Rollup merge of #63559 - eddyb:v0-mangling-off-by-1, r=estebank

rustc_codegen_utils: account for 1-indexed anonymous lifetimes in v0 mangling.

I don't really understand why `anonymize_late_bound_regions` starts with `BrAnon(1)` instead of `BrAnon(0)`, but it does (maybe @nikomatsakis knows?): https://github.com/rust-lang/rust/blob/c43d03a19f326f4a323569328cc501e86eb6d22e/src/librustc/ty/fold.rs#L696-L712

Thankfully, the mangling format and demangler implementations are fine, and I just needed to offset the anonymized lifetime indices by `1` to get the correct mangling.

cc @alexcrichton @michaelwoerister

1 files changed, 10 insertions, 2 deletions

diff --git a/src/librustc_codegen_utils/symbol_names/v0.rs b/src/librustc_codegen_utils/symbol_names/v0.rs
index 47601da8b7b..8d6a1d757e0 100644
--- a/src/librustc_codegen_utils/symbol_names/v0.rs
+++ b/src/librustc_codegen_utils/symbol_names/v0.rs
@@ -198,10 +198,14 @@ impl SymbolMangler<'tcx> {
 
         let lifetimes = regions.into_iter().map(|br| {
             match br {
-                ty::BrAnon(i) => i + 1,
+                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),
             }
-        }).max().unwrap_or(0);
+        }).max().map_or(0, |max| max + 1);
 
         self.push_opt_integer_62("G", lifetimes as u64);
         lifetime_depths.end += lifetimes;
@@ -297,6 +301,10 @@ 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;