Rollup merge of #124135 - petrochenkov:deleglob, r=fmease

delegation: Implement glob delegation

Support delegating to all trait methods in one go.
Overriding globs with explicit definitions is also supported.

The implementation is generally based on the design from rust-lang/rfcs#3530 (comment), but unlike with list delegation in #123413 we cannot expand glob delegation eagerly.
We have to enqueue it into the queue of unexpanded macros (most other macros are processed this way too), and then a glob delegation waits in that queue until its trait path is resolved, and enough code expands to generate the identifier list produced from the glob.

Glob delegation is only allowed in impls, and can only point to traits.
Supporting it in other places gives very little practical benefit, but significantly raises the implementation complexity.

Part of #118212.

compiler/rustc_ast/src/ast.rs

@@ -3161,13 +3161,16 @@ 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>>,
 }
 
@@ -3294,7 +3297,7 @@ 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>),
 }
@@ -3375,7 +3378,7 @@ 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

@@ -1162,7 +1162,14 @@ 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);
@@ -1176,10 +1183,12 @@ 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 {
@@ -1218,7 +1227,14 @@ 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);
@@ -1232,10 +1248,12 @@ 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

@@ -408,7 +408,14 @@ 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));
                 }
@@ -421,10 +428,12 @@ 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);
@@ -837,7 +846,14 @@ 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));
                 }
@@ -850,10 +866,12 @@ 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)
 }
@@ -387,15 +393,15 @@ 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,
             ),
         }
@@ -579,28 +585,28 @@ 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() {
@@ -614,21 +620,28 @@ 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 `{$token}`
@@ -58,6 +58,9 @@ expand_feature_removed =
     .label = feature has been removed
     .reason = {$reason}
 
+expand_glob_delegation_outside_impls =
+    glob delegation is only supported in impls
+
 expand_helper_attribute_name_invalid =
     `{$name}` cannot be a name of derive helper attribute
 

compiler/rustc_expand/src/base.rs

@@ -357,6 +357,10 @@ 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) => {
@@ -714,6 +718,9 @@ 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.
@@ -748,7 +755,9 @@ 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,
@@ -922,6 +931,32 @@ 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,
@@ -1030,6 +1065,16 @@ 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 +435,16 @@ 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,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_glob_delegation_outside_impls)]
+pub(crate) struct GlobDelegationOutsideImpls {
     #[primary_span]
     pub span: Span,
 }