Auto merge of #122511 - matthiaskrgr:rollup-swzilin, r=matthiaskrgr

Rollup of 10 pull requests

Successful merges:

 - #117118 ([AIX] Remove AixLinker's debuginfo() implementation)
 - #121650 (change std::process to drop supplementary groups based on CAP_SETGID)
 - #121764 (Make incremental sessions identity no longer depend on the crate names provided by source code)
 - #122212 (Copy byval argument to alloca if alignment is insufficient)
 - #122322 (coverage: Initial support for branch coverage instrumentation)
 - #122373 (Fix the conflict problem between the diagnostics fixes of lint `unnecessary_qualification`  and  `unused_imports`)
 - #122479 (Implement `Duration::as_millis_{f64,f32}`)
 - #122487 (Rename `StmtKind::Local` variant into `StmtKind::Let`)
 - #122498 (Update version of cc crate)
 - #122503 (Make `SubdiagMessageOp` well-formed)

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

compiler/rustc_ast/src/ast.rs

@@ -1021,7 +1021,7 @@ impl Stmt {
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum StmtKind {
     /// A local (let) binding.
-    Local(P<Local>),
+    Let(P<Local>),
     /// An item definition.
     Item(P<Item>),
     /// Expr without trailing semi-colon.

compiler/rustc_ast/src/ast_traits.rs

@@ -182,7 +182,7 @@ impl<T: HasTokens> HasTokens for Option<T> {
 impl HasTokens for StmtKind {
     fn tokens(&self) -> Option<&LazyAttrTokenStream> {
         match self {
-            StmtKind::Local(local) => local.tokens.as_ref(),
+            StmtKind::Let(local) => local.tokens.as_ref(),
             StmtKind::Item(item) => item.tokens(),
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => expr.tokens(),
             StmtKind::Empty => return None,
@@ -191,7 +191,7 @@ impl HasTokens for StmtKind {
     }
     fn tokens_mut(&mut self) -> Option<&mut Option<LazyAttrTokenStream>> {
         match self {
-            StmtKind::Local(local) => Some(&mut local.tokens),
+            StmtKind::Let(local) => Some(&mut local.tokens),
             StmtKind::Item(item) => item.tokens_mut(),
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => expr.tokens_mut(),
             StmtKind::Empty => return None,
@@ -355,7 +355,7 @@ impl HasAttrs for StmtKind {
 
     fn attrs(&self) -> &[Attribute] {
         match self {
-            StmtKind::Local(local) => &local.attrs,
+            StmtKind::Let(local) => &local.attrs,
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => expr.attrs(),
             StmtKind::Item(item) => item.attrs(),
             StmtKind::Empty => &[],
@@ -365,7 +365,7 @@ impl HasAttrs for StmtKind {
 
     fn visit_attrs(&mut self, f: impl FnOnce(&mut AttrVec)) {
         match self {
-            StmtKind::Local(local) => f(&mut local.attrs),
+            StmtKind::Let(local) => f(&mut local.attrs),
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => expr.visit_attrs(f),
             StmtKind::Item(item) => item.visit_attrs(f),
             StmtKind::Empty => {}

compiler/rustc_ast/src/mut_visit.rs

@@ -1567,7 +1567,7 @@ pub fn noop_flat_map_stmt_kind<T: MutVisitor>(
     vis: &mut T,
 ) -> SmallVec<[StmtKind; 1]> {
     match kind {
-        StmtKind::Local(mut local) => smallvec![StmtKind::Local({
+        StmtKind::Let(mut local) => smallvec![StmtKind::Let({
             vis.visit_local(&mut local);
             local
         })],

compiler/rustc_ast/src/visit.rs

@@ -787,7 +787,7 @@ pub fn walk_block<'a, V: Visitor<'a>>(visitor: &mut V, block: &'a Block) -> V::R
 
 pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) -> V::Result {
     match &statement.kind {
-        StmtKind::Local(local) => try_visit!(visitor.visit_local(local)),
+        StmtKind::Let(local) => try_visit!(visitor.visit_local(local)),
         StmtKind::Item(item) => try_visit!(visitor.visit_item(item)),
         StmtKind::Expr(expr) | StmtKind::Semi(expr) => try_visit!(visitor.visit_expr(expr)),
         StmtKind::Empty => {}

compiler/rustc_ast_lowering/src/block.rs

@@ -32,11 +32,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let mut expr = None;
         while let [s, tail @ ..] = ast_stmts {
             match &s.kind {
-                StmtKind::Local(local) => {
+                StmtKind::Let(local) => {
                     let hir_id = self.lower_node_id(s.id);
                     let local = self.lower_local(local);
                     self.alias_attrs(hir_id, local.hir_id);
-                    let kind = hir::StmtKind::Local(local);
+                    let kind = hir::StmtKind::Let(local);
                     let span = self.lower_span(s.span);
                     stmts.push(hir::Stmt { hir_id, kind, span });
                 }

compiler/rustc_ast_lowering/src/lib.rs

@@ -2356,7 +2356,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             span: self.lower_span(span),
             ty: None,
         };
-        self.stmt(span, hir::StmtKind::Local(self.arena.alloc(local)))
+        self.stmt(span, hir::StmtKind::Let(self.arena.alloc(local)))
     }
 
     fn block_expr(&mut self, expr: &'hir hir::Expr<'hir>) -> &'hir hir::Block<'hir> {

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1212,7 +1212,7 @@ impl<'a> State<'a> {
     fn print_stmt(&mut self, st: &ast::Stmt) {
         self.maybe_print_comment(st.span.lo());
         match &st.kind {
-            ast::StmtKind::Local(loc) => {
+            ast::StmtKind::Let(loc) => {
                 self.print_outer_attributes(&loc.attrs);
                 self.space_if_not_bol();
                 self.ibox(INDENT_UNIT);

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -616,7 +616,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
                     // FIXME: We make sure that this is a normal top-level binding,
                     // but we could suggest `todo!()` for all uninitalized bindings in the pattern pattern
-                    if let hir::StmtKind::Local(hir::Local { span, ty, init: None, pat, .. }) =
+                    if let hir::StmtKind::Let(hir::Local { span, ty, init: None, pat, .. }) =
                         &ex.kind
                         && let hir::PatKind::Binding(..) = pat.kind
                         && span.contains(self.decl_span)

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -558,7 +558,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     hir::intravisit::walk_stmt(self, stmt);
                     let expr = match stmt.kind {
                         hir::StmtKind::Semi(expr) | hir::StmtKind::Expr(expr) => expr,
-                        hir::StmtKind::Local(hir::Local { init: Some(expr), .. }) => expr,
+                        hir::StmtKind::Let(hir::Local { init: Some(expr), .. }) => expr,
                         _ => {
                             return;
                         }
@@ -1305,7 +1305,7 @@ struct BindingFinder {
 impl<'tcx> Visitor<'tcx> for BindingFinder {
     type Result = ControlFlow<hir::HirId>;
     fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) -> Self::Result {
-        if let hir::StmtKind::Local(local) = s.kind
+        if let hir::StmtKind::Let(local) = s.kind
             && local.pat.span == self.span
         {
             ControlFlow::Break(local.hir_id)

compiler/rustc_codegen_llvm/src/abi.rs

@@ -203,57 +203,63 @@ impl<'ll, 'tcx> ArgAbiExt<'ll, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
         val: &'ll Value,
         dst: PlaceRef<'tcx, &'ll Value>,
     ) {
-        if self.is_ignore() {
+        match &self.mode {
-            return;
+            PassMode::Ignore => {}
-        }
+            // Sized indirect arguments
-        if self.is_sized_indirect() {
+            PassMode::Indirect { attrs, meta_attrs: None, on_stack: _ } => {
-            OperandValue::Ref(val, None, self.layout.align.abi).store(bx, dst)
+                let align = attrs.pointee_align.unwrap_or(self.layout.align.abi);
-        } else if self.is_unsized_indirect() {
+                OperandValue::Ref(val, None, align).store(bx, dst);
-            bug!("unsized `ArgAbi` must be handled through `store_fn_arg`");
+            }
-        } else if let PassMode::Cast { cast, pad_i32: _ } = &self.mode {
+            // Unsized indirect qrguments
-            // FIXME(eddyb): Figure out when the simpler Store is safe, clang
+            PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => {
-            // uses it for i16 -> {i8, i8}, but not for i24 -> {i8, i8, i8}.
+                bug!("unsized `ArgAbi` must be handled through `store_fn_arg`");
-            let can_store_through_cast_ptr = false;
+            }
-            if can_store_through_cast_ptr {
+            PassMode::Cast { cast, pad_i32: _ } => {
-                bx.store(val, dst.llval, self.layout.align.abi);
+                // FIXME(eddyb): Figure out when the simpler Store is safe, clang
-            } else {
+                // uses it for i16 -> {i8, i8}, but not for i24 -> {i8, i8, i8}.
-                // The actual return type is a struct, but the ABI
+                let can_store_through_cast_ptr = false;
-                // adaptation code has cast it into some scalar type. The
+                if can_store_through_cast_ptr {
-                // code that follows is the only reliable way I have
+                    bx.store(val, dst.llval, self.layout.align.abi);
-                // found to do a transform like i64 -> {i32,i32}.
+                } else {
-                // Basically we dump the data onto the stack then memcpy it.
+                    // The actual return type is a struct, but the ABI
-                //
+                    // adaptation code has cast it into some scalar type. The
-                // Other approaches I tried:
+                    // code that follows is the only reliable way I have
-                // - Casting rust ret pointer to the foreign type and using Store
+                    // found to do a transform like i64 -> {i32,i32}.
-                //   is (a) unsafe if size of foreign type > size of rust type and
+                    // Basically we dump the data onto the stack then memcpy it.
-                //   (b) runs afoul of strict aliasing rules, yielding invalid
+                    //
-                //   assembly under -O (specifically, the store gets removed).
+                    // Other approaches I tried:
-                // - Truncating foreign type to correct integral type and then
+                    // - Casting rust ret pointer to the foreign type and using Store
-                //   bitcasting to the struct type yields invalid cast errors.
+                    //   is (a) unsafe if size of foreign type > size of rust type and
-
+                    //   (b) runs afoul of strict aliasing rules, yielding invalid
-                // We instead thus allocate some scratch space...
+                    //   assembly under -O (specifically, the store gets removed).
-                let scratch_size = cast.size(bx);
+                    // - Truncating foreign type to correct integral type and then
-                let scratch_align = cast.align(bx);
+                    //   bitcasting to the struct type yields invalid cast errors.
-                let llscratch = bx.alloca(cast.llvm_type(bx), scratch_align);
+
-                bx.lifetime_start(llscratch, scratch_size);
+                    // We instead thus allocate some scratch space...
-
+                    let scratch_size = cast.size(bx);
-                // ... where we first store the value...
+                    let scratch_align = cast.align(bx);
-                bx.store(val, llscratch, scratch_align);
+                    let llscratch = bx.alloca(cast.llvm_type(bx), scratch_align);
-
+                    bx.lifetime_start(llscratch, scratch_size);
-                // ... and then memcpy it to the intended destination.
+
-                bx.memcpy(
+                    // ... where we first store the value...
-                    dst.llval,
+                    bx.store(val, llscratch, scratch_align);
-                    self.layout.align.abi,
+
-                    llscratch,
+                    // ... and then memcpy it to the intended destination.
-                    scratch_align,
+                    bx.memcpy(
-                    bx.const_usize(self.layout.size.bytes()),
+                        dst.llval,
-                    MemFlags::empty(),
+                        self.layout.align.abi,
-                );
+                        llscratch,
-
+                        scratch_align,
-                bx.lifetime_end(llscratch, scratch_size);
+                        bx.const_usize(self.layout.size.bytes()),
+                        MemFlags::empty(),
+                    );
+
+                    bx.lifetime_end(llscratch, scratch_size);
+                }
+            }
+            _ => {
+                OperandRef::from_immediate_or_packed_pair(bx, val, self.layout).val.store(bx, dst);
             }
-        } else {
-            OperandRef::from_immediate_or_packed_pair(bx, val, self.layout).val.store(bx, dst);
         }
     }
 

compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs

@@ -164,6 +164,15 @@ impl CounterMappingRegion {
                 end_line,
                 end_col,
             ),
+            MappingKind::Branch { true_term, false_term } => Self::branch_region(
+                Counter::from_term(true_term),
+                Counter::from_term(false_term),
+                local_file_id,
+                start_line,
+                start_col,
+                end_line,
+                end_col,
+            ),
         }
     }
 
@@ -188,9 +197,6 @@ impl CounterMappingRegion {
         }
     }
 
-    // This function might be used in the future; the LLVM API is still evolving, as is coverage
-    // support.
-    #[allow(dead_code)]
     pub(crate) fn branch_region(
         counter: Counter,
         false_counter: Counter,

compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs

@@ -88,7 +88,7 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
         match coverage.kind {
             // Marker statements have no effect during codegen,
             // so return early and don't create `func_coverage`.
-            CoverageKind::SpanMarker => return,
+            CoverageKind::SpanMarker | CoverageKind::BlockMarker { .. } => return,
             // Match exhaustively to ensure that newly-added kinds are classified correctly.
             CoverageKind::CounterIncrement { .. } | CoverageKind::ExpressionUsed { .. } => {}
         }
@@ -108,7 +108,7 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
 
         let Coverage { kind } = coverage;
         match *kind {
-            CoverageKind::SpanMarker => unreachable!(
+            CoverageKind::SpanMarker | CoverageKind::BlockMarker { .. } => unreachable!(
                 "unexpected marker statement {kind:?} should have caused an early return"
             ),
             CoverageKind::CounterIncrement { id } => {

