Rollup of 6 pull requests

INSTALL.md

@@ -48,7 +48,7 @@ If building LLVM from source, you'll need additional tools:
   [LLVM's documentation](https://llvm.org/docs/GettingStarted.html#host-c-toolchain-both-compiler-and-standard-library)
 * `ninja`, or GNU `make` 3.81 or later (Ninja is recommended, especially on
   Windows)
-* `cmake` 3.13.4 or later
+* `cmake` version listed on [LLVM's documentation](https://llvm.org/docs/GettingStarted.html#software)
 * `libstdc++-static` may be required on some Linux distributions such as Fedora
   and Ubuntu
 

compiler/rustc_lint/messages.ftl

@@ -439,6 +439,9 @@ lint_lintpass_by_hand = implementing `LintPass` by hand
 lint_macro_expanded_macro_exports_accessed_by_absolute_paths = macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths
     .note = the macro is defined here
 
+lint_macro_expr_fragment_specifier_2024_migration =
+    the `expr` fragment specifier will accept more expressions in the 2024 edition
+    .suggestion = to keep the existing behavior, use the `expr_2021` fragment specifier
 lint_macro_is_private = macro `{$ident}` is private
 
 lint_macro_rule_never_used = rule #{$n} of macro `{$name}` is never used

compiler/rustc_lint/src/lib.rs

@@ -60,6 +60,7 @@ mod late;
 mod let_underscore;
 mod levels;
 mod lints;
+mod macro_expr_fragment_specifier_2024_migration;
 mod map_unit_fn;
 mod methods;
 mod multiple_supertrait_upcastable;
@@ -97,6 +98,7 @@ use impl_trait_overcaptures::ImplTraitOvercaptures;
 use internal::*;
 use invalid_from_utf8::*;
 use let_underscore::*;
+use macro_expr_fragment_specifier_2024_migration::*;
 use map_unit_fn::*;
 use methods::*;
 use multiple_supertrait_upcastable::*;
@@ -170,6 +172,7 @@ early_lint_methods!(
             IncompleteInternalFeatures: IncompleteInternalFeatures,
             RedundantSemicolons: RedundantSemicolons,
             UnusedDocComment: UnusedDocComment,
+            Expr2024: Expr2024,
         ]
     ]
 );

compiler/rustc_lint/src/lints.rs

@@ -317,6 +317,13 @@ pub struct BuiltinTypeAliasGenericBounds<'a, 'b> {
     pub sub: Option<SuggestChangingAssocTypes<'a, 'b>>,
 }
 
+#[derive(LintDiagnostic)]
+#[diag(lint_macro_expr_fragment_specifier_2024_migration)]
+pub struct MacroExprFragment2024 {
+    #[suggestion(code = "expr_2021", applicability = "machine-applicable")]
+    pub suggestion: Span,
+}
+
 pub struct BuiltinTypeAliasGenericBoundsSuggestion {
     pub suggestions: Vec<(Span, String)>,
 }

