Rollup merge of #52765 - sinkuu:remove_nonzeroing_move_opt, r=pnkfelix

Remove unused "-Zenable_nonzeroing_move_hints" flag

Removing a dead option which seems to be a remnant of the old drop-flag system.

diff --combined src/librustc/session/config.rs
index 4490b2f3fa91a599171364fddcfb2a64ea1629fd,9d25d1cad6f5330852f3dc8a725b52a9d6ffa5cd..9fbf4e7c6a0f4fb965ded3488bf3a840aea73564
--- 1/src/librustc/session/config.rs
--- 2/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@@ -455,28 -455,15 +455,28 @@@ pub enum BorrowckMode 
      Ast,
      Mir,
      Compare,
 +    Migrate,
  }
  
  impl BorrowckMode {
 +    /// Should we run the MIR-based borrow check, but also fall back
 +    /// on the AST borrow check if the MIR-based one errors.
 +    pub fn migrate(self) -> bool {
 +        match self {
 +            BorrowckMode::Ast => false,
 +            BorrowckMode::Compare => false,
 +            BorrowckMode::Mir => false,
 +            BorrowckMode::Migrate => true,
 +        }
 +    }
 +
      /// Should we emit the AST-based borrow checker errors?
      pub fn use_ast(self) -> bool {
          match self {
              BorrowckMode::Ast => true,
              BorrowckMode::Compare => true,
              BorrowckMode::Mir => false,
 +            BorrowckMode::Migrate => false,
          }
      }
      /// Should we emit the MIR-based borrow checker errors?
@@@ -485,7 -472,6 +485,7 @@@
              BorrowckMode::Ast => false,
              BorrowckMode::Compare => true,
              BorrowckMode::Mir => true,
 +            BorrowckMode::Migrate => true,
          }
      }
  }
@@@ -1141,7 -1127,7 +1141,7 @@@ options! {DebuggingOptions, DebuggingSe
      emit_end_regions: bool = (false, parse_bool, [UNTRACKED],
          "emit EndRegion as part of MIR; enable transforms that solely process EndRegion"),
      borrowck: Option<String> = (None, parse_opt_string, [UNTRACKED],
 -        "select which borrowck is used (`ast`, `mir`, or `compare`)"),
 +        "select which borrowck is used (`ast`, `mir`, `migrate`, or `compare`)"),
      two_phase_borrows: bool = (false, parse_bool, [UNTRACKED],
          "use two-phase reserved/active distinction for `&mut` borrows in MIR borrowck"),
      two_phase_beyond_autoref: bool = (false, parse_bool, [UNTRACKED],
@@@ -1247,8 -1233,6 +1247,6 @@@
            "for every macro invocation, print its name and arguments"),
      debug_macros: bool = (false, parse_bool, [TRACKED],
            "emit line numbers debug info inside macros"),
-     enable_nonzeroing_move_hints: bool = (false, parse_bool, [TRACKED],
-           "force nonzeroing move optimization on"),
      keep_hygiene_data: bool = (false, parse_bool, [UNTRACKED],
            "don't clear the hygiene data after analysis"),
      keep_ast: bool = (false, parse_bool, [UNTRACKED],
@@@ -2182,7 -2166,6 +2180,7 @@@ pub fn build_session_options_and_crate_
          None | Some("ast") => BorrowckMode::Ast,
          Some("mir") => BorrowckMode::Mir,
          Some("compare") => BorrowckMode::Compare,
 +        Some("migrate") => BorrowckMode::Migrate,
          Some(m) => early_error(error_format, &format!("unknown borrowck mode `{}`", m)),
      };
  
@@@ -3168,10 -3151,6 +3166,6 @@@ mod tests 
          opts.debugging_opts.force_overflow_checks = Some(true);
          assert!(reference.dep_tracking_hash() != opts.dep_tracking_hash());
  
-         opts = reference.clone();
-         opts.debugging_opts.enable_nonzeroing_move_hints = true;
-         assert!(reference.dep_tracking_hash() != opts.dep_tracking_hash());
- 
          opts = reference.clone();
          opts.debugging_opts.show_span = Some(String::from("abc"));
          assert!(reference.dep_tracking_hash() != opts.dep_tracking_hash());