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.

compiler/rustc_trait_selection/src/error_reporting/infer/region.rs

@@ -842,14 +842,14 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         lifetime: Region<'tcx>,
         add_lt_suggs: &mut Vec<(Span, String)>,
     ) -> String {
-        struct LifetimeReplaceVisitor<'tcx, 'a> {
+        struct LifetimeReplaceVisitor<'a, 'tcx> {
             tcx: TyCtxt<'tcx>,
             needle: hir::LifetimeName,
             new_lt: &'a str,
             add_lt_suggs: &'a mut Vec<(Span, String)>,
         }
 
-        impl<'hir, 'tcx> hir::intravisit::Visitor<'hir> for LifetimeReplaceVisitor<'tcx, '_> {
+        impl<'hir, 'tcx> hir::intravisit::Visitor<'hir> for LifetimeReplaceVisitor<'_, 'tcx> {
             fn visit_lifetime(&mut self, lt: &'hir hir::Lifetime) {
                 if lt.res == self.needle {
                     self.add_lt_suggs.push(lt.suggestion(self.new_lt));

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

@@ -61,9 +61,9 @@ pub enum CoroutineInteriorOrUpvar {
 // This type provides a uniform interface to retrieve data on coroutines, whether it originated from
 // the local crate being compiled or from a foreign crate.
 #[derive(Debug)]
-struct CoroutineData<'tcx, 'a>(&'a TypeckResults<'tcx>);
+struct CoroutineData<'a, 'tcx>(&'a TypeckResults<'tcx>);
 
-impl<'tcx, 'a> CoroutineData<'tcx, 'a> {
+impl<'a, 'tcx> CoroutineData<'a, 'tcx> {
     /// Try to get information about variables captured by the coroutine that matches a type we are
     /// looking for with `ty_matches` function. We uses it to find upvar which causes a failure to
     /// meet an obligation

compiler/rustc_trait_selection/src/traits/query/normalize.rs

@@ -25,7 +25,7 @@ use crate::traits::{
 };
 
 #[extension(pub trait QueryNormalizeExt<'tcx>)]
-impl<'cx, 'tcx> At<'cx, 'tcx> {
+impl<'a, 'tcx> At<'a, 'tcx> {
     /// Normalize `value` in the context of the inference context,
     /// yielding a resulting type, or an error if `value` cannot be
     /// normalized. If you don't care about regions, you should prefer
@@ -160,9 +160,9 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxEscapingBoundVarVisitor {
     }
 }
 
-struct QueryNormalizer<'cx, 'tcx> {
-    infcx: &'cx InferCtxt<'tcx>,
-    cause: &'cx ObligationCause<'tcx>,
+struct QueryNormalizer<'a, 'tcx> {
+    infcx: &'a InferCtxt<'tcx>,
+    cause: &'a ObligationCause<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     obligations: Vec<PredicateObligation<'tcx>>,
     cache: SsoHashMap<Ty<'tcx>, Ty<'tcx>>,
@@ -170,7 +170,7 @@ struct QueryNormalizer<'cx, 'tcx> {
     universes: Vec<Option<ty::UniverseIndex>>,
 }
 
-impl<'cx, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'cx, 'tcx> {
+impl<'a, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'a, 'tcx> {
     type Error = NoSolution;
 
     fn cx(&self) -> TyCtxt<'tcx> {

compiler/rustc_trait_selection/src/traits/util.rs

@@ -332,8 +332,8 @@ pub fn with_replaced_escaping_bound_vars<
     }
 }
 
-pub struct BoundVarReplacer<'me, 'tcx> {
-    infcx: &'me InferCtxt<'tcx>,
+pub struct BoundVarReplacer<'a, 'tcx> {
+    infcx: &'a InferCtxt<'tcx>,
     // These three maps track the bound variable that were replaced by placeholders. It might be
     // nice to remove these since we already have the `kind` in the placeholder; we really just need
     // the `var` (but we *could* bring that into scope if we were to track them as we pass them).
@@ -345,15 +345,15 @@ pub struct BoundVarReplacer<'me, 'tcx> {
     current_index: ty::DebruijnIndex,
     // The `UniverseIndex` of the binding levels above us. These are optional, since we are lazy:
     // we don't actually create a universe until we see a bound var we have to replace.
-    universe_indices: &'me mut Vec<Option<ty::UniverseIndex>>,
+    universe_indices: &'a mut Vec<Option<ty::UniverseIndex>>,
 }
 
-impl<'me, 'tcx> BoundVarReplacer<'me, 'tcx> {
+impl<'a, 'tcx> BoundVarReplacer<'a, 'tcx> {
     /// Returns `Some` if we *were* able to replace bound vars. If there are any bound vars that
     /// use a binding level above `universe_indices.len()`, we fail.
     pub fn replace_bound_vars<T: TypeFoldable<TyCtxt<'tcx>>>(
-        infcx: &'me InferCtxt<'tcx>,
-        universe_indices: &'me mut Vec<Option<ty::UniverseIndex>>,
+        infcx: &'a InferCtxt<'tcx>,
+        universe_indices: &'a mut Vec<Option<ty::UniverseIndex>>,
         value: T,
     ) -> (
         T,
@@ -479,22 +479,22 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for BoundVarReplacer<'_, 'tcx> {
 }
 
 /// The inverse of [`BoundVarReplacer`]: replaces placeholders with the bound vars from which they came.
-pub struct PlaceholderReplacer<'me, 'tcx> {
-    infcx: &'me InferCtxt<'tcx>,
+pub struct PlaceholderReplacer<'a, 'tcx> {
+    infcx: &'a InferCtxt<'tcx>,
     mapped_regions: FxIndexMap<ty::PlaceholderRegion, ty::BoundRegion>,
     mapped_types: FxIndexMap<ty::PlaceholderType, ty::BoundTy>,
     mapped_consts: BTreeMap<ty::PlaceholderConst, ty::BoundVar>,
-    universe_indices: &'me [Option<ty::UniverseIndex>],
+    universe_indices: &'a [Option<ty::UniverseIndex>],
     current_index: ty::DebruijnIndex,
 }
 
-impl<'me, 'tcx> PlaceholderReplacer<'me, 'tcx> {
+impl<'a, 'tcx> PlaceholderReplacer<'a, 'tcx> {
     pub fn replace_placeholders<T: TypeFoldable<TyCtxt<'tcx>>>(
-        infcx: &'me InferCtxt<'tcx>,
+        infcx: &'a InferCtxt<'tcx>,
         mapped_regions: FxIndexMap<ty::PlaceholderRegion, ty::BoundRegion>,
         mapped_types: FxIndexMap<ty::PlaceholderType, ty::BoundTy>,
         mapped_consts: BTreeMap<ty::PlaceholderConst, ty::BoundVar>,
-        universe_indices: &'me [Option<ty::UniverseIndex>],
+        universe_indices: &'a [Option<ty::UniverseIndex>],
         value: T,
     ) -> T {
         let mut replacer = PlaceholderReplacer {