compiler/rustc_lint/src/macro_expr_fragment_specifier_2024_migration.rs

@@ -0,0 +1,155 @@
+//! Migration code for the `expr_fragment_specifier_2024`
+//! rule.
+use tracing::debug;
+
+use rustc_ast::token::Token;
+use rustc_ast::token::TokenKind;
+use rustc_ast::tokenstream::TokenStream;
+use rustc_ast::tokenstream::TokenTree;
+use rustc_session::declare_lint;
+use rustc_session::declare_lint_pass;
+use rustc_session::lint::FutureIncompatibilityReason;
+use rustc_span::edition::Edition;
+use rustc_span::sym;
+
+use crate::lints::MacroExprFragment2024;
+use crate::EarlyLintPass;
+
+declare_lint! {
+    /// The `edition_2024_expr_fragment_specifier` lint detects the use of
+    /// `expr` fragments in macros during migration to the 2024 edition.
+    ///
+    /// The `expr` fragment specifier will accept more expressions in the 2024
+    /// edition. To maintain the behavior from the 2021 edition and earlier, use
+    /// the `expr_2021` fragment specifier.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,edition2021,compile_fail
+    /// #![deny(edition_2024_expr_fragment_specifier)]
+    /// macro_rules! m {
+    ///   ($e:expr) => {
+    ///       $e
+    ///   }
+    /// }
+    ///
+    /// fn main() {
+    ///    m!(1);
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Rust [editions] allow the language to evolve without breaking backwards
+    /// compatibility. This lint catches code that uses [macro matcher fragment
+    /// specifiers] that have changed meaning in the 2024 edition. If you switch
+    /// to the new edition without updating the code, your macros may behave
+    /// differently.
+    ///
+    /// In the 2024 edition, the `expr` fragment specifier `expr` will also
+    /// match `const { ... }` blocks. This means if a macro had a pattern that
+    /// matched `$e:expr` and another that matches `const { $e: expr }`, for
+    /// example, that under the 2024 edition the first pattern would match while
+    /// in the 2021 and earlier editions the second pattern would match. To keep
+    /// the old behavior, use the `expr_2021` fragment specifier.
+    ///
+    /// This lint detects macros whose behavior might change due to the changing
+    /// meaning of the `expr` fragment specifier. It is "allow" by default
+    /// because the code is perfectly valid in older editions. The [`cargo fix`]
+    /// tool with the `--edition` flag will switch this lint to "warn" and
+    /// automatically apply the suggested fix from the compiler. This provides a
+    /// completely automated way to update old code for a new edition.
+    ///
+    /// Using `cargo fix --edition` with this lint will ensure that your code
+    /// retains the same behavior. This may not be the desired, as macro authors
+    /// often will want their macros to use the latest grammar for matching
+    /// expressions. Be sure to carefully review changes introduced by this lint
+    /// to ensure the macros implement the desired behavior.
+    ///
+    /// [editions]: https://doc.rust-lang.org/edition-guide/
+    /// [macro matcher fragment specifiers]: https://doc.rust-lang.org/nightly/edition-guide/rust-2024/macro-fragment-specifiers.html
+    /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
+    pub EDITION_2024_EXPR_FRAGMENT_SPECIFIER,
+    Allow,
+    "The `expr` fragment specifier will accept more expressions in the 2024 edition. \
+    To keep the existing behavior, use the `expr_2021` fragment specifier.",
+    @future_incompatible = FutureIncompatibleInfo {
+        reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
+        reference: "Migration Guide <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/macro-fragment-specifiers.html>",
+    };
+}
+
+declare_lint_pass!(Expr2024 => [EDITION_2024_EXPR_FRAGMENT_SPECIFIER,]);
+
+impl Expr2024 {
+    fn check_tokens(&mut self, cx: &crate::EarlyContext<'_>, tokens: &TokenStream) {
+        let mut prev_colon = false;
+        let mut prev_identifier = false;
+        let mut prev_dollar = false;
+        for tt in tokens.trees() {
+            debug!(
+                "check_tokens: {:?} - colon {prev_dollar} - ident {prev_identifier} - colon {prev_colon}",
+                tt
+            );
+            match tt {
+                TokenTree::Token(token, _) => match token.kind {
+                    TokenKind::Dollar => {
+                        prev_dollar = true;
+                        continue;
+                    }
+                    TokenKind::Ident(..) | TokenKind::NtIdent(..) => {
+                        if prev_colon && prev_identifier && prev_dollar {
+                            self.check_ident_token(cx, token);
+                        } else if prev_dollar {
+                            prev_identifier = true;
+                            continue;
+                        }
+                    }
+                    TokenKind::Colon => {
+                        if prev_dollar && prev_identifier {
+                            prev_colon = true;
+                            continue;
+                        }
+                    }
+                    _ => {}
+                },
+                TokenTree::Delimited(.., tts) => self.check_tokens(cx, tts),
+            }
+            prev_colon = false;
+            prev_identifier = false;
+            prev_dollar = false;
+        }
+    }
+
+    fn check_ident_token(&mut self, cx: &crate::EarlyContext<'_>, token: &Token) {
+        debug!("check_ident_token: {:?}", token);
+        let (sym, edition) = match token.kind {
+            TokenKind::Ident(sym, _) => (sym, Edition::Edition2024),
+            _ => return,
+        };
+
+        debug!("token.span.edition(): {:?}", token.span.edition());
+        if token.span.edition() >= edition {
+            return;
+        }
+
+        if sym != sym::expr {
+            return;
+        }
+
+        debug!("emitting lint");
+        cx.builder.emit_span_lint(
+            &EDITION_2024_EXPR_FRAGMENT_SPECIFIER,
+            token.span.into(),
+            MacroExprFragment2024 { suggestion: token.span },
+        );
+    }
+}
+
+impl EarlyLintPass for Expr2024 {
+    fn check_mac_def(&mut self, cx: &crate::EarlyContext<'_>, mc: &rustc_ast::MacroDef) {
+        self.check_tokens(cx, &mc.body.tokens);
+    }
+}

