Auto merge of rust-lang#94548 - matthiaskrgr:rollup-spa38z8, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#93562 (Update the documentation for `{As,Into,From}Raw{Fd,Handle,Socket}`.)
 - rust-lang#94101 (rustdoc: add test cases for hidden enum variants)
 - rust-lang#94484 (8 - Make more use of `let_chains`)
 - rust-lang#94522 (Remove out-of-context line at end of E0284 message)
 - rust-lang#94534 (Re-export (unstable) core::ffi types from std::ffi)
 - rust-lang#94536 (Move transmute_undefined_repr back to nursery again)
 - rust-lang#94537 (Use ? operator in one instance instead of manual match)
 - rust-lang#94544 (Add some examples to comments in mbe code)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_error_codes/src/error_codes/E0284.md

@@ -30,5 +30,3 @@ fn main() {
     d = d + m;
 }
 ```
-
-Note that the type of `v` can now be inferred from the type of `temp`.

compiler/rustc_expand/src/mbe/macro_parser.rs

@@ -345,6 +345,38 @@ fn initial_matcher_pos<'root, 'tt>(ms: &'tt [TokenTree]) -> MatcherPos<'root, 't
 /// token tree. The depth of the `NamedMatch` structure will therefore depend
 /// only on the nesting depth of `ast::TTSeq`s in the originating
 /// token tree it was derived from.
+///
+/// In layman's terms: `NamedMatch` will form a tree representing nested matches of a particular
+/// meta variable. For example, if we are matching the following macro against the following
+/// invocation...
+///
+/// ```rust
+/// macro_rules! foo {
+///   ($($($x:ident),+);+) => {}
+/// }
+///
+/// foo!(a, b, c, d; a, b, c, d, e);
+/// ```
+///
+/// Then, the tree will have the following shape:
+///
+/// ```rust
+/// MatchedSeq([
+///   MatchedSeq([
+///     MatchedNonterminal(a),
+///     MatchedNonterminal(b),
+///     MatchedNonterminal(c),
+///     MatchedNonterminal(d),
+///   ]),
+///   MatchedSeq([
+///     MatchedNonterminal(a),
+///     MatchedNonterminal(b),
+///     MatchedNonterminal(c),
+///     MatchedNonterminal(d),
+///     MatchedNonterminal(e),
+///   ])
+/// ])
+/// ```
 #[derive(Debug, Clone)]
 crate enum NamedMatch {
     MatchedSeq(Lrc<NamedMatchVec>),

compiler/rustc_expand/src/mbe/transcribe.rs

@@ -358,6 +358,12 @@ impl LockstepIterSize {
 /// Note that if `repeats` does not match the exact correct depth of a meta-var,
 /// `lookup_cur_matched` will return `None`, which is why this still works even in the presence of
 /// multiple nested matcher sequences.
+///
+/// Example: `$($($x $y)+*);+` -- we need to make sure that `x` and `y` repeat the same amount as
+/// each other at the given depth when the macro was invoked. If they don't it might mean they were
+/// declared at unequal depths or there was a compile bug. For example, if we have 3 repetitions of
+/// the outer sequence and 4 repetitions of the inner sequence for `x`, we should have the same for
+/// `y`; otherwise, we can't transcribe them both at the given depth.
 fn lockstep_iter_size(
     tree: &mbe::TokenTree,
     interpolations: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>,

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -606,17 +606,16 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     // don't show type `_`
                     err.span_label(span, format!("this expression has type `{}`", ty));
                 }
-                if let Some(ty::error::ExpectedFound { found, .. }) = exp_found {
-                    if ty.is_box() && ty.boxed_ty() == found {
-                        if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
-                            err.span_suggestion(
-                                span,
-                                "consider dereferencing the boxed value",
-                                format!("*{}", snippet),
-                                Applicability::MachineApplicable,
-                            );
-                        }
-                    }
+                if let Some(ty::error::ExpectedFound { found, .. }) = exp_found
+                    && ty.is_box() && ty.boxed_ty() == found
+                    && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
+                {
+                    err.span_suggestion(
+                        span,
+                        "consider dereferencing the boxed value",
+                        format!("*{}", snippet),
+                        Applicability::MachineApplicable,
+                    );
                 }
             }
             ObligationCauseCode::Pattern { origin_expr: false, span: Some(span), .. } => {
@@ -1748,13 +1747,12 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         self.check_and_note_conflicting_crates(diag, terr);
         self.tcx.note_and_explain_type_err(diag, terr, cause, span, body_owner_def_id.to_def_id());
 
-        if let Some(ValuePairs::PolyTraitRefs(exp_found)) = values {
-            if let ty::Closure(def_id, _) = exp_found.expected.skip_binder().self_ty().kind() {
-                if let Some(def_id) = def_id.as_local() {
-                    let span = self.tcx.def_span(def_id);
-                    diag.span_note(span, "this closure does not fulfill the lifetime requirements");
-                }
-            }
+        if let Some(ValuePairs::PolyTraitRefs(exp_found)) = values
+            && let ty::Closure(def_id, _) = exp_found.expected.skip_binder().self_ty().kind()
+            && let Some(def_id) = def_id.as_local()
+        {
+            let span = self.tcx.def_span(def_id);
+            diag.span_note(span, "this closure does not fulfill the lifetime requirements");
         }
 
         // It reads better to have the error origin as the final
@@ -2046,19 +2044,16 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                         // containing a single character, perhaps the user meant to write `'c'` to
                         // specify a character literal (issue #92479)
