implied_bounds: clarify our assumptions

2 files changed, 62 insertions, 0 deletions

diff --git a/compiler/rustc_ty_utils/src/implied_bounds.rs b/compiler/rustc_ty_utils/src/implied_bounds.rs
new file mode 100644
index 00000000000..a77ea440aaa
--- /dev/null
+++ b/compiler/rustc_ty_utils/src/implied_bounds.rs
@@ -0,0 +1,60 @@
+use crate::rustc_middle::ty::DefIdTree;
+use rustc_hir::{def::DefKind, def_id::DefId};
+use rustc_middle::ty::{self, Ty, TyCtxt};
+
+pub fn provide(providers: &mut ty::query::Providers) {
+    *providers = ty::query::Providers { assumed_wf_types, ..*providers };
+}
+
+fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx ty::List<Ty<'tcx>> {
+    match tcx.def_kind(def_id) {
+        DefKind::Fn => {
+            let sig = tcx.fn_sig(def_id);
+            let liberated_sig = tcx.liberate_late_bound_regions(def_id, sig);
+            liberated_sig.inputs_and_output
+        }
+        DefKind::AssocFn => {
+            let sig = tcx.fn_sig(def_id);
+            let liberated_sig = tcx.liberate_late_bound_regions(def_id, sig);
+            let mut assumed_wf_types: Vec<_> =
+                tcx.assumed_wf_types(tcx.parent(def_id)).as_slice().into();
+            assumed_wf_types.extend(liberated_sig.inputs_and_output);
+            tcx.intern_type_list(&assumed_wf_types)
+        }
+        DefKind::Impl => match tcx.impl_trait_ref(def_id) {
+            Some(trait_ref) => {
+                let types: Vec<_> = trait_ref.substs.types().collect();
+                tcx.intern_type_list(&types)
+            }
+            // Only the impl self type
+            None => tcx.intern_type_list(&[tcx.type_of(def_id)]),
+        },
+        DefKind::AssocConst | DefKind::AssocTy => tcx.assumed_wf_types(tcx.parent(def_id)),
+        DefKind::Mod
+        | DefKind::Struct
+        | DefKind::Union
+        | DefKind::Enum
+        | DefKind::Variant
+        | DefKind::Trait
+        | DefKind::TyAlias
+        | DefKind::ForeignTy
+        | DefKind::TraitAlias
+        | DefKind::TyParam
+        | DefKind::Const
+        | DefKind::ConstParam
+        | DefKind::Static(_)
+        | DefKind::Ctor(_, _)
+        | DefKind::Macro(_)
+        | DefKind::ExternCrate
+        | DefKind::Use
+        | DefKind::ForeignMod
+        | DefKind::AnonConst
+        | DefKind::InlineConst
+        | DefKind::OpaqueTy
+        | DefKind::Field
+        | DefKind::LifetimeParam
+        | DefKind::GlobalAsm
+        | DefKind::Closure
+        | DefKind::Generator => ty::List::empty(),
+    }
+}
diff --git a/compiler/rustc_ty_utils/src/lib.rs b/compiler/rustc_ty_utils/src/lib.rs
index 09f5c2a11aa..55d82693994 100644
--- a/compiler/rustc_ty_utils/src/lib.rs
+++ b/compiler/rustc_ty_utils/src/lib.rs
@@ -21,6 +21,7 @@ use rustc_middle::ty::query::Providers;
 mod assoc;
 mod common_traits;
 mod consts;
+mod implied_bounds;
 pub mod instance;
 mod needs_drop;
 pub mod representability;
@@ -30,6 +31,7 @@ pub fn provide(providers: &mut Providers) {
     assoc::provide(providers);
     common_traits::provide(providers);
     consts::provide(providers);
+    implied_bounds::provide(providers);
     needs_drop::provide(providers);
     ty::provide(providers);
     instance::provide(providers);