Rename and reorder lots of lifetimes.

- Replace non-standard names like 's, 'p, 'rg, 'ck, 'parent, 'this, and
  'me with vanilla 'a. These are cases where the original name isn't
  really any more informative than 'a.
- Replace names like 'cx, 'mir, and 'body with vanilla 'a when the lifetime
  applies to multiple fields and so the original lifetime name isn't
  really accurate.
- Put 'tcx last in lifetime lists, and 'a before 'b.

Author: nnethercote

Diff for: compiler/rustc_borrowck/src/constraints/graph.rs

@@ -97,11 +97,11 @@ impl<D: ConstraintGraphDirection> ConstraintGraph<D> {
     /// Given the constraint set from which this graph was built
     /// creates a region graph so that you can iterate over *regions*
     /// and not constraints.
-    pub(crate) fn region_graph<'rg, 'tcx>(
-        &'rg self,
-        set: &'rg OutlivesConstraintSet<'tcx>,
+    pub(crate) fn region_graph<'a, 'tcx>(
+        &'a self,
+        set: &'a OutlivesConstraintSet<'tcx>,
         static_region: RegionVid,
-    ) -> RegionGraph<'rg, 'tcx, D> {
+    ) -> RegionGraph<'a, 'tcx, D> {
         RegionGraph::new(set, self, static_region)
     }
 
@@ -130,15 +130,15 @@ impl<D: ConstraintGraphDirection> ConstraintGraph<D> {
     }
 }
 
-pub(crate) struct Edges<'s, 'tcx, D: ConstraintGraphDirection> {
-    graph: &'s ConstraintGraph<D>,
-    constraints: &'s OutlivesConstraintSet<'tcx>,
+pub(crate) struct Edges<'a, 'tcx, D: ConstraintGraphDirection> {
+    graph: &'a ConstraintGraph<D>,
+    constraints: &'a OutlivesConstraintSet<'tcx>,
     pointer: Option<OutlivesConstraintIndex>,
     next_static_idx: Option<usize>,
     static_region: RegionVid,
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirection> Iterator for Edges<'s, 'tcx, D> {
+impl<'a, 'tcx, D: ConstraintGraphDirection> Iterator for Edges<'a, 'tcx, D> {
     type Item = OutlivesConstraint<'tcx>;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -171,55 +171,55 @@ impl<'s, 'tcx, D: ConstraintGraphDirection> Iterator for Edges<'s, 'tcx, D> {
 /// This struct brings together a constraint set and a (normal, not
 /// reverse) constraint graph. It implements the graph traits and is
 /// usd for doing the SCC computation.
-pub(crate) struct RegionGraph<'s, 'tcx, D: ConstraintGraphDirection> {
-    set: &'s OutlivesConstraintSet<'tcx>,
-    constraint_graph: &'s ConstraintGraph<D>,
+pub(crate) struct RegionGraph<'a, 'tcx, D: ConstraintGraphDirection> {
+    set: &'a OutlivesConstraintSet<'tcx>,
+    constraint_graph: &'a ConstraintGraph<D>,
     static_region: RegionVid,
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirection> RegionGraph<'s, 'tcx, D> {
+impl<'a, 'tcx, D: ConstraintGraphDirection> RegionGraph<'a, 'tcx, D> {
     /// Creates a "dependency graph" where each region constraint `R1:
     /// R2` is treated as an edge `R1 -> R2`. We use this graph to
     /// construct SCCs for region inference but also for error
     /// reporting.
     pub(crate) fn new(
-        set: &'s OutlivesConstraintSet<'tcx>,
-        constraint_graph: &'s ConstraintGraph<D>,
+        set: &'a OutlivesConstraintSet<'tcx>,
+        constraint_graph: &'a ConstraintGraph<D>,
         static_region: RegionVid,
     ) -> Self {
         Self { set, constraint_graph, static_region }
     }
 
     /// Given a region `R`, iterate over all regions `R1` such that
     /// there exists a constraint `R: R1`.
-    pub(crate) fn outgoing_regions(&self, region_sup: RegionVid) -> Successors<'s, 'tcx, D> {
+    pub(crate) fn outgoing_regions(&self, region_sup: RegionVid) -> Successors<'a, 'tcx, D> {
         Successors {
             edges: self.constraint_graph.outgoing_edges(region_sup, self.set, self.static_region),
         }
     }
 }
 
