Remove OutlivesEnvironmentBuilder.

`OutlivesEnvironment::new` can call `OutlivesEnvironment::with_bounds`
with an empty `extra_bounds`. And once that's done,
`OutlivesEnvironmentBuilder` has a single use and can be inlined and
removed into `OutlivesEnvironment::with_bounds`.

Author: nnethercote

compiler/rustc_infer/src/infer/outlives/env.rs

@@ -1,8 +1,7 @@
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_data_structures::transitive_relation::TransitiveRelationBuilder;
-use rustc_middle::bug;
-use rustc_middle::ty::{self,Region};
-use tracing::{debug, instrument};
+use rustc_middle::{bug, ty};
+use tracing::debug;
 
 usesuper::explicit_outlives_bounds;
 usecrate::infer::GenericKind;
@@ -54,94 +53,44 @@ pub struct OutlivesEnvironment<'tcx> {
 region_bound_pairs:RegionBoundPairs<'tcx>,
 }
 
-/// Builder of OutlivesEnvironment.
-#[derive(Debug)]
-structOutlivesEnvironmentBuilder<'tcx>{
-param_env: ty::ParamEnv<'tcx>,
-region_relation:TransitiveRelationBuilder<Region<'tcx>>,
-region_bound_pairs:RegionBoundPairs<'tcx>,
-}
-
 /// "Region-bound pairs" tracks outlives relations that are known to
 /// be true, either because of explicit where-clauses like `T: 'a` or
 /// because of implied bounds.
 pubtypeRegionBoundPairs<'tcx> = FxIndexSet<ty::OutlivesPredicate<'tcx,GenericKind<'tcx>>>;
 
 impl<'tcx>OutlivesEnvironment<'tcx>{
-/// Create a builder using `ParamEnv` and add explicit outlives bounds into it.
-fnbuilder(param_env: ty::ParamEnv<'tcx>) -> OutlivesEnvironmentBuilder<'tcx>{
-letmut builder = OutlivesEnvironmentBuilder{
- param_env,
-region_relation:Default::default(),
-region_bound_pairs:Default::default(),
-};
-
- builder.add_outlives_bounds(explicit_outlives_bounds(param_env));
-
- builder
-}
-
-#[inline]
 /// Create a new `OutlivesEnvironment` without extra outlives bounds.
+#[inline]
 pubfnnew(param_env: ty::ParamEnv<'tcx>) -> Self{
-Self::builder(param_env).build()
+Self::with_bounds(param_env,vec![])
 }
 
 /// Create a new `OutlivesEnvironment` with extra outlives bounds.
 pubfnwith_bounds(
 param_env: ty::ParamEnv<'tcx>,
 extra_bounds:implIntoIterator<Item = OutlivesBound<'tcx>>,
 ) -> Self{
-letmut builder = Self::builder(param_env);
- builder.add_outlives_bounds(extra_bounds);
- builder.build()
-}
+letmut region_relation = TransitiveRelationBuilder::default();
+letmut region_bound_pairs = RegionBoundPairs::default();
 
-/// Borrows current value of the `free_region_map`.
-pubfnfree_region_map(&self) -> &FreeRegionMap<'tcx>{
-&self.free_region_map
-}
-
-/// Borrows current `region_bound_pairs`.
-pubfnregion_bound_pairs(&self) -> &RegionBoundPairs<'tcx>{
-&self.region_bound_pairs
-}
-}
-
-impl<'tcx>OutlivesEnvironmentBuilder<'tcx>{
-#[inline]
-#[instrument(level = "debug")]
-fnbuild(self) -> OutlivesEnvironment<'tcx>{
-OutlivesEnvironment{
-param_env:self.param_env,
-free_region_map:FreeRegionMap{relation:self.region_relation.freeze()},
-region_bound_pairs:self.region_bound_pairs,
-}
-}
-
-/// Processes outlives bounds that are known to hold, whether from implied or other sources.
-fnadd_outlives_bounds<I>(&mutself,outlives_bounds:I)
-where
-I:IntoIterator<Item = OutlivesBound<'tcx>>,
-{
 // Record relationships such as `T:'x` that don't go into the
 // free-region-map but which we use here.
-for outlives_bound inoutlives_bounds{
+for outlives_bound inexplicit_outlives_bounds(param_env).chain(extra_bounds){
 debug!("add_outlives_bounds: outlives_bound={:?}", outlives_bound);
 match outlives_bound {
 OutlivesBound::RegionSubParam(r_a, param_b) => {
-self.region_bound_pairs
+ region_bound_pairs
 .insert(ty::OutlivesPredicate(GenericKind::Param(param_b), r_a));
 }
 OutlivesBound::RegionSubAlias(r_a, alias_b) => {
-self.region_bound_pairs
+ region_bound_pairs
 .insert(ty::OutlivesPredicate(GenericKind::Alias(alias_b), r_a));
 }
 OutlivesBound::RegionSubRegion(r_a, r_b) => match(*r_a,*r_b){
 (
  ty::ReStatic | ty::ReEarlyParam(_) | ty::ReLateParam(_),
  ty::ReStatic | ty::ReEarlyParam(_) | ty::ReLateParam(_),
-) => self.region_relation.add(r_a, r_b),
+) => region_relation.add(r_a, r_b),
 (ty::ReError(_), _) | (_, ty::ReError(_)) => {}
 // FIXME(#109628): We shouldn't have existential variables in implied bounds.
 // Panic here once the linked issue is resolved!
@@ -150,5 +99,21 @@ impl<'tcx> OutlivesEnvironmentBuilder<'tcx> {
 },
 }
 }
+
+OutlivesEnvironment{
+ param_env,
+free_region_map:FreeRegionMap{relation: region_relation.freeze()},
+ region_bound_pairs,
+}
+}
+
+/// Borrows current value of the `free_region_map`.
+pubfnfree_region_map(&self) -> &FreeRegionMap<'tcx>{
+&self.free_region_map
+}
+
+/// Borrows current `region_bound_pairs`.
+pubfnregion_bound_pairs(&self) -> &RegionBoundPairs<'tcx>{
+&self.region_bound_pairs
 }
 }