compiler/rustc_next_trait_solver/src/solve/mod.rs

@@ -48,12 +48,20 @@ enum GoalEvaluationKind {
     Nested,
 }
 
+// FIXME(trait-system-refactor-initiative#117): we don't detect whether a response
+// ended up pulling down any universes.
 fn has_no_inference_or_external_constraints<I: Interner>(
     response: ty::Canonical<I, Response<I>>,
 ) -> bool {
-    response.value.external_constraints.region_constraints.is_empty()
-        && response.value.var_values.is_identity()
-        && response.value.external_constraints.opaque_types.is_empty()
+    let ExternalConstraintsData {
+        ref region_constraints,
+        ref opaque_types,
+        ref normalization_nested_goals,
+    } = *response.value.external_constraints;
+    response.value.var_values.is_identity()
+        && region_constraints.is_empty()
+        && opaque_types.is_empty()
+        && normalization_nested_goals.is_empty()
 }
 
 impl<'a, D, I> EvalCtxt<'a, D>

compiler/rustc_next_trait_solver/src/solve/search_graph.rs

@@ -71,7 +71,7 @@ struct StackEntry<I: Interner> {
     /// C :- D
     /// D :- C
     /// ```
-    cycle_participants: HashSet<CanonicalInput<I>>,
+    nested_goals: HashSet<CanonicalInput<I>>,
     /// Starts out as `None` and gets set when rerunning this
     /// goal in case we encounter a cycle.
     provisional_result: Option<QueryResult<I>>,
@@ -139,18 +139,11 @@ impl<I: Interner> SearchGraph<I> {
         self.mode
     }
 
-    /// Pops the highest goal from the stack, lazily updating the
-    /// the next goal in the stack.
-    ///
-    /// Directly popping from the stack instead of using this method
-    /// would cause us to not track overflow and recursion depth correctly.
-    fn pop_stack(&mut self) -> StackEntry<I> {
-        let elem = self.stack.pop().unwrap();
-        if let Some(last) = self.stack.raw.last_mut() {
-            last.reached_depth = last.reached_depth.max(elem.reached_depth);
-            last.encountered_overflow |= elem.encountered_overflow;
+    fn update_parent_goal(&mut self, reached_depth: StackDepth, encountered_overflow: bool) {
+        if let Some(parent) = self.stack.raw.last_mut() {
+            parent.reached_depth = parent.reached_depth.max(reached_depth);
+            parent.encountered_overflow |= encountered_overflow;
         }
-        elem
     }
 
     pub(super) fn is_empty(&self) -> bool {
@@ -222,8 +215,8 @@ impl<I: Interner> SearchGraph<I> {
         let current_cycle_root = &mut stack[current_root.as_usize()];
         for entry in cycle_participants {
             entry.non_root_cycle_participant = entry.non_root_cycle_participant.max(Some(head));
-            current_cycle_root.cycle_participants.insert(entry.input);
-            current_cycle_root.cycle_participants.extend(mem::take(&mut entry.cycle_participants));
+            current_cycle_root.nested_goals.insert(entry.input);
+            current_cycle_root.nested_goals.extend(mem::take(&mut entry.nested_goals));
         }
     }
 
@@ -342,7 +335,7 @@ impl<I: Interner> SearchGraph<I> {
                 non_root_cycle_participant: None,
                 encountered_overflow: false,
                 has_been_used: HasBeenUsed::empty(),
-                cycle_participants: Default::default(),
+                nested_goals: Default::default(),
                 provisional_result: None,
             };
             assert_eq!(self.stack.push(entry), depth);
@@ -364,14 +357,16 @@ impl<I: Interner> SearchGraph<I> {
             }
 
             debug!("canonical cycle overflow");
-            let current_entry = self.pop_stack();
+            let current_entry = self.stack.pop().unwrap();
             debug_assert!(current_entry.has_been_used.is_empty());
             let result = Self::response_no_constraints(cx, input, Certainty::overflow(false));
             (current_entry, result)
         });
 
         let proof_tree = inspect.finalize_canonical_goal_evaluation(cx);
 