                         (ty::Char, ty::Ref(_, r, _)) if r.is_str() => {
-                            if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) {
-                                if let Some(code) =
-                                    code.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
-                                {
-                                    if code.chars().count() == 1 {
-                                        err.span_suggestion(
-                                            span,
-                                            "if you meant to write a `char` literal, use single quotes",
-                                            format!("'{}'", code),
-                                            Applicability::MachineApplicable,
-                                        );
-                                    }
-                                }
+                            if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
+                                && let Some(code) = code.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
+                                && code.chars().count() == 1
+                            {
+                                err.span_suggestion(
+                                    span,
+                                    "if you meant to write a `char` literal, use single quotes",
+                                    format!("'{}'", code),
+                                    Applicability::MachineApplicable,
+                                );
                             }
                         }
                         // If a string was expected and the found expression is a character literal,
@@ -2080,18 +2075,16 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                         _ => {}
                     }
                 }
-                if let MatchExpressionArm(box MatchExpressionArmCause { source, .. }) =
-                    *trace.cause.code()
+                let code = trace.cause.code();
+                if let &MatchExpressionArm(box MatchExpressionArmCause { source, .. }) = code
+                    && let hir::MatchSource::TryDesugar = source
+                    && let Some((expected_ty, found_ty)) = self.values_str(trace.values)
                 {
-                    if let hir::MatchSource::TryDesugar = source {
-                        if let Some((expected_ty, found_ty)) = self.values_str(trace.values) {
-                            err.note(&format!(
-                                "`?` operator cannot convert from `{}` to `{}`",
-                                found_ty.content(),
-                                expected_ty.content(),
-                            ));
-                        }
-                    }
+                    err.note(&format!(
+                        "`?` operator cannot convert from `{}` to `{}`",
+                        found_ty.content(),
+                        expected_ty.content(),
+                    ));
                 }
                 err
             }

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -114,28 +114,25 @@ impl<'a, 'tcx> Visitor<'tcx> for FindHirNodeVisitor<'a, 'tcx> {
     }
 
     fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
-        if let ExprKind::Match(scrutinee, [_, arm], MatchSource::ForLoopDesugar) = expr.kind {
-            if let Some(pat) = arm.pat.for_loop_some() {
-                if let Some(ty) = self.node_ty_contains_target(pat.hir_id) {
-                    self.found_for_loop_iter = Some(scrutinee);
-                    self.found_node_ty = Some(ty);
-                    return;
-                }
-            }
+        if let ExprKind::Match(scrutinee, [_, arm], MatchSource::ForLoopDesugar) = expr.kind
+            && let Some(pat) = arm.pat.for_loop_some()
+            && let Some(ty) = self.node_ty_contains_target(pat.hir_id)
+        {
+            self.found_for_loop_iter = Some(scrutinee);
+            self.found_node_ty = Some(ty);
+            return;
         }
-        if let ExprKind::MethodCall(segment, exprs, _) = expr.kind {
-            if segment.ident.span == self.target_span
-                && Some(self.target)
-                    == self.infcx.in_progress_typeck_results.and_then(|typeck_results| {
-                        typeck_results
-                            .borrow()
-                            .node_type_opt(exprs.first().unwrap().hir_id)
-                            .map(Into::into)
-                    })
-            {
-                self.found_exact_method_call = Some(&expr);
-                return;
-            }
+        if let ExprKind::MethodCall(segment, exprs, _) = expr.kind
+            && segment.ident.span == self.target_span
+            && Some(self.target) == self.infcx.in_progress_typeck_results.and_then(|typeck_results| {
+                typeck_results
+                    .borrow()
+                    .node_type_opt(exprs.first().unwrap().hir_id)
+                    .map(Into::into)
+            })
+        {
+            self.found_exact_method_call = Some(&expr);
+            return;
         }
 
         // FIXME(const_generics): Currently, any uninferred `const` generics arguments
@@ -602,10 +599,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         );
 
         let use_diag = local_visitor.found_use_diagnostic.as_ref();
-        if let Some(use_diag) = use_diag {
-            if use_diag.applies_to(err_span) {
-                use_diag.attach_note(&mut err);
-            }
+        if let Some(use_diag) = use_diag && use_diag.applies_to(err_span) {
+            use_diag.attach_note(&mut err);
         }
 
         let param_type = arg_data.kind.descr();
@@ -736,29 +731,27 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 //    |               help: specify type like: `<Impl as Into<u32>>::into(foo_impl)`
                 //    |
