Bad error message for calling a method on a field of a promoted expression

[ben-albrecht]

Summary of Problem

I encountered an internal module error message when I called a method (lines()) on a field (stdout) of a promoted expression of objects (subprocess).

I have not attempted to distill the reproducer past this, so I am not confident in how generally this error message applies.

I ran into this when modifying my interface of f() from f(s: [] string) -> f(s: string)), and started getting unintentional promotion.

Steps to Reproduce

Source Code:

use Spawn;

proc f(s: string) {
  var p = spawnshell(s, stdout=PIPE, stderr=PIPE);
  p.communicate();
  return p;
}

var p = f(['ls', '-l']);
var lines = p.stdout.lines(); // <-- offending expression

Compile command:

> chpl Lines.chpl
$CHPL_HOME/modules/internal/ChapelIteratorSupport.chpl:283: error: illegal return of value where type is expected

> chpl Lines.chpl --devel
$CHPL_HOME/modules/internal/ChapelIteratorSupport.chpl:278: In function 'chpl_iteratorShapeStaticTypeOrVoid':
$CHPL_HOME/modules/internal/ChapelIteratorSupport.chpl:283: error: illegal return of value where type is expected
$CHPL_HOME/modules/internal/ChapelIteratorSupport.chpl:166: Function 'chpl_iteratorShapeStaticTypeOrVoid' instantiated as: chpl_iteratorShapeStaticTypeOrVoid(type ir = _ir_lines__ref_channel_F_dynamic_T)

Configuration Information

• Output of chpl --version: chpl version 1.21.0 pre-release (f3e74adea4)

[bradcray]

It looks to me as though the none on ChapelIteratorSupport.chpl:283 should be nothing. Does making that change help? (I don't have a clean copy of master to test with quickly). It looks like the callsite is correctly expecting nothing to come back as the sentinel.

If PR-ing this fix, we should either change these nothings back to void or change the procedure name to say Nothing rather than Void.

(I'm guessing this code path isn't tested or that @daviditen would've run into this problem when making the change in ed48984).

[bradcray]

OK, I beat you to it: Making the change gives the following error message:

testit2.chpl:10: error: creating an array of arrays using a for- or forall-expression is not supported, except when using a for-expression over a range

which I think is correct (i.e., I think your code is trying to do this and that we don't currently support it).