-pub(crate) struct Successors<'s, 'tcx, D: ConstraintGraphDirection> {
-    edges: Edges<'s, 'tcx, D>,
+pub(crate) struct Successors<'a, 'tcx, D: ConstraintGraphDirection> {
+    edges: Edges<'a, 'tcx, D>,
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirection> Iterator for Successors<'s, 'tcx, D> {
+impl<'a, 'tcx, D: ConstraintGraphDirection> Iterator for Successors<'a, 'tcx, D> {
     type Item = RegionVid;
 
     fn next(&mut self) -> Option<Self::Item> {
         self.edges.next().map(|c| D::end_region(&c))
     }
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirection> graph::DirectedGraph for RegionGraph<'s, 'tcx, D> {
+impl<'a, 'tcx, D: ConstraintGraphDirection> graph::DirectedGraph for RegionGraph<'a, 'tcx, D> {
     type Node = RegionVid;
 
     fn num_nodes(&self) -> usize {
         self.constraint_graph.first_constraints.len()
     }
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirection> graph::Successors for RegionGraph<'s, 'tcx, D> {
+impl<'a, 'tcx, D: ConstraintGraphDirection> graph::Successors for RegionGraph<'a, 'tcx, D> {
     fn successors(&self, node: Self::Node) -> impl Iterator<Item = Self::Node> {
         self.outgoing_regions(node)
     }

Diff for: compiler/rustc_borrowck/src/dataflow.rs

@@ -113,16 +113,16 @@ pub struct Borrows<'a, 'tcx> {
     borrows_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
-struct OutOfScopePrecomputer<'mir, 'tcx> {
+struct OutOfScopePrecomputer<'a, 'tcx> {
     visited: BitSet<mir::BasicBlock>,
     visit_stack: Vec<mir::BasicBlock>,
-    body: &'mir Body<'tcx>,
-    regioncx: &'mir RegionInferenceContext<'tcx>,
+    body: &'a Body<'tcx>,
+    regioncx: &'a RegionInferenceContext<'tcx>,
     borrows_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
-impl<'mir, 'tcx> OutOfScopePrecomputer<'mir, 'tcx> {
-    fn new(body: &'mir Body<'tcx>, regioncx: &'mir RegionInferenceContext<'tcx>) -> Self {
+impl<'a, 'tcx> OutOfScopePrecomputer<'a, 'tcx> {
+    fn new(body: &'a Body<'tcx>, regioncx: &'a RegionInferenceContext<'tcx>) -> Self {
         OutOfScopePrecomputer {
             visited: BitSet::new_empty(body.basic_blocks.len()),
             visit_stack: vec![],
@@ -225,17 +225,17 @@ pub fn calculate_borrows_out_of_scope_at_location<'tcx>(
     prec.borrows_out_of_scope_at_location
 }
 
-struct PoloniusOutOfScopePrecomputer<'mir, 'tcx> {
+struct PoloniusOutOfScopePrecomputer<'a, 'tcx> {
     visited: BitSet<mir::BasicBlock>,
     visit_stack: Vec<mir::BasicBlock>,
-    body: &'mir Body<'tcx>,
-    regioncx: &'mir RegionInferenceContext<'tcx>,
+    body: &'a Body<'tcx>,
+    regioncx: &'a RegionInferenceContext<'tcx>,
 
     loans_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
-impl<'mir, 'tcx> PoloniusOutOfScopePrecomputer<'mir, 'tcx> {
-    fn new(body: &'mir Body<'tcx>, regioncx: &'mir RegionInferenceContext<'tcx>) -> Self {
+impl<'a, 'tcx> PoloniusOutOfScopePrecomputer<'a, 'tcx> {
+    fn new(body: &'a Body<'tcx>, regioncx: &'a RegionInferenceContext<'tcx>) -> Self {
         Self {
             visited: BitSet::new_empty(body.basic_blocks.len()),
             visit_stack: vec![],

Diff for: compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -3540,7 +3540,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         location: Location,
         mpi: MovePathIndex,
     ) -> (Vec<MoveSite>, Vec<Location>) {
-        fn predecessor_locations<'tcx, 'a>(
+        fn predecessor_locations<'a, 'tcx>(
             body: &'a mir::Body<'tcx>,
             location: Location,
         ) -> impl Iterator<Item = Location> + Captures<'tcx> + 'a {

