Improve comment formatting.

By reflowing comment lines that are too long, and a few that are very
short. Plus some other very minor formatting tweaks.

Author: nnethercote

compiler/rustc_mir_transform/src/add_retag.rs

@@ -60,7 +60,9 @@ impl<'tcx> crate::MirPass<'tcx> for AddRetag {
         let basic_blocks = body.basic_blocks.as_mut();
         let local_decls = &body.local_decls;
         let needs_retag = |place: &Place<'tcx>| {
-            !place.is_indirect_first_projection() // we're not really interested in stores to "outside" locations, they are hard to keep track of anyway
+            // We're not really interested in stores to "outside" locations, they are hard to keep
+            // track of anyway.
+            !place.is_indirect_first_projection()
                 && may_contain_reference(place.ty(&*local_decls, tcx).ty, /*depth*/ 3, tcx)
                 && !local_decls[place.local].is_deref_temp()
         };
@@ -129,9 +131,9 @@ impl<'tcx> crate::MirPass<'tcx> for AddRetag {
                     StatementKind::Assign(box (ref place, ref rvalue)) => {
                         let add_retag = match rvalue {
                             // Ptr-creating operations already do their own internal retagging, no
-                            // need to also add a retag statement.
-                            // *Except* if we are deref'ing a Box, because those get desugared to directly working
-                            // with the inner raw pointer! That's relevant for `RawPtr` as Miri otherwise makes it
+                            // need to also add a retag statement. *Except* if we are deref'ing a
+                            // Box, because those get desugared to directly working with the inner
+                            // raw pointer! That's relevant for `RawPtr` as Miri otherwise makes it
                             // a NOP when the original pointer is already raw.
                             Rvalue::RawPtr(_mutbl, place) => {
                                 // Using `is_box_global` here is a bit sketchy: if this code is

compiler/rustc_mir_transform/src/check_const_item_mutation.rs

@@ -123,6 +123,7 @@ impl<'tcx> Visitor<'tcx> for ConstMutationChecker<'_, 'tcx> {
         self.super_statement(stmt, loc);
         self.target_local = None;
     }
+
     fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, loc: Location) {
         if let Rvalue::Ref(_, BorrowKind::Mut { .. }, place) = rvalue {
             let local = place.local;

compiler/rustc_mir_transform/src/copy_prop.rs

@@ -140,7 +140,8 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> {
 
     fn visit_operand(&mut self, operand: &mut Operand<'tcx>, loc: Location) {
         if let Operand::Move(place) = *operand
-            // A move out of a projection of a copy is equivalent to a copy of the original projection.
+            // A move out of a projection of a copy is equivalent to a copy of the original
+            // projection.
             && !place.is_indirect_first_projection()
             && !self.fully_moved.contains(place.local)
         {

compiler/rustc_mir_transform/src/coverage/mod.rs

@@ -279,7 +279,8 @@ fn inject_mcdc_statements<'tcx>(
     basic_coverage_blocks: &CoverageGraph,
     extracted_mappings: &ExtractedMappings,
 ) {
-    // Inject test vector update first because `inject_statement` always insert new statement at head.
+    // Inject test vector update first because `inject_statement` always insert new statement at
+    // head.
     for &mappings::MCDCDecision {
         span: _,
         ref end_bcbs,

compiler/rustc_mir_transform/src/dataflow_const_prop.rs

@@ -647,7 +647,8 @@ fn try_write_constant<'tcx>(
         ty::FnDef(..) => {}
 
         // Those are scalars, must be handled above.
-        ty::Bool | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Char => throw_machine_stop_str!("primitive type with provenance"),
+        ty::Bool | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Char =>
+            throw_machine_stop_str!("primitive type with provenance"),
 
         ty::Tuple(elem_tys) => {
             for (i, elem) in elem_tys.iter().enumerate() {

compiler/rustc_mir_transform/src/deduce_param_attrs.rs

@@ -42,9 +42,9 @@ impl<'tcx> Visitor<'tcx> for DeduceReadOnly {
             }
             PlaceContext::NonMutatingUse(NonMutatingUseContext::RawBorrow) => {
                 // Whether mutating though a `&raw const` is allowed is still undecided, so we
-                // disable any sketchy `readonly` optimizations for now.
-                // But we only need to do this if the pointer would point into the argument.
-                // IOW: for indirect places, like `&raw (*local).field`, this surely cannot mutate `local`.
+                // disable any sketchy `readonly` optimizations for now. But we only need to do
+                // this if the pointer would point into the argument. IOW: for indirect places,
+                // like `&raw (*local).field`, this surely cannot mutate `local`.
                 !place.is_indirect()
             }
             PlaceContext::NonMutatingUse(..) | PlaceContext::NonUse(..) => {

