Rollup merge of #78545 - jackh726:anonymous, r=oli-obk

Make anonymous binders start at 0

A few changes to some test outputs, but these actually look *more* correct to me.

12 files changed, 24 insertions, 32 deletions

diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index 0e5e22dcaae..13bf24bf8cf 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -684,7 +684,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     /// Rewrite any late-bound regions so that they are anonymous. Region numbers are
-    /// assigned starting at 1 and increasing monotonically in the order traversed
+    /// assigned starting at 0 and increasing monotonically in the order traversed
     /// by the fold operation.
     ///
     /// The chief purpose of this function is to canonicalize regions so that two
@@ -698,8 +698,9 @@ impl<'tcx> TyCtxt<'tcx> {
         let mut counter = 0;
         Binder::bind(
             self.replace_late_bound_regions(sig, |_| {
+                let r = self.mk_region(ty::ReLateBound(ty::INNERMOST, ty::BrAnon(counter)));
                 counter += 1;
-                self.mk_region(ty::ReLateBound(ty::INNERMOST, ty::BrAnon(counter)))
+                r
             })
             .0,
         )
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index 7833385cbc9..1ff043ae91f 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -200,15 +200,9 @@ impl SymbolMangler<'tcx> {
 
         let lifetimes = regions
             .into_iter()
-            .map(|br| {
-                match br {
-                    ty::BrAnon(i) => {
-                        // FIXME(eddyb) for some reason, `anonymize_late_bound_regions` starts at `1`.
-                        assert_ne!(i, 0);
-                        i - 1
-                    }
-                    _ => bug!("symbol_names: non-anonymized region `{:?}` in `{:?}`", br, value),
-                }
+            .map(|br| match br {
+                ty::BrAnon(i) => i,
+                _ => bug!("symbol_names: non-anonymized region `{:?}` in `{:?}`", br, value),
             })
             .max()
             .map_or(0, |max| max + 1);
@@ -327,10 +321,6 @@ impl Printer<'tcx> for SymbolMangler<'tcx> {
             // Late-bound lifetimes use indices starting at 1,
             // see `BinderLevel` for more details.
             ty::ReLateBound(debruijn, ty::BrAnon(i)) => {
-                // FIXME(eddyb) for some reason, `anonymize_late_bound_regions` starts at `1`.
-                assert_ne!(i, 0);
-                let i = i - 1;
-
                 let binder = &self.binders[self.binders.len() - 1 - debruijn.index()];
                 let depth = binder.lifetime_depths.start + i;
 
diff --git a/compiler/rustc_typeck/src/check/generator_interior.rs b/compiler/rustc_typeck/src/check/generator_interior.rs
index 4473aa2081f..5bd8ff6cde7 100644
--- a/compiler/rustc_typeck/src/check/generator_interior.rs
+++ b/compiler/rustc_typeck/src/check/generator_interior.rs
@@ -186,8 +186,9 @@ pub fn resolve_interior<'a, 'tcx>(
                 // which means that none of the regions inside relate to any other, even if
                 // typeck had previously found constraints that would cause them to be related.
                 let folded = fcx.tcx.fold_regions(&erased, &mut false, |_, current_depth| {
+                    let r = fcx.tcx.mk_region(ty::ReLateBound(current_depth, ty::BrAnon(counter)));
                     counter += 1;
-                    fcx.tcx.mk_region(ty::ReLateBound(current_depth, ty::BrAnon(counter)))
+                    r
                 });
 
