[Bug]: Reductions over distributed arrays in default arguments cause compiler segfaults

[jabraham17]

Summary of Problem

Description: Using a distributed array in a reduce expression that is the default argument for a function causes the compiler to segfault

Is this a blocking issue with no known work-arounds? I don't have a good workaround that keeps the code looking clean

Steps to Reproduce

Source Code:

use BlockDist;

const D = blockDist.createDomain({1..10, 1..10}); // I also observed this with Stencil, it is not specific to the distribution
// using a non-distributed array works perfectly fine
// const D = {1..10, 1..10};
var A: [D] int = 2;

proc foo(a: [], m = (min reduce a)) { // it does not matter the reduction
  writeln("arr ", a);
  writeln("min ", m);
}
foo(A);
// explicitly specifying the default also works
foo(A, min reduce A);

Compile command: chpl foo.chpl

Associated Future Test(s): test/functions/default-arguments/default-arg-reduce-distributed.chpl

Configuration Information

• Output of chpl --version: chpl version 2.1.0 pre-release (281481ec66)
• Output of $CHPL_HOME/util/printchplenv --anonymize:

  CHPL_TARGET_PLATFORM: darwin
  CHPL_TARGET_COMPILER: llvm
  CHPL_TARGET_ARCH: arm64
  CHPL_TARGET_CPU: native *
  CHPL_LOCALE_MODEL: flat
  CHPL_COMM: gasnet *
  CHPL_COMM_SUBSTRATE: udp
  CHPL_GASNET_SEGMENT: everything
  CHPL_TASKS: qthreads *
  CHPL_LAUNCHER: amudprun
  CHPL_TIMERS: generic
  CHPL_UNWIND: none
  CHPL_MEM: jemalloc *
  CHPL_ATOMICS: cstdlib
  CHPL_NETWORK_ATOMICS: none
  CHPL_GMP: system *
  CHPL_HWLOC: bundled *
  CHPL_RE2: bundled *
  CHPL_LLVM: system *
  CHPL_AUX_FILESYS: none

• Back-end compiler and version, e.g. gcc --version or clang --version: built with LLVM version 18.1.4

[jabraham17]

Noting that I hit this while working on https://github.com/chapel-lang/chapel/pull/24924. One workaround is to extract the default argument out as a separate helper function.

proc helper(a: []) do return min reduce a;
proc foo(a: [], m = helper(a)) { 
   ...
}