Move `name` field from `AssocItem` to `AssocKind` variants.

To accurately reflect that RPITIT assoc items don't have a name. This
avoids the use of `kw::Empty` to mean "no name", which is error prone.

Helps with #137978.

3 files changed, 28 insertions, 21 deletions

diff --git a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
index 55f698b8f21..a757329bcf2 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
@@ -895,12 +895,19 @@ impl<'tcx> Stable<'tcx> for ty::AssocKind {
     type T = stable_mir::ty::AssocKind;
 
     fn stable(&self, tables: &mut Tables<'_>) -> Self::T {
-        use stable_mir::ty::AssocKind;
+        use stable_mir::ty::{AssocKind, AssocTypeData};
         match *self {
-            ty::AssocKind::Const => AssocKind::Const,
-            ty::AssocKind::Fn { has_self } => AssocKind::Fn { has_self },
-            ty::AssocKind::Type { opt_rpitit_info } => AssocKind::Type {
-                opt_rpitit_info: opt_rpitit_info.map(|rpitit| rpitit.stable(tables)),
+            ty::AssocKind::Const { name } => AssocKind::Const { name: name.to_string() },
+            ty::AssocKind::Fn { name, has_self } => {
+                AssocKind::Fn { name: name.to_string(), has_self }
+            }
+            ty::AssocKind::Type { data } => AssocKind::Type {
+                data: match data {
+                    ty::AssocTypeData::Normal(name) => AssocTypeData::Normal(name.to_string()),
+                    ty::AssocTypeData::Rpitit(rpitit) => {
+                        AssocTypeData::Rpitit(rpitit.stable(tables))
+                    }
+                },
             },
         }
     }
@@ -924,7 +931,6 @@ impl<'tcx> Stable<'tcx> for ty::AssocItem {
     fn stable(&self, tables: &mut Tables<'_>) -> Self::T {
         stable_mir::ty::AssocItem {
             def_id: tables.assoc_def(self.def_id),
-            name: self.name.to_string(),
             kind: self.kind.stable(tables),
             container: self.container.stable(tables),
             trait_item_def_id: self.trait_item_def_id.map(|did| tables.assoc_def(did)),
diff --git a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
index 9fa97763907..8a6be0cd37a 100644
--- a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
+++ b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
@@ -22,9 +22,9 @@ impl Display for Ty {
 impl Display for AssocKind {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match self {
-            AssocKind::Fn { has_self: true } => write!(f, "method"),
-            AssocKind::Fn { has_self: false } => write!(f, "associated function"),
-            AssocKind::Const => write!(f, "associated const"),
+            AssocKind::Fn { has_self: true, .. } => write!(f, "method"),
+            AssocKind::Fn { has_self: false, .. } => write!(f, "associated function"),
+            AssocKind::Const { .. } => write!(f, "associated const"),
             AssocKind::Type { .. } => write!(f, "associated type"),
         }
     }
diff --git a/compiler/rustc_smir/src/stable_mir/ty.rs b/compiler/rustc_smir/src/stable_mir/ty.rs
index 6eac0885d76..4b153007bd8 100644
--- a/compiler/rustc_smir/src/stable_mir/ty.rs
+++ b/compiler/rustc_smir/src/stable_mir/ty.rs
@@ -1578,7 +1578,6 @@ crate_def! {
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
 pub struct AssocItem {
     pub def_id: AssocDef,
-    pub name: Symbol,
     pub kind: AssocKind,
     pub container: AssocItemContainer,
 
@@ -1587,18 +1586,20 @@ pub struct AssocItem {
     pub trait_item_def_id: Option<AssocDef>,
 }
 
+#[derive(Clone, PartialEq, Debug, Eq, Serialize)]
+pub enum AssocTypeData {
+    Normal(Symbol),
+    /// The associated type comes from an RPITIT. It has no name, and the
+    /// `ImplTraitInTraitData` provides additional information about its
+    /// source.
+    Rpitit(ImplTraitInTraitData),
+}
+
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
 pub enum AssocKind {
-    Const,
-    Fn {
-        has_self: bool,
-    },
-    Type {
-        /// `Some` if the associated type comes from an RPITIT. The
-        /// `ImplTraitInTraitData` provides additional information about its
-        /// source.
-        opt_rpitit_info: Option<ImplTraitInTraitData>,
-    },
+    Const { name: Symbol },
+    Fn { name: Symbol, has_self: bool },
+    Type { data: AssocTypeData },
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
@@ -1615,6 +1616,6 @@ pub enum ImplTraitInTraitData {
 
 impl AssocItem {
     pub fn is_impl_trait_in_trait(&self) -> bool {
-        matches!(self.kind, AssocKind::Type { opt_rpitit_info: Some(_) })
+        matches!(self.kind, AssocKind::Type { data: AssocTypeData::Rpitit(_) })
     }
 }