                 cause.ty = folded;
diff --git a/src/test/ui/closure-expected-type/expect-fn-supply-fn.stderr b/src/test/ui/closure-expected-type/expect-fn-supply-fn.stderr
index 0de15dfa735..7a4ff779410 100644
--- a/src/test/ui/closure-expected-type/expect-fn-supply-fn.stderr
+++ b/src/test/ui/closure-expected-type/expect-fn-supply-fn.stderr
@@ -6,7 +6,7 @@ LL |     with_closure_expecting_fn_with_free_region(|x: fn(&'x u32), y| {});
    |
    = note: expected fn pointer `fn(&u32)`
               found fn pointer `fn(&'x u32)`
-note: the anonymous lifetime #2 defined on the body at 16:48...
+note: the anonymous lifetime #1 defined on the body at 16:48...
   --> $DIR/expect-fn-supply-fn.rs:16:48
    |
 LL |     with_closure_expecting_fn_with_free_region(|x: fn(&'x u32), y| {});
@@ -30,7 +30,7 @@ note: the lifetime `'x` as defined on the function body at 13:36...
    |
 LL | fn expect_free_supply_free_from_fn<'x>(x: &'x u32) {
    |                                    ^^
-note: ...does not necessarily outlive the anonymous lifetime #2 defined on the body at 16:48
+note: ...does not necessarily outlive the anonymous lifetime #1 defined on the body at 16:48
   --> $DIR/expect-fn-supply-fn.rs:16:48
    |
 LL |     with_closure_expecting_fn_with_free_region(|x: fn(&'x u32), y| {});
diff --git a/src/test/ui/closures/closure-expected-type/expect-region-supply-region-2.stderr b/src/test/ui/closures/closure-expected-type/expect-region-supply-region-2.stderr
index 7f527904a69..07a67a61834 100644
--- a/src/test/ui/closures/closure-expected-type/expect-region-supply-region-2.stderr
+++ b/src/test/ui/closures/closure-expected-type/expect-region-supply-region-2.stderr
@@ -6,7 +6,7 @@ LL |     closure_expecting_bound(|x: &'x u32| {
    |
    = note: expected reference `&u32`
               found reference `&'x u32`
-note: the anonymous lifetime #2 defined on the body at 14:29...
+note: the anonymous lifetime #1 defined on the body at 14:29...
   --> $DIR/expect-region-supply-region-2.rs:14:29
    |
 LL |       closure_expecting_bound(|x: &'x u32| {
@@ -37,7 +37,7 @@ note: the lifetime `'x` as defined on the function body at 9:30...
    |
 LL | fn expect_bound_supply_named<'x>() {
    |                              ^^
-note: ...does not necessarily outlive the anonymous lifetime #2 defined on the body at 14:29
+note: ...does not necessarily outlive the anonymous lifetime #1 defined on the body at 14:29
   --> $DIR/expect-region-supply-region-2.rs:14:29
    |
 LL |       closure_expecting_bound(|x: &'x u32| {
diff --git a/src/test/ui/issues/issue-10291.stderr b/src/test/ui/issues/issue-10291.stderr
index 4fff4ee866c..ff51aa3acf4 100644
--- a/src/test/ui/issues/issue-10291.stderr
+++ b/src/test/ui/issues/issue-10291.stderr
@@ -4,7 +4,7 @@ error[E0312]: lifetime of reference outlives lifetime of borrowed content...
 LL |         x
    |         ^
    |
-note: ...the reference is valid for the anonymous lifetime #2 defined on the body at 2:69...
+note: ...the reference is valid for the anonymous lifetime #1 defined on the body at 2:69...
   --> $DIR/issue-10291.rs:2:69
    |
 LL |       drop::<Box<dyn for<'z> FnMut(&'z isize) -> &'z isize>>(Box::new(|z| {
diff --git a/src/test/ui/issues/issue-52533-1.stderr b/src/test/ui/issues/issue-52533-1.stderr
index dd37d3e5593..4247d551565 100644
--- a/src/test/ui/issues/issue-52533-1.stderr
+++ b/src/test/ui/issues/issue-52533-1.stderr
@@ -6,12 +6,12 @@ LL |     gimme(|x, y| y)
    |
    = note: expected reference `&Foo<'_, '_, u32>`
               found reference `&Foo<'_, '_, u32>`
-note: the anonymous lifetime #4 defined on the body at 9:11...
+note: the anonymous lifetime #3 defined on the body at 9:11...
   --> $DIR/issue-52533-1.rs:9:11
    |
 LL |     gimme(|x, y| y)
    |           ^^^^^^^^
-note: ...does not necessarily outlive the anonymous lifetime #3 defined on the body at 9:11
+note: ...does not necessarily outlive the anonymous lifetime #2 defined on the body at 9:11
   --> $DIR/issue-52533-1.rs:9:11
    |
 LL |     gimme(|x, y| y)
diff --git a/src/test/ui/issues/issue-52533.stderr b/src/test/ui/issues/issue-52533.stderr
index 58654800207..4e41620eecf 100644
--- a/src/test/ui/issues/issue-52533.stderr
+++ b/src/test/ui/issues/issue-52533.stderr
@@ -4,12 +4,12 @@ error[E0312]: lifetime of reference outlives lifetime of borrowed content...
 LL |     foo(|a, b| b)
    |                ^
    |
-note: ...the reference is valid for the anonymous lifetime #2 defined on the body at 5:9...
+note: ...the reference is valid for the anonymous lifetime #1 defined on the body at 5:9...
   --> $DIR/issue-52533.rs:5:9
