comparisons between uint and 0 aren't folded by the compiler

[bradcray]

Feature request

Summary of Problem

Given a comparison between a uint and 0 that is known to always be true by definition such as 'a > 0' or 'a >= 0', I believe the compiler should param fold this conditional as it does with other obvious facts. It doesn't currently at present because the overload that handles this case returns 'true' along one branch (when the other arg is a param 0) and calls the execution time comparison in the other branch; so the routine can't be a param routine and can't be folded.

A potential fix is to break the routine into two using a where clause to disambiguate and making the obvious case a param function and the other case not. But this runs into bugs in our handling of where clauses which is another issue (#5236).

Steps to Reproduce

Source Code:

config var x: uint;

if (x < 0) then
  compilerError("This should never happen");

Compile command:
chpl foo.chpl

Execution command:
./a.out

Configuration Information

• Output of chpl --version: 1.14.0.a771ec7
• Output of $CHPL_HOME/util/printchplenv --anonymize: N/A
• Back-end compiler and version, e.g. gcc --version or clang --version: N/A
• (For Cray systems only) Output of module list: N/A

[bradcray]

PR #5277 makes an attempt to fix this issue using the new where clause fixes introduced in PR #5275 but is currently failing with three tests.

[mppf]

PR #11570 has some related changes. See #11570 (comment)