Rollup merge of #123922 - TDecking:base_n_magic_removal, r=jieyouxu

Remove magic constants when using `base_n`.

Some use cases of `base_n` use number literals instead of the predefined constants. The latter are more descriptive so it might be better to use those instead.

compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/encode.rs

@@ -736,7 +736,7 @@ fn encode_ty_name(tcx: TyCtxt<'_>, def_id: DefId) -> String {
 /// <https://rust-lang.github.io/rfcs/2603-rust-symbol-name-mangling-v0.html>).
 fn to_disambiguator(num: u64) -> String {
     if let Some(num) = num.checked_sub(1) {
-        format!("s{}_", base_n::encode(num as u128, 62))
+        format!("s{}_", base_n::encode(num as u128, base_n::ALPHANUMERIC_ONLY))
     } else {
         "s_".to_string()
     }
@@ -746,7 +746,7 @@ fn to_disambiguator(num: u64) -> String {
 /// <https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangle.seq-id>).
 fn to_seq_id(num: usize) -> String {
     if let Some(num) = num.checked_sub(1) {
-        base_n::encode(num as u128, 36).to_uppercase()
+        base_n::encode(num as u128, base_n::CASE_INSENSITIVE).to_uppercase()
     } else {
         "".to_string()
     }

compiler/rustc_symbol_mangling/src/v0.rs

@@ -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, 62, output);
+        base_n::push_str(x as u128, base_n::ALPHANUMERIC_ONLY, output);
     }
     output.push('_');
 }