Rollup merge of #97446 - cjgillot:get-generics, r=michaelwoerister

Make hir().get_generics and generics_of consistent.

Fetching generics from a HIR node is currently implemented differently in 4 different places.
This PR makes the 4 implementations call the single `hir::Node::generics`, which implements the more general version from `generics_of` query.

compiler/rustc_hir/src/hir.rs

@@ -3004,13 +3004,12 @@ impl ItemKind<'_> {
         Some(match *self {
             ItemKind::Fn(_, ref generics, _)
             | ItemKind::TyAlias(_, ref generics)
-            | ItemKind::OpaqueTy(OpaqueTy {
-                ref generics, origin: OpaqueTyOrigin::TyAlias, ..
-            })
+            | ItemKind::OpaqueTy(OpaqueTy { ref generics, .. })
             | ItemKind::Enum(_, ref generics)
             | ItemKind::Struct(_, ref generics)
             | ItemKind::Union(_, ref generics)
             | ItemKind::Trait(_, _, ref generics, _, _)
+            | ItemKind::TraitAlias(ref generics, _)
             | ItemKind::Impl(Impl { ref generics, .. }) => generics,
             _ => return None,
         })
@@ -3210,13 +3209,8 @@ impl<'hir> OwnerNode<'hir> {
         }
     }
 
-    pub fn generics(&self) -> Option<&'hir Generics<'hir>> {
-        match self {
-            OwnerNode::TraitItem(TraitItem { generics, .. })
-            | OwnerNode::ImplItem(ImplItem { generics, .. }) => Some(generics),
-            OwnerNode::Item(item) => item.kind.generics(),
-            _ => None,
-        }
+    pub fn generics(self) -> Option<&'hir Generics<'hir>> {
+        Node::generics(self.into())
     }
 
     pub fn def_id(self) -> LocalDefId {
@@ -3403,9 +3397,12 @@ impl<'hir> Node<'hir> {
         }
     }
 
-    pub fn generics(&self) -> Option<&'hir Generics<'hir>> {
+    pub fn generics(self) -> Option<&'hir Generics<'hir>> {
         match self {
-            Node::TraitItem(TraitItem { generics, .. })
+            Node::ForeignItem(ForeignItem {
+                kind: ForeignItemKind::Fn(_, _, generics), ..
+            })
+            | Node::TraitItem(TraitItem { generics, .. })
             | Node::ImplItem(ImplItem { generics, .. }) => Some(generics),
             Node::Item(item) => item.kind.generics(),
             _ => None,

compiler/rustc_middle/src/hir/map/mod.rs

@@ -361,27 +361,7 @@ impl<'hir> Map<'hir> {
 
     pub fn get_generics(self, id: LocalDefId) -> Option<&'hir Generics<'hir>> {
         let node = self.tcx.hir_owner(id)?;
-        match node.node {
-            OwnerNode::ImplItem(impl_item) => Some(&impl_item.generics),
-            OwnerNode::TraitItem(trait_item) => Some(&trait_item.generics),
-            OwnerNode::ForeignItem(ForeignItem {
-                kind: ForeignItemKind::Fn(_, _, generics),
-                ..
-            })
-            | OwnerNode::Item(Item {
-                kind:
-                    ItemKind::Fn(_, generics, _)
-                    | ItemKind::TyAlias(_, generics)
-                    | ItemKind::Enum(_, generics)
-                    | ItemKind::Struct(_, generics)
-                    | ItemKind::Union(_, generics)
-                    | ItemKind::Trait(_, _, generics, ..)
-                    | ItemKind::TraitAlias(generics, _)
-                    | ItemKind::Impl(Impl { generics, .. }),
-                ..
-            }) => Some(generics),
-            _ => None,
-        }
+        node.node.generics()
     }
 
     pub fn item(self, id: ItemId) -> &'hir Item<'hir> {

compiler/rustc_typeck/src/collect.rs

@@ -1588,41 +1588,20 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
         _ => None,
     };
 
-    let mut opt_self = None;
-    let mut allow_defaults = false;
-
     let no_generics = hir::Generics::empty();
-    let ast_generics = match node {
-        Node::TraitItem(item) => &item.generics,
-
-        Node::ImplItem(item) => &item.generics,
-
+    let ast_generics = node.generics().unwrap_or(&no_generics);
+    let (opt_self, allow_defaults) = match node {
         Node::Item(item) => {
             match item.kind {
-                ItemKind::Fn(.., ref generics, _)
-                | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
-
-                ItemKind::TyAlias(_, ref generics)
-                | ItemKind::Enum(_, ref generics)
-                | ItemKind::Struct(_, ref generics)
-                | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
-                | ItemKind::Union(_, ref generics) => {
-                    allow_defaults = true;
-                    generics
-                }
-
-                ItemKind::Trait(_, _, ref generics, ..)
-                | ItemKind::TraitAlias(ref generics, ..) => {
+                ItemKind::Trait(..) | ItemKind::TraitAlias(..) => {
                     // Add in the self type parameter.
                     //
                     // Something of a hack: use the node id for the trait, also as
                     // the node id for the Self type parameter.
-                    let param_id = item.def_id;
-
-                    opt_self = Some(ty::GenericParamDef {
+                    let opt_self = Some(ty::GenericParamDef {
                         index: 0,
                         name: kw::SelfUpper,
-                        def_id: param_id.to_def_id(),
+                        def_id,
                         pure_wrt_drop: false,
                         kind: ty::GenericParamDefKind::Type {
                             has_default: false,
@@ -1631,21 +1610,17 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
                         },
                     });
 
-                    allow_defaults = true;
-                    generics
+                    (opt_self, true)
                 }
-
-                _ => &no_generics,
+                ItemKind::TyAlias(..)
+                | ItemKind::Enum(..)
+                | ItemKind::Struct(..)
+                | ItemKind::OpaqueTy(..)
+                | ItemKind::Union(..) => (None, true),
+                _ => (None, false),
             }
         }
-
-        Node::ForeignItem(item) => match item.kind {
-            ForeignItemKind::Static(..) => &no_generics,
-            ForeignItemKind::Fn(_, _, ref generics) => generics,
-            ForeignItemKind::Type => &no_generics,
-        },
-
-        _ => &no_generics,
+        _ => (None, false),
     };
 
     let has_self = opt_self.is_some();