From ab36a2fe16006a34c7d19baa6ef8e23f6ec079cc Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Wed, 19 Oct 2022 18:34:01 +0000
Subject: Revert "Unify tcx.constness and param env constness checks"

This reverts commit bef8681a1837790f2745c1f6a7f8214af2fd7f5d.
This reverts commit c646c4d403d8c88cd3450f859fbdc34ec26d5bb5.
---
 compiler/rustc_ty_utils/src/ty.rs | 69 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 68 insertions(+), 1 deletion(-)

(limited to 'compiler/rustc_ty_utils/src')

diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index 196d70614e7..cd9d2296405 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -137,10 +137,77 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
     let local_did = def_id.as_local();
     let hir_id = local_did.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id));
 
+    let constness = match hir_id {
+        Some(hir_id) => match tcx.hir().get(hir_id) {
+            hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
+                if tcx.is_const_default_method(def_id) =>
+            {
+                hir::Constness::Const
+            }
+
+            hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(..), .. })
+            | hir::Node::Item(hir::Item { kind: hir::ItemKind::Static(..), .. })
+            | hir::Node::TraitItem(hir::TraitItem {
+                kind: hir::TraitItemKind::Const(..), ..
+            })
+            | hir::Node::AnonConst(_)
+            | hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
+            | hir::Node::ImplItem(hir::ImplItem {
+                kind:
+                    hir::ImplItemKind::Fn(
+                        hir::FnSig {
+                            header: hir::FnHeader { constness: hir::Constness::Const, .. },
+                            ..
+                        },
+                        ..,
+                    ),
+                ..
+            }) => hir::Constness::Const,
+
+            hir::Node::ImplItem(hir::ImplItem {
+                kind: hir::ImplItemKind::Type(..) | hir::ImplItemKind::Fn(..),
+                ..
+            }) => {
+                let parent_hir_id = tcx.hir().get_parent_node(hir_id);
+                match tcx.hir().get(parent_hir_id) {
+                    hir::Node::Item(hir::Item {
+                        kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
+                        ..
+                    }) => *constness,
+                    _ => span_bug!(
+                        tcx.def_span(parent_hir_id.owner),
+                        "impl item's parent node is not an impl",
+                    ),
+                }
+            }
+
+            hir::Node::Item(hir::Item {
+                kind:
+                    hir::ItemKind::Fn(hir::FnSig { header: hir::FnHeader { constness, .. }, .. }, ..),
+                ..
+            })
+            | hir::Node::TraitItem(hir::TraitItem {
+                kind:
+                    hir::TraitItemKind::Fn(
+                        hir::FnSig { header: hir::FnHeader { constness, .. }, .. },
+                        ..,
+                    ),
+                ..
+            })
+            | hir::Node::Item(hir::Item {
+                kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
+                ..
+            }) => *constness,
+
+            _ => hir::Constness::NotConst,
+        },
+        None => hir::Constness::NotConst,
+    };
+
     let unnormalized_env = ty::ParamEnv::new(
         tcx.intern_predicates(&predicates),
         traits::Reveal::UserFacing,
-        tcx.constness(def_id),
+        constness,
     );
 
     let body_id =
-- 
cgit 1.4.1-3-g733a5


From 43f2c37f9350b2bed0b81bf858e7478869d8c306 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Wed, 19 Oct 2022 19:05:15 +0000
Subject: Note discrepancies in constness calculation

---
 compiler/rustc_ty_utils/src/ty.rs | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'compiler/rustc_ty_utils/src')

diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index cd9d2296405..3eebb4ace47 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -137,6 +137,7 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
     let local_did = def_id.as_local();
     let hir_id = local_did.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id));
 
+    // FIXME(consts): This is not exactly in line with the constness query.
     let constness = match hir_id {
         Some(hir_id) => match tcx.hir().get(hir_id) {
             hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
@@ -201,6 +202,10 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
 
             _ => hir::Constness::NotConst,
         },
+        // FIXME(consts): It's suspicious that a param-env for a foreign item
+        // will always have NotConst param-env, though we don't typically use
+        // that param-env for anything meaningful right now, so it's likely
+        // not an issue.
         None => hir::Constness::NotConst,
     };
 
-- 
cgit 1.4.1-3-g733a5