Auto merge of #44766 - sunjay:lift_generics, r=nikomatsakis

Move Generics from MethodSig to TraitItem and ImplItem

As part of `rust-impl-period/WG-compiler-traits`, we want to "lift" `Generics` from `MethodSig` into `TraitItem` and `ImplItem`. This is in preparation for adding associated type generics. (https://github.com/rust-lang/rust/issues/44265#issuecomment-331172238)

Currently this change is only made in the AST. In the future, it may also impact the HIR. (Still discussing)

To understand this PR, it's probably best to start from the changes to `ast.rs` and then work your way to the other files to understand the far reaching effects of this change.

r? @nikomatsakis

7 files changed, 38 insertions, 32 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index f445def9e03..b985ac78056 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -1178,7 +1178,6 @@ pub struct MethodSig {
     pub constness: Spanned<Constness>,
     pub abi: Abi,
     pub decl: P<FnDecl>,
-    pub generics: Generics,
 }
 
 /// Represents an item declaration within a trait declaration,
@@ -1190,6 +1189,7 @@ pub struct TraitItem {
     pub id: NodeId,
     pub ident: Ident,
     pub attrs: Vec<Attribute>,
+    pub generics: Generics,
     pub node: TraitItemKind,
     pub span: Span,
     /// See `Item::tokens` for what this is
@@ -1211,6 +1211,7 @@ pub struct ImplItem {
     pub vis: Visibility,
     pub defaultness: Defaultness,
     pub attrs: Vec<Attribute>,
+    pub generics: Generics,
     pub node: ImplItemKind,
     pub span: Span,
     /// See `Item::tokens` for what this is
diff --git a/src/libsyntax/ext/placeholders.rs b/src/libsyntax/ext/placeholders.rs
index 4fc2b92d3cd..2f5b386346b 100644
--- a/src/libsyntax/ext/placeholders.rs
+++ b/src/libsyntax/ext/placeholders.rs
@@ -32,6 +32,7 @@ pub fn placeholder(kind: ExpansionKind, id: ast::NodeId) -> Expansion {
 
     let ident = keywords::Invalid.ident();
     let attrs = Vec::new();
+    let generics = ast::Generics::default();
     let vis = ast::Visibility::Inherited;
     let span = DUMMY_SP;
     let expr_placeholder = || P(ast::Expr {
@@ -49,12 +50,12 @@ pub fn placeholder(kind: ExpansionKind, id: ast::NodeId) -> Expansion {
             tokens: None,
         }))),
         ExpansionKind::TraitItems => Expansion::TraitItems(SmallVector::one(ast::TraitItem {
-            id, span, ident, attrs,
+            id, span, ident, attrs, generics,
             node: ast::TraitItemKind::Macro(mac_placeholder()),
             tokens: None,
         })),
         ExpansionKind::ImplItems => Expansion::ImplItems(SmallVector::one(ast::ImplItem {
-            id, span, ident, vis, attrs,
+            id, span, ident, vis, attrs, generics,
             node: ast::ImplItemKind::Macro(mac_placeholder()),
             defaultness: ast::Defaultness::Final,
             tokens: None,
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 9060a613bc1..326f8cef6b3 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -1526,7 +1526,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 span: Span,
                 _node_id: NodeId) {
         // check for const fn declarations
-        if let FnKind::ItemFn(_, _, _, Spanned { node: ast::Constness::Const, .. }, _, _, _) =
+        if let FnKind::ItemFn(_, _, Spanned { node: ast::Constness::Const, .. }, _, _, _) =
             fn_kind {
             gate_feature_post!(&self, const_fn, span, "const fn is unstable");
         }
@@ -1536,7 +1536,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
         // point.
 
         match fn_kind {
-            FnKind::ItemFn(_, _, _, _, abi, _, _) |
+            FnKind::ItemFn(_, _, _, abi, _, _) |
             FnKind::Method(_, &ast::MethodSig { abi, .. }, _, _) => {
                 self.check_abi(abi, span);
             }
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index d7d491db71f..518386a2ad2 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -943,6 +943,7 @@ pub fn noop_fold_trait_item<T: Folder>(i: TraitItem, folder: &mut T)
         id: folder.new_id(i.id),
         ident: folder.fold_ident(i.ident),
         attrs: fold_attrs(i.attrs, folder),
+        generics: folder.fold_generics(i.generics),
         node: match i.node {
             TraitItemKind::Const(ty, default) => {
                 TraitItemKind::Const(folder.fold_ty(ty),
@@ -972,6 +973,7 @@ pub fn noop_fold_impl_item<T: Folder>(i: ImplItem, folder: &mut T)
         vis: folder.fold_vis(i.vis),
         ident: folder.fold_ident(i.ident),
         attrs: fold_attrs(i.attrs, folder),
+        generics: folder.fold_generics(i.generics),
         defaultness: i.defaultness,
         node: match i.node  {
             ast::ImplItemKind::Const(ty, expr) => {
@@ -1074,7 +1076,6 @@ pub fn noop_fold_foreign_item<T: Folder>(ni: ForeignItem, folder: &mut T) -> For
 
 pub fn noop_fold_method_sig<T: Folder>(sig: MethodSig, folder: &mut T) -> MethodSig {
     MethodSig {
-        generics: folder.fold_generics(sig.generics),
         abi: sig.abi,
         unsafety: sig.unsafety,
         constness: sig.constness,
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 8fd2bad4e44..07fa2a4d1a7 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -1287,10 +1287,10 @@ impl<'a> Parser<'a> {
                          mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
         let lo = self.span;
 
