[New module system] Submodule with structural assignment hangs while loading

[WeeknightMVP]

// T.cry
module T where
  // sanity check: functions outside submodule each load
  f : {n} [1][n] -> [n]
  f [x] = x

  p : {a,b} (a,b) -> a
  p (x,_) = x

  interface submodule I where
    type n : #

  submodule F where
    import interface submodule I

    h : [1][n] -> [n]
    h [x] = x         // hangs
    // h = f             // loads
    // h = head          // loads
    // h x = x @ 0       // loads

    g : {m} [1][m] -> [m]
    g [x] = x         // hangs
    // g = f             // loads
    // g = head          // loads
    // g x = x @ 0       // loads

    q : {b} (b,_) -> b
    q (x,_) = x       // hangs
    // q x = x.0         // hangs
    // q x = y           // hangs
    //   where
    //     (y,z) = x
    // q = p             // loads
    // q = undefined     // loads

  submodule P1 where
    type n = 1

  submodule S = submodule F { submodule P1 }

  import submodule S

$ git clone https://github.com/GaloisInc/cryptol
$ cd cryptol
$ git submodule update --init --recursive
$ git switch functors-merge
$ ./cry build
$ ./cry run
Cryptol> :l T.cry
Loading module Cryptol
Loading module T
[hangs]

Submodule definitions with structural assignments or tuple accessors (regardless of interface imports or parameter use) cause load attempts to hang, whereas corresponding definitions outside submodules load quickly.

[yav]

Thanks for reporting this! I just pushed a commit that should hopefully solve the issue. Please let us know if you encounter any other issues.