Rollup merge of #138376 - nnethercote:hir-ItemKind-ident-precursors, r=compiler-errors

Item-related cleanups

I have been looking at `hir::Item` closely and found a few minor cleanup opportunities.

r? ```@spastorino```

Author: matthiaskrgr

Diff for: compiler/rustc_hir/src/hir.rs

@@ -4332,16 +4332,6 @@ pub enum OwnerNode<'hir> {
 }
 
 impl<'hir> OwnerNode<'hir> {
-    pub fn ident(&self) -> Option<Ident> {
-        match self {
-            OwnerNode::Item(Item { ident, .. })
-            | OwnerNode::ForeignItem(ForeignItem { ident, .. })
-            | OwnerNode::ImplItem(ImplItem { ident, .. })
-            | OwnerNode::TraitItem(TraitItem { ident, .. }) => Some(*ident),
-            OwnerNode::Crate(..) | OwnerNode::Synthetic => None,
-        }
-    }
-
     pub fn span(&self) -> Span {
         match self {
             OwnerNode::Item(Item { span, .. })

Diff for: compiler/rustc_hir_pretty/src/lib.rs

@@ -553,24 +553,6 @@ impl<'a> State<'a> {
         self.word(";")
     }
 
-    fn print_item_type(
-        &mut self,
-        item: &hir::Item<'_>,
-        generics: &hir::Generics<'_>,
-        inner: impl Fn(&mut Self),
-    ) {
-        self.head("type");
-        self.print_ident(item.ident);
-        self.print_generic_params(generics.params);
-        self.end(); // end the inner ibox
-
-        self.print_where_clause(generics);
-        self.space();
-        inner(self);
-        self.word(";");
-        self.end(); // end the outer ibox
-    }
-
     fn print_item(&mut self, item: &hir::Item<'_>) {
         self.hardbreak_if_not_bol();
         self.maybe_print_comment(item.span.lo());
@@ -683,10 +665,17 @@ impl<'a> State<'a> {
                 self.end()
             }
             hir::ItemKind::TyAlias(ty, generics) => {
-                self.print_item_type(item, generics, |state| {
-                    state.word_space("=");
-                    state.print_type(ty);
-                });
+                self.head("type");
+                self.print_ident(item.ident);
+                self.print_generic_params(generics.params);
+                self.end(); // end the inner ibox
+
+                self.print_where_clause(generics);
+                self.space();
+                self.word_space("=");
+                self.print_type(ty);
+                self.word(";");
+                self.end(); // end the outer ibox
             }
             hir::ItemKind::Enum(ref enum_definition, params) => {
                 self.print_enum_def(enum_definition, params, item.ident.name, item.span);

Diff for: compiler/rustc_parse/src/parser/item.rs

@@ -646,7 +646,7 @@ impl<'a> Parser<'a> {
 
         let impl_items = self.parse_item_list(attrs, |p| p.parse_impl_item(ForceCollect::No))?;
 
-        let item_kind = match ty_second {
+        let (of_trait, self_ty) = match ty_second {
             Some(ty_second) => {
                 // impl Trait for Type
                 if !has_for {
@@ -679,31 +679,20 @@ impl<'a> Parser<'a> {
                 };
                 let trait_ref = TraitRef { path, ref_id: ty_first.id };
 
-                ItemKind::Impl(Box::new(Impl {
-                    safety,
-                    polarity,
-                    defaultness,
-                    constness,
-                    generics,
-                    of_trait: Some(trait_ref),
-                    self_ty: ty_second,
-                    items: impl_items,
-                }))
-            }
-            None => {
-                // impl Type
-                ItemKind::Impl(Box::new(Impl {
-                    safety,
-                    polarity,
-                    defaultness,
-                    constness,
-                    generics,
-                    of_trait: None,
-                    self_ty: ty_first,
-                    items: impl_items,
-                }))
+                (Some(trait_ref), ty_second)
             }
+            None => (None, ty_first), // impl Type
         };
+        let item_kind = ItemKind::Impl(Box::new(Impl {
+            safety,
+            polarity,
+            defaultness,
+            constness,
+            generics,
+            of_trait,
+            self_ty,
+            items: impl_items,
+        }));
 
         Ok((Ident::empty(), item_kind))
     }