-        let (name, node) = if self.eat_keyword(keywords::Type) {
+        let (name, node, generics) = if self.eat_keyword(keywords::Type) {
             let TyParam {ident, bounds, default, ..} = self.parse_ty_param(vec![])?;
             self.expect(&token::Semi)?;
-            (ident, TraitItemKind::Type(bounds, default))
+            (ident, TraitItemKind::Type(bounds, default), ast::Generics::default())
         } else if self.is_const_item() {
             self.expect_keyword(keywords::Const)?;
             let ident = self.parse_ident()?;
@@ -1305,7 +1305,7 @@ impl<'a> Parser<'a> {
                 self.expect(&token::Semi)?;
                 None
             };
-            (ident, TraitItemKind::Const(ty, default))
+            (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
         } else if self.token.is_path_start() {
             // trait item macro.
             // code copied from parse_macro_use_or_failure... abstraction!
@@ -1328,7 +1328,7 @@ impl<'a> Parser<'a> {
             }
 
             let mac = respan(lo.to(self.prev_span), Mac_ { path: pth, tts: tts });
-            (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac))
+            (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
         } else {
             let (constness, unsafety, abi) = self.parse_fn_front_matter()?;
 
@@ -1341,13 +1341,12 @@ impl<'a> Parser<'a> {
                 // definition...
                 p.parse_arg_general(false)
             })?;
-
             generics.where_clause = self.parse_where_clause()?;
+
             let sig = ast::MethodSig {
                 unsafety,
                 constness,
                 decl: d,
-                generics,
                 abi,
             };
 
@@ -1370,13 +1369,14 @@ impl<'a> Parser<'a> {
                     return Err(self.fatal(&format!("expected `;` or `{{`, found `{}`", token_str)));
                 }
             };
-            (ident, ast::TraitItemKind::Method(sig, body))
+            (ident, ast::TraitItemKind::Method(sig, body), generics)
         };
 
         Ok(TraitItem {
             id: ast::DUMMY_NODE_ID,
             ident: name,
             attrs,
+            generics,
             node,
             span: lo.to(self.prev_span),
             tokens: None,
@@ -4901,12 +4901,12 @@ impl<'a> Parser<'a> {
         let lo = self.span;
         let vis = self.parse_visibility(false)?;
         let defaultness = self.parse_defaultness()?;
-        let (name, node) = if self.eat_keyword(keywords::Type) {
+        let (name, node, generics) = if self.eat_keyword(keywords::Type) {
             let name = self.parse_ident()?;
             self.expect(&token::Eq)?;
             let typ = self.parse_ty()?;
             self.expect(&token::Semi)?;
-            (name, ast::ImplItemKind::Type(typ))
+            (name, ast::ImplItemKind::Type(typ), ast::Generics::default())
         } else if self.is_const_item() {
             self.expect_keyword(keywords::Const)?;
             let name = self.parse_ident()?;
@@ -4915,11 +4915,11 @@ impl<'a> Parser<'a> {
             self.expect(&token::Eq)?;
             let expr = self.parse_expr()?;
             self.expect(&token::Semi)?;
-            (name, ast::ImplItemKind::Const(typ, expr))
+            (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
         } else {
-            let (name, inner_attrs, node) = self.parse_impl_method(&vis, at_end)?;
+            let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
             attrs.extend(inner_attrs);
-            (name, node)
+            (name, node, generics)
         };
 
         Ok(ImplItem {
@@ -4929,6 +4929,7 @@ impl<'a> Parser<'a> {
             vis,
             defaultness,
             attrs,
+            generics,
             node,
             tokens: None,
         })
@@ -4986,7 +4987,8 @@ impl<'a> Parser<'a> {
 
     /// Parse a method or a macro invocation in a trait impl.
     fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
-                         -> PResult<'a, (Ident, Vec<ast::Attribute>, ast::ImplItemKind)> {
+                         -> PResult<'a, (Ident, Vec<ast::Attribute>, ast::Generics,
+                             ast::ImplItemKind)> {
         // code copied from parse_macro_use_or_failure... abstraction!
         if self.token.is_path_start() {
             // Method macro.
@@ -5013,7 +5015,8 @@ impl<'a> Parser<'a> {
             }
 
