delegation: Implement glob delegation

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 {