    |
 LL |     foo(|a, b| b)
    |         ^^^^^^^^
-note: ...but the borrowed content is only valid for the anonymous lifetime #3 defined on the body at 5:9
+note: ...but the borrowed content is only valid for the anonymous lifetime #2 defined on the body at 5:9
   --> $DIR/issue-52533.rs:5:9
    |
 LL |     foo(|a, b| b)
diff --git a/src/test/ui/regions/regions-nested-fns.stderr b/src/test/ui/regions/regions-nested-fns.stderr
index 9e405d83140..eeec0cc7862 100644
--- a/src/test/ui/regions/regions-nested-fns.stderr
+++ b/src/test/ui/regions/regions-nested-fns.stderr
@@ -4,7 +4,7 @@ error[E0495]: cannot infer an appropriate lifetime due to conflicting requiremen
 LL |     let mut ay = &y;
    |                  ^^
    |
-note: first, the lifetime cannot outlive the anonymous lifetime #2 defined on the body at 7:58...
+note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the body at 7:58...
   --> $DIR/regions-nested-fns.rs:7:58
    |
 LL |       ignore::<Box<dyn for<'z> FnMut(&'z isize)>>(Box::new(|z| {
@@ -19,7 +19,7 @@ note: ...so that reference does not outlive borrowed content
    |
 LL |         ay = z;
    |              ^
-note: but, the lifetime must be valid for the anonymous lifetime #2 defined on the body at 13:72...
+note: but, the lifetime must be valid for the anonymous lifetime #1 defined on the body at 13:72...
   --> $DIR/regions-nested-fns.rs:13:72
    |
 LL |       ignore::< Box<dyn for<'z> FnMut(&'z isize) -> &'z isize>>(Box::new(|z| {
@@ -48,7 +48,7 @@ error[E0312]: lifetime of reference outlives lifetime of borrowed content...
 LL |         if false { return x; }
    |                           ^
    |
-note: ...the reference is valid for the anonymous lifetime #2 defined on the body at 13:72...
+note: ...the reference is valid for the anonymous lifetime #1 defined on the body at 13:72...
   --> $DIR/regions-nested-fns.rs:13:72
    |
 LL |       ignore::< Box<dyn for<'z> FnMut(&'z isize) -> &'z isize>>(Box::new(|z| {
diff --git a/src/test/ui/regions/regions-ret-borrowed-1.stderr b/src/test/ui/regions/regions-ret-borrowed-1.stderr
index 2c4769d8e37..bba968cfde4 100644
--- a/src/test/ui/regions/regions-ret-borrowed-1.stderr
+++ b/src/test/ui/regions/regions-ret-borrowed-1.stderr
@@ -4,7 +4,7 @@ error[E0495]: cannot infer an appropriate lifetime due to conflicting requiremen
 LL |     with(|o| o)
    |              ^
    |
-note: first, the lifetime cannot outlive the anonymous lifetime #2 defined on the body at 10:10...
+note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the body at 10:10...
   --> $DIR/regions-ret-borrowed-1.rs:10:10
    |
 LL |     with(|o| o)
diff --git a/src/test/ui/regions/regions-ret-borrowed.stderr b/src/test/ui/regions/regions-ret-borrowed.stderr
index da560107cea..4b93ca0ae67 100644
--- a/src/test/ui/regions/regions-ret-borrowed.stderr
+++ b/src/test/ui/regions/regions-ret-borrowed.stderr
@@ -4,7 +4,7 @@ error[E0495]: cannot infer an appropriate lifetime due to conflicting requiremen
 LL |     with(|o| o)
    |              ^
    |
-note: first, the lifetime cannot outlive the anonymous lifetime #2 defined on the body at 13:10...
+note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the body at 13:10...
   --> $DIR/regions-ret-borrowed.rs:13:10
    |
 LL |     with(|o| o)
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-infer-argument-types-two-region-pointers.stderr b/src/test/ui/unboxed-closures/unboxed-closures-infer-argument-types-two-region-pointers.stderr
index 526055ba04b..bd20fd26180 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-infer-argument-types-two-region-pointers.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-infer-argument-types-two-region-pointers.stderr
@@ -4,7 +4,7 @@ error[E0312]: lifetime of reference outlives lifetime of borrowed content...
 LL |         x.set(y);
    |               ^
    |
-note: ...the reference is valid for the anonymous lifetime #3 defined on the body at 16:14...
+note: ...the reference is valid for the anonymous lifetime #2 defined on the body at 16:14...
   --> $DIR/unboxed-closures-infer-argument-types-two-region-pointers.rs:16:14
    |
 LL |       doit(0, &|x, y| {
@@ -12,7 +12,7 @@ LL |       doit(0, &|x, y| {
 LL | |         x.set(y);
 LL | |     });
    | |_____^
-note: ...but the borrowed content is only valid for the anonymous lifetime #4 defined on the body at 16:14
+note: ...but the borrowed content is only valid for the anonymous lifetime #3 defined on the body at 16:14
   --> $DIR/unboxed-closures-infer-argument-types-two-region-pointers.rs:16:14
    |
 LL |       doit(0, &|x, y| {