Auto merge of #72627 - Dylan-DPC:rollup-bavnoq5, r=Dylan-DPC

Rollup of 6 pull requests

Successful merges:

 - #72270 (add a lint against references to packed fields)
 - #72294 (JS cleanup)
 - #72342 (Warn about unused crate deps)
 - #72401 (Use correct function for detecting `const fn` in unsafety checking)
 - #72581 (Allow unlabeled breaks from desugared `?` in labeled blocks)
 - #72592 (Update books)

Failed merges:

r? @ghost

src/librustc_lint/lib.rs

@@ -276,6 +276,7 @@ fn register_builtins(store: &mut LintStore, no_interleave_lints: bool) {
         UNUSED_ALLOCATION,
         UNUSED_DOC_COMMENTS,
         UNUSED_EXTERN_CRATES,
+        UNUSED_CRATE_DEPENDENCIES,
         UNUSED_FEATURES,
         UNUSED_LABELS,
         UNUSED_PARENS,

src/librustc_metadata/creader.rs

@@ -5,6 +5,7 @@ use crate::rmeta::{CrateDep, CrateMetadata, CrateNumMap, CrateRoot, MetadataBlob
 
 use rustc_ast::expand::allocator::{global_allocator_spans, AllocatorKind};
 use rustc_ast::{ast, attr};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::struct_span_err;
@@ -18,6 +19,7 @@ use rustc_middle::middle::cstore::{
 };
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{self, CrateType};
+use rustc_session::lint;
 use rustc_session::output::validate_crate_name;
 use rustc_session::search_paths::PathKind;
 use rustc_session::{CrateDisambiguator, Session};
@@ -49,6 +51,7 @@ pub struct CrateLoader<'a> {
     local_crate_name: Symbol,
     // Mutable output.
     cstore: CStore,
+    used_extern_options: FxHashSet<Symbol>,
 }
 
 pub enum LoadedMacro {
@@ -205,6 +208,7 @@ impl<'a> CrateLoader<'a> {
                 allocator_kind: None,
                 has_global_allocator: false,
             },
+            used_extern_options: Default::default(),
         }
     }
 
@@ -445,6 +449,9 @@ impl<'a> CrateLoader<'a> {
         dep_kind: DepKind,
         dep: Option<(&'b CratePaths, &'b CrateDep)>,
     ) -> CrateNum {
+        if dep.is_none() {
+            self.used_extern_options.insert(name);
+        }
         self.maybe_resolve_crate(name, span, dep_kind, dep).unwrap_or_else(|err| err.report())
     }
 
@@ -839,6 +846,26 @@ impl<'a> CrateLoader<'a> {
         });
     }
 
+    fn report_unused_deps(&mut self, krate: &ast::Crate) {
+        // Make a point span rather than covering the whole file
+        let span = krate.span.shrink_to_lo();
+        // Complain about anything left over
+        for (name, _) in self.sess.opts.externs.iter() {
+            if !self.used_extern_options.contains(&Symbol::intern(name)) {
+                self.sess.parse_sess.buffer_lint(
+                    lint::builtin::UNUSED_CRATE_DEPENDENCIES,
+                    span,
+                    ast::CRATE_NODE_ID,
+                    &format!(
+                        "external crate `{}` unused in `{}`: remove the dependency or add `use {} as _;`",
+                        name,
+                        self.local_crate_name,
+                        name),
+                );
+            }
+        }
+    }
+
     pub fn postprocess(&mut self, krate: &ast::Crate) {
         self.inject_profiler_runtime();
         self.inject_allocator_crate(krate);
@@ -847,6 +874,8 @@ impl<'a> CrateLoader<'a> {
         if log_enabled!(log::Level::Info) {
             dump_crates(&self.cstore);
         }
+
+        self.report_unused_deps(krate);
     }
 
     pub fn process_extern_crate(

src/librustc_mir/transform/check_packed_ref.rs

@@ -0,0 +1,66 @@
+use rustc_middle::mir::visit::{PlaceContext, Visitor};
+use rustc_middle::mir::*;
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_session::lint::builtin::UNALIGNED_REFERENCES;
+
+use crate::transform::{MirPass, MirSource};
+use crate::util;
+
+pub struct CheckPackedRef;
+
+impl<'tcx> MirPass<'tcx> for CheckPackedRef {
+    fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, body: &mut Body<'tcx>) {
+        let param_env = tcx.param_env(src.instance.def_id());
+        let source_info = SourceInfo::outermost(body.span);
+        let mut checker = PackedRefChecker { body, tcx, param_env, source_info };
+        checker.visit_body(&body);
+    }
+}
+
+struct PackedRefChecker<'a, 'tcx> {
+    body: &'a Body<'tcx>,
+    tcx: TyCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    source_info: SourceInfo,
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for PackedRefChecker<'a, 'tcx> {
+    fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
+        // Make sure we know where in the MIR we are.
+        self.source_info = terminator.source_info;
+        self.super_terminator(terminator, location);
+    }
+
+    fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
+        // Make sure we know where in the MIR we are.
+        self.source_info = statement.source_info;
+        self.super_statement(statement, location);
+    }
+
+    fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
+        if context.is_borrow() {
+            if util::is_disaligned(self.tcx, self.body, self.param_env, *place) {
+                let source_info = self.source_info;
+                let lint_root = self.body.source_scopes[source_info.scope]
+                    .local_data
+                    .as_ref()
+                    .assert_crate_local()
+                    .lint_root;
+                self.tcx.struct_span_lint_hir(
+                    UNALIGNED_REFERENCES,
+                    lint_root,
+                    source_info.span,
+                    |lint| {
+                        lint.build(&format!("reference to packed field is unaligned",))
+                            .note(
+                                "fields of packed structs are not properly aligned, and creating \
+                                a misaligned reference is undefined behavior (even if that \
+                                reference is never dereferenced)",
+                            )
+                            .emit()
+                    },
+                );
+            }
+        }
+    }
+}

src/librustc_mir/transform/check_unsafety.rs

@@ -14,7 +14,7 @@ use rustc_span::symbol::{sym, Symbol};
 
 use std::ops::Bound;
 
