Auto merge of rust-lang#128605 - futile:expand1-cont, r=<try>

Make declarative macro expansion a part of query system (cont. of rust-lang#125356)

This is a continuation of the effort to make declarative macro expansion a part of the query system from rust-lang#125356 by `@SparrowLii.`

#### Description from that PR:

> This is an attempt to make the macro expansion a part of incremental compilation.
>
> Processing of procedural macros is difficult since they may involve interactions with the external environment. Declaring macros is a good start.
>
> **It is not yet possible to test the effect of this PR on incremental compilation since the new query is declared as eval_always.**

#### Status of this PR:

* It is rebased against a much more recent `master` commit
* It contains the original commits from rust-lang#125356 (in a rebased form)
* It adds the missing implementation for retrying macro matching that provides (better) error diagnostics
  * This was done by refactoring `rustc_expand::mbe::diagnostics::failed_to_match_macro()` to only require a `ParseSess` instead of an `ExtCtxt`. Otherwise, `ExtCtxt` would need to be in the interface of `TcxMacroExpander`, which is not possible, because `ExtCtxt` is part of `rustc_expand`, which depends on the crate that contains `TcxMacroExpander`, `rustc_middle`, and thus would introduce a circular dependency.
  * This refactoring moved the retrying down into the `impl TcxMacroExpander for MacroRulesMacroExpander` (this is just a change compared to the original PR, otherwise not important to know).
* This PR passes `./x test tests/ui`, which produced errors before that were all due to the missing implementation of retry macro matching.
* This PR does **not** yet contain changes for the open discussions from rust-lang#125356. I wanted to fix the tests first before tackling them, and I also need to figure out what the best solutions for them are. I'd welcome any help/support with this, e.g., opening up a corresponding discussion on this PR with a summary/the final decided fix if available :)

In general, I'm new to working on rustc, so would be thankful for a bit more background/explanations in discussions and comments :) Thanks! :)

(tangentially relevant: rust-lang#99515)

Cargo.lock

@@ -3690,6 +3690,7 @@ dependencies = [
  "rustc_lexer",
  "rustc_lint_defs",
  "rustc_macros",
+ "rustc_middle",
  "rustc_parse",
  "rustc_serialize",
  "rustc_session",

compiler/rustc_ast/src/token.rs

@@ -1,5 +1,6 @@
 use std::borrow::Cow;
 use std::fmt;
+use std::hash::Hash;
 
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::Lrc;
@@ -21,7 +22,7 @@ use crate::ast;
 use crate::ptr::P;
 use crate::util::case::Case;
 
-#[derive(Clone, Copy, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
+#[derive(Clone, Copy, PartialEq, Encodable, Decodable, Debug, HashStable_Generic, Hash)]
 pub enum CommentKind {
     Line,
     Block,

compiler/rustc_ast/src/tokenstream.rs

@@ -105,7 +105,6 @@ where
         }
     }
 }
-
 pub trait ToAttrTokenStream: sync::DynSend + sync::DynSync {
     fn to_attr_token_stream(&self) -> AttrTokenStream;
 }

compiler/rustc_expand/Cargo.toml

@@ -20,6 +20,7 @@ rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_lexer = { path = "../rustc_lexer" }
 rustc_lint_defs = { path = "../rustc_lint_defs" }
 rustc_macros = { path = "../rustc_macros" }
+rustc_middle = { path = "../rustc_middle" }
 rustc_parse = { path = "../rustc_parse" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }

compiler/rustc_expand/src/base.rs

@@ -15,6 +15,7 @@ use rustc_data_structures::sync::{self, Lrc};
 use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed, PResult};
 use rustc_feature::Features;
 use rustc_lint_defs::{BufferedEarlyLint, RegisteredTools};
+use rustc_middle::expand::TcxMacroExpander;
 use rustc_parse::parser::Parser;
 use rustc_parse::MACRO_ARGUMENTS;
 use rustc_session::config::CollapseMacroDebuginfo;
@@ -676,6 +677,11 @@ pub enum SyntaxExtensionKind {
         Box<dyn TTMacroExpander + sync::DynSync + sync::DynSend>,
     ),
 