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1081,6 +1081,21 @@ fn link_natively<'a>(
         }
     }
 
+    if sess.target.is_like_aix {
+        let stripcmd = "/usr/bin/strip";
+        match strip {
+            Strip::Debuginfo => {
+                // FIXME: AIX's strip utility only offers option to strip line number information.
+                strip_symbols_with_external_utility(sess, stripcmd, out_filename, Some("-l"))
+            }
+            Strip::Symbols => {
+                // Must be noted this option might remove symbol __aix_rust_metadata and thus removes .info section which contains metadata.
+                strip_symbols_with_external_utility(sess, stripcmd, out_filename, Some("-r"))
+            }
+            Strip::None => {}
+        }
+    }
+
     Ok(())
 }
 

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -1640,16 +1640,7 @@ impl<'a> Linker for AixLinker<'a> {
 
     fn ehcont_guard(&mut self) {}
 
-    fn debuginfo(&mut self, strip: Strip, _: &[PathBuf]) {
+    fn debuginfo(&mut self, _: Strip, _: &[PathBuf]) {}
-        match strip {
-            Strip::None => {}
-            // FIXME: -s strips the symbol table, line number information
-            // and relocation information.
-            Strip::Debuginfo | Strip::Symbols => {
-                self.cmd.arg("-s");
-            }
-        }
-    }
 
     fn no_crt_objects(&mut self) {}
 

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -377,29 +377,45 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 }
             }
 
-            if arg.is_sized_indirect() {
+            match arg.mode {
-                // Don't copy an indirect argument to an alloca, the caller
+                // Sized indirect arguments
-                // already put it in a temporary alloca and gave it up.
+                PassMode::Indirect { attrs, meta_attrs: None, on_stack: _ } => {
-                // FIXME: lifetimes
+                    // Don't copy an indirect argument to an alloca, the caller already put it
-                let llarg = bx.get_param(llarg_idx);
+                    // in a temporary alloca and gave it up.
-                llarg_idx += 1;
+                    // FIXME: lifetimes
-                LocalRef::Place(PlaceRef::new_sized(llarg, arg.layout))
+                    if let Some(pointee_align) = attrs.pointee_align
-            } else if arg.is_unsized_indirect() {
+                        && pointee_align < arg.layout.align.abi
-                // As the storage for the indirect argument lives during
+                    {
-                // the whole function call, we just copy the fat pointer.
+                        // ...unless the argument is underaligned, then we need to copy it to
-                let llarg = bx.get_param(llarg_idx);
+                        // a higher-aligned alloca.
-                llarg_idx += 1;
+                        let tmp = PlaceRef::alloca(bx, arg.layout);
-                let llextra = bx.get_param(llarg_idx);
+                        bx.store_fn_arg(arg, &mut llarg_idx, tmp);
-                llarg_idx += 1;
+                        LocalRef::Place(tmp)
-                let indirect_operand = OperandValue::Pair(llarg, llextra);
+                    } else {
+                        let llarg = bx.get_param(llarg_idx);
+                        llarg_idx += 1;
+                        LocalRef::Place(PlaceRef::new_sized(llarg, arg.layout))
+                    }
+                }
+                // Unsized indirect qrguments
+                PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => {
+                    // As the storage for the indirect argument lives during
+                    // the whole function call, we just copy the fat pointer.
+                    let llarg = bx.get_param(llarg_idx);
+                    llarg_idx += 1;
+                    let llextra = bx.get_param(llarg_idx);
+                    llarg_idx += 1;
+                    let indirect_operand = OperandValue::Pair(llarg, llextra);
 
-                let tmp = PlaceRef::alloca_unsized_indirect(bx, arg.layout);
+                    let tmp = PlaceRef::alloca_unsized_indirect(bx, arg.layout);
-                indirect_operand.store(bx, tmp);
+                    indirect_operand.store(bx, tmp);
-                LocalRef::UnsizedPlace(tmp)
+                    LocalRef::UnsizedPlace(tmp)
-            } else {
+                }
-                let tmp = PlaceRef::alloca(bx, arg.layout);
+                _ => {
-                bx.store_fn_arg(arg, &mut llarg_idx, tmp);
+                    let tmp = PlaceRef::alloca(bx, arg.layout);
-                LocalRef::Place(tmp)
+                    bx.store_fn_arg(arg, &mut llarg_idx, tmp);
+                    LocalRef::Place(tmp)
+                }
             }
         })
         .collect::<Vec<_>>();

compiler/rustc_driver_impl/src/lib.rs

@@ -28,7 +28,7 @@ use rustc_errors::{
     markdown, ColorConfig, DiagCtxt, ErrCode, ErrorGuaranteed, FatalError, PResult,
 };
 use rustc_feature::find_gated_cfg;
-use rustc_interface::util::{self, collect_crate_types, get_codegen_backend};
+use rustc_interface::util::{self, get_codegen_backend};
 use rustc_interface::{interface, Queries};
 use rustc_lint::unerased_lint_store;
 use rustc_metadata::creader::MetadataLoader;
@@ -37,6 +37,7 @@ use rustc_session::config::{nightly_options, CG_OPTIONS, Z_OPTIONS};
 use rustc_session::config::{ErrorOutputType, Input, OutFileName, OutputType};
 use rustc_session::getopts::{self, Matches};
 use rustc_session::lint::{Lint, LintId};
+use rustc_session::output::collect_crate_types;
 use rustc_session::{config, filesearch, EarlyDiagCtxt, Session};
 use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::source_map::FileLoader;

compiler/rustc_errors/src/diagnostic.rs

@@ -189,7 +189,8 @@ where
     );
 }
 
-pub trait SubdiagMessageOp<G> = Fn(&mut Diag<'_, G>, SubdiagMessage) -> SubdiagMessage;
+pub trait SubdiagMessageOp<G: EmissionGuarantee> =
+    Fn(&mut Diag<'_, G>, SubdiagMessage) -> SubdiagMessage;
 
 /// Trait implemented by lint types. This should not be implemented manually. Instead, use
 /// `#[derive(LintDiagnostic)]` -- see [rustc_macros::LintDiagnostic].

compiler/rustc_expand/src/build.rs

@@ -218,7 +218,7 @@ impl<'a> ExtCtxt<'a> {
     }
 
     pub fn stmt_local(&self, local: P<ast::Local>, span: Span) -> ast::Stmt {
-        ast::Stmt { id: ast::DUMMY_NODE_ID, kind: ast::StmtKind::Local(local), span }
+        ast::Stmt { id: ast::DUMMY_NODE_ID, kind: ast::StmtKind::Let(local), span }
     }
 
     pub fn stmt_item(&self, sp: Span, item: P<ast::Item>) -> ast::Stmt {

compiler/rustc_expand/src/expand.rs

@@ -1389,7 +1389,7 @@ impl InvocationCollectorNode for ast::Stmt {
             StmtKind::Item(item) => matches!(item.kind, ItemKind::MacCall(..)),
             StmtKind::Semi(expr) => matches!(expr.kind, ExprKind::MacCall(..)),
             StmtKind::Expr(..) => unreachable!(),
-            StmtKind::Local(..) | StmtKind::Empty => false,
+            StmtKind::Let(..) | StmtKind::Empty => false,
         }
     }
     fn take_mac_call(self) -> (P<ast::MacCall>, Self::AttrsTy, AddSemicolon) {

compiler/rustc_hir/src/hir.rs

@@ -1209,7 +1209,7 @@ pub struct Stmt<'hir> {
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
 pub enum StmtKind<'hir> {
     /// A local (`let`) binding.
-    Local(&'hir Local<'hir>),
+    Let(&'hir Local<'hir>),
 
     /// An item binding.
     Item(ItemId),

compiler/rustc_hir/src/intravisit.rs

@@ -627,7 +627,7 @@ pub fn walk_block<'v, V: Visitor<'v>>(visitor: &mut V, block: &'v Block<'v>) ->
 pub fn walk_stmt<'v, V: Visitor<'v>>(visitor: &mut V, statement: &'v Stmt<'v>) -> V::Result {
     try_visit!(visitor.visit_id(statement.hir_id));
     match statement.kind {
-        StmtKind::Local(ref local) => visitor.visit_local(local),
+        StmtKind::Let(ref local) => visitor.visit_local(local),
         StmtKind::Item(item) => visitor.visit_nested_item(item),
         StmtKind::Expr(ref expression) | StmtKind::Semi(ref expression) => {
             visitor.visit_expr(expression)

compiler/rustc_hir_analysis/src/check/errs.rs

@@ -27,7 +27,7 @@ pub fn maybe_expr_static_mut(tcx: TyCtxt<'_>, expr: hir::Expr<'_>) {
 
 /// Check for shared or mutable references of `static mut` inside statement
 pub fn maybe_stmt_static_mut(tcx: TyCtxt<'_>, stmt: hir::Stmt<'_>) {
-    if let hir::StmtKind::Local(loc) = stmt.kind
+    if let hir::StmtKind::Let(loc) = stmt.kind
         && let hir::PatKind::Binding(ba, _, _, _) = loc.pat.kind
         && matches!(ba.0, rustc_ast::ByRef::Yes)
         && let Some(init) = loc.init

compiler/rustc_hir_analysis/src/check/region.rs

@@ -123,7 +123,7 @@ fn resolve_block<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, blk: &'tcx h
 
         for (i, statement) in blk.stmts.iter().enumerate() {
             match statement.kind {
-                hir::StmtKind::Local(hir::Local { els: Some(els), .. }) => {
+                hir::StmtKind::Let(hir::Local { els: Some(els), .. }) => {
                     // Let-else has a special lexical structure for variables.
                     // First we take a checkpoint of the current scope context here.
                     let mut prev_cx = visitor.cx;
@@ -146,7 +146,7 @@ fn resolve_block<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, blk: &'tcx h
                     // From now on, we continue normally.
                     visitor.cx = prev_cx;
                 }
-                hir::StmtKind::Local(..) => {
+                hir::StmtKind::Let(..) => {
                     // Each declaration introduces a subscope for bindings
                     // introduced by the declaration; this subscope covers a
                     // suffix of the block. Each subscope in a block has the

compiler/rustc_hir_pretty/src/lib.rs

@@ -864,7 +864,7 @@ impl<'a> State<'a> {
     fn print_stmt(&mut self, st: &hir::Stmt<'_>) {
         self.maybe_print_comment(st.span.lo());
         match st.kind {
-            hir::StmtKind::Local(loc) => {
+            hir::StmtKind::Let(loc) => {
                 self.print_local(loc.init, loc.els, |this| this.print_local_decl(loc));
             }
             hir::StmtKind::Item(item) => self.ann.nested(self, Nested::Item(item)),
@@ -2307,7 +2307,7 @@ fn expr_requires_semi_to_be_stmt(e: &hir::Expr<'_>) -> bool {
 /// seen the semicolon, and thus don't need another.
 fn stmt_ends_with_semi(stmt: &hir::StmtKind<'_>) -> bool {
     match *stmt {
-        hir::StmtKind::Local(_) => true,
+        hir::StmtKind::Let(_) => true,
         hir::StmtKind::Item(_) => false,
         hir::StmtKind::Expr(e) => expr_requires_semi_to_be_stmt(e),
         hir::StmtKind::Semi(..) => false,

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -371,11 +371,11 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
 
     fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) {
         match stmt.kind {
-            hir::StmtKind::Local(hir::Local { pat, init: Some(expr), els, .. }) => {
+            hir::StmtKind::Let(hir::Local { pat, init: Some(expr), els, .. }) => {
                 self.walk_local(expr, pat, *els, |_| {})
             }
 
-            hir::StmtKind::Local(_) => {}
+            hir::StmtKind::Let(_) => {}
 
             hir::StmtKind::Item(_) => {
                 // We don't visit nested items in this visitor,

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1593,7 +1593,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // Don't do all the complex logic below for `DeclItem`.
         match stmt.kind {
             hir::StmtKind::Item(..) => return,
-            hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
+            hir::StmtKind::Let(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
         }
 
         self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
@@ -1602,7 +1602,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let old_diverges = self.diverges.replace(Diverges::Maybe);
 
         match stmt.kind {
-            hir::StmtKind::Local(l) => {
+            hir::StmtKind::Let(l) => {
                 self.check_decl_local(l);
             }
             // Ignore for now.
@@ -1765,7 +1765,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                             [
                                                 hir::Stmt {
                                                     kind:
-                                                        hir::StmtKind::Local(hir::Local {
+                                                        hir::StmtKind::Let(hir::Local {
                                                             source:
                                                                 hir::LocalSource::AssignDesugar(_),
                                                             ..

