009 reject group under alternation

✓ Passing This code compiles and runs correctly.

Code

// Cut-2 restriction: no capture groups under alternation — a group on an
// untaken branch has no span, and "empty when skipped" is a silent lie.
// Rejected loudly at the match site.
import std/io
import std/regex

std/regex:match("b")
| `a|(?<x>b)` { x } |> std/io:print.ln("{{ x:s }}")
| no-match |> std/io:print.ln("no")

input.k

Must contain:

GroupUnderAlternation

Error Verification

Actual Compiler Output

🎯 Compiler coordination: Passes: 14 (flow-based: frontend, analysis, emission)
Error: output_emitted.zig:10:16: error: regex: cannot compile pattern `a|(?<x>b)`: GroupUnