delegation: Implement glob delegation

Author: petrochenkov

compiler/rustc_ast/src/ast.rs

@@ -3149,13 +3149,16 @@ pub struct Delegation {
     pub path: Path,
     pub rename: Option<Ident>,
     pub body: Option<P<Block>>,
+    /// The item was expanded from a glob delegation item.
+    pub from_glob: bool,
 }
 
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct DelegationMac {
     pub qself: Option<P<QSelf>>,
     pub prefix: Path,
-    pub suffixes: ThinVec<(Ident, Option<Ident>)>,
+    // Some for list delegation, and None for glob delegation.
+    pub suffixes: Option<ThinVec<(Ident, Option<Ident>)>>,
     pub body: Option<P<Block>>,
 }
 
@@ -3278,7 +3281,7 @@ pub enum ItemKind {
     ///
     /// E.g. `reuse <Type as Trait>::name { target_expr_template }`.
     Delegation(Box<Delegation>),
-    /// A list delegation item (`reuse prefix::{a, b, c}`).
+    /// A list or glob delegation item (`reuse prefix::{a, b, c}`, `reuse prefix::*`).
     /// Treated similarly to a macro call and expanded early.
     DelegationMac(Box<DelegationMac>),
 }
@@ -3359,7 +3362,7 @@ pub enum AssocItemKind {
     MacCall(P<MacCall>),
     /// An associated delegation item.
     Delegation(Box<Delegation>),
-    /// An associated delegation item list.
+    /// An associated list or glob delegation item.
     DelegationMac(Box<DelegationMac>),
 }
 

compiler/rustc_ast/src/mut_visit.rs

@@ -1159,7 +1159,14 @@ impl NoopVisitItemKind for ItemKind {
             }
             ItemKind::MacCall(m) => vis.visit_mac_call(m),
             ItemKind::MacroDef(def) => vis.visit_macro_def(def),
-            ItemKind::Delegation(box Delegation { id, qself, path, rename, body }) => {
+            ItemKind::Delegation(box Delegation {
+                id,
+                qself,
+                path,
+                rename,
+                body,
+                from_glob: _,
+            }) => {
                 vis.visit_id(id);
                 vis.visit_qself(qself);
                 vis.visit_path(path);
@@ -1173,10 +1180,12 @@ impl NoopVisitItemKind for ItemKind {
             ItemKind::DelegationMac(box DelegationMac { qself, prefix, suffixes, body }) => {
                 vis.visit_qself(qself);
                 vis.visit_path(prefix);
-                for (ident, rename) in suffixes {
-                    vis.visit_ident(ident);
-                    if let Some(rename) = rename {
-                        vis.visit_ident(rename);
+                if let Some(suffixes) = suffixes {
+                    for (ident, rename) in suffixes {
+                        vis.visit_ident(ident);
+                        if let Some(rename) = rename {
+                            vis.visit_ident(rename);
+                        }
                     }
                 }
                 if let Some(body) = body {
@@ -1215,7 +1224,14 @@ impl NoopVisitItemKind for AssocItemKind {
                 visit_opt(ty, |ty| visitor.visit_ty(ty));
             }
             AssocItemKind::MacCall(mac) => visitor.visit_mac_call(mac),
-            AssocItemKind::Delegation(box Delegation { id, qself, path, rename, body }) => {
+            AssocItemKind::Delegation(box Delegation {
+                id,
+                qself,
+                path,
+                rename,
+                body,
+                from_glob: _,
+            }) => {
                 visitor.visit_id(id);
                 visitor.visit_qself(qself);
                 visitor.visit_path(path);
@@ -1229,10 +1245,12 @@ impl NoopVisitItemKind for AssocItemKind {
             AssocItemKind::DelegationMac(box DelegationMac { qself, prefix, suffixes, body }) => {
                 visitor.visit_qself(qself);
                 visitor.visit_path(prefix);
-                for (ident, rename) in suffixes {
-                    visitor.visit_ident(ident);
-                    if let Some(rename) = rename {
-                        visitor.visit_ident(rename);
+                if let Some(suffixes) = suffixes {
+                    for (ident, rename) in suffixes {
+                        visitor.visit_ident(ident);
+                        if let Some(rename) = rename {
+                            visitor.visit_ident(rename);
+                        }
                     }
                 }
                 if let Some(body) = body {