-use crate::const_eval::{is_const_fn, is_min_const_fn};
+use crate::const_eval::is_min_const_fn;
 use crate::util;
 
 pub struct UnsafetyChecker<'a, 'tcx> {
@@ -527,7 +527,7 @@ fn unsafety_check_result(tcx: TyCtxt<'_>, def_id: LocalDefId) -> UnsafetyCheckRe
     let (const_context, min_const_fn) = match tcx.hir().body_owner_kind(id) {
         hir::BodyOwnerKind::Closure => (false, false),
         hir::BodyOwnerKind::Fn => {
-            (is_const_fn(tcx, def_id.to_def_id()), is_min_const_fn(tcx, def_id.to_def_id()))
+            (tcx.is_const_fn_raw(def_id.to_def_id()), is_min_const_fn(tcx, def_id.to_def_id()))
         }
         hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => (true, false),
     };

src/librustc_mir/transform/mod.rs

@@ -17,6 +17,7 @@ pub mod add_call_guards;
 pub mod add_moves_for_packed_drops;
 pub mod add_retag;
 pub mod check_consts;
+pub mod check_packed_ref;
 pub mod check_unsafety;
 pub mod cleanup_post_borrowck;
 pub mod const_prop;
@@ -228,10 +229,11 @@ fn mir_const_qualif(tcx: TyCtxt<'_>, def_id: DefId) -> ConstQualifs {
     validator.qualifs_in_return_place()
 }
 
+/// Make MIR ready for const evaluation. This is run on all MIR, not just on consts!
 fn mir_const(tcx: TyCtxt<'_>, def_id: DefId) -> Steal<Body<'_>> {
     let def_id = def_id.expect_local();
 
-    // Unsafety check uses the raw mir, so make sure it is run
+    // Unsafety check uses the raw mir, so make sure it is run.
     let _ = tcx.unsafety_check_result(def_id);
 
     let mut body = tcx.mir_built(def_id).steal();
@@ -247,6 +249,8 @@ fn mir_const(tcx: TyCtxt<'_>, def_id: DefId) -> Steal<Body<'_>> {
         None,
         MirPhase::Const,
         &[&[
+            // MIR-level lints.
+            &check_packed_ref::CheckPackedRef,
             // What we need to do constant evaluation.
             &simplify::SimplifyCfg::new("initial"),
             &rustc_peek::SanityCheck,

src/librustc_passes/loops.rs

@@ -9,6 +9,7 @@ use rustc_middle::hir::map::Map;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
+use rustc_span::hygiene::DesugaringKind;
 use rustc_span::Span;
 
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -203,7 +204,7 @@ impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
         label: &Destination,
         cf_type: &str,
     ) -> bool {
-        if self.cx == LabeledBlock {
+        if !span.is_desugaring(DesugaringKind::QuestionMark) && self.cx == LabeledBlock {
             if label.label.is_none() {
                 struct_span_err!(
                     self.sess,

src/librustc_session/lint/builtin.rs

@@ -71,6 +71,12 @@ declare_lint! {
     "extern crates that are never used"
 }
 
+declare_lint! {
+    pub UNUSED_CRATE_DEPENDENCIES,
+    Allow,
+    "crate dependencies that are never used"
+}
+
 declare_lint! {
     pub UNUSED_QUALIFICATIONS,
     Allow,
@@ -216,10 +222,16 @@ declare_lint! {
     "lints that have been renamed or removed"
 }
 
+declare_lint! {
+    pub UNALIGNED_REFERENCES,
+    Allow,
+    "detects unaligned references to fields of packed structs",
+}
+
 declare_lint! {
     pub SAFE_PACKED_BORROWS,
     Warn,
-    "safe borrows of fields of packed structs were was erroneously allowed",
+    "safe borrows of fields of packed structs were erroneously allowed",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #46043 <https://github.com/rust-lang/rust/issues/46043>",
         edition: None,
@@ -523,6 +535,7 @@ declare_lint_pass! {
         UNCONDITIONAL_PANIC,
         UNUSED_IMPORTS,
         UNUSED_EXTERN_CRATES,
+        UNUSED_CRATE_DEPENDENCIES,
         UNUSED_QUALIFICATIONS,
         UNKNOWN_LINTS,
         UNUSED_VARIABLES,
@@ -545,6 +558,7 @@ declare_lint_pass! {
         INVALID_TYPE_PARAM_DEFAULT,
         CONST_ERR,
         RENAMED_AND_REMOVED_LINTS,
+        UNALIGNED_REFERENCES,
         SAFE_PACKED_BORROWS,
         PATTERNS_IN_FNS_WITHOUT_BODY,
         MISSING_FRAGMENT_SPECIFIER,