+    TcxLegacyBang(
+        /// An expander with signature TokenStream -> AST.
+        Lrc<dyn TcxMacroExpander + sync::DynSync + sync::DynSend>,
+    ),
+
     /// A token-based attribute macro.
     Attr(
         /// An expander with signature (TokenStream, TokenStream) -> TokenStream.
@@ -754,7 +760,8 @@ impl SyntaxExtension {
         match self.kind {
             SyntaxExtensionKind::Bang(..)
             | SyntaxExtensionKind::LegacyBang(..)
-            | SyntaxExtensionKind::GlobDelegation(..) => MacroKind::Bang,
+            | SyntaxExtensionKind::GlobDelegation(..)
+            | SyntaxExtensionKind::TcxLegacyBang(..) => MacroKind::Bang,
             SyntaxExtensionKind::Attr(..)
             | SyntaxExtensionKind::LegacyAttr(..)
             | SyntaxExtensionKind::NonMacroAttr => MacroKind::Attr,
@@ -1072,6 +1079,12 @@ pub trait ResolverExpand {
         trait_def_id: DefId,
         impl_def_id: LocalDefId,
     ) -> Result<Vec<(Ident, Option<Ident>)>, Indeterminate>;
+
+    fn expand_legacy_bang(
+        &self,
+        invoc_id: LocalExpnId,
+        current_expansion: LocalExpnId,
+    ) -> Result<(TokenStream, usize), (Span, ErrorGuaranteed)>;
 }
 
 pub trait LintStoreExpand {

compiler/rustc_expand/src/expand.rs

@@ -12,13 +12,14 @@ use rustc_ast::visit::{self, try_visit, walk_list, AssocCtxt, Visitor, VisitorRe
 use rustc_ast::{
     AssocItemKind, AstNodeWrapper, AttrArgs, AttrStyle, AttrVec, ExprKind, ForeignItemKind,
     HasAttrs, HasNodeId, Inline, ItemKind, MacStmtStyle, MetaItemKind, ModKind, NestedMetaItem,
-    NodeId, PatKind, StmtKind, TyKind,
+    NodeId, PatKind, StmtKind, TyKind, DUMMY_NODE_ID,
 };
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::PResult;
 use rustc_feature::Features;
+use rustc_middle::ty::TyCtxt;
 use rustc_parse::parser::{
     AttemptLocalParseRecovery, CommaRecoveryMode, ForceCollect, Parser, RecoverColon, RecoverComma,
 };
@@ -40,6 +41,7 @@ use crate::errors::{
     WrongFragmentKind,
 };
 use crate::mbe::diagnostics::annotate_err_with_kind;
+use crate::mbe::macro_rules::{trace_macros_note, ParserAnyMacro};
 use crate::module::{mod_dir_path, parse_external_mod, DirOwnership, ParsedExternalMod};
 use crate::placeholders::{placeholder, PlaceholderExpander};
 
@@ -394,6 +396,18 @@ pub struct MacroExpander<'a, 'b> {
     monotonic: bool, // cf. `cx.monotonic_expander()`
 }
 
+pub fn expand_legacy_bang<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    key: (LocalExpnId, LocalExpnId),
+) -> Result<(&'tcx TokenStream, usize), (Span, ErrorGuaranteed)> {
+    let (invoc_id, current_expansion) = key;
+    let map = tcx.macro_map.borrow();
+    let (arg, span, expander) = map.get(&invoc_id).as_ref().unwrap();
+    expander
+        .expand(&tcx.sess, *span, arg.clone(), current_expansion)
+        .map(|(tts, i)| (tcx.arena.alloc(tts) as &TokenStream, i))
+}
+
 impl<'a, 'b> MacroExpander<'a, 'b> {
     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
         MacroExpander { cx, monotonic }
@@ -679,6 +693,63 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                         Err(guar) => return ExpandResult::Ready(fragment_kind.dummy(span, guar)),
                     }
                 }
+                SyntaxExtensionKind::TcxLegacyBang(expander) => {
+                    // Macros defined in the current crate have a real node id,
+                    // whereas macros from an external crate have a dummy id.
+                    if self.cx.trace_macros() {
+                        let msg = format!(
+                            "expanding `{}! {{ {} }}`",
+                            expander.name(),
+                            pprust::tts_to_string(&mac.args.tokens)
+                        );
+                        trace_macros_note(&mut self.cx.expansions, span, msg);
+                    }
+
+                    // Macros defined in the current crate have a real node id,
+                    // whereas macros from an external crate have a dummy id.\
+                    let tok_result: Box<dyn MacResult> = match self
+                        .cx
+                        .resolver
+                        .expand_legacy_bang(invoc.expansion_data.id, self.cx.current_expansion.id)
+                    {
+                        Ok((tts, i)) => {
+                            if self.cx.trace_macros() {
+                                let msg = format!("to `{}`", pprust::tts_to_string(&tts));
+                                trace_macros_note(&mut self.cx.expansions, span, msg);
+                            }
+                            let is_local = expander.node_id() != DUMMY_NODE_ID;
+                            if is_local {
+                                self.cx.resolver.record_macro_rule_usage(expander.node_id(), i);
+                            }
+
+                            // Let the context choose how to interpret the result.
+                            // Weird, but useful for X-macros.
+                            Box::new(ParserAnyMacro::new(
+                                Parser::new(&self.cx.sess.psess, tts.clone(), None),
+                                // Pass along the original expansion site and the name of the macro,
+                                // so we can print a useful error message if the parse of the expanded
+                                // macro leaves unparsed tokens.
+                                span,
+                                expander.name(),
+                                self.cx.current_expansion.lint_node_id,
+                                self.cx.current_expansion.is_trailing_mac,
+                                expander.arm_span(i),
+                                is_local,
+                            ))
+                        }
+                        Err((span, guar)) => {
+                            self.cx.trace_macros_diag();
+                            DummyResult::any(span, guar)
+                        }
+                    };
+                    let result = if let Some(result) = fragment_kind.make_from(tok_result) {
+                        result
+                    } else {
+                        let guar = self.error_wrong_fragment_kind(fragment_kind, &mac, span);
+                        fragment_kind.dummy(span, guar)
+                    };
+                    result
+                }
                 SyntaxExtensionKind::LegacyBang(expander) => {
                     let tok_result = match expander.expand(self.cx, span, mac.args.tokens.clone()) {
                         ExpandResult::Ready(tok_result) => tok_result,