compiler/rustc_ast/src/visit.rs

@@ -398,7 +398,14 @@ impl WalkItemKind for ItemKind {
             }
             ItemKind::MacCall(mac) => try_visit!(visitor.visit_mac_call(mac)),
             ItemKind::MacroDef(ts) => try_visit!(visitor.visit_mac_def(ts, item.id)),
-            ItemKind::Delegation(box Delegation { id, qself, path, rename, body }) => {
+            ItemKind::Delegation(box Delegation {
+                id,
+                qself,
+                path,
+                rename,
+                body,
+                from_glob: _,
+            }) => {
                 if let Some(qself) = qself {
                     try_visit!(visitor.visit_ty(&qself.ty));
                 }
@@ -411,10 +418,12 @@ impl WalkItemKind for ItemKind {
                     try_visit!(visitor.visit_ty(&qself.ty));
                 }
                 try_visit!(visitor.visit_path(prefix, item.id));
-                for (ident, rename) in suffixes {
-                    visitor.visit_ident(*ident);
-                    if let Some(rename) = rename {
-                        visitor.visit_ident(*rename);
+                if let Some(suffixes) = suffixes {
+                    for (ident, rename) in suffixes {
+                        visitor.visit_ident(*ident);
+                        if let Some(rename) = rename {
+                            visitor.visit_ident(*rename);
+                        }
                     }
                 }
                 visit_opt!(visitor, visit_block, body);
@@ -823,7 +832,14 @@ impl WalkItemKind for AssocItemKind {
             AssocItemKind::MacCall(mac) => {
                 try_visit!(visitor.visit_mac_call(mac));
             }
-            AssocItemKind::Delegation(box Delegation { id, qself, path, rename, body }) => {
+            AssocItemKind::Delegation(box Delegation {
+                id,
+                qself,
+                path,
+                rename,
+                body,
+                from_glob: _,
+            }) => {
                 if let Some(qself) = qself {
                     try_visit!(visitor.visit_ty(&qself.ty));
                 }
@@ -836,10 +852,12 @@ impl WalkItemKind for AssocItemKind {
                     try_visit!(visitor.visit_ty(&qself.ty));
                 }
                 try_visit!(visitor.visit_path(prefix, item.id));
-                for (ident, rename) in suffixes {
-                    visitor.visit_ident(*ident);
-                    if let Some(rename) = rename {
-                        visitor.visit_ident(*rename);
+                if let Some(suffixes) = suffixes {
+                    for (ident, rename) in suffixes {
+                        visitor.visit_ident(*ident);
+                        if let Some(rename) = rename {
+                            visitor.visit_ident(*rename);
+                        }
                     }
                 }
                 visit_opt!(visitor, visit_block, body);

compiler/rustc_ast_pretty/src/pprust/state/item.rs

@@ -9,6 +9,12 @@ use rustc_ast::ptr::P;
 use rustc_ast::ModKind;
 use rustc_span::symbol::Ident;
 
+enum DelegationKind<'a> {
+    Single,
+    List(&'a [(Ident, Option<Ident>)]),
+    Glob,
+}
+
 fn visibility_qualified(vis: &ast::Visibility, s: &str) -> String {
     format!("{}{}", State::to_string(|s| s.print_visibility(vis)), s)
 }
@@ -380,15 +386,15 @@ impl<'a> State<'a> {
                 &item.vis,
                 &deleg.qself,
                 &deleg.path,
-                None,
+                DelegationKind::Single,
                 &deleg.body,
             ),
             ast::ItemKind::DelegationMac(deleg) => self.print_delegation(
                 &item.attrs,
                 &item.vis,
                 &deleg.qself,
                 &deleg.prefix,
-                Some(&deleg.suffixes),
+                deleg.suffixes.as_ref().map_or(DelegationKind::Glob, |s| DelegationKind::List(s)),
                 &deleg.body,
             ),
         }
@@ -572,28 +578,28 @@ impl<'a> State<'a> {
                 vis,
                 &deleg.qself,
                 &deleg.path,
-                None,
+                DelegationKind::Single,
                 &deleg.body,
             ),
             ast::AssocItemKind::DelegationMac(deleg) => self.print_delegation(
                 &item.attrs,
                 vis,
                 &deleg.qself,
                 &deleg.prefix,
-                Some(&deleg.suffixes),
+                deleg.suffixes.as_ref().map_or(DelegationKind::Glob, |s| DelegationKind::List(s)),
                 &deleg.body,
             ),
         }
         self.ann.post(self, AnnNode::SubItem(id))
     }
 
-    pub(crate) fn print_delegation(
+    fn print_delegation(
         &mut self,
         attrs: &[ast::Attribute],
         vis: &ast::Visibility,
         qself: &Option<P<ast::QSelf>>,
         path: &ast::Path,
-        suffixes: Option<&[(Ident, Option<Ident>)]>,
+        kind: DelegationKind<'_>,
         body: &Option<P<ast::Block>>,
     ) {
         if body.is_some() {
@@ -607,21 +613,28 @@ impl<'a> State<'a> {
         } else {
             self.print_path(path, false, 0);
         }
-        if let Some(suffixes) = suffixes {
-            self.word("::");
-            self.word("{");
-            for (i, (ident, rename)) in suffixes.iter().enumerate() {
-                self.print_ident(*ident);
-                if let Some(rename) = rename {
-                    self.nbsp();
-                    self.word_nbsp("as");
-                    self.print_ident(*rename);
-                }
-                if i != suffixes.len() - 1 {
-                    self.word_space(",");
+        match kind {
+            DelegationKind::Single => {}
+            DelegationKind::List(suffixes) => {
+                self.word("::");
+                self.word("{");
+                for (i, (ident, rename)) in suffixes.iter().enumerate() {
+                    self.print_ident(*ident);
+                    if let Some(rename) = rename {
+                        self.nbsp();
+                        self.word_nbsp("as");
+                        self.print_ident(*rename);
+                    }
+                    if i != suffixes.len() - 1 {
+                        self.word_space(",");
+                    }
                 }
+                self.word("}");
+            }
+            DelegationKind::Glob => {
+                self.word("::");
+                self.word("*");
             }
-            self.word("}");
         }
         if let Some(body) = body {
             self.nbsp();

compiler/rustc_expand/messages.ftl

@@ -35,8 +35,8 @@ expand_duplicate_matcher_binding = duplicate matcher binding
     .label = duplicate binding
     .label2 = previous binding
 
