desc { "resolving instance `{}`", ty::Instance::new(key.value.0, key.value.1) }
     }

compiler/rustc_middle/src/ty/instance.rs

@@ -334,6 +334,9 @@ impl<'tcx> fmt::Display for Instance<'tcx> {
     }
 }
 
+#[derive(Clone, Copy, Debug, Eq, Hash, HashStable, PartialEq, TypeFoldable, TypeVisitable)]
+pub struct InstanceOfArg<'tcx>(pub DefId, pub GenericArgsRef<'tcx>);
+
 impl<'tcx> Instance<'tcx> {
     pub fn new(def_id: DefId, args: GenericArgsRef<'tcx>) -> Instance<'tcx> {
         assert!(
@@ -400,7 +403,7 @@ impl<'tcx> Instance<'tcx> {
         // below is more likely to ignore the bounds in scope (e.g. if the only
         // generic parameters mentioned by `args` were lifetime ones).
         let args = tcx.erase_regions(args);
-        tcx.resolve_instance(tcx.erase_regions(param_env.and((def_id, args))))
+        tcx.resolve_instance(tcx.erase_regions(param_env.and(InstanceOfArg(def_id, args))))
     }
 
     pub fn expect_resolve(

compiler/rustc_middle/src/ty/mod.rs

@@ -90,7 +90,9 @@ pub use self::consts::{
 pub use self::context::{
     tls, CtxtInterners, DeducedParamAttrs, FreeRegionInfo, GlobalCtxt, Lift, TyCtxt, TyCtxtFeed,
 };
-pub use self::instance::{Instance, InstanceDef, ShortInstance, UnusedGenericParams};
+pub use self::instance::{
+    Instance, InstanceDef, InstanceOfArg, ShortInstance, UnusedGenericParams,
+};
 pub use self::list::List;
 pub use self::parameterized::ParameterizedOverTcx;
 pub use self::rvalue_scopes::RvalueScopes;

compiler/rustc_ty_utils/src/instance.rs

@@ -14,9 +14,9 @@ use crate::errors::UnexpectedFnPtrAssociatedItem;
 
 fn resolve_instance<'tcx>(
     tcx: TyCtxt<'tcx>,
-    key: ty::ParamEnvAnd<'tcx, (DefId, GenericArgsRef<'tcx>)>,
+    key: ty::ParamEnvAnd<'tcx, ty::InstanceOfArg<'tcx>>,
 ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
-    let (param_env, (def_id, args)) = key.into_parts();
+    let (param_env, ty::InstanceOfArg(def_id, args)) = key.into_parts();
 
     let result = if let Some(trait_def_id) = tcx.trait_of_item(def_id) {
         debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env);