compiler/rustc_mir_transform/src/deduplicate_blocks.rs

@@ -69,8 +69,8 @@ fn find_duplicates(body: &Body<'_>) -> FxHashMap<BasicBlock, BasicBlock> {
     // For example, if bb1, bb2 and bb3 are duplicates, we will first insert bb3 in same_hashes.
     // Then we will see that bb2 is a duplicate of bb3,
     // and insert bb2 with the replacement bb3 in the duplicates list.
-    // When we see bb1, we see that it is a duplicate of bb3, and therefore insert it in the duplicates list
-    // with replacement bb3.
+    // When we see bb1, we see that it is a duplicate of bb3, and therefore insert it in the
+    // duplicates list with replacement bb3.
     // When the duplicates are removed, we will end up with only bb3.
     for (bb, bbd) in body.basic_blocks.iter_enumerated().rev().filter(|(_, bbd)| !bbd.is_cleanup) {
         // Basic blocks can get really big, so to avoid checking for duplicates in basic blocks
@@ -105,7 +105,8 @@ struct BasicBlockHashable<'tcx, 'a> {
 impl Hash for BasicBlockHashable<'_, '_> {
     fn hash<H: Hasher>(&self, state: &mut H) {
         hash_statements(state, self.basic_block_data.statements.iter());
-        // Note that since we only hash the kind, we lose span information if we deduplicate the blocks
+        // Note that since we only hash the kind, we lose span information if we deduplicate the
+        // blocks.
         self.basic_block_data.terminator().kind.hash(state);
     }
 }

compiler/rustc_mir_transform/src/early_otherwise_branch.rs

@@ -261,8 +261,8 @@ fn evaluate_candidate<'tcx>(
         // };
         // ```
         //
-        // Hoisting the `discriminant(Q)` out of the `A` arm causes us to compute the discriminant of an
-        // invalid value, which is UB.
+        // Hoisting the `discriminant(Q)` out of the `A` arm causes us to compute the discriminant
+        // of an invalid value, which is UB.
         // In order to fix this, **we would either need to show that the discriminant computation of
         // `place` is computed in all branches**.
         // FIXME(#95162) For the moment, we adopt a conservative approach and

compiler/rustc_mir_transform/src/elaborate_drops.rs

@@ -20,8 +20,8 @@ use tracing::{debug, instrument};
 use crate::deref_separator::deref_finder;
 
 /// During MIR building, Drop terminators are inserted in every place where a drop may occur.
-/// However, in this phase, the presence of these terminators does not guarantee that a destructor will run,
-/// as the target of the drop may be uninitialized.
+/// However, in this phase, the presence of these terminators does not guarantee that a destructor
+/// will run, as the target of the drop may be uninitialized.
 /// In general, the compiler cannot determine at compile time whether a destructor will run or not.
 ///
 /// At a high level, this pass refines Drop to only run the destructor if the
@@ -30,10 +30,10 @@ use crate::deref_separator::deref_finder;
 /// Once this is complete, Drop terminators in the MIR correspond to a call to the "drop glue" or
 /// "drop shim" for the type of the dropped place.
 ///
-/// This pass relies on dropped places having an associated move path, which is then used to determine
-/// the initialization status of the place and its descendants.
-/// It's worth noting that a MIR containing a Drop without an associated move path is probably ill formed,
-/// as it would allow running a destructor on a place behind a reference:
+/// This pass relies on dropped places having an associated move path, which is then used to
+/// determine the initialization status of the place and its descendants.
+/// It's worth noting that a MIR containing a Drop without an associated move path is probably ill
+/// formed, as it would allow running a destructor on a place behind a reference:
 ///
 /// ```text
 /// fn drop_term<T>(t: &mut T) {
@@ -377,8 +377,8 @@ impl<'a, 'tcx> ElaborateDropsCtxt<'a, 'tcx> {
                         );
                     }
                     // A drop and replace behind a pointer/array/whatever.
-                    // The borrow checker requires that these locations are initialized before the assignment,
-                    // so we just leave an unconditional drop.
+                    // The borrow checker requires that these locations are initialized before the
+                    // assignment, so we just leave an unconditional drop.
                     assert!(!data.is_cleanup);
                 }
             }

compiler/rustc_mir_transform/src/ffi_unwind_calls.rs

@@ -60,8 +60,9 @@ fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
         let fn_def_id = match ty.kind() {
             ty::FnPtr(..) => None,
             &ty::FnDef(def_id, _) => {
-                // Rust calls cannot themselves create foreign unwinds (even if they use a non-Rust ABI).
-                // So the leak of the foreign unwind into Rust can only be elsewhere, not here.
+                // Rust calls cannot themselves create foreign unwinds (even if they use a non-Rust
+                // ABI). So the leak of the foreign unwind into Rust can only be elsewhere, not
+                // here.
                 if !tcx.is_foreign_item(def_id) {
                     continue;
                 }

compiler/rustc_mir_transform/src/function_item_references.rs

@@ -92,8 +92,8 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
                             {
                                 let mut span = self.nth_arg_span(args, arg_num);
                                 if span.from_expansion() {
-                                    // The operand's ctxt wouldn't display the lint since it's inside a macro so
-                                    // we have to use the callsite's ctxt.
+                                    // The operand's ctxt wouldn't display the lint since it's
+                                    // inside a macro so we have to use the callsite's ctxt.
                                     let callsite_ctxt = span.source_callsite().ctxt();
                                     span = span.with_ctxt(callsite_ctxt);
                                 }