-expand_empty_delegation_list =
-    empty list delegation is not supported
+expand_empty_delegation_mac =
+    empty {$kind} delegation is not supported
 
 expand_expected_paren_or_brace =
     expected `(` or `{"{"}`, found `{$token}`

compiler/rustc_expand/src/base.rs

@@ -358,6 +358,10 @@ where
     }
 }
 
+pub trait GlobDelegationExpander {
+    fn expand(&self, ecx: &mut ExtCtxt<'_>) -> ExpandResult<Vec<(Ident, Option<Ident>)>, ()>;
+}
+
 // Use a macro because forwarding to a simple function has type system issues
 macro_rules! make_stmts_default {
     ($me:expr) => {
@@ -715,6 +719,9 @@ pub enum SyntaxExtensionKind {
         /// The produced AST fragment is appended to the input AST fragment.
         Box<dyn MultiItemModifier + sync::DynSync + sync::DynSend>,
     ),
+
+    /// A glob delegation.
+    GlobDelegation(Box<dyn GlobDelegationExpander + sync::DynSync + sync::DynSend>),
 }
 
 /// A struct representing a macro definition in "lowered" form ready for expansion.
@@ -749,7 +756,9 @@ impl SyntaxExtension {
     /// Returns which kind of macro calls this syntax extension.
     pub fn macro_kind(&self) -> MacroKind {
         match self.kind {
-            SyntaxExtensionKind::Bang(..) | SyntaxExtensionKind::LegacyBang(..) => MacroKind::Bang,
+            SyntaxExtensionKind::Bang(..)
+            | SyntaxExtensionKind::LegacyBang(..)
+            | SyntaxExtensionKind::GlobDelegation(..) => MacroKind::Bang,
             SyntaxExtensionKind::Attr(..)
             | SyntaxExtensionKind::LegacyAttr(..)
             | SyntaxExtensionKind::NonMacroAttr => MacroKind::Attr,
@@ -923,6 +932,32 @@ impl SyntaxExtension {
         SyntaxExtension::default(SyntaxExtensionKind::NonMacroAttr, edition)
     }
 
+    pub fn glob_delegation(
+        trait_def_id: DefId,
+        impl_def_id: LocalDefId,
+        edition: Edition,
+    ) -> SyntaxExtension {
+        struct GlobDelegationExpanderImpl {
+            trait_def_id: DefId,
+            impl_def_id: LocalDefId,
+        }
+        impl GlobDelegationExpander for GlobDelegationExpanderImpl {
+            fn expand(
+                &self,
+                ecx: &mut ExtCtxt<'_>,
+            ) -> ExpandResult<Vec<(Ident, Option<Ident>)>, ()> {
+                match ecx.resolver.glob_delegation_suffixes(self.trait_def_id, self.impl_def_id) {
+                    Ok(suffixes) => ExpandResult::Ready(suffixes),
+                    Err(Indeterminate) if ecx.force_mode => ExpandResult::Ready(Vec::new()),
+                    Err(Indeterminate) => ExpandResult::Retry(()),
+                }
+            }
+        }
+
+        let expander = GlobDelegationExpanderImpl { trait_def_id, impl_def_id };
+        SyntaxExtension::default(SyntaxExtensionKind::GlobDelegation(Box::new(expander)), edition)
+    }
+
     pub fn expn_data(
         &self,
         parent: LocalExpnId,
@@ -1031,6 +1066,16 @@ pub trait ResolverExpand {
 
     /// Tools registered with `#![register_tool]` and used by tool attributes and lints.
     fn registered_tools(&self) -> &RegisteredTools;
+
+    /// Mark this invocation id as a glob delegation.
+    fn register_glob_delegation(&mut self, invoc_id: LocalExpnId);
+
+    /// Names of specific methods to which glob delegation expands.
+    fn glob_delegation_suffixes(
+        &mut self,
+        trait_def_id: DefId,
+        impl_def_id: LocalDefId,
+    ) -> Result<Vec<(Ident, Option<Ident>)>, Indeterminate>;
 }
 
 pub trait LintStoreExpand {

compiler/rustc_expand/src/errors.rs

@@ -435,8 +435,9 @@ pub struct ExpectedParenOrBrace<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(expand_empty_delegation_list)]
-pub(crate) struct EmptyDelegationList {
+#[diag(expand_empty_delegation_mac)]
+pub(crate) struct EmptyDelegationMac {
     #[primary_span]
     pub span: Span,
+    pub kind: String,
 }