Diff for: compiler/rustc_borrowck/src/diagnostics/find_use.rs

@@ -21,15 +21,15 @@ pub(crate) fn find<'tcx>(
     uf.find()
 }
 
-struct UseFinder<'cx, 'tcx> {
-    body: &'cx Body<'tcx>,
-    regioncx: &'cx Rc<RegionInferenceContext<'tcx>>,
+struct UseFinder<'a, 'tcx> {
+    body: &'a Body<'tcx>,
+    regioncx: &'a Rc<RegionInferenceContext<'tcx>>,
     tcx: TyCtxt<'tcx>,
     region_vid: RegionVid,
     start_point: Location,
 }
 
-impl<'cx, 'tcx> UseFinder<'cx, 'tcx> {
+impl<'a, 'tcx> UseFinder<'a, 'tcx> {
     fn find(&mut self) -> Option<Cause> {
         let mut queue = VecDeque::new();
         let mut visited = FxIndexSet::default();
@@ -93,8 +93,8 @@ impl<'cx, 'tcx> UseFinder<'cx, 'tcx> {
     }
 }
 
-struct DefUseVisitor<'cx, 'tcx> {
-    body: &'cx Body<'tcx>,
+struct DefUseVisitor<'a, 'tcx> {
+    body: &'a Body<'tcx>,
     tcx: TyCtxt<'tcx>,
     region_vid: RegionVid,
     def_use_result: Option<DefUseResult>,
@@ -106,7 +106,7 @@ enum DefUseResult {
     UseDrop { local: Local },
 }
 
-impl<'cx, 'tcx> Visitor<'tcx> for DefUseVisitor<'cx, 'tcx> {
+impl<'a, 'tcx> Visitor<'tcx> for DefUseVisitor<'a, 'tcx> {
     fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
         let local_ty = self.body.local_decls[local].ty;
 

Diff for: compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -558,7 +558,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 ty: Ty<'tcx>,
                 suggested: bool,
             }
-            impl<'a, 'cx, 'tcx> Visitor<'tcx> for SuggestIndexOperatorAlternativeVisitor<'a, 'cx, 'tcx> {
+            impl<'a, 'infcx, 'tcx> Visitor<'tcx> for SuggestIndexOperatorAlternativeVisitor<'a, 'infcx, 'tcx> {
                 fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt<'tcx>) {
                     hir::intravisit::walk_stmt(self, stmt);
                     let expr = match stmt.kind {

Diff for: compiler/rustc_borrowck/src/polonius/loan_invalidations.rs

@@ -32,18 +32,18 @@ pub(super) fn emit_loan_invalidations<'tcx>(
     visitor.visit_body(body);
 }
 
-struct LoanInvalidationsGenerator<'cx, 'tcx> {
+struct LoanInvalidationsGenerator<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    all_facts: &'cx mut AllFacts,
-    location_table: &'cx LocationTable,
-    body: &'cx Body<'tcx>,
-    dominators: &'cx Dominators<BasicBlock>,
-    borrow_set: &'cx BorrowSet<'tcx>,
+    all_facts: &'a mut AllFacts,
+    location_table: &'a LocationTable,
+    body: &'a Body<'tcx>,
+    dominators: &'a Dominators<BasicBlock>,
+    borrow_set: &'a BorrowSet<'tcx>,
 }
 
 /// Visits the whole MIR and generates `invalidates()` facts.
 /// Most of the code implementing this was stolen from `borrow_check/mod.rs`.
-impl<'cx, 'tcx> Visitor<'tcx> for LoanInvalidationsGenerator<'cx, 'tcx> {
+impl<'a, 'tcx> Visitor<'tcx> for LoanInvalidationsGenerator<'a, 'tcx> {
     fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
         self.check_activations(location);
 
@@ -212,7 +212,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for LoanInvalidationsGenerator<'cx, 'tcx> {
     }
 }
 
-impl<'cx, 'tcx> LoanInvalidationsGenerator<'cx, 'tcx> {
+impl<'a, 'tcx> LoanInvalidationsGenerator<'a, 'tcx> {
     /// Simulates mutation of a place.
     fn mutate_place(&mut self, location: Location, place: Place<'tcx>, kind: AccessDepth) {
         self.access_place(