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1599,7 +1599,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     fn is_local_statement(&self, id: hir::HirId) -> bool {
         let node = self.tcx.hir_node(id);
-        matches!(node, Node::Stmt(Stmt { kind: StmtKind::Local(..), .. }))
+        matches!(node, Node::Stmt(Stmt { kind: StmtKind::Let(..), .. }))
     }
 
     /// Suggest that `&T` was cloned instead of `T` because `T` does not implement `Clone`,

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -2221,7 +2221,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 impl<'v> Visitor<'v> for LetVisitor {
                     type Result = ControlFlow<Option<&'v hir::Expr<'v>>>;
                     fn visit_stmt(&mut self, ex: &'v hir::Stmt<'v>) -> Self::Result {
-                        if let hir::StmtKind::Local(&hir::Local { pat, init, .. }) = ex.kind
+                        if let hir::StmtKind::Let(&hir::Local { pat, init, .. }) = ex.kind
                             && let Binding(_, _, ident, ..) = pat.kind
                             && ident.name == self.ident_name
                         {

compiler/rustc_hir_typeck/src/upvar.rs

@@ -217,7 +217,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 bug!();
             };
             for stmt in block.stmts {
-                let hir::StmtKind::Local(hir::Local {
+                let hir::StmtKind::Let(hir::Local {
                     init: Some(init),
                     source: hir::LocalSource::AsyncFn,
                     pat,

compiler/rustc_incremental/src/persist/fs.rs

@@ -110,8 +110,9 @@ use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_data_structures::{base_n, flock};
 use rustc_errors::ErrorGuaranteed;
 use rustc_fs_util::{link_or_copy, try_canonicalize, LinkOrCopy};
+use rustc_session::config::CrateType;
+use rustc_session::output::{collect_crate_types, find_crate_name};
 use rustc_session::{Session, StableCrateId};
-use rustc_span::Symbol;
 
 use std::fs as std_fs;
 use std::io::{self, ErrorKind};
@@ -205,11 +206,7 @@ pub fn in_incr_comp_dir(incr_comp_session_dir: &Path, file_name: &str) -> PathBu
 /// The garbage collection will take care of it.
 ///
 /// [`rustc_interface::queries::dep_graph`]: ../../rustc_interface/struct.Queries.html#structfield.dep_graph
-pub(crate) fn prepare_session_directory(
+pub(crate) fn prepare_session_directory(sess: &Session) -> Result<(), ErrorGuaranteed> {
-    sess: &Session,
-    crate_name: Symbol,
-    stable_crate_id: StableCrateId,
-) -> Result<(), ErrorGuaranteed> {
     if sess.opts.incremental.is_none() {
         return Ok(());
     }
@@ -219,7 +216,7 @@ pub(crate) fn prepare_session_directory(
     debug!("prepare_session_directory");
 
     // {incr-comp-dir}/{crate-name-and-disambiguator}
-    let crate_dir = crate_path(sess, crate_name, stable_crate_id);
+    let crate_dir = crate_path(sess);
     debug!("crate-dir: {}", crate_dir.display());
     create_dir(sess, &crate_dir, "crate")?;
 
@@ -604,9 +601,18 @@ fn string_to_timestamp(s: &str) -> Result<SystemTime, &'static str> {
     Ok(UNIX_EPOCH + duration)
 }
 
-fn crate_path(sess: &Session, crate_name: Symbol, stable_crate_id: StableCrateId) -> PathBuf {
+fn crate_path(sess: &Session) -> PathBuf {
     let incr_dir = sess.opts.incremental.as_ref().unwrap().clone();
 
+    let crate_name = find_crate_name(sess, &[]);
+    let crate_types = collect_crate_types(sess, &[]);
+    let stable_crate_id = StableCrateId::new(
+        crate_name,
+        crate_types.contains(&CrateType::Executable),
+        sess.opts.cg.metadata.clone(),
+        sess.cfg_version,
+    );
+
     let stable_crate_id = base_n::encode(stable_crate_id.as_u64() as u128, INT_ENCODE_BASE);
 
     let crate_name = format!("{crate_name}-{stable_crate_id}");

compiler/rustc_incremental/src/persist/load.rs

@@ -8,8 +8,8 @@ use rustc_middle::query::on_disk_cache::OnDiskCache;
 use rustc_serialize::opaque::MemDecoder;
 use rustc_serialize::Decodable;
 use rustc_session::config::IncrementalStateAssertion;
-use rustc_session::{Session, StableCrateId};
+use rustc_session::Session;
-use rustc_span::{ErrorGuaranteed, Symbol};
+use rustc_span::ErrorGuaranteed;
 use std::path::{Path, PathBuf};
 
 use super::data::*;
@@ -190,13 +190,9 @@ pub fn load_query_result_cache(sess: &Session) -> Option<OnDiskCache<'_>> {
 
 /// Setups the dependency graph by loading an existing graph from disk and set up streaming of a
 /// new graph to an incremental session directory.
-pub fn setup_dep_graph(
+pub fn setup_dep_graph(sess: &Session) -> Result<DepGraph, ErrorGuaranteed> {
-    sess: &Session,
-    crate_name: Symbol,
-    stable_crate_id: StableCrateId,
-) -> Result<DepGraph, ErrorGuaranteed> {
     // `load_dep_graph` can only be called after `prepare_session_directory`.
-    prepare_session_directory(sess, crate_name, stable_crate_id)?;
+    prepare_session_directory(sess)?;
 
     let res = sess.opts.build_dep_graph().then(|| load_dep_graph(sess));
 

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

@@ -2139,7 +2139,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         // the same span as the error and the type is specified.
                         if let hir::Stmt {
                             kind:
-                                hir::StmtKind::Local(hir::Local {
+                                hir::StmtKind::Let(hir::Local {
                                     init: Some(hir::Expr { span: init_span, .. }),
                                     ty: Some(array_ty),
                                     ..

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

@@ -585,7 +585,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             }
 
             fn visit_stmt(&mut self, ex: &'v hir::Stmt<'v>) -> Self::Result {
-                if let hir::StmtKind::Local(hir::Local {
+                if let hir::StmtKind::Let(hir::Local {
                     span,
                     pat: hir::Pat { .. },
                     ty: None,
@@ -824,7 +824,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
         let hir = self.tcx.hir();
         for stmt in blk.stmts.iter().rev() {
-            let hir::StmtKind::Local(local) = &stmt.kind else {
+            let hir::StmtKind::Let(local) = &stmt.kind else {
                 continue;
             };
             local.pat.walk(&mut find_compatible_candidates);

compiler/rustc_interface/messages.ftl

@@ -48,6 +48,3 @@ interface_rustc_error_unexpected_annotation =
 
 interface_temps_dir_error =
     failed to find or create the directory specified by `--temps-dir`
-
-interface_unsupported_crate_type_for_target =
-    dropping unsupported crate type `{$crate_type}` for target `{$target_triple}`

compiler/rustc_interface/src/errors.rs

@@ -1,7 +1,5 @@
 use rustc_macros::Diagnostic;
-use rustc_session::config::CrateType;
 use rustc_span::{Span, Symbol};
-use rustc_target::spec::TargetTriple;
 
 use std::io;
 use std::path::Path;
@@ -90,13 +88,6 @@ pub struct FailedWritingFile<'a> {
 #[diag(interface_proc_macro_crate_panic_abort)]
 pub struct ProcMacroCratePanicAbort;
 
-#[derive(Diagnostic)]
-#[diag(interface_unsupported_crate_type_for_target)]
-pub struct UnsupportedCrateTypeForTarget<'a> {
-    pub crate_type: CrateType,
-    pub target_triple: &'a TargetTriple,
-}
-
 #[derive(Diagnostic)]
 #[diag(interface_multiple_output_types_adaption)]
 pub struct MultipleOutputTypesAdaption;

compiler/rustc_interface/src/queries.rs

@@ -18,7 +18,7 @@ use rustc_middle::ty::{GlobalCtxt, TyCtxt};
 use rustc_serialize::opaque::FileEncodeResult;
 use rustc_session::config::{self, CrateType, OutputFilenames, OutputType};
 use rustc_session::cstore::Untracked;
-use rustc_session::output::find_crate_name;
+use rustc_session::output::{collect_crate_types, find_crate_name};
 use rustc_session::Session;
 use rustc_span::symbol::sym;
 use std::any::Any;
@@ -128,7 +128,7 @@ impl<'tcx> Queries<'tcx> {
 
             // parse `#[crate_name]` even if `--crate-name` was passed, to make sure it matches.
             let crate_name = find_crate_name(sess, &pre_configured_attrs);
-            let crate_types = util::collect_crate_types(sess, &pre_configured_attrs);
+            let crate_types = collect_crate_types(sess, &pre_configured_attrs);
             let stable_crate_id = StableCrateId::new(
                 crate_name,
                 crate_types.contains(&CrateType::Executable),
@@ -136,7 +136,7 @@ impl<'tcx> Queries<'tcx> {
                 sess.cfg_version,
             );
             let outputs = util::build_output_filenames(&pre_configured_attrs, sess);
-            let dep_graph = setup_dep_graph(sess, crate_name, stable_crate_id)?;
+            let dep_graph = setup_dep_graph(sess)?;
 
             let cstore = FreezeLock::new(Box::new(CStore::new(
                 self.compiler.codegen_backend.metadata_loader(),

compiler/rustc_interface/src/util.rs

@@ -7,14 +7,15 @@ use rustc_data_structures::sync;
 use rustc_metadata::{load_symbol_from_dylib, DylibError};
 use rustc_parse::validate_attr;
 use rustc_session as session;
-use rustc_session::config::{self, Cfg, CrateType, OutFileName, OutputFilenames, OutputTypes};
+use rustc_session::config::{Cfg, OutFileName, OutputFilenames, OutputTypes};
 use rustc_session::filesearch::sysroot_candidates;
 use rustc_session::lint::{self, BuiltinLintDiag, LintBuffer};
-use rustc_session::{filesearch, output, Session};
+use rustc_session::{filesearch, Session};
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::edition::Edition;
-use rustc_span::symbol::{sym, Symbol};
+use rustc_span::symbol::sym;
 use rustc_target::spec::Target;
+use session::output::{categorize_crate_type, CRATE_TYPES};
 use session::EarlyDiagCtxt;
 use std::env::consts::{DLL_PREFIX, DLL_SUFFIX};
 use std::path::{Path, PathBuf};
@@ -399,67 +400,6 @@ pub(crate) fn check_attr_crate_type(
     }
 }
 
-const CRATE_TYPES: &[(Symbol, CrateType)] = &[
-    (sym::rlib, CrateType::Rlib),
-    (sym::dylib, CrateType::Dylib),
-    (sym::cdylib, CrateType::Cdylib),
-    (sym::lib, config::default_lib_output()),
-    (sym::staticlib, CrateType::Staticlib),
-    (sym::proc_dash_macro, CrateType::ProcMacro),
-    (sym::bin, CrateType::Executable),
-];
-
-fn categorize_crate_type(s: Symbol) -> Option<CrateType> {
-    Some(CRATE_TYPES.iter().find(|(key, _)| *key == s)?.1)
-}
-
-pub fn collect_crate_types(session: &Session, attrs: &[ast::Attribute]) -> Vec<CrateType> {
-    // If we're generating a test executable, then ignore all other output
-    // styles at all other locations
-    if session.opts.test {
-        return vec![CrateType::Executable];
-    }
-
-    // Only check command line flags if present. If no types are specified by
-    // command line, then reuse the empty `base` Vec to hold the types that
-    // will be found in crate attributes.
-    // JUSTIFICATION: before wrapper fn is available
-    #[allow(rustc::bad_opt_access)]
-    let mut base = session.opts.crate_types.clone();
-    if base.is_empty() {
-        let attr_types = attrs.iter().filter_map(|a| {
-            if a.has_name(sym::crate_type)
-                && let Some(s) = a.value_str()
-            {
-                categorize_crate_type(s)
-            } else {
-                None
-            }
-        });
-        base.extend(attr_types);
-        if base.is_empty() {
-            base.push(output::default_output_for_target(session));
-        } else {
-            base.sort();
-            base.dedup();
-        }
-    }
-
-    base.retain(|crate_type| {
-        if output::invalid_output_for_target(session, *crate_type) {
-            session.dcx().emit_warn(errors::UnsupportedCrateTypeForTarget {
-                crate_type: *crate_type,
-                target_triple: &session.opts.target_triple,
-            });
-            false
-        } else {
-            true
-        }
-    });
-
-    base
-}
-
 fn multiple_output_types_to_stdout(
     output_types: &OutputTypes,
     single_output_file_is_stdout: bool,

compiler/rustc_lint/src/builtin.rs

@@ -989,7 +989,7 @@ fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &
 impl EarlyLintPass for UnusedDocComment {
     fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
         let kind = match stmt.kind {
-            ast::StmtKind::Local(..) => "statements",
+            ast::StmtKind::Let(..) => "statements",
             // Disabled pending discussion in #78306
             ast::StmtKind::Item(..) => return,
             // expressions will be reported by `check_expr`.

