Attempting to partially apply a constructor causes a crash in ponyc

[chalcolith]

The following program (playground link) causes a crash in the compiler:

class A
  let n: USize

  new create(n': USize) =>
    n = n'

actor Main
  new create(env: Env) =>
    let a1 = A(1)
    let ctor = A~create(2)
    let a: A = ctor()

The backtrace is:

/home/gordon/Dev/Pony/ponyc_main/src/libponyc/codegen/genexpr.c:314: gen_assign_cast: Assertion `r_value != GEN_NOTNEEDED` failed.

Backtrace:
  ../../../build/debug/ponyc(ponyint_assert_fail+0x8f) [0x5606be9f621f]
  ../../../build/debug/ponyc(gen_assign_cast+0x5c) [0x5606be91892c]
  ../../../build/debug/ponyc(gen_call+0x678) [0x5606be911808]
  ../../../build/debug/ponyc(gen_expr+0x1b4) [0x5606be918564]
  ../../../build/debug/ponyc(gen_assign+0x47) [0x5606be923777]
  ../../../build/debug/ponyc(gen_expr+0x30d) [0x5606be9186bd]
  ../../../build/debug/ponyc(gen_seq+0x49) [0x5606be9ca479]
  ../../../build/debug/ponyc(gen_expr+0x72) [0x5606be918422]
  ../../../build/debug/ponyc(+0x6eed05) [0x5606be91ad05]
  ../../../build/debug/ponyc(+0x6edfe5) [0x5606be919fe5]
  ../../../build/debug/ponyc(genfun_method_bodies+0x8f) [0x5606be919e5f]
  ../../../build/debug/ponyc(gentypes+0x332) [0x5606be9323f2]
  ../../../build/debug/ponyc(genexe+0x2a6) [0x5606be917ac6]
  ../../../build/debug/ponyc(codegen+0xc9) [0x5606be90cbd9]
  ../../../build/debug/ponyc(generate_passes+0x2c) [0x5606be95ff8c]
  ../../../build/debug/ponyc(+0x6d58cc) [0x5606be9018cc]
  ../../../build/debug/ponyc(main+0x243) [0x5606be901723]
  /lib/x86_64-linux-gnu/libc.so.6(+0x2a1ca) [0x7f75368931ca]
  /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x8b) [0x7f753689328b]
  ../../../build/debug/ponyc(_start+0x25) [0x5606be901415]
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Aborted (core dumped)

Not sure why an LLVM warning is showing up in there, as this is an assert in ponyc code.

[jemc]

We discussed in the sync call.

• The failed assert is basically telling us that the compiler thinks the 2 value is not used, being output as GEN_NOTNEEDED is
• I tried briefly to find the cause during the call, but didn't find it - will need more investigation.