Diff for: compiler/rustc_borrowck/src/polonius/loan_kills.rs

@@ -25,15 +25,15 @@ pub(super) fn emit_loan_kills<'tcx>(
     }
 }
 
-struct LoanKillsGenerator<'cx, 'tcx> {
+struct LoanKillsGenerator<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    all_facts: &'cx mut AllFacts,
-    location_table: &'cx LocationTable,
-    borrow_set: &'cx BorrowSet<'tcx>,
-    body: &'cx Body<'tcx>,
+    all_facts: &'a mut AllFacts,
+    location_table: &'a LocationTable,
+    borrow_set: &'a BorrowSet<'tcx>,
+    body: &'a Body<'tcx>,
 }
 
-impl<'cx, 'tcx> Visitor<'tcx> for LoanKillsGenerator<'cx, 'tcx> {
+impl<'a, 'tcx> Visitor<'tcx> for LoanKillsGenerator<'a, 'tcx> {
     fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
         // Also record CFG facts here.
         self.all_facts.cfg_edge.push((

Diff for: compiler/rustc_borrowck/src/type_check/free_region_relations.rs

@@ -181,12 +181,12 @@ impl UniversalRegionRelations<'_> {
     }
 }
 
-struct UniversalRegionRelationsBuilder<'this, 'tcx> {
-    infcx: &'this InferCtxt<'tcx>,
+struct UniversalRegionRelationsBuilder<'a, 'tcx> {
+    infcx: &'a InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     universal_regions: Rc<UniversalRegions<'tcx>>,
     implicit_region_bound: ty::Region<'tcx>,
-    constraints: &'this mut MirTypeckRegionConstraints<'tcx>,
+    constraints: &'a mut MirTypeckRegionConstraints<'tcx>,
 
     // outputs:
     outlives: TransitiveRelationBuilder<RegionVid>,

Diff for: compiler/rustc_borrowck/src/type_check/liveness/mod.rs

@@ -148,12 +148,12 @@ fn record_regular_live_regions<'tcx>(
 }
 
 /// Visitor looking for regions that should be live within rvalues or calls.
-struct LiveVariablesVisitor<'cx, 'tcx> {
+struct LiveVariablesVisitor<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    liveness_constraints: &'cx mut LivenessValues,
+    liveness_constraints: &'a mut LivenessValues,
 }
 
-impl<'cx, 'tcx> Visitor<'tcx> for LiveVariablesVisitor<'cx, 'tcx> {
+impl<'a, 'tcx> Visitor<'tcx> for LiveVariablesVisitor<'a, 'tcx> {
     /// We sometimes have `args` within an rvalue, or within a
     /// call. Make them live at the location where they appear.
     fn visit_args(&mut self, args: &GenericArgsRef<'tcx>, location: Location) {
@@ -188,7 +188,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for LiveVariablesVisitor<'cx, 'tcx> {
     }
 }
 
-impl<'cx, 'tcx> LiveVariablesVisitor<'cx, 'tcx> {
+impl<'a, 'tcx> LiveVariablesVisitor<'a, 'tcx> {
     /// Some variable is "regular live" at `location` -- i.e., it may be used later. This means that
     /// all regions appearing in the type of `value` must be live at `location`.
     fn record_regions_live_at<T>(&mut self, value: T, location: Location)

Diff for: compiler/rustc_borrowck/src/type_check/liveness/polonius.rs

@@ -11,13 +11,13 @@ use crate::location::{LocationIndex, LocationTable};
 type VarPointRelation = Vec<(Local, LocationIndex)>;
 type PathPointRelation = Vec<(MovePathIndex, LocationIndex)>;
 
-struct UseFactsExtractor<'me, 'tcx> {
-    var_defined_at: &'me mut VarPointRelation,
-    var_used_at: &'me mut VarPointRelation,
-    location_table: &'me LocationTable,
-    var_dropped_at: &'me mut VarPointRelation,
-    move_data: &'me MoveData<'tcx>,
-    path_accessed_at_base: &'me mut PathPointRelation,
+struct UseFactsExtractor<'a, 'tcx> {
+    var_defined_at: &'a mut VarPointRelation,
+    var_used_at: &'a mut VarPointRelation,
+    location_table: &'a LocationTable,
+    var_dropped_at: &'a mut VarPointRelation,
+    move_data: &'a MoveData<'tcx>,
+    path_accessed_at_base: &'a mut PathPointRelation,
 }
 