compiler/rustc_lint/src/unused.rs

@@ -914,7 +914,7 @@ trait UnusedDelimLint {
 
     fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
         match s.kind {
-            StmtKind::Local(ref local) if Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX => {
+            StmtKind::Let(ref local) if Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX => {
                 if let Some((init, els)) = local.kind.init_else_opt() {
                     let ctx = match els {
                         None => UnusedDelimsCtx::AssignedValue,
@@ -1189,7 +1189,7 @@ impl EarlyLintPass for UnusedParens {
     }
 
     fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
-        if let StmtKind::Local(ref local) = s.kind {
+        if let StmtKind::Let(ref local) = s.kind {
             self.check_unused_parens_pat(cx, &local.pat, true, false, (true, false));
         }
 

compiler/rustc_lint_defs/src/builtin.rs

@@ -557,6 +557,7 @@ declare_lint! {
     /// fn main() {
     ///     use foo::bar;
     ///     foo::bar();
+    ///     bar();
     /// }
     /// ```
     ///

compiler/rustc_middle/src/hir/map/mod.rs

@@ -653,7 +653,7 @@ impl<'hir> Map<'hir> {
                 | Node::ForeignItem(_)
                 | Node::TraitItem(_)
                 | Node::ImplItem(_)
-                | Node::Stmt(Stmt { kind: StmtKind::Local(_), .. }) => break,
+                | Node::Stmt(Stmt { kind: StmtKind::Let(_), .. }) => break,
                 Node::Expr(expr @ Expr { kind: ExprKind::If(..) | ExprKind::Match(..), .. }) => {
                     return Some(expr);
                 }

compiler/rustc_middle/src/hooks/mod.rs

@@ -6,6 +6,7 @@
 use crate::mir;
 use crate::query::TyCtxtAt;
 use crate::ty::{Ty, TyCtxt};
+use rustc_span::def_id::LocalDefId;
 use rustc_span::DUMMY_SP;
 
 macro_rules! declare_hooks {
@@ -70,4 +71,10 @@ declare_hooks! {
 
     /// Getting a &core::panic::Location referring to a span.
     hook const_caller_location(file: rustc_span::Symbol, line: u32, col: u32) -> mir::ConstValue<'tcx>;
+
+    /// Returns `true` if this def is a function-like thing that is eligible for
+    /// coverage instrumentation under `-Cinstrument-coverage`.
+    ///
+    /// (Eligible functions might nevertheless be skipped for other reasons.)
+    hook is_eligible_for_coverage(key: LocalDefId) -> bool;
 }

compiler/rustc_middle/src/mir/coverage.rs

@@ -2,10 +2,19 @@
 
 use rustc_index::IndexVec;
 use rustc_macros::HashStable;
-use rustc_span::Symbol;
+use rustc_span::{Span, Symbol};
 
 use std::fmt::{self, Debug, Formatter};
 
+rustc_index::newtype_index! {
+    /// Used by [`CoverageKind::BlockMarker`] to mark blocks during THIR-to-MIR
+    /// lowering, so that those blocks can be identified later.
+    #[derive(HashStable)]
+    #[encodable]
+    #[debug_format = "BlockMarkerId({})"]
+    pub struct BlockMarkerId {}
+}
+
 rustc_index::newtype_index! {
     /// ID of a coverage counter. Values ascend from 0.
     ///
@@ -83,6 +92,12 @@ pub enum CoverageKind {
     /// codegen.
     SpanMarker,
 
+    /// Marks its enclosing basic block with an ID that can be referred to by
+    /// side data in [`BranchInfo`].
+    ///
+    /// Has no effect during codegen.
+    BlockMarker { id: BlockMarkerId },
+
     /// Marks the point in MIR control flow represented by a coverage counter.
     ///
     /// This is eventually lowered to `llvm.instrprof.increment` in LLVM IR.
@@ -107,6 +122,7 @@ impl Debug for CoverageKind {
         use CoverageKind::*;
         match self {
             SpanMarker => write!(fmt, "SpanMarker"),
+            BlockMarker { id } => write!(fmt, "BlockMarker({:?})", id.index()),
             CounterIncrement { id } => write!(fmt, "CounterIncrement({:?})", id.index()),
             ExpressionUsed { id } => write!(fmt, "ExpressionUsed({:?})", id.index()),
         }
@@ -163,14 +179,18 @@ pub struct Expression {
 pub enum MappingKind {
     /// Associates a normal region of code with a counter/expression/zero.
     Code(CovTerm),
+    /// Associates a branch region with separate counters for true and false.
+    Branch { true_term: CovTerm, false_term: CovTerm },
 }
 
 impl MappingKind {
     /// Iterator over all coverage terms in this mapping kind.
     pub fn terms(&self) -> impl Iterator<Item = CovTerm> {
-        let one = |a| std::iter::once(a);
+        let one = |a| std::iter::once(a).chain(None);
+        let two = |a, b| std::iter::once(a).chain(Some(b));
         match *self {
             Self::Code(term) => one(term),
+            Self::Branch { true_term, false_term } => two(true_term, false_term),
         }
     }
 
@@ -179,6 +199,9 @@ impl MappingKind {
     pub fn map_terms(&self, map_fn: impl Fn(CovTerm) -> CovTerm) -> Self {
         match *self {
             Self::Code(term) => Self::Code(map_fn(term)),
+            Self::Branch { true_term, false_term } => {
+                Self::Branch { true_term: map_fn(true_term), false_term: map_fn(false_term) }
+            }
         }
     }
 }
@@ -202,3 +225,22 @@ pub struct FunctionCoverageInfo {
     pub expressions: IndexVec<ExpressionId, Expression>,
     pub mappings: Vec<Mapping>,
 }
+
+/// Branch information recorded during THIR-to-MIR lowering, and stored in MIR.
+#[derive(Clone, Debug)]
+#[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
+pub struct BranchInfo {
+    /// 1 more than the highest-numbered [`CoverageKind::BlockMarker`] that was
+    /// injected into the MIR body. This makes it possible to allocate per-ID
+    /// data structures without having to scan the entire body first.
+    pub num_block_markers: usize,
+    pub branch_spans: Vec<BranchSpan>,
+}
+
+#[derive(Clone, Debug)]
+#[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
+pub struct BranchSpan {
+    pub span: Span,
+    pub true_marker: BlockMarkerId,
+    pub false_marker: BlockMarkerId,
+}

compiler/rustc_middle/src/mir/mod.rs

@@ -403,6 +403,12 @@ pub struct Body<'tcx> {
 
     pub tainted_by_errors: Option<ErrorGuaranteed>,
 
+    /// Branch coverage information collected during MIR building, to be used by
+    /// the `InstrumentCoverage` pass.
+    ///
+    /// Only present if branch coverage is enabled and this function is eligible.
+    pub coverage_branch_info: Option<Box<coverage::BranchInfo>>,
+
     /// Per-function coverage information added by the `InstrumentCoverage`
     /// pass, to be used in conjunction with the coverage statements injected
     /// into this body's blocks.
@@ -450,6 +456,7 @@ impl<'tcx> Body<'tcx> {
             is_polymorphic: false,
             injection_phase: None,
             tainted_by_errors,
+            coverage_branch_info: None,
             function_coverage_info: None,
         };
         body.is_polymorphic = body.has_non_region_param();
@@ -479,6 +486,7 @@ impl<'tcx> Body<'tcx> {
             is_polymorphic: false,
             injection_phase: None,
             tainted_by_errors: None,
+            coverage_branch_info: None,
             function_coverage_info: None,
         };
         body.is_polymorphic = body.has_non_region_param();

compiler/rustc_middle/src/mir/pretty.rs

@@ -461,6 +461,9 @@ pub fn write_mir_intro<'tcx>(
     // Add an empty line before the first block is printed.
     writeln!(w)?;
 
+    if let Some(branch_info) = &body.coverage_branch_info {
+        write_coverage_branch_info(branch_info, w)?;
+    }
     if let Some(function_coverage_info) = &body.function_coverage_info {
         write_function_coverage_info(function_coverage_info, w)?;
     }
@@ -468,6 +471,25 @@ pub fn write_mir_intro<'tcx>(
     Ok(())
 }
 
+fn write_coverage_branch_info(
+    branch_info: &coverage::BranchInfo,
+    w: &mut dyn io::Write,
+) -> io::Result<()> {
+    let coverage::BranchInfo { branch_spans, .. } = branch_info;
+
+    for coverage::BranchSpan { span, true_marker, false_marker } in branch_spans {
+        writeln!(
+            w,
+            "{INDENT}coverage branch {{ true: {true_marker:?}, false: {false_marker:?} }} => {span:?}",
+        )?;
+    }
+    if !branch_spans.is_empty() {
+        writeln!(w)?;
+    }
+
+    Ok(())
+}
+
 fn write_function_coverage_info(
     function_coverage_info: &coverage::FunctionCoverageInfo,
     w: &mut dyn io::Write,

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -405,6 +405,7 @@ TrivialTypeTraversalImpls! {
     ::rustc_hir::HirId,
     ::rustc_hir::MatchSource,
     ::rustc_target::asm::InlineAsmRegOrRegClass,
+    crate::mir::coverage::BlockMarkerId,
     crate::mir::coverage::CounterId,
     crate::mir::coverage::ExpressionId,
     crate::mir::Local,

compiler/rustc_mir_build/src/build/coverageinfo.rs

@@ -0,0 +1,148 @@
+use std::assert_matches::assert_matches;
+use std::collections::hash_map::Entry;
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_middle::mir::coverage::{BlockMarkerId, BranchSpan, CoverageKind};
+use rustc_middle::mir::{self, BasicBlock, UnOp};
+use rustc_middle::thir::{ExprId, ExprKind, Thir};
+use rustc_middle::ty::TyCtxt;
+use rustc_span::def_id::LocalDefId;
+
+use crate::build::Builder;
+
+pub(crate) struct BranchInfoBuilder {
+    /// Maps condition expressions to their enclosing `!`, for better instrumentation.
+    nots: FxHashMap<ExprId, NotInfo>,
+
+    num_block_markers: usize,
+    branch_spans: Vec<BranchSpan>,
+}
+
+#[derive(Clone, Copy)]
+struct NotInfo {
+    /// When visiting the associated expression as a branch condition, treat this
+    /// enclosing `!` as the branch condition instead.
+    enclosing_not: ExprId,
+    /// True if the associated expression is nested within an odd number of `!`
+    /// expressions relative to `enclosing_not` (inclusive of `enclosing_not`).
+    is_flipped: bool,
+}
+
+impl BranchInfoBuilder {
+    /// Creates a new branch info builder, but only if branch coverage instrumentation
+    /// is enabled and `def_id` represents a function that is eligible for coverage.
+    pub(crate) fn new_if_enabled(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<Self> {
+        if tcx.sess.instrument_coverage_branch() && tcx.is_eligible_for_coverage(def_id) {
+            Some(Self { nots: FxHashMap::default(), num_block_markers: 0, branch_spans: vec![] })
+        } else {
+            None
+        }
+    }
+
+    /// Unary `!` expressions inside an `if` condition are lowered by lowering
+    /// their argument instead, and then reversing the then/else arms of that `if`.
+    ///
+    /// That's awkward for branch coverage instrumentation, so to work around that
+    /// we pre-emptively visit any affected `!` expressions, and record extra
+    /// information that [`Builder::visit_coverage_branch_condition`] can use to
+    /// synthesize branch instrumentation for the enclosing `!`.
+    pub(crate) fn visit_unary_not(&mut self, thir: &Thir<'_>, unary_not: ExprId) {
+        assert_matches!(thir[unary_not].kind, ExprKind::Unary { op: UnOp::Not, .. });
+
+        self.visit_with_not_info(
+            thir,
+            unary_not,
+            // Set `is_flipped: false` for the `!` itself, so that its enclosed
+            // expression will have `is_flipped: true`.
+            NotInfo { enclosing_not: unary_not, is_flipped: false },
+        );
+    }
+
+    fn visit_with_not_info(&mut self, thir: &Thir<'_>, expr_id: ExprId, not_info: NotInfo) {
+        match self.nots.entry(expr_id) {
+            // This expression has already been marked by an enclosing `!`.
+            Entry::Occupied(_) => return,
+            Entry::Vacant(entry) => entry.insert(not_info),
+        };
+
+        match thir[expr_id].kind {
+            ExprKind::Unary { op: UnOp::Not, arg } => {
+                // Invert the `is_flipped` flag for the contents of this `!`.
+                let not_info = NotInfo { is_flipped: !not_info.is_flipped, ..not_info };
+                self.visit_with_not_info(thir, arg, not_info);
+            }
+            ExprKind::Scope { value, .. } => self.visit_with_not_info(thir, value, not_info),
+            ExprKind::Use { source } => self.visit_with_not_info(thir, source, not_info),
+            // All other expressions (including `&&` and `||`) don't need any
+            // special handling of their contents, so stop visiting.
+            _ => {}
+        }
+    }
+
+    fn next_block_marker_id(&mut self) -> BlockMarkerId {
+        let id = BlockMarkerId::from_usize(self.num_block_markers);
+        self.num_block_markers += 1;
+        id
+    }
+
+    pub(crate) fn into_done(self) -> Option<Box<mir::coverage::BranchInfo>> {
+        let Self { nots: _, num_block_markers, branch_spans } = self;
+
+        if num_block_markers == 0 {
+            assert!(branch_spans.is_empty());
+            return None;
+        }
+
+        Some(Box::new(mir::coverage::BranchInfo { num_block_markers, branch_spans }))
+    }
+}
+
+impl Builder<'_, '_> {
+    /// If branch coverage is enabled, inject marker statements into `then_block`
+    /// and `else_block`, and record their IDs in the table of branch spans.
+    pub(crate) fn visit_coverage_branch_condition(
+        &mut self,
+        mut expr_id: ExprId,
+        mut then_block: BasicBlock,
+        mut else_block: BasicBlock,
+    ) {
+        // Bail out if branch coverage is not enabled for this function.
+        let Some(branch_info) = self.coverage_branch_info.as_ref() else { return };
+
+        // If this condition expression is nested within one or more `!` expressions,
+        // replace it with the enclosing `!` collected by `visit_unary_not`.
+        if let Some(&NotInfo { enclosing_not, is_flipped }) = branch_info.nots.get(&expr_id) {
+            expr_id = enclosing_not;
+            if is_flipped {
+                std::mem::swap(&mut then_block, &mut else_block);
+            }
+        }
+        let source_info = self.source_info(self.thir[expr_id].span);
+
+        // Now that we have `source_info`, we can upgrade to a &mut reference.
+        let branch_info = self.coverage_branch_info.as_mut().expect("upgrading & to &mut");
+
+        let mut inject_branch_marker = |block: BasicBlock| {
+            let id = branch_info.next_block_marker_id();
+
+            let marker_statement = mir::Statement {
+                source_info,
+                kind: mir::StatementKind::Coverage(Box::new(mir::Coverage {
+                    kind: CoverageKind::BlockMarker { id },
+                })),
+            };
+            self.cfg.push(block, marker_statement);
+
+            id
+        };
+
+        let true_marker = inject_branch_marker(then_block);
+        let false_marker = inject_branch_marker(else_block);
+
+        branch_info.branch_spans.push(BranchSpan {
+            span: source_info.span,
+            true_marker,
+            false_marker,
+        });
+    }
+}

compiler/rustc_mir_build/src/build/custom/mod.rs

@@ -60,6 +60,7 @@ pub(super) fn build_custom_mir<'tcx>(
         tainted_by_errors: None,
         injection_phase: None,
         pass_count: 0,
+        coverage_branch_info: None,
         function_coverage_info: None,
     };
 

