Internal errors with newSeq when custom `=` operator is defined

[alaviss]

Code snippet (compile with --newruntime):

when not defined(nimNewRuntime):
  {.error: "This bug could only be reproduced with --newruntime".}

type
  Obj = object
    a: int

proc `=`(a: var Obj, b: Obj) = discard

let a = newSeq[Obj]()

Compilation output:

Hint: used config file '/etc/nim.cfg' [Conf]
Hint: system [Processing]
Hint: objarr [Processing]
objarr.nim(10, 20) Error: internal error: expr: param not init src_109252
Traceback from system (most recent call last)

nim version:

Nim Compiler Version 0.18.1 [Linux: amd64]
Copyright (c) 2006-2018 by Andreas Rumpf

git hash: cc5140d8b6ea8ca65ec9b74348cf23aec09d6723
active boot switches: -d:release -d:nativeStackTrace

[genotrance]

No longer crashes but generated code doesn't compile with gcc, regardless of --newruntime.

-------- OUTPUT --------
Hint: used config file 'c:\users\gt\Desktop\DL\programming\nimdevel\config\nim.cfg' [Conf]
Hint: system [Processing]
Hint: temp [Processing]
CC: VIB875C.tmp.21_temp
CC: stdlib_system
Error: execution of an external compiler program 'gcc.exe -c  -w -mno-ms-bitfields  -Ic:\users\gt\Desktop\DL\programming\nimdevel\lib -o C:\Users\gt\nimcache\temp_d\stdlib_system.c.o C:\Users\gt\nimcache\temp_d\stdlib_system.c' failed with exit code: 1

C:\Users\gt\nimcache\temp_d\stdlib_system.c: In function 'newSeq_kmO3ioyZ049a9c9bCzOlDezdg':
C:\Users\gt\nimcache\temp_d\stdlib_system.c:5923:58: error: 'NTI_UW8FCIB89blIV05Z3XFj8dQ_' undeclared (first use in this function); did you mean 'tySequence_UW8FCIB89blIV05Z3XFj8dQ'?
  result = (tySequence_UW8FCIB89blIV05Z3XFj8dQ*) newSeq((&NTI_UW8FCIB89blIV05Z3XFj8dQ_), len);
                                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                                          tySequence_UW8FCIB89blIV05Z3XFj8dQ
C:\Users\gt\nimcache\temp_d\stdlib_system.c:5923:58: note: each undeclared identifier is reported only once for each function it appears in
------------------------

[alaviss]

Compiles correctly with d2f7ecb

Should a test case be added for this issue?