Function merge

crates/compile/src/compile.rs:2877–2911

Merge two sorted sequences of mutual constants into one sorted sequence.

(
  left: Vec<&'a MutConst>,
  right: Vec<&'a MutConst>,
  ctx: &MutCtx,
  cache: &mut BlockCache,
  stt: &CompileState,
)

  match (x.as_data(), y.as_data()) {
    (ExprData::Mvar(..), _) | (_, ExprData::Mvar(..)) => {
      Err(CompileError::UnsupportedExpr {
        desc: "metavariable in comparison".into(),
      })
    },
    (ExprData::Fvar(..), _) | (_, ExprData::Fvar(..)) => {
      Err(CompileError::UnsupportedExpr { desc: "fvar in comparison".into() })
    },
    (ExprData::Mdata(_, x, _), ExprData::Mdata(_, y, _)) => {
      compare_expr(x, y, mut_ctx, x_lvls, y_lvls, stt)
    },
    (ExprData::Mdata(_, x, _), _) => {
      compare_expr(x, y, mut_ctx, x_lvls, y_lvls, stt)
    },
    (_, ExprData::Mdata(_, y, _)) => {
      compare_expr(x, y, mut_ctx, x_lvls, y_lvls, stt)
    },
    (ExprData::Bvar(x, _), ExprData::Bvar(y, _)) => Ok(SOrd::cmp(x, y)),
    (ExprData::Bvar(..), _) => Ok(SOrd::lt(true)),
    (_, ExprData::Bvar(..)) => Ok(SOrd::gt(true)),
    (ExprData::Sort(x, _), ExprData::Sort(y, _)) => {
      compare_level(x, y, x_lvls, y_lvls)
    },
    (ExprData::Sort(..), _) => Ok(SOrd::lt(true)),
    (_, ExprData::Sort(..)) => Ok(SOrd::gt(true)),
    (ExprData::Const(x, xls, _), ExprData::Const(y, yls, _)) => {
      let us =
        SOrd::try_zip(|a, b| compare_level(a, b, x_lvls, y_lvls), xls, yls)?;
      if us.ordering != Ordering::Equal {
        Ok(us)
      } else if x == y {
        Ok(SOrd::eq(true))
      } else {
        match (mut_ctx.get(x), mut_ctx.get(y)) {
          (Some(nx), Some(ny)) => Ok(SOrd::weak_cmp(nx, ny)),
          (Some(..), _) => Ok(SOrd::lt(true)),
          (None, Some(..)) => Ok(SOrd::gt(true)),
          (None, None) => {
            compare_external_refs(x, y, stt, "compare_expr(Const)")