compiler/rustc_expand/src/lib.rs

@@ -26,6 +26,7 @@ mod placeholders;
 mod proc_macro_server;
 
 pub use mbe::macro_rules::compile_declarative_macro;
+use rustc_middle::query::Providers;
 pub mod base;
 pub mod config;
 pub mod expand;
@@ -34,4 +35,8 @@ pub mod module;
 #[allow(rustc::untranslatable_diagnostic)]
 pub mod proc_macro;
 
+pub fn provide(providers: &mut Providers) {
+    providers.expand_legacy_bang = expand::expand_legacy_bang;
+}
+
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }

compiler/rustc_expand/src/mbe/diagnostics.rs

@@ -3,42 +3,40 @@ use std::borrow::Cow;
 use rustc_ast::token::{self, Token, TokenKind};
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast_pretty::pprust;
-use rustc_errors::{Applicability, Diag, DiagMessage};
+use rustc_errors::{Applicability, Diag, DiagCtxtHandle, DiagMessage};
 use rustc_macros::Subdiagnostic;
 use rustc_parse::parser::{Parser, Recovery};
+use rustc_session::parse::ParseSess;
 use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::Ident;
 use rustc_span::{ErrorGuaranteed, Span};
 use tracing::debug;
 
 use super::macro_rules::{parser_from_cx, NoopTracker};
-use crate::base::{DummyResult, ExtCtxt, MacResult};
 use crate::expand::{parse_ast_fragment, AstFragmentKind};
 use crate::mbe::macro_parser::ParseResult::*;
 use crate::mbe::macro_parser::{MatcherLoc, NamedParseResult, TtParser};
 use crate::mbe::macro_rules::{try_match_macro, Tracker};
 
-pub(super) fn failed_to_match_macro<'cx>(
-    cx: &'cx mut ExtCtxt<'_>,
+pub(crate) fn failed_to_match_macro(
+    psess: &ParseSess,
     sp: Span,
     def_span: Span,
     name: Ident,
     arg: TokenStream,
     lhses: &[Vec<MatcherLoc>],
-) -> Box<dyn MacResult + 'cx> {
-    let psess = &cx.sess.psess;
-
+) -> (Span, ErrorGuaranteed) {
     // An error occurred, try the expansion again, tracking the expansion closely for better
     // diagnostics.
-    let mut tracker = CollectTrackerAndEmitter::new(cx, sp);
+    let mut tracker = CollectTrackerAndEmitter::new(psess.dcx(), sp);
 
     let try_success_result = try_match_macro(psess, name, &arg, lhses, &mut tracker);
 
     if try_success_result.is_ok() {
         // Nonterminal parser recovery might turn failed matches into successful ones,
         // but for that it must have emitted an error already
         assert!(
-            tracker.cx.dcx().has_errors().is_some(),
+            tracker.dcx.has_errors().is_some(),
             "Macro matching returned a success on the second try"
         );
     }
@@ -50,15 +48,15 @@ pub(super) fn failed_to_match_macro<'cx>(
 
     let Some(BestFailure { token, msg: label, remaining_matcher, .. }) = tracker.best_failure
     else {
-        return DummyResult::any(sp, cx.dcx().span_delayed_bug(sp, "failed to match a macro"));
+        return (sp, psess.dcx().span_delayed_bug(sp, "failed to match a macro"));
     };
 
     let span = token.span.substitute_dummy(sp);
 