 // A Visitor to walk through the MIR and extract point-wise facts

Diff for: compiler/rustc_builtin_macros/src/global_allocator.rs

@@ -65,7 +65,7 @@ struct AllocFnFactory<'a, 'b> {
     span: Span,
     ty_span: Span,
     global: Ident,
-    cx: &'b ExtCtxt<'a>,
+    cx: &'a ExtCtxt<'b>,
 }
 
 impl AllocFnFactory<'_, '_> {

Diff for: compiler/rustc_const_eval/src/check_consts/check.rs

@@ -166,12 +166,12 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
     }
 }
 
-struct LocalReturnTyVisitor<'ck, 'mir, 'tcx> {
+struct LocalReturnTyVisitor<'a, 'mir, 'tcx> {
     kind: LocalKind,
-    checker: &'ck mut Checker<'mir, 'tcx>,
+    checker: &'a mut Checker<'mir, 'tcx>,
 }
 
-impl<'ck, 'mir, 'tcx> TypeVisitor<TyCtxt<'tcx>> for LocalReturnTyVisitor<'ck, 'mir, 'tcx> {
+impl<'a, 'mir, 'tcx> TypeVisitor<TyCtxt<'tcx>> for LocalReturnTyVisitor<'a, 'mir, 'tcx> {
     fn visit_ty(&mut self, t: Ty<'tcx>) {
         match t.kind() {
             ty::FnPtr(..) => {}

Diff for: compiler/rustc_const_eval/src/interpret/memory.rs

@@ -1114,7 +1114,7 @@ impl<'a, 'tcx, M: Machine<'tcx>> std::fmt::Debug for DumpAllocs<'a, 'tcx, M> {
 }
 
 /// Reading and writing.
-impl<'tcx, 'a, Prov: Provenance, Extra, Bytes: AllocBytes>
+impl<'a, 'tcx, Prov: Provenance, Extra, Bytes: AllocBytes>
     AllocRefMut<'a, 'tcx, Prov, Extra, Bytes>
 {
     pub fn as_ref<'b>(&'b self) -> AllocRef<'b, 'tcx, Prov, Extra, Bytes> {
@@ -1162,7 +1162,7 @@ impl<'tcx, 'a, Prov: Provenance, Extra, Bytes: AllocBytes>
     }
 }
 
-impl<'tcx, 'a, Prov: Provenance, Extra, Bytes: AllocBytes> AllocRef<'a, 'tcx, Prov, Extra, Bytes> {
+impl<'a, 'tcx, Prov: Provenance, Extra, Bytes: AllocBytes> AllocRef<'a, 'tcx, Prov, Extra, Bytes> {
     /// `range` is relative to this allocation reference, not the base of the allocation.
     pub fn read_scalar(
         &self,

Diff for: compiler/rustc_const_eval/src/interpret/projection.rs

@@ -101,15 +101,15 @@ pub trait Projectable<'tcx, Prov: Provenance>: Sized + std::fmt::Debug {
 }
 
 /// A type representing iteration over the elements of an array.
-pub struct ArrayIterator<'tcx, 'a, Prov: Provenance, P: Projectable<'tcx, Prov>> {
+pub struct ArrayIterator<'a, 'tcx, Prov: Provenance, P: Projectable<'tcx, Prov>> {
     base: &'a P,
     range: Range<u64>,
     stride: Size,
     field_layout: TyAndLayout<'tcx>,
     _phantom: PhantomData<Prov>, // otherwise it says `Prov` is never used...
 }
 
-impl<'tcx, 'a, Prov: Provenance, P: Projectable<'tcx, Prov>> ArrayIterator<'tcx, 'a, Prov, P> {
+impl<'a, 'tcx, Prov: Provenance, P: Projectable<'tcx, Prov>> ArrayIterator<'a, 'tcx, Prov, P> {
     /// Should be the same `ecx` on each call, and match the one used to create the iterator.
     pub fn next<M: Machine<'tcx, Provenance = Prov>>(
         &mut self,
@@ -273,7 +273,7 @@ where
     pub fn project_array_fields<'a, P: Projectable<'tcx, M::Provenance>>(
         &self,
         base: &'a P,
-    ) -> InterpResult<'tcx, ArrayIterator<'tcx, 'a, M::Provenance, P>> {
+    ) -> InterpResult<'tcx, ArrayIterator<'a, 'tcx, M::Provenance, P>> {
         let abi::FieldsShape::Array { stride, .. } = base.layout().fields else {
             span_bug!(self.cur_span(), "project_array_fields: expected an array layout");
         };