cgen: fix option reference string interpolation

[cyphercodes]

Fixes #27752

This fixes C generation for string interpolation of references to option values, such as ${&val} where val is ?int.

The interpolation stringification path now materializes the existing option-payload-reference lowering into a temporary before adding the generated nil check/string call, avoiding invalid generated C such as &&val.data.

A regression test covers both a payload option and none.

Tests

V_C_ERROR_BUG_REPORT_DISABLED=1 ./v test vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_test.v
V_C_ERROR_BUG_REPORT_DISABLED=1 ./v test vlib/v/tests/options/option_reference_of_option_test.v
git diff --check

[GGRei]

This looks good for the direct ?int case, but one case mentioned in #27752 is still missing, an alias such as type MaybeInt = ?int still generates &&val.data and fails during C compilation.

Could you also handle the aliased option type and add a regression case for it? After that, the issue should be fully covered.

[medvednikov]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

Reviewed commit: b6a80fd4e5

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[medvednikov]

lots of ci errors

[cyphercodes]

Updated this to cover the aliased option case from the review.

What changed:

• detect option aliases when deciding whether &option string interpolation needs an option-payload temporary
• generate the temporary as ?&T after unaliasing, so aliased ?T avoids the bad &&val.data C output
• added regression coverage for type MaybeInt = ?int

Verification run locally:

• ./v self
• ./v -showcc -cg -keepc -o /tmp/alias_option_ref /tmp/alias_option_ref.v (prints &Option(42))
• ./v -showcc -cg -keepc -o /tmp/string_interp_test vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_test.v
• /tmp/string_interp_test
• git diff --check

[GGRei]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Can't wait for the next one!

Reviewed commit: 79a5bc77f0

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[GGRei]

The red CI jobs appear to share the same root cause, the chained && match right_expr { ... } expression in vlib/v/gen/c/str.v generates invalid C around a goto. The build then stops early, causing the remaining CI failures.

Can you fix it plz?

[cyphercodes]

Updated to avoid the && match right_expr { ... } condition in vlib/v/gen/c/str.v that was generating invalid C around a goto.

Verification run locally:

• make -j2
• ./v self
• ./v -cc gcc -showcc -cg -keepc -o /tmp/alias_option_ref /tmp/alias_option_ref.v + /tmp/alias_option_ref (prints &Option(42))
• ./v -cc gcc -showcc -cg -keepc -o /tmp/string_interp_test vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_test.v + /tmp/string_interp_test
• git diff --check