             let mac = respan(lo.to(self.prev_span), Mac_ { path: pth, tts: tts });
-            Ok((keywords::Invalid.ident(), vec![], ast::ImplItemKind::Macro(mac)))
+            Ok((keywords::Invalid.ident(), vec![], ast::Generics::default(),
+                ast::ImplItemKind::Macro(mac)))
         } else {
             let (constness, unsafety, abi) = self.parse_fn_front_matter()?;
             let ident = self.parse_ident()?;
@@ -5022,8 +5025,7 @@ impl<'a> Parser<'a> {
             generics.where_clause = self.parse_where_clause()?;
             *at_end = true;
             let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
-            Ok((ident, inner_attrs, ast::ImplItemKind::Method(ast::MethodSig {
-                generics,
+            Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(ast::MethodSig {
                 abi,
                 unsafety,
                 constness,
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 02f871c58c7..b9a7fa04a06 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1525,6 +1525,7 @@ impl<'a> State<'a> {
 
     pub fn print_method_sig(&mut self,
                             ident: ast::Ident,
+                            generics: &ast::Generics,
                             m: &ast::MethodSig,
                             vis: &ast::Visibility)
                             -> io::Result<()> {
@@ -1533,7 +1534,7 @@ impl<'a> State<'a> {
                       m.constness.node,
                       m.abi,
                       Some(ident),
-                      &m.generics,
+                      &generics,
                       vis)
     }
 
@@ -1553,7 +1554,7 @@ impl<'a> State<'a> {
                 if body.is_some() {
                     self.head("")?;
                 }
-                self.print_method_sig(ti.ident, sig, &ast::Visibility::Inherited)?;
+                self.print_method_sig(ti.ident, &ti.generics, sig, &ast::Visibility::Inherited)?;
                 if let Some(ref body) = *body {
                     self.nbsp()?;
                     self.print_block_with_attrs(body, &ti.attrs)?;
@@ -1592,7 +1593,7 @@ impl<'a> State<'a> {
             }
             ast::ImplItemKind::Method(ref sig, ref body) => {
                 self.head("")?;
-                self.print_method_sig(ii.ident, sig, &ii.vis)?;
+                self.print_method_sig(ii.ident, &ii.generics, sig, &ii.vis)?;
                 self.nbsp()?;
                 self.print_block_with_attrs(body, &ii.attrs)?;
             }
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 521c6030eba..078a63cba20 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -31,7 +31,7 @@ use codemap::Spanned;
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub enum FnKind<'a> {
     /// fn foo() or extern "Abi" fn foo()
-    ItemFn(Ident, &'a Generics, Unsafety, Spanned<Constness>, Abi, &'a Visibility, &'a Block),
+    ItemFn(Ident, Unsafety, Spanned<Constness>, Abi, &'a Visibility, &'a Block),
 
     /// fn foo(&self)
     Method(Ident, &'a MethodSig, Option<&'a Visibility>, &'a Block),
@@ -247,7 +247,8 @@ pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
             visitor.visit_expr(expr);
         }
         ItemKind::Fn(ref declaration, unsafety, constness, abi, ref generics, ref body) => {
-            visitor.visit_fn(FnKind::ItemFn(item.ident, generics, unsafety,
+            visitor.visit_generics(generics);
+            visitor.visit_fn(FnKind::ItemFn(item.ident, unsafety,
                                             constness, abi, &item.vis, body),
                              declaration,
                              item.span,
@@ -538,13 +539,11 @@ pub fn walk_fn<'a, V>(visitor: &mut V, kind: FnKind<'a>, declaration: &'a FnDecl
     where V: Visitor<'a>,
 {
     match kind {
-        FnKind::ItemFn(_, generics, _, _, _, _, body) => {
-            visitor.visit_generics(generics);
+        FnKind::ItemFn(_, _, _, _, _, body) => {
             walk_fn_decl(visitor, declaration);
             visitor.visit_block(body);
         }
-        FnKind::Method(_, sig, _, body) => {
-            visitor.visit_generics(&sig.generics);
+        FnKind::Method(_, _, _, body) => {
             walk_fn_decl(visitor, declaration);
             visitor.visit_block(body);
         }
@@ -558,13 +557,13 @@ pub fn walk_fn<'a, V>(visitor: &mut V, kind: FnKind<'a>, declaration: &'a FnDecl
 pub fn walk_trait_item<'a, V: Visitor<'a>>(visitor: &mut V, trait_item: &'a TraitItem) {
     visitor.visit_ident(trait_item.span, trait_item.ident);
     walk_list!(visitor, visit_attribute, &trait_item.attrs);
+    visitor.visit_generics(&trait_item.generics);
     match trait_item.node {
         TraitItemKind::Const(ref ty, ref default) => {
             visitor.visit_ty(ty);
             walk_list!(visitor, visit_expr, default);
         }
         TraitItemKind::Method(ref sig, None) => {
-            visitor.visit_generics(&sig.generics);
             walk_fn_decl(visitor, &sig.decl);
         }
         TraitItemKind::Method(ref sig, Some(ref body)) => {
@@ -585,6 +584,7 @@ pub fn walk_impl_item<'a, V: Visitor<'a>>(visitor: &mut V, impl_item: &'a ImplIt
     visitor.visit_vis(&impl_item.vis);
     visitor.visit_ident(impl_item.span, impl_item.ident);
     walk_list!(visitor, visit_attribute, &impl_item.attrs);
+    visitor.visit_generics(&impl_item.generics);
     match impl_item.node {
         ImplItemKind::Const(ref ty, ref expr) => {
             visitor.visit_ty(ty);