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -105,6 +105,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 success_block.unit()
             }
             ExprKind::Unary { op: UnOp::Not, arg } => {
+                // Improve branch coverage instrumentation by noting conditions
+                // nested within one or more `!` expressions.
+                // (Skipped if branch coverage is not enabled.)
+                if let Some(branch_info) = this.coverage_branch_info.as_mut() {
+                    branch_info.visit_unary_not(this.thir, expr_id);
+                }
+
                 let local_scope = this.local_scope();
                 let (success_block, failure_block) =
                     this.in_if_then_scope(local_scope, expr_span, |this| {
@@ -149,6 +156,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let else_block = this.cfg.start_new_block();
                 let term = TerminatorKind::if_(operand, then_block, else_block);
 
+                // Record branch coverage info for this condition.
+                // (Does nothing if branch coverage is not enabled.)
+                this.visit_coverage_branch_condition(expr_id, then_block, else_block);
+
                 let source_info = this.source_info(expr_span);
                 this.cfg.terminate(block, source_info, term);
                 this.break_for_else(else_block, source_info);

compiler/rustc_mir_build/src/build/mod.rs

@@ -234,6 +234,10 @@ struct Builder<'a, 'tcx> {
     // the root (most of them do) and saves us from retracing many sub-paths
     // many times, and rechecking many nodes.
     lint_level_roots_cache: GrowableBitSet<hir::ItemLocalId>,
+
+    /// Collects additional coverage information during MIR building.
+    /// Only present if branch coverage is enabled and this function is eligible.
+    coverage_branch_info: Option<coverageinfo::BranchInfoBuilder>,
 }
 
 type CaptureMap<'tcx> = SortedIndexMultiMap<usize, hir::HirId, Capture<'tcx>>;
@@ -807,6 +811,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             unit_temp: None,
             var_debug_info: vec![],
             lint_level_roots_cache: GrowableBitSet::new_empty(),
+            coverage_branch_info: coverageinfo::BranchInfoBuilder::new_if_enabled(tcx, def),
         };
 
         assert_eq!(builder.cfg.start_new_block(), START_BLOCK);
@@ -826,7 +831,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
         }
 
-        Body::new(
+        let mut body = Body::new(
             MirSource::item(self.def_id.to_def_id()),
             self.cfg.basic_blocks,
             self.source_scopes,
@@ -837,7 +842,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             self.fn_span,
             self.coroutine,
             None,
-        )
+        );
+        body.coverage_branch_info = self.coverage_branch_info.and_then(|b| b.into_done());
+        body
     }
 
     fn insert_upvar_arg(&mut self) {
@@ -1111,6 +1118,7 @@ pub(crate) fn parse_float_into_scalar(
 
 mod block;
 mod cfg;
+mod coverageinfo;
 mod custom;
 mod expr;
 mod matches;

compiler/rustc_mir_build/src/thir/cx/block.rs

@@ -63,7 +63,7 @@ impl<'tcx> Cx<'tcx> {
                         // ignore for purposes of the MIR
                         None
                     }
-                    hir::StmtKind::Local(local) => {
+                    hir::StmtKind::Let(local) => {
                         let remainder_scope = region::Scope {
                             id: block_id,
                             data: region::ScopeData::Remainder(region::FirstStatementIndex::new(

compiler/rustc_mir_transform/src/coverage/mod.rs

@@ -14,7 +14,6 @@ use self::spans::{BcbMapping, BcbMappingKind, CoverageSpans};
 use crate::MirPass;
 
 use rustc_middle::hir;
-use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::coverage::*;
 use rustc_middle::mir::{
     self, BasicBlock, BasicBlockData, Coverage, SourceInfo, Statement, StatementKind, Terminator,
@@ -44,7 +43,7 @@ impl<'tcx> MirPass<'tcx> for InstrumentCoverage {
 
         let def_id = mir_source.def_id().expect_local();
 
-        if !is_eligible_for_coverage(tcx, def_id) {
+        if !tcx.is_eligible_for_coverage(def_id) {
             trace!("InstrumentCoverage skipped for {def_id:?} (not eligible)");
             return;
         }
@@ -140,6 +139,10 @@ fn create_mappings<'tcx>(
         .filter_map(|&BcbMapping { kind: bcb_mapping_kind, span }| {
             let kind = match bcb_mapping_kind {
                 BcbMappingKind::Code(bcb) => MappingKind::Code(term_for_bcb(bcb)),
+                BcbMappingKind::Branch { true_bcb, false_bcb } => MappingKind::Branch {
+                    true_term: term_for_bcb(true_bcb),
+                    false_term: term_for_bcb(false_bcb),
+                },
             };
             let code_region = make_code_region(source_map, file_name, span, body_span)?;
             Some(Mapping { kind, code_region })
@@ -349,37 +352,6 @@ fn check_code_region(code_region: CodeRegion) -> Option<CodeRegion> {
     }
 }
 
-fn is_eligible_for_coverage(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
-    // Only instrument functions, methods, and closures (not constants since they are evaluated
-    // at compile time by Miri).
-    // FIXME(#73156): Handle source code coverage in const eval, but note, if and when const
-    // expressions get coverage spans, we will probably have to "carve out" space for const
-    // expressions from coverage spans in enclosing MIR's, like we do for closures. (That might
-    // be tricky if const expressions have no corresponding statements in the enclosing MIR.
-    // Closures are carved out by their initial `Assign` statement.)
-    if !tcx.def_kind(def_id).is_fn_like() {
-        trace!("InstrumentCoverage skipped for {def_id:?} (not an fn-like)");
-        return false;
-    }
-
-    // Don't instrument functions with `#[automatically_derived]` on their
-    // enclosing impl block, on the assumption that most users won't care about
-    // coverage for derived impls.
-    if let Some(impl_of) = tcx.impl_of_method(def_id.to_def_id())
-        && tcx.is_automatically_derived(impl_of)
-    {
-        trace!("InstrumentCoverage skipped for {def_id:?} (automatically derived)");
-        return false;
-    }
-
-    if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::NO_COVERAGE) {
-        trace!("InstrumentCoverage skipped for {def_id:?} (`#[coverage(off)]`)");
-        return false;
-    }
-
-    true
-}
-
 /// Function information extracted from HIR by the coverage instrumentor.
 #[derive(Debug)]
 struct ExtractedHirInfo {

compiler/rustc_mir_transform/src/coverage/query.rs

@@ -1,14 +1,49 @@
-use super::*;
-
 use rustc_data_structures::captures::Captures;
-use rustc_middle::mir::coverage::*;
+use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
-use rustc_middle::mir::{Body, CoverageIdsInfo};
+use rustc_middle::mir::coverage::{CounterId, CoverageKind};
-use rustc_middle::query::Providers;
+use rustc_middle::mir::{Body, Coverage, CoverageIdsInfo, Statement, StatementKind};
-use rustc_middle::ty::{self};
+use rustc_middle::query::TyCtxtAt;
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_middle::util::Providers;
+use rustc_span::def_id::LocalDefId;
 
-/// A `query` provider for retrieving coverage information injected into MIR.
+/// Registers query/hook implementations related to coverage.
 pub(crate) fn provide(providers: &mut Providers) {
-    providers.coverage_ids_info = |tcx, def_id| coverage_ids_info(tcx, def_id);
+    providers.hooks.is_eligible_for_coverage =
+        |TyCtxtAt { tcx, .. }, def_id| is_eligible_for_coverage(tcx, def_id);
+    providers.queries.coverage_ids_info = coverage_ids_info;
+}
+
+/// Hook implementation for [`TyCtxt::is_eligible_for_coverage`].
+fn is_eligible_for_coverage(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
+    // Only instrument functions, methods, and closures (not constants since they are evaluated
+    // at compile time by Miri).
+    // FIXME(#73156): Handle source code coverage in const eval, but note, if and when const
+    // expressions get coverage spans, we will probably have to "carve out" space for const
+    // expressions from coverage spans in enclosing MIR's, like we do for closures. (That might
+    // be tricky if const expressions have no corresponding statements in the enclosing MIR.
+    // Closures are carved out by their initial `Assign` statement.)
+    if !tcx.def_kind(def_id).is_fn_like() {
+        trace!("InstrumentCoverage skipped for {def_id:?} (not an fn-like)");
+        return false;
+    }
+
+    // Don't instrument functions with `#[automatically_derived]` on their
+    // enclosing impl block, on the assumption that most users won't care about
+    // coverage for derived impls.
+    if let Some(impl_of) = tcx.impl_of_method(def_id.to_def_id())
+        && tcx.is_automatically_derived(impl_of)
+    {
+        trace!("InstrumentCoverage skipped for {def_id:?} (automatically derived)");
+        return false;
+    }
+
+    if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::NO_COVERAGE) {
+        trace!("InstrumentCoverage skipped for {def_id:?} (`#[coverage(off)]`)");
+        return false;
+    }
+
+    true
 }
 
 /// Query implementation for `coverage_ids_info`.

compiler/rustc_mir_transform/src/coverage/spans.rs

@@ -13,6 +13,8 @@ mod from_mir;
 pub(super) enum BcbMappingKind {
     /// Associates an ordinary executable code span with its corresponding BCB.
     Code(BasicCoverageBlock),
+    /// Associates a branch span with BCBs for its true and false arms.
+    Branch { true_bcb: BasicCoverageBlock, false_bcb: BasicCoverageBlock },
 }
 
 #[derive(Debug)]
@@ -66,6 +68,12 @@ pub(super) fn generate_coverage_spans(
             // Each span produced by the generator represents an ordinary code region.
             BcbMapping { kind: BcbMappingKind::Code(bcb), span }
         }));
+
+        mappings.extend(from_mir::extract_branch_mappings(
+            mir_body,
+            hir_info.body_span,
+            basic_coverage_blocks,
+        ));
     }
 
     if mappings.is_empty() {
@@ -80,6 +88,10 @@ pub(super) fn generate_coverage_spans(
     for &BcbMapping { kind, span: _ } in &mappings {
         match kind {
             BcbMappingKind::Code(bcb) => insert(bcb),
+            BcbMappingKind::Branch { true_bcb, false_bcb } => {
+                insert(true_bcb);
+                insert(false_bcb);
+            }
         }
     }
 

compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs

@@ -1,7 +1,9 @@
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxHashSet;
+use rustc_index::IndexVec;
+use rustc_middle::mir::coverage::{BlockMarkerId, BranchSpan, CoverageKind};
 use rustc_middle::mir::{
-    self, AggregateKind, FakeReadCause, Rvalue, Statement, StatementKind, Terminator,
+    self, AggregateKind, BasicBlock, FakeReadCause, Rvalue, Statement, StatementKind, Terminator,
     TerminatorKind,
 };
 use rustc_span::{ExpnKind, MacroKind, Span, Symbol};
@@ -9,6 +11,7 @@ use rustc_span::{ExpnKind, MacroKind, Span, Symbol};
 use crate::coverage::graph::{
     BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph, START_BCB,
 };
+use crate::coverage::spans::{BcbMapping, BcbMappingKind};
 use crate::coverage::ExtractedHirInfo;
 
 /// Traverses the MIR body to produce an initial collection of coverage-relevant
@@ -179,8 +182,6 @@ fn is_closure_like(statement: &Statement<'_>) -> bool {
 /// If the MIR `Statement` has a span contributive to computing coverage spans,
 /// return it; otherwise return `None`.
 fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
-    use mir::coverage::CoverageKind;
-
     match statement.kind {
         // These statements have spans that are often outside the scope of the executed source code
         // for their parent `BasicBlock`.
@@ -225,6 +226,11 @@ fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
             Some(statement.source_info.span)
         }
 