compiler/rustc_mir_transform/src/gvn.rs

@@ -139,8 +139,8 @@ fn propagate_ssa<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
                 // Try to get some insight.
                 AssignedValue::Rvalue(rvalue) => {
                     let value = state.simplify_rvalue(rvalue, location);
-                    // FIXME(#112651) `rvalue` may have a subtype to `local`. We can only mark `local` as
-                    // reusable if we have an exact type match.
+                    // FIXME(#112651) `rvalue` may have a subtype to `local`. We can only mark
+                    // `local` as reusable if we have an exact type match.
                     if state.local_decls[local].ty != rvalue.ty(state.local_decls, tcx) {
                         return;
                     }
@@ -480,7 +480,8 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
                 let pointer = self.evaluated[local].as_ref()?;
                 let mut mplace = self.ecx.deref_pointer(pointer).ok()?;
                 for proj in place.projection.iter().skip(1) {
-                    // We have no call stack to associate a local with a value, so we cannot interpret indexing.
+                    // We have no call stack to associate a local with a value, so we cannot
+                    // interpret indexing.
                     if matches!(proj, ProjectionElem::Index(_)) {
                         return None;
                     }
@@ -1382,7 +1383,8 @@ fn op_to_prop_const<'tcx>(
         return Some(ConstValue::ZeroSized);
     }
 
-    // Do not synthetize too large constants. Codegen will just memcpy them, which we'd like to avoid.
+    // Do not synthetize too large constants. Codegen will just memcpy them, which we'd like to
+    // avoid.
     if !matches!(op.layout.abi, Abi::Scalar(..) | Abi::ScalarPair(..)) {
         return None;
     }

compiler/rustc_mir_transform/src/inline.rs

@@ -568,7 +568,8 @@ impl<'tcx> Inliner<'tcx> {
                 // if the no-attribute function ends up with the same instruction set anyway.
                 return Err("Cannot move inline-asm across instruction sets");
             } else if let TerminatorKind::TailCall { .. } = term.kind {
-                // FIXME(explicit_tail_calls): figure out how exactly functions containing tail calls can be inlined (and if they even should)
+                // FIXME(explicit_tail_calls): figure out how exactly functions containing tail
+                // calls can be inlined (and if they even should)
                 return Err("can't inline functions with tail calls");
             } else {
                 work_list.extend(term.successors())

compiler/rustc_mir_transform/src/known_panics_lint.rs

@@ -1,8 +1,6 @@
-//! A lint that checks for known panics like
-//! overflows, division by zero,
-//! out-of-bound access etc.
-//! Uses const propagation to determine the
-//! values of operands during checks.
+//! A lint that checks for known panics like overflows, division by zero,
+//! out-of-bound access etc. Uses const propagation to determine the values of
+//! operands during checks.
 
 use std::fmt::Debug;
 
@@ -562,7 +560,8 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
 
                 let val = self.use_ecx(|this| this.ecx.binary_op(bin_op, &left, &right))?;
                 if matches!(val.layout.abi, Abi::ScalarPair(..)) {
-                    // FIXME `Value` should properly support pairs in `Immediate`... but currently it does not.
+                    // FIXME `Value` should properly support pairs in `Immediate`... but currently
+                    // it does not.
                     let (val, overflow) = val.to_pair(&self.ecx);
                     Value::Aggregate {
                         variant: VariantIdx::ZERO,

compiler/rustc_mir_transform/src/large_enums.rs

@@ -16,8 +16,7 @@ use rustc_target::abi::{HasDataLayout, Size, TagEncoding, Variants};
 ///   Large([u32; 1024]),
 /// }
 /// ```
-/// Instead of emitting moves of the large variant,
-/// Perform a memcpy instead.
+/// Instead of emitting moves of the large variant, perform a memcpy instead.
 /// Based off of [this HackMD](https://hackmd.io/@ft4bxUsFT5CEUBmRKYHr7w/rJM8BBPzD).
 ///
 /// In summary, what this does is at runtime determine which enum variant is active,
@@ -34,6 +33,7 @@ impl<'tcx> crate::MirPass<'tcx> for EnumSizeOpt {
         // https://github.com/rust-lang/rust/pull/85158#issuecomment-1101836457
         sess.opts.unstable_opts.unsound_mir_opts || sess.mir_opt_level() >= 3
     }
+
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         // NOTE: This pass may produce different MIR based on the alignment of the target
         // platform, but it will still be valid.
@@ -116,6 +116,7 @@ impl EnumSizeOpt {
         let alloc = tcx.reserve_and_set_memory_alloc(tcx.mk_const_alloc(alloc));
         Some((*adt_def, num_discrs, *alloc_cache.entry(ty).or_insert(alloc)))
     }
+
     fn optim<'tcx>(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let mut alloc_cache = FxHashMap::default();
         let body_did = body.source.def_id();