int(...) string parsing fails for short prefixed strings and underscore inputs

[BI71317]

Summary

This issue is about runtime 'string-to-int' path in builtin.codon, int._from_str.

Not the earlier parser-level integer literal issue from #783 .

Two problems were found in stdlib/internal/builtin.codon:

• short prefixed (especially, with length 3) strings such as 0x0, 0b1, or 0o6 fail
• numeric strings containing underscores such as 1_101 or 0b1_101 fail

Problem 1: short prefixed strings

Inputs like below should work:

int("0b0", 0)
int("0x1", 0)
int("0o6", 0)

But Instead, they shows below error.

ValueError: invalid literal for int() with base 0: '0b0'

Raised from: int._from_str:0.parse_error.0:0
/home/swchoi/src/codon/install/lib/codon/stdlib/internal/builtin.codon:380:13
Aborted (core dumped)

Problem 2: underscores in numeric strings

Inputs like below should work:

print("w08 python gap string underscores binary")
print(int("1_101", 2))
print(int("0b1_101", 0))

And they shows

w08 python gap string underscores binary
ValueError: invalid literal for int() with base 2: '1_101'

Raised from: int._from_str:0.parse_error.0:0
/home/swchoi/src/codon/install/lib/codon/stdlib/internal/builtin.codon:380:13

Backtrace:
  [0x75cd18ad1738] int._from_str:0.parse_error.0:0[str,int].1342 at /home/swchoi/src/codon/install/lib/codon/stdlib/internal/builtin.codon:380:13
  [0x75cd18ad24d3] int._from_str:0[str,int].1390 at /home/swchoi/src/codon/install/lib/codon/stdlib/internal/builtin.codon:457:29
  [0x75cd18ad250f] int.__new__:1[str,int].1393 at /home/swchoi/src/codon/install/lib/codon/stdlib/internal/types/int.codon:14:33
  [0x75cd18ad5090] main.0 at /home/swchoi/src/test_code/codon_counter_exp/w08_python_gap_string_underscores_binary.codon:2:20
Aborted (core dumped)

This issue is seperate from #783 I think.

Since this issue is not octal-only, and affects every prefixed numeric strings.