+        StatementKind::Coverage(box mir::Coverage {
+            // Block markers are used for branch coverage, so ignore them here.
+            kind: CoverageKind::BlockMarker {..}
+        }) => None,
+
         StatementKind::Coverage(box mir::Coverage {
             // These coverage statements should not exist prior to coverage instrumentation.
             kind: CoverageKind::CounterIncrement { .. } | CoverageKind::ExpressionUsed { .. }
@@ -358,3 +364,51 @@ impl SpanFromMir {
         Self { span, visible_macro, bcb, is_hole }
     }
 }
+
+pub(super) fn extract_branch_mappings(
+    mir_body: &mir::Body<'_>,
+    body_span: Span,
+    basic_coverage_blocks: &CoverageGraph,
+) -> Vec<BcbMapping> {
+    let Some(branch_info) = mir_body.coverage_branch_info.as_deref() else {
+        return vec![];
+    };
+
+    let mut block_markers = IndexVec::<BlockMarkerId, Option<BasicBlock>>::from_elem_n(
+        None,
+        branch_info.num_block_markers,
+    );
+
+    // Fill out the mapping from block marker IDs to their enclosing blocks.
+    for (bb, data) in mir_body.basic_blocks.iter_enumerated() {
+        for statement in &data.statements {
+            if let StatementKind::Coverage(coverage) = &statement.kind
+                && let CoverageKind::BlockMarker { id } = coverage.kind
+            {
+                block_markers[id] = Some(bb);
+            }
+        }
+    }
+
+    branch_info
+        .branch_spans
+        .iter()
+        .filter_map(|&BranchSpan { span: raw_span, true_marker, false_marker }| {
+            // For now, ignore any branch span that was introduced by
+            // expansion. This makes things like assert macros less noisy.
+            if !raw_span.ctxt().outer_expn_data().is_root() {
+                return None;
+            }
+            let (span, _) = unexpand_into_body_span_with_visible_macro(raw_span, body_span)?;
+
+            let bcb_from_marker = |marker: BlockMarkerId| {
+                Some(basic_coverage_blocks.bcb_from_bb(block_markers[marker]?)?)
+            };
+
+            let true_bcb = bcb_from_marker(true_marker)?;
+            let false_bcb = bcb_from_marker(false_marker)?;
+
+            Some(BcbMapping { kind: BcbMappingKind::Branch { true_bcb, false_bcb }, span })
+        })
+        .collect::<Vec<_>>()
+}

compiler/rustc_mir_transform/src/lib.rs

@@ -37,8 +37,9 @@ use rustc_middle::mir::{
     LocalDecl, MirPass, MirPhase, Operand, Place, ProjectionElem, Promoted, RuntimePhase, Rvalue,
     SourceInfo, Statement, StatementKind, TerminatorKind, START_BLOCK,
 };
-use rustc_middle::query::Providers;
+use rustc_middle::query;
 use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt};
+use rustc_middle::util::Providers;
 use rustc_span::{source_map::Spanned, sym, DUMMY_SP};
 use rustc_trait_selection::traits;
 
@@ -124,7 +125,7 @@ pub fn provide(providers: &mut Providers) {
     ffi_unwind_calls::provide(providers);
     shim::provide(providers);
     cross_crate_inline::provide(providers);
-    *providers = Providers {
+    providers.queries = query::Providers {
         mir_keys,
         mir_const,
         mir_const_qualif,
@@ -139,7 +140,7 @@ pub fn provide(providers: &mut Providers) {
         mir_inliner_callees: inline::cycle::mir_inliner_callees,
         promoted_mir,
         deduced_param_attrs: deduce_param_attrs::deduced_param_attrs,
-        ..*providers
+        ..providers.queries
     };
 }
 

compiler/rustc_parse/src/parser/stmt.rs

@@ -254,7 +254,7 @@ impl<'a> Parser<'a> {
                 let local = this.parse_local(attrs)?;
                 // FIXME - maybe capture semicolon in recovery?
                 Ok((
-                    this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)),
+                    this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Let(local)),
                     TrailingToken::None,
                 ))
             })?;
@@ -278,7 +278,7 @@ impl<'a> Parser<'a> {
             } else {
                 TrailingToken::None
             };
-            Ok((this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)), trailing))
+            Ok((this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Let(local)), trailing))
         })
     }
 
@@ -764,7 +764,7 @@ impl<'a> Parser<'a> {
                 }
             }
             StmtKind::Expr(_) | StmtKind::MacCall(_) => {}
-            StmtKind::Local(local) if let Err(mut e) = self.expect_semi() => {
+            StmtKind::Let(local) if let Err(mut e) = self.expect_semi() => {
                 // We might be at the `,` in `let x = foo<bar, baz>;`. Try to recover.
                 match &mut local.kind {
                     LocalKind::Init(expr) | LocalKind::InitElse(expr, _) => {
@@ -820,7 +820,7 @@ impl<'a> Parser<'a> {
                 }
                 eat_semi = false;
             }
-            StmtKind::Empty | StmtKind::Item(_) | StmtKind::Local(_) | StmtKind::Semi(_) => {
+            StmtKind::Empty | StmtKind::Item(_) | StmtKind::Let(_) | StmtKind::Semi(_) => {
                 eat_semi = false
             }
         }

compiler/rustc_passes/src/check_attr.rs

@@ -2444,7 +2444,7 @@ impl<'tcx> Visitor<'tcx> for CheckAttrVisitor<'tcx> {
 
     fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt<'tcx>) {
         // When checking statements ignore expressions, they will be checked later.
-        if let hir::StmtKind::Local(l) = stmt.kind {
+        if let hir::StmtKind::Let(l) = stmt.kind {
             self.check_attributes(l.hir_id, stmt.span, Target::Statement, None);
         }
         intravisit::walk_stmt(self, stmt)

compiler/rustc_passes/src/hir_stats.rs

@@ -277,7 +277,7 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
     fn visit_stmt(&mut self, s: &'v hir::Stmt<'v>) {
         record_variants!(
             (self, s, s.kind, Id::Node(s.hir_id), hir, Stmt, StmtKind),
-            [Local, Item, Expr, Semi]
+            [Let, Item, Expr, Semi]
         );
         hir_visit::walk_stmt(self, s)
     }
@@ -539,7 +539,7 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
     fn visit_stmt(&mut self, s: &'v ast::Stmt) {
         record_variants!(
             (self, s, s.kind, Id::None, ast, Stmt, StmtKind),
-            [Local, Item, Expr, Semi, Empty, MacCall]
+            [Let, Item, Expr, Semi, Empty, MacCall]
         );
         ast_visit::walk_stmt(self, s)
     }

compiler/rustc_passes/src/liveness.rs

@@ -771,7 +771,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
 
     fn propagate_through_stmt(&mut self, stmt: &hir::Stmt<'_>, succ: LiveNode) -> LiveNode {
         match stmt.kind {
-            hir::StmtKind::Local(local) => {
+            hir::StmtKind::Let(local) => {
                 // Note: we mark the variable as defined regardless of whether
                 // there is an initializer. Initially I had thought to only mark
                 // the live variable as defined if it was initialized, and then we

compiler/rustc_passes/src/naked_functions.rs

@@ -280,7 +280,7 @@ impl<'tcx> Visitor<'tcx> for CheckInlineAssembly<'tcx> {
     fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt<'tcx>) {
         match stmt.kind {
             StmtKind::Item(..) => {}
-            StmtKind::Local(..) => {
+            StmtKind::Let(..) => {
                 self.items.push((ItemKind::NonAsm, stmt.span));
             }
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => {

compiler/rustc_resolve/src/check_unused.rs

@@ -23,18 +23,19 @@
 //  - `check_unused` finally emits the diagnostics based on the data generated
 //    in the last step
 
-use crate::imports::ImportKind;
+use crate::imports::{Import, ImportKind};
 use crate::module_to_string;
 use crate::Resolver;
 
-use crate::NameBindingKind;
+use crate::{LexicalScopeBinding, NameBindingKind};
 use rustc_ast as ast;
 use rustc_ast::visit::{self, Visitor};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap, FxIndexSet};
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::{pluralize, MultiSpan};
 use rustc_hir::def::{DefKind, Res};
-use rustc_session::lint::builtin::{MACRO_USE_EXTERN_CRATE, UNUSED_EXTERN_CRATES, UNUSED_IMPORTS};
+use rustc_session::lint::builtin::{MACRO_USE_EXTERN_CRATE, UNUSED_EXTERN_CRATES};
+use rustc_session::lint::builtin::{UNUSED_IMPORTS, UNUSED_QUALIFICATIONS};
 use rustc_session::lint::BuiltinLintDiag;
 use rustc_span::symbol::{kw, Ident};
 use rustc_span::{Span, DUMMY_SP};
@@ -514,8 +515,59 @@ impl Resolver<'_, '_> {
             }
         }
 
+        let mut redundant_imports = UnordSet::default();
         for import in check_redundant_imports {
-            self.check_for_redundant_imports(import);
+            if self.check_for_redundant_imports(import)
+                && let Some(id) = import.id()
+            {
+                redundant_imports.insert(id);
+            }
+        }
+
+        // The lint fixes for unused_import and unnecessary_qualification may conflict.
+        // Deleting both unused imports and unnecessary segments of an item may result
+        // in the item not being found.
+        for unn_qua in &self.potentially_unnecessary_qualifications {
+            if let LexicalScopeBinding::Item(name_binding) = unn_qua.binding
+                && let NameBindingKind::Import { import, .. } = name_binding.kind
+                && (is_unused_import(import, &unused_imports)
+                    || is_redundant_import(import, &redundant_imports))
+            {
+                continue;
+            }
+
+            self.lint_buffer.buffer_lint_with_diagnostic(
+                UNUSED_QUALIFICATIONS,
+                unn_qua.node_id,
+                unn_qua.path_span,
+                "unnecessary qualification",
+                BuiltinLintDiag::UnusedQualifications { removal_span: unn_qua.removal_span },
+            );
+        }
+
+        fn is_redundant_import(
+            import: Import<'_>,
+            redundant_imports: &UnordSet<ast::NodeId>,
+        ) -> bool {
+            if let Some(id) = import.id()
+                && redundant_imports.contains(&id)
+            {
+                return true;
+            }
+            false
+        }
+
+        fn is_unused_import(
+            import: Import<'_>,
+            unused_imports: &FxIndexMap<ast::NodeId, UnusedImport>,
+        ) -> bool {
+            if let Some(unused_import) = unused_imports.get(&import.root_id)
+                && let Some(id) = import.id()
+                && unused_import.unused.contains(&id)
+            {
+                return true;
+            }
+            false
         }
     }
 }

compiler/rustc_resolve/src/imports.rs

@@ -1306,7 +1306,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         None
     }
 
-    pub(crate) fn check_for_redundant_imports(&mut self, import: Import<'a>) {
+    pub(crate) fn check_for_redundant_imports(&mut self, import: Import<'a>) -> bool {
         // This function is only called for single imports.
         let ImportKind::Single {
             source, target, ref source_bindings, ref target_bindings, id, ..
@@ -1317,12 +1317,12 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
 
         // Skip if the import is of the form `use source as target` and source != target.
         if source != target {
-            return;
+            return false;
         }
 
         // Skip if the import was produced by a macro.
         if import.parent_scope.expansion != LocalExpnId::ROOT {
-            return;
+            return false;
         }
 
         // Skip if we are inside a named module (in contrast to an anonymous
@@ -1332,7 +1332,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         if import.used.get() == Some(Used::Other)
             || self.effective_visibilities.is_exported(self.local_def_id(id))
         {
-            return;
+            return false;
         }
 
         let mut is_redundant = true;
@@ -1375,7 +1375,10 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 format!("the item `{source}` is imported redundantly"),
                 BuiltinLintDiag::RedundantImport(redundant_spans, source),
             );
+            return true;
         }
+
+        false
     }
 
     fn resolve_glob_import(&mut self, import: Import<'a>) {

compiler/rustc_resolve/src/late.rs

@@ -580,6 +580,15 @@ impl MaybeExported<'_> {
     }
 }
 
+/// Used for recording UnnecessaryQualification.
+#[derive(Debug)]
+pub(crate) struct UnnecessaryQualification<'a> {
+    pub binding: LexicalScopeBinding<'a>,
+    pub node_id: NodeId,
+    pub path_span: Span,
+    pub removal_span: Span,
+}
+
 #[derive(Default)]
 struct DiagMetadata<'ast> {
     /// The current trait's associated items' ident, used for diagnostic suggestions.
@@ -4654,20 +4663,16 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
             let ns = if i + 1 == path.len() { ns } else { TypeNS };
             let res = self.r.partial_res_map.get(&seg.id?)?.full_res()?;
             let binding = self.resolve_ident_in_lexical_scope(seg.ident, ns, None, None)?;
-
+            (res == binding.res()).then_some((seg, binding))
-            (res == binding.res()).then_some(seg)
         });
 
