Rollup merge of rust-lang#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

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;
 

src/test/ui/symbol-names/impl1.rs

@@ -64,9 +64,9 @@ fn main() {
             //[legacy]~^ ERROR symbol-name(_ZN198_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$RP$$u2b$impl1..AutoTrait$u3b$$u20$_$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method
             //[legacy]~| ERROR demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method
             //[legacy]~| ERROR demangling-alt(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method)
-             //[v0]~^^^^ ERROR symbol-name(_RNvXNCNvCs4fqI2P2rA04_5impl14mains_0ARDNtB6_3Foop5AssocFG0_KCRL0_hEuNtB6_9AutoTraitEL_j3_NtB2_3Bar6method)
-                //[v0]~| ERROR demangling(<[&dyn impl1[317d481089b8c8fe]::Foo<Assoc = for<'a, 'b> extern "C" fn(&'b u8)> + impl1[317d481089b8c8fe]::AutoTrait; 3: usize] as impl1[317d481089b8c8fe]::main::{closure#1}::Bar>::method)
-                //[v0]~| ERROR demangling-alt(<[&dyn impl1::Foo<Assoc = for<'a, 'b> extern "C" fn(&'b u8)> + impl1::AutoTrait; 3] as impl1::main::{closure#1}::Bar>::method)
+             //[v0]~^^^^ ERROR symbol-name(_RNvXNCNvCs4fqI2P2rA04_5impl14mains_0ARDNtB6_3Foop5AssocFG_KCRL0_hEuNtB6_9AutoTraitEL_j3_NtB2_3Bar6method)
+                //[v0]~| ERROR demangling(<[&dyn impl1[317d481089b8c8fe]::Foo<Assoc = for<'a> extern "C" fn(&'a u8)> + impl1[317d481089b8c8fe]::AutoTrait; 3: usize] as impl1[317d481089b8c8fe]::main::{closure#1}::Bar>::method)
+                //[v0]~| ERROR demangling-alt(<[&dyn impl1::Foo<Assoc = for<'a> extern "C" fn(&'a u8)> + impl1::AutoTrait; 3] as impl1::main::{closure#1}::Bar>::method)
             #[rustc_def_path]
             //[legacy]~^ ERROR def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
                //[v0]~^^ ERROR def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)

src/test/ui/symbol-names/impl1.v0.stderr

@@ -46,19 +46,19 @@ error: def-path(bar::<impl foo::Foo>::baz)
 LL |         #[rustc_def_path]
    |         ^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RNvXNCNvCs4fqI2P2rA04_5impl14mains_0ARDNtB6_3Foop5AssocFG0_KCRL0_hEuNtB6_9AutoTraitEL_j3_NtB2_3Bar6method)
+error: symbol-name(_RNvXNCNvCs4fqI2P2rA04_5impl14mains_0ARDNtB6_3Foop5AssocFG_KCRL0_hEuNtB6_9AutoTraitEL_j3_NtB2_3Bar6method)
   --> $DIR/impl1.rs:63:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling(<[&dyn impl1[317d481089b8c8fe]::Foo<Assoc = for<'a, 'b> extern "C" fn(&'b u8)> + impl1[317d481089b8c8fe]::AutoTrait; 3: usize] as impl1[317d481089b8c8fe]::main::{closure#1}::Bar>::method)
+error: demangling(<[&dyn impl1[317d481089b8c8fe]::Foo<Assoc = for<'a> extern "C" fn(&'a u8)> + impl1[317d481089b8c8fe]::AutoTrait; 3: usize] as impl1[317d481089b8c8fe]::main::{closure#1}::Bar>::method)
   --> $DIR/impl1.rs:63:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling-alt(<[&dyn impl1::Foo<Assoc = for<'a, 'b> extern "C" fn(&'b u8)> + impl1::AutoTrait; 3] as impl1::main::{closure#1}::Bar>::method)
+error: demangling-alt(<[&dyn impl1::Foo<Assoc = for<'a> extern "C" fn(&'a u8)> + impl1::AutoTrait; 3] as impl1::main::{closure#1}::Bar>::method)
   --> $DIR/impl1.rs:63:13
    |
 LL |             #[rustc_symbol_name]