+        self.update_parent_goal(final_entry.reached_depth, final_entry.encountered_overflow);
+
         // We're now done with this goal. In case this goal is involved in a larger cycle
         // do not remove it from the provisional cache and update its provisional result.
         // We only add the root of cycles to the global cache.
@@ -394,15 +389,15 @@ impl<I: Interner> SearchGraph<I> {
             //
             // We must not use the global cache entry of a root goal if a cycle
             // participant is on the stack. This is necessary to prevent unstable
-            // results. See the comment of `StackEntry::cycle_participants` for
+            // results. See the comment of `StackEntry::nested_goals` for
             // more details.
             self.global_cache(cx).insert(
                 cx,
                 input,
                 proof_tree,
                 reached_depth,
                 final_entry.encountered_overflow,
-                final_entry.cycle_participants,
+                final_entry.nested_goals,
                 dep_node,
                 result,
             )
@@ -441,14 +436,9 @@ impl<I: Interner> SearchGraph<I> {
             }
         }
 
-        // Update the reached depth of the current goal to make sure
-        // its state is the same regardless of whether we've used the
-        // global cache or not.
+        // Adjust the parent goal as if we actually computed this goal.
         let reached_depth = self.stack.next_index().plus(additional_depth);
-        if let Some(last) = self.stack.raw.last_mut() {
-            last.reached_depth = last.reached_depth.max(reached_depth);
-            last.encountered_overflow |= encountered_overflow;
-        }
+        self.update_parent_goal(reached_depth, encountered_overflow);
 
         Some(result)
     }
@@ -477,7 +467,7 @@ impl<I: Interner> SearchGraph<I> {
         F: FnMut(&mut Self, &mut ProofTreeBuilder<D>) -> QueryResult<I>,
     {
         let result = prove_goal(self, inspect);
-        let stack_entry = self.pop_stack();
+        let stack_entry = self.stack.pop().unwrap();
         debug_assert_eq!(stack_entry.input, input);
 
         // If the current goal is not the root of a cycle, we are done.
@@ -554,27 +544,27 @@ impl<I: Interner> SearchGraph<I> {
                 non_root_cycle_participant,
                 encountered_overflow: _,
                 has_been_used,
-                ref cycle_participants,
+                ref nested_goals,
                 provisional_result,
             } = *entry;
             let cache_entry = provisional_cache.get(&entry.input).unwrap();
             assert_eq!(cache_entry.stack_depth, Some(depth));
             if let Some(head) = non_root_cycle_participant {
                 assert!(head < depth);
-                assert!(cycle_participants.is_empty());
+                assert!(nested_goals.is_empty());
                 assert_ne!(stack[head].has_been_used, HasBeenUsed::empty());
 
                 let mut current_root = head;
                 while let Some(parent) = stack[current_root].non_root_cycle_participant {
                     current_root = parent;
                 }
-                assert!(stack[current_root].cycle_participants.contains(&input));
+                assert!(stack[current_root].nested_goals.contains(&input));
             }
 
-            if !cycle_participants.is_empty() {
+            if !nested_goals.is_empty() {
                 assert!(provisional_result.is_some() || !has_been_used.is_empty());
                 for entry in stack.iter().take(depth.as_usize()) {
-                    assert_eq!(cycle_participants.get(&entry.input), None);
+                    assert_eq!(nested_goals.get(&entry.input), None);
                 }
             }
         }

library/core/src/error.rs

@@ -1008,8 +1008,15 @@ impl<'a> Iterator for Source<'a> {
         self.current = self.current.and_then(Error::source);
         current
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        if self.current.is_some() { (1, None) } else { (0, Some(0)) }
+    }
 }
 
+#[unstable(feature = "error_iter", issue = "58520")]
+impl<'a> crate::iter::FusedIterator for Source<'a> {}
+
 #[stable(feature = "error_by_ref", since = "1.51.0")]
 impl<'a, T: Error + ?Sized> Error for &'a T {
     #[allow(deprecated, deprecated_in_future)]