Automatically calculated value member of expr nodes in asr

[Oshanath]

• Created the function make_ImplicitCast_t_value() in ASRUtils that will create an implicit cast node and calculate the value attribute if possible. If not possible, function is identical to make_ImplicitCast_t().

• Replaced the make_ImplicitCast_t() calls in implicitcast_helper() with make_ImplicitCast_t_value().

• Uncommented test case in integration_tests/test_complex.py now passes. (Does not pass in the main branch)

• Made the function make_ImplicitCast_t_value() non-inline since it will be large.

• IntegerToReal cast fails test cases in integration_tests/test_builtin_pow.py. When both arguments of the pow() are integer and right arg is negative, IntegerToReal cast node gets created with a constantReal_t as the argument.

• IntegerToInteger cast fails test cases in integration_tests/test_types_01.py.

• So both of the above casts along with IntegerToLogical remain unimplemented for now.

Fixes #294

[certik]

Yes, this is exactly how to do it, thanks for submitting the PR! I have to review the details of the new function carefully, but overall this is what I had in mind. I'll review it carefully hopefully tomorrow.

[czgdp1807]

Some more tests may be? For better coverage.

[Oshanath]

Do you have any tips as to how I can write some tests to check whether an implicit cast node has a compile time value?

[czgdp1807]

I think value calculation will happen while visiting ImplicitCast node. So, adding tests which will require implicit cast should do the job. Like, c = a + b where a, b and c all are of different types.

[czgdp1807]

Why is this PR closed?

[certik]

I don't know. I just reviewed PR #319 which seems to be the successor of this one.