-    let mut err = cx.dcx().struct_span_err(span, parse_failure_msg(&token, None));
+    let mut err = psess.dcx().struct_span_err(span, parse_failure_msg(&token, None));
     err.span_label(span, label);
-    if !def_span.is_dummy() && !cx.source_map().is_imported(def_span) {
-        err.span_label(cx.source_map().guess_head_span(def_span), "when calling this macro");
+    if !def_span.is_dummy() && !psess.source_map().is_imported(def_span) {
+        err.span_label(psess.source_map().guess_head_span(def_span), "when calling this macro");
     }
 
     annotate_doc_comment(&mut err, psess.source_map(), span);
@@ -76,7 +74,7 @@ pub(super) fn failed_to_match_macro<'cx>(
         err.note("captured metavariables except for `:tt`, `:ident` and `:lifetime` cannot be compared to other tokens");
         err.note("see <https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment> for more information");
 
-        if !def_span.is_dummy() && !cx.source_map().is_imported(def_span) {
+        if !def_span.is_dummy() && !psess.source_map().is_imported(def_span) {
             err.help("try using `:tt` instead in the macro definition");
         }
     }
@@ -104,18 +102,17 @@ pub(super) fn failed_to_match_macro<'cx>(
         }
     }
     let guar = err.emit();
-    cx.trace_macros_diag();
-    DummyResult::any(sp, guar)
+    (sp, guar)
 }
 
 /// The tracker used for the slow error path that collects useful info for diagnostics.
-struct CollectTrackerAndEmitter<'a, 'cx, 'matcher> {
-    cx: &'a mut ExtCtxt<'cx>,
+struct CollectTrackerAndEmitter<'dcx, 'matcher> {
+    dcx: DiagCtxtHandle<'dcx>,
     remaining_matcher: Option<&'matcher MatcherLoc>,
     /// Which arm's failure should we report? (the one furthest along)
     best_failure: Option<BestFailure>,
     root_span: Span,
-    result: Option<Box<dyn MacResult + 'cx>>,
+    result: Option<(Span, ErrorGuaranteed)>,
 }
 
 struct BestFailure {
@@ -131,7 +128,7 @@ impl BestFailure {
     }
 }
 
-impl<'a, 'cx, 'matcher> Tracker<'matcher> for CollectTrackerAndEmitter<'a, 'cx, 'matcher> {
+impl<'dcx, 'matcher> Tracker<'matcher> for CollectTrackerAndEmitter<'dcx, 'matcher> {
     type Failure = (Token, u32, &'static str);
 
     fn build_failure(tok: Token, position: u32, msg: &'static str) -> Self::Failure {
@@ -151,7 +148,7 @@ impl<'a, 'cx, 'matcher> Tracker<'matcher> for CollectTrackerAndEmitter<'a, 'cx,
             Success(_) => {
                 // Nonterminal parser recovery might turn failed matches into successful ones,
                 // but for that it must have emitted an error already
-                self.cx.dcx().span_delayed_bug(
+                self.dcx.span_delayed_bug(
                     self.root_span,
                     "should not collect detailed info for successful macro match",
                 );
@@ -177,10 +174,10 @@ impl<'a, 'cx, 'matcher> Tracker<'matcher> for CollectTrackerAndEmitter<'a, 'cx,
             }
             Error(err_sp, msg) => {
                 let span = err_sp.substitute_dummy(self.root_span);
-                let guar = self.cx.dcx().span_err(span, msg.clone());
-                self.result = Some(DummyResult::any(span, guar));
+                let guar = self.dcx.span_err(span, msg.clone());
+                self.result = Some((span, guar));
             }
-            ErrorReported(guar) => self.result = Some(DummyResult::any(self.root_span, *guar)),
+            ErrorReported(guar) => self.result = Some((self.root_span, *guar)),
         }
     }
 
@@ -193,9 +190,9 @@ impl<'a, 'cx, 'matcher> Tracker<'matcher> for CollectTrackerAndEmitter<'a, 'cx,
     }
 }
 
-impl<'a, 'cx> CollectTrackerAndEmitter<'a, 'cx, '_> {
-    fn new(cx: &'a mut ExtCtxt<'cx>, root_span: Span) -> Self {
-        Self { cx, remaining_matcher: None, best_failure: None, root_span, result: None }
+impl<'dcx> CollectTrackerAndEmitter<'dcx, '_> {
+    fn new(dcx: DiagCtxtHandle<'dcx>, root_span: Span) -> Self {
+        Self { dcx, remaining_matcher: None, best_failure: None, root_span, result: None }
     }
 }