                 //    = note: cannot satisfy `Impl: Into<_>`
-                if !impl_candidates.is_empty() && e.span.contains(span) {
-                    if let Some(expr) = exprs.first() {
-                        if let ExprKind::Path(hir::QPath::Resolved(_, path)) = expr.kind {
-                            if let [path_segment] = path.segments {
-                                let candidate_len = impl_candidates.len();
-                                let suggestions = impl_candidates.iter().map(|candidate| {
-                                    format!(
-                                        "{}::{}({})",
-                                        candidate, segment.ident, path_segment.ident
-                                    )
-                                });
-                                err.span_suggestions(
-                                    e.span,
-                                    &format!(
-                                        "use the fully qualified path for the potential candidate{}",
-                                        pluralize!(candidate_len),
-                                    ),
-                                    suggestions,
-                                    Applicability::MaybeIncorrect,
-                                );
-                            }
-                        }
-                    };
+                if !impl_candidates.is_empty() && e.span.contains(span)
+                    && let Some(expr) = exprs.first()
+                    && let ExprKind::Path(hir::QPath::Resolved(_, path)) = expr.kind
+                    && let [path_segment] = path.segments
+                {
+                    let candidate_len = impl_candidates.len();
+                    let suggestions = impl_candidates.iter().map(|candidate| {
+                        format!(
+                            "{}::{}({})",
+                            candidate, segment.ident, path_segment.ident
+                        )
+                    });
+                    err.span_suggestions(
+                        e.span,
+                        &format!(
+                            "use the fully qualified path for the potential candidate{}",
+                            pluralize!(candidate_len),
+                        ),
+                        suggestions,
+                        Applicability::MaybeIncorrect,
+                    );
                 }
                 // Suggest specifying type params or point out the return type of the call:
                 //

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -223,35 +223,32 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         let fn_returns = tcx.return_type_impl_or_dyn_traits(anon_reg_sup.def_id);
 
         let mut override_error_code = None;
-        if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = &sup_origin {
-            if let ObligationCauseCode::UnifyReceiver(ctxt) = cause.code() {
-                // Handle case of `impl Foo for dyn Bar { fn qux(&self) {} }` introducing a
-                // `'static` lifetime when called as a method on a binding: `bar.qux()`.
-                if self.find_impl_on_dyn_trait(&mut err, param.param_ty, &ctxt) {
-                    override_error_code = Some(ctxt.assoc_item.name);
-                }
-            }
+        if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = &sup_origin
+            && let ObligationCauseCode::UnifyReceiver(ctxt) = cause.code()
+            // Handle case of `impl Foo for dyn Bar { fn qux(&self) {} }` introducing a
+            // `'static` lifetime when called as a method on a binding: `bar.qux()`.
+            && self.find_impl_on_dyn_trait(&mut err, param.param_ty, &ctxt)
+        {
+            override_error_code = Some(ctxt.assoc_item.name);
         }
-        if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = &sub_origin {
-            let code = match cause.code() {
+
+        if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = &sub_origin
+            && let code = match cause.code() {
                 ObligationCauseCode::MatchImpl(parent, ..) => parent.code(),
                 _ => cause.code(),
-            };
-            if let (ObligationCauseCode::ItemObligation(item_def_id), None) =
-                (code, override_error_code)
+            }
+            && let (ObligationCauseCode::ItemObligation(item_def_id), None) = (code, override_error_code)
+        {
+            // Same case of `impl Foo for dyn Bar { fn qux(&self) {} }` introducing a `'static`
+            // lifetime as above, but called using a fully-qualified path to the method:
+            // `Foo::qux(bar)`.
+            let mut v = TraitObjectVisitor(FxHashSet::default());
+            v.visit_ty(param.param_ty);
+            if let Some((ident, self_ty)) =
+                self.get_impl_ident_and_self_ty_from_trait(*item_def_id, &v.0)
+                && self.suggest_constrain_dyn_trait_in_impl(&mut err, &v.0, ident, self_ty)
             {
-                // Same case of `impl Foo for dyn Bar { fn qux(&self) {} }` introducing a `'static`
-                // lifetime as above, but called using a fully-qualified path to the method:
-                // `Foo::qux(bar)`.
-                let mut v = TraitObjectVisitor(FxHashSet::default());
-                v.visit_ty(param.param_ty);
-                if let Some((ident, self_ty)) =
-                    self.get_impl_ident_and_self_ty_from_trait(*item_def_id, &v.0)
-                {
-                    if self.suggest_constrain_dyn_trait_in_impl(&mut err, &v.0, ident, self_ty) {
-                        override_error_code = Some(ident.name);
-                    }
-                }
+                override_error_code = Some(ident.name);
             }
         }
         if let (Some(ident), true) = (override_error_code, fn_returns.is_empty()) {