-        if let Some(unqualified) = unqualified {
+        if let Some((seg, binding)) = unqualified {
-            self.r.lint_buffer.buffer_lint_with_diagnostic(
+            self.r.potentially_unnecessary_qualifications.push(UnnecessaryQualification {
-                lint::builtin::UNUSED_QUALIFICATIONS,
+                binding,
-                finalize.node_id,
+                node_id: finalize.node_id,
-                finalize.path_span,
+                path_span: finalize.path_span,
-                "unnecessary qualification",
+                removal_span: path[0].ident.span.until(seg.ident.span),
-                lint::BuiltinLintDiag::UnusedQualifications {
+            });
-                    removal_span: path[0].ident.span.until(unqualified.ident.span),
-                },
-            );
         }
     }
 }

compiler/rustc_resolve/src/lib.rs

@@ -68,7 +68,7 @@ use std::fmt;
 
 use diagnostics::{ImportSuggestion, LabelSuggestion, Suggestion};
 use imports::{Import, ImportData, ImportKind, NameResolution};
-use late::{HasGenericParams, PathSource, PatternSource};
+use late::{HasGenericParams, PathSource, PatternSource, UnnecessaryQualification};
 use macros::{MacroRulesBinding, MacroRulesScope, MacroRulesScopeRef};
 
 use crate::effective_visibilities::EffectiveVisibilitiesVisitor;
@@ -372,7 +372,7 @@ impl<'a> From<&'a ast::PathSegment> for Segment {
 /// This refers to the thing referred by a name. The difference between `Res` and `Item` is that
 /// items are visible in their whole block, while `Res`es only from the place they are defined
 /// forward.
-#[derive(Debug)]
+#[derive(Debug, Copy, Clone)]
 enum LexicalScopeBinding<'a> {
     Item(NameBinding<'a>),
     Res(Res),
@@ -1105,6 +1105,8 @@ pub struct Resolver<'a, 'tcx> {
 
     potentially_unused_imports: Vec<Import<'a>>,
 
+    potentially_unnecessary_qualifications: Vec<UnnecessaryQualification<'a>>,
+
     /// Table for mapping struct IDs into struct constructor IDs,
     /// it's not used during normal resolution, only for better error reporting.
     /// Also includes of list of each fields visibility
@@ -1464,6 +1466,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             local_macro_def_scopes: FxHashMap::default(),
             name_already_seen: FxHashMap::default(),
             potentially_unused_imports: Vec::new(),
+            potentially_unnecessary_qualifications: Default::default(),
             struct_constructors: Default::default(),
             unused_macros: Default::default(),
             unused_macro_rules: Default::default(),

compiler/rustc_session/messages.ftl

@@ -111,4 +111,7 @@ session_unleashed_feature_help_unnamed = skipping check that does not even have
 
 session_unstable_virtual_function_elimination = `-Zvirtual-function-elimination` requires `-Clto`
 
+session_unsupported_crate_type_for_target =
+    dropping unsupported crate type `{$crate_type}` for target `{$target_triple}`
+
 session_unsupported_dwarf_version = requested DWARF version {$dwarf_version} is greater than 5

compiler/rustc_session/src/config.rs

@@ -146,7 +146,7 @@ pub enum InstrumentCoverage {
 /// Individual flag values controlled by `-Z coverage-options`.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub struct CoverageOptions {
-    /// Add branch coverage instrumentation (placeholder flag; not yet implemented).
+    /// Add branch coverage instrumentation.
     pub branch: bool,
 }
 

compiler/rustc_session/src/errors.rs

@@ -10,7 +10,7 @@ use rustc_macros::Diagnostic;
 use rustc_span::{Span, Symbol};
 use rustc_target::spec::{SplitDebuginfo, StackProtector, TargetTriple};
 
-use crate::parse::ParseSess;
+use crate::{config::CrateType, parse::ParseSess};
 
 pub struct FeatureGateError {
     pub span: MultiSpan,
@@ -345,6 +345,13 @@ pub(crate) struct BinaryFloatLiteralNotSupported {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(session_unsupported_crate_type_for_target)]
+pub struct UnsupportedCrateTypeForTarget<'a> {
+    pub crate_type: CrateType,
+    pub target_triple: &'a TargetTriple,
+}
+
 pub fn report_lit_error(
     psess: &ParseSess,
     err: LitError,

compiler/rustc_session/src/output.rs

@@ -1,7 +1,7 @@
 //! Related to out filenames of compilation (e.g. binaries).
-use crate::config::{CrateType, Input, OutFileName, OutputFilenames, OutputType};
+use crate::config::{self, CrateType, Input, OutFileName, OutputFilenames, OutputType};
 use crate::errors::{
-    CrateNameDoesNotMatch, CrateNameEmpty, CrateNameInvalid, FileIsNotWriteable,
+    self, CrateNameDoesNotMatch, CrateNameEmpty, CrateNameInvalid, FileIsNotWriteable,
     InvalidCharacterInCrateName, InvalidCrateNameHelp,
 };
 use crate::Session;
@@ -200,3 +200,64 @@ pub fn invalid_output_for_target(sess: &Session, crate_type: CrateType) -> bool
 
     false
 }
+
+pub const CRATE_TYPES: &[(Symbol, CrateType)] = &[
+    (sym::rlib, CrateType::Rlib),
+    (sym::dylib, CrateType::Dylib),
+    (sym::cdylib, CrateType::Cdylib),
+    (sym::lib, config::default_lib_output()),
+    (sym::staticlib, CrateType::Staticlib),
+    (sym::proc_dash_macro, CrateType::ProcMacro),
+    (sym::bin, CrateType::Executable),
+];
+
+pub fn categorize_crate_type(s: Symbol) -> Option<CrateType> {
+    Some(CRATE_TYPES.iter().find(|(key, _)| *key == s)?.1)
+}
+
+pub fn collect_crate_types(session: &Session, attrs: &[ast::Attribute]) -> Vec<CrateType> {
+    // If we're generating a test executable, then ignore all other output
+    // styles at all other locations
+    if session.opts.test {
+        return vec![CrateType::Executable];
+    }
+
+    // Only check command line flags if present. If no types are specified by
+    // command line, then reuse the empty `base` Vec to hold the types that
+    // will be found in crate attributes.
+    // JUSTIFICATION: before wrapper fn is available
+    #[allow(rustc::bad_opt_access)]
+    let mut base = session.opts.crate_types.clone();
+    if base.is_empty() {
+        let attr_types = attrs.iter().filter_map(|a| {
+            if a.has_name(sym::crate_type)
+                && let Some(s) = a.value_str()
+            {
+                categorize_crate_type(s)
+            } else {
+                None
+            }
+        });
+        base.extend(attr_types);
+        if base.is_empty() {
+            base.push(default_output_for_target(session));
+        } else {
+            base.sort();
+            base.dedup();
+        }
+    }
+
+    base.retain(|crate_type| {
+        if invalid_output_for_target(session, *crate_type) {
+            session.dcx().emit_warn(errors::UnsupportedCrateTypeForTarget {
+                crate_type: *crate_type,
+                target_triple: &session.opts.target_triple,
+            });
+            false
+        } else {
+            true
+        }
+    });
+
+    base
+}

compiler/rustc_target/src/abi/call/mod.rs

@@ -633,10 +633,8 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
     /// If the resulting alignment differs from the type's alignment,
     /// the argument will be copied to an alloca with sufficient alignment,
     /// either in the caller (if the type's alignment is lower than the byval alignment)
-    /// or in the callee† (if the type's alignment is higher than the byval alignment),
+    /// or in the callee (if the type's alignment is higher than the byval alignment),
     /// to ensure that Rust code never sees an underaligned pointer.
-    ///
-    /// † This is currently broken, see <https://github.com/rust-lang/rust/pull/122212>.
     pub fn make_indirect_byval(&mut self, byval_align: Option<Align>) {
         assert!(!self.layout.is_unsized(), "used byval ABI for unsized layout");
         self.make_indirect();

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -763,7 +763,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
         let hir_id = self.tcx.local_def_id_to_hir_id(def_id.as_local()?);
         match self.tcx.parent_hir_node(hir_id) {
-            hir::Node::Stmt(hir::Stmt { kind: hir::StmtKind::Local(local), .. }) => {
+            hir::Node::Stmt(hir::Stmt { kind: hir::StmtKind::Let(local), .. }) => {
                 get_name(err, &local.pat.kind)
             }
             // Different to previous arm because one is `&hir::Local` and the other

library/core/src/time.rs

@@ -856,6 +856,48 @@ impl Duration {
         (self.secs as f32) + (self.nanos.0 as f32) / (NANOS_PER_SEC as f32)
     }
 
+    /// Returns the number of milliseconds contained by this `Duration` as `f64`.
+    ///
+    /// The returned value does include the fractional (nanosecond) part of the duration.
+    ///
+    /// # Examples
+    /// ```
+    /// #![feature(duration_millis_float)]
+    /// use std::time::Duration;
+    ///
+    /// let dur = Duration::new(2, 345_678_000);
+    /// assert_eq!(dur.as_millis_f64(), 2345.678);
+    /// ```
+    #[unstable(feature = "duration_millis_float", issue = "122451")]
+    #[must_use]
+    #[inline]
+    #[rustc_const_unstable(feature = "duration_consts_float", issue = "72440")]
+    pub const fn as_millis_f64(&self) -> f64 {
+        (self.secs as f64) * (MILLIS_PER_SEC as f64)
+            + (self.nanos.0 as f64) / (NANOS_PER_MILLI as f64)
+    }
+
+    /// Returns the number of milliseconds contained by this `Duration` as `f32`.
+    ///
+    /// The returned value does include the fractional (nanosecond) part of the duration.
+    ///
+    /// # Examples
+    /// ```
+    /// #![feature(duration_millis_float)]
+    /// use std::time::Duration;
+    ///
+    /// let dur = Duration::new(2, 345_678_000);
+    /// assert_eq!(dur.as_millis_f32(), 2345.678);
+    /// ```
+    #[unstable(feature = "duration_millis_float", issue = "122451")]
+    #[must_use]
+    #[inline]
+    #[rustc_const_unstable(feature = "duration_consts_float", issue = "72440")]
+    pub const fn as_millis_f32(&self) -> f32 {
+        (self.secs as f32) * (MILLIS_PER_SEC as f32)
+            + (self.nanos.0 as f32) / (NANOS_PER_MILLI as f32)
+    }
+
     /// Creates a new `Duration` from the specified number of seconds represented
     /// as `f64`.
     ///

library/profiler_builtins/Cargo.toml

@@ -13,4 +13,4 @@ core = { path = "../core" }
 compiler_builtins = { version = "0.1.0", features = ['rustc-dep-of-std'] }
 
 [build-dependencies]
-cc = "1.0.69"
+cc = "1.0.90"

library/std/src/os/unix/process.rs

@@ -39,6 +39,13 @@ pub trait CommandExt: Sealed {
     /// Sets the child process's user ID. This translates to a
     /// `setuid` call in the child process. Failure in the `setuid`
     /// call will cause the spawn to fail.
+    ///
+    /// # Notes
+    ///
+    /// This will also trigger a call to `setgroups(0, NULL)` in the child
+    /// process if no groups have been specified.
+    /// This removes supplementary groups that might have given the child
+    /// unwanted permissions.
     #[stable(feature = "rust1", since = "1.0.0")]
     fn uid(&mut self, id: UserId) -> &mut process::Command;
 

library/std/src/sys/pal/unix/process/process_unix.rs

@@ -330,14 +330,22 @@ impl Command {
             if let Some(u) = self.get_uid() {
                 // When dropping privileges from root, the `setgroups` call
                 // will remove any extraneous groups. We only drop groups
-                // if the current uid is 0 and we weren't given an explicit
+                // if we have CAP_SETGID and we weren't given an explicit
                 // set of groups. If we don't call this, then even though our
                 // uid has dropped, we may still have groups that enable us to
                 // do super-user things.
                 //FIXME: Redox kernel does not support setgroups yet
                 #[cfg(not(target_os = "redox"))]
-                if libc::getuid() == 0 && self.get_groups().is_none() {
+                if self.get_groups().is_none() {
-                    cvt(libc::setgroups(0, crate::ptr::null()))?;
+                    let res = cvt(libc::setgroups(0, crate::ptr::null()));
+                    if let Err(e) = res {
+                        // Here we ignore the case of not having CAP_SETGID.
+                        // An alternative would be to require CAP_SETGID (in
+                        // addition to CAP_SETUID) for setting the UID.
+                        if e.raw_os_error() != Some(libc::EPERM) {
+                            return Err(e.into());
+                        }
+                    }
                 }
                 cvt(libc::setuid(u as uid_t))?;
             }

src/doc/rustc/src/instrument-coverage.md

@@ -352,7 +352,7 @@ This unstable option provides finer control over some aspects of coverage
 instrumentation. Pass one or more of the following values, separated by commas.
 
 - `branch` or `no-branch`
-  - Placeholder for potential branch coverage support in the future.
+  - Enables or disables branch coverage instrumentation.
 
