Stabilize the size of incr comp object file names

compiler/rustc_symbol_mangling/src/v0.rs

@@ -1,4 +1,4 @@
-use rustc_data_structures::base_n;
+use rustc_data_structures::base_n::ToBaseN;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::intern::Interned;
 use rustc_hir as hir;
@@ -831,7 +831,7 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
 ///   e.g. `1` becomes `"0_"`, `62` becomes `"Z_"`, etc.
 pub(crate) fn push_integer_62(x: u64, output: &mut String) {
     if let Some(x) = x.checked_sub(1) {
-        base_n::push_str(x as u128, base_n::ALPHANUMERIC_ONLY, output);
+        output.push_str(&x.to_base(62));
     }
     output.push('_');
 }