 ## Other references
 

src/doc/unstable-book/src/compiler-flags/coverage-options.md

@@ -5,4 +5,4 @@ This option controls details of the coverage instrumentation performed by
 
 Multiple options can be passed, separated by commas. Valid options are:
 
-- `branch` or `no-branch`: Placeholder for future branch coverage support.
+- `branch` or `no-branch`: Enables or disables branch coverage instrumentation.

src/tools/clippy/clippy_lints/src/attrs/utils.rs

@@ -52,7 +52,7 @@ fn is_relevant_block(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_
             .as_ref()
             .map_or(false, |e| is_relevant_expr(cx, typeck_results, e)),
         |stmt| match &stmt.kind {
-            StmtKind::Local(_) => true,
+            StmtKind::Let(_) => true,
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(cx, typeck_results, expr),
             StmtKind::Item(_) => false,
         },

src/tools/clippy/clippy_lints/src/copies.rs

@@ -349,7 +349,7 @@ impl BlockEq {
 
 /// If the statement is a local, checks if the bound names match the expected list of names.
 fn eq_binding_names(s: &Stmt<'_>, names: &[(HirId, Symbol)]) -> bool {
-    if let StmtKind::Local(l) = s.kind {
+    if let StmtKind::Let(l) = s.kind {
         let mut i = 0usize;
         let mut res = true;
         l.pat.each_binding_or_first(&mut |_, _, _, name| {
@@ -389,7 +389,7 @@ fn eq_stmts(
     eq: &mut HirEqInterExpr<'_, '_, '_>,
     moved_bindings: &mut Vec<(HirId, Symbol)>,
 ) -> bool {
-    (if let StmtKind::Local(l) = stmt.kind {
+    (if let StmtKind::Let(l) = stmt.kind {
         let old_count = moved_bindings.len();
         l.pat.each_binding_or_first(&mut |_, id, _, name| {
             moved_bindings.push((id, name.name));
@@ -432,7 +432,7 @@ fn scan_block_for_eq<'tcx>(
         .iter()
         .enumerate()
         .find(|&(i, stmt)| {
-            if let StmtKind::Local(l) = stmt.kind
+            if let StmtKind::Let(l) = stmt.kind
                 && needs_ordered_drop(cx, cx.typeck_results().node_type(l.hir_id))
             {
                 local_needs_ordered_drop = true;
@@ -509,7 +509,7 @@ fn scan_block_for_eq<'tcx>(
                 // Clear out all locals seen at the end so far. None of them can be moved.
                 let stmts = &blocks[0].stmts;
                 for stmt in &stmts[stmts.len() - init..=stmts.len() - offset] {
-                    if let StmtKind::Local(l) = stmt.kind {
+                    if let StmtKind::Let(l) = stmt.kind {
                         l.pat.each_binding_or_first(&mut |_, id, _, _| {
                             // FIXME(rust/#120456) - is `swap_remove` correct?
                             eq.locals.swap_remove(&id);

src/tools/clippy/clippy_lints/src/default.rs

@@ -121,7 +121,7 @@ impl<'tcx> LateLintPass<'tcx> for Default {
             // find all binding statements like `let mut _ = T::default()` where `T::default()` is the
             // `default` method of the `Default` trait, and store statement index in current block being
             // checked and the name of the bound variable
-            let (local, variant, binding_name, binding_type, span) = if let StmtKind::Local(local) = stmt.kind
+            let (local, variant, binding_name, binding_type, span) = if let StmtKind::Let(local) = stmt.kind
                 // only take `let ...` statements
                 && let Some(expr) = local.init
                 && !any_parent_is_automatically_derived(cx.tcx, expr.hir_id)

src/tools/clippy/clippy_lints/src/default_numeric_fallback.rs

@@ -221,7 +221,7 @@ impl<'a, 'tcx> Visitor<'tcx> for NumericFallbackVisitor<'a, 'tcx> {
     fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) {
         match stmt.kind {
             // we cannot check the exact type since it's a hir::Ty which does not implement `is_numeric`
-            StmtKind::Local(local) => self.ty_bounds.push(ExplicitTyBound(local.ty.is_some())),
+            StmtKind::Let(local) => self.ty_bounds.push(ExplicitTyBound(local.ty.is_some())),
 
             _ => self.ty_bounds.push(ExplicitTyBound(false)),
         }

src/tools/clippy/clippy_lints/src/entry.rs

@@ -423,7 +423,7 @@ impl<'tcx> Visitor<'tcx> for InsertSearcher<'_, 'tcx> {
                 }
             },
             StmtKind::Expr(e) => self.visit_expr(e),
-            StmtKind::Local(l) => {
+            StmtKind::Let(l) => {
                 self.visit_pat(l.pat);
                 if let Some(e) = l.init {
                     self.allow_insert_closure &= !self.in_tail_pos;

src/tools/clippy/clippy_lints/src/explicit_write.rs

@@ -102,7 +102,7 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitWrite {
 fn look_in_block<'tcx, 'hir>(cx: &LateContext<'tcx>, kind: &'tcx ExprKind<'hir>) -> &'tcx ExprKind<'hir> {
     if let ExprKind::Block(block, _label @ None) = kind
         && let Block {
-            stmts: [Stmt { kind: StmtKind::Local(local), .. }],
+            stmts: [Stmt { kind: StmtKind::Let(local), .. }],
             expr: Some(expr_end_of_block),
             rules: BlockCheckMode::DefaultBlock,
             ..

src/tools/clippy/clippy_lints/src/let_if_seq.rs

@@ -61,7 +61,7 @@ impl<'tcx> LateLintPass<'tcx> for LetIfSeq {
         let mut it = block.stmts.iter().peekable();
         while let Some(stmt) = it.next() {
             if let Some(expr) = it.peek()
-                && let hir::StmtKind::Local(local) = stmt.kind
+                && let hir::StmtKind::Let(local) = stmt.kind
                 && let hir::PatKind::Binding(mode, canonical_id, ident, None) = local.pat.kind
                 && let hir::StmtKind::Expr(if_) = expr.kind
                 && let hir::ExprKind::If(

src/tools/clippy/clippy_lints/src/loops/manual_memcpy.rs

@@ -410,7 +410,7 @@ fn get_assignments<'a, 'tcx>(
     stmts
         .iter()
         .filter_map(move |stmt| match stmt.kind {
-            StmtKind::Local(..) | StmtKind::Item(..) => None,
+            StmtKind::Let(..) | StmtKind::Item(..) => None,
             StmtKind::Expr(e) | StmtKind::Semi(e) => Some(e),
         })
         .chain(*expr)

src/tools/clippy/clippy_lints/src/loops/manual_while_let_some.rs

@@ -72,7 +72,7 @@ fn is_vec_pop_unwrap(cx: &LateContext<'_>, expr: &Expr<'_>, is_empty_recv: &Expr
 }
 
 fn check_local(cx: &LateContext<'_>, stmt: &Stmt<'_>, is_empty_recv: &Expr<'_>, loop_span: Span) {
-    if let StmtKind::Local(local) = stmt.kind
+    if let StmtKind::Let(local) = stmt.kind
         && let Some(init) = local.init
         && is_vec_pop_unwrap(cx, init, is_empty_recv)
     {

src/tools/clippy/clippy_lints/src/loops/never_loop.rs

@@ -137,7 +137,7 @@ fn stmt_to_expr<'tcx>(stmt: &Stmt<'tcx>) -> Option<(&'tcx Expr<'tcx>, Option<&'t
     match stmt.kind {
         StmtKind::Semi(e) | StmtKind::Expr(e) => Some((e, None)),
         // add the let...else expression (if present)
-        StmtKind::Local(local) => local.init.map(|init| (init, local.els)),
+        StmtKind::Let(local) => local.init.map(|init| (init, local.els)),
         StmtKind::Item(..) => None,
     }
 }

src/tools/clippy/clippy_lints/src/loops/while_let_loop.rs

@@ -11,7 +11,7 @@ use rustc_lint::LateContext;
 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, loop_block: &'tcx Block<'_>) {
     let (init, has_trailing_exprs) = match (loop_block.stmts, loop_block.expr) {
         ([stmt, stmts @ ..], expr) => {
-            if let StmtKind::Local(&Local {
+            if let StmtKind::Let(&Local {
                 init: Some(e),
                 els: None,
                 ..

src/tools/clippy/clippy_lints/src/manual_let_else.rs

@@ -53,7 +53,7 @@ impl<'tcx> QuestionMark {
             return;
         }
 
-        if let StmtKind::Local(local) = stmt.kind
+        if let StmtKind::Let(local) = stmt.kind
             && let Some(init) = local.init
             && local.els.is_none()
             && local.ty.is_none()

src/tools/clippy/clippy_lints/src/map_unit_fn.rs

@@ -138,7 +138,7 @@ fn reduce_unit_expression(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<
                     // If block only contains statements,
                     // reduce `{ X; }` to `X` or `X;`
                     match inner_stmt.kind {
-                        hir::StmtKind::Local(local) => Some(local.span),
+                        hir::StmtKind::Let(local) => Some(local.span),
                         hir::StmtKind::Expr(e) => Some(e.span),
                         hir::StmtKind::Semi(..) => Some(inner_stmt.span),
                         hir::StmtKind::Item(..) => None,

src/tools/clippy/clippy_lints/src/methods/needless_collect.rs

@@ -424,7 +424,7 @@ fn get_expr_and_hir_id_from_stmt<'v>(stmt: &'v Stmt<'v>) -> Option<(&'v Expr<'v>
     match stmt.kind {
         StmtKind::Expr(expr) | StmtKind::Semi(expr) => Some((expr, None)),
         StmtKind::Item(..) => None,
-        StmtKind::Local(Local { init, pat, .. }) => {
+        StmtKind::Let(Local { init, pat, .. }) => {
             if let PatKind::Binding(_, hir_id, ..) = pat.kind {
                 init.map(|init_expr| (init_expr, Some(hir_id)))
             } else {

src/tools/clippy/clippy_lints/src/methods/str_splitn.rs

@@ -198,7 +198,7 @@ fn indirect_usage<'tcx>(
     binding: HirId,
     ctxt: SyntaxContext,
 ) -> Option<IndirectUsage<'tcx>> {
-    if let StmtKind::Local(&Local {
+    if let StmtKind::Let(&Local {
         pat: Pat {
             kind: PatKind::Binding(BindingAnnotation::NONE, _, ident, None),
             ..

src/tools/clippy/clippy_lints/src/methods/unnecessary_result_map_or_else.rs

@@ -27,7 +27,7 @@ fn emit_lint(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, def_arg: &E
 
 fn get_last_chain_binding_hir_id(mut hir_id: HirId, statements: &[Stmt<'_>]) -> Option<HirId> {
     for stmt in statements {
-        if let StmtKind::Local(local) = stmt.kind
+        if let StmtKind::Let(local) = stmt.kind
             && let Some(init) = local.init
             && let ExprKind::Path(QPath::Resolved(_, path)) = init.kind
             && let hir::def::Res::Local(local_hir_id) = path.res

src/tools/clippy/clippy_lints/src/misc.rs

@@ -143,7 +143,7 @@ impl<'tcx> LateLintPass<'tcx> for LintPass {
 
     fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) {
         if !in_external_macro(cx.tcx.sess, stmt.span)
-            && let StmtKind::Local(local) = stmt.kind
+            && let StmtKind::Let(local) = stmt.kind
             && let PatKind::Binding(BindingAnnotation(ByRef::Yes, mutabl), .., name, None) = local.pat.kind
             && let Some(init) = local.init
             // Do not emit if clippy::ref_patterns is not allowed to avoid having two lints for the same issue.

src/tools/clippy/clippy_lints/src/mixed_read_write_in_expression.rs

@@ -97,7 +97,7 @@ impl<'tcx> LateLintPass<'tcx> for EvalOrderDependence {
     }
     fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) {
         match stmt.kind {
-            StmtKind::Local(local) => {
+            StmtKind::Let(local) => {
                 if let Local { init: Some(e), .. } = local {
                     DivergenceVisitor { cx }.visit_expr(e);
                 }
@@ -291,7 +291,7 @@ fn check_stmt<'tcx>(vis: &mut ReadVisitor<'_, 'tcx>, stmt: &'tcx Stmt<'_>) -> St
         StmtKind::Expr(expr) | StmtKind::Semi(expr) => check_expr(vis, expr),
         // If the declaration is of a local variable, check its initializer
         // expression if it has one. Otherwise, keep going.
-        StmtKind::Local(local) => local
+        StmtKind::Let(local) => local
             .init
             .as_ref()
             .map_or(StopEarly::KeepGoing, |expr| check_expr(vis, expr)),

src/tools/clippy/clippy_lints/src/needless_late_init.rs

@@ -86,7 +86,7 @@ fn contains_let(cond: &Expr<'_>) -> bool {
 }
 
 fn stmt_needs_ordered_drop(cx: &LateContext<'_>, stmt: &Stmt<'_>) -> bool {
-    let StmtKind::Local(local) = stmt.kind else {
+    let StmtKind::Let(local) = stmt.kind else {
         return false;
     };
     !local.pat.walk_short(|pat| {

src/tools/clippy/clippy_lints/src/no_effect.rs

@@ -174,7 +174,7 @@ impl NoEffect {
                 );
                 return true;
             }
-        } else if let StmtKind::Local(local) = stmt.kind {
+        } else if let StmtKind::Let(local) = stmt.kind {
             if !is_lint_allowed(cx, NO_EFFECT_UNDERSCORE_BINDING, local.hir_id)
                 && !matches!(local.source, LocalSource::AsyncFn)
                 && let Some(init) = local.init

src/tools/clippy/clippy_lints/src/pattern_type_mismatch.rs

@@ -82,7 +82,7 @@ declare_lint_pass!(PatternTypeMismatch => [PATTERN_TYPE_MISMATCH]);
 
 impl<'tcx> LateLintPass<'tcx> for PatternTypeMismatch {
     fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) {
-        if let StmtKind::Local(local) = stmt.kind {
+        if let StmtKind::Let(local) = stmt.kind {
             if in_external_macro(cx.sess(), local.pat.span) {
                 return;
             }

src/tools/clippy/clippy_lints/src/question_mark.rs

@@ -109,7 +109,7 @@ fn find_let_else_ret_expression<'hir>(block: &'hir Block<'hir>) -> Option<&'hir
 }
 
 fn check_let_some_else_return_none(cx: &LateContext<'_>, stmt: &Stmt<'_>) {
-    if let StmtKind::Local(Local {
+    if let StmtKind::Let(Local {
         pat,
         init: Some(init_expr),
         els: Some(els),

src/tools/clippy/clippy_lints/src/read_zero_byte_vec.rs

@@ -56,7 +56,7 @@ impl<'tcx> LateLintPass<'tcx> for ReadZeroByteVec {
                 return;
             }
 
-            if let StmtKind::Local(local) = stmt.kind
+            if let StmtKind::Let(local) = stmt.kind
                 && let Local {
                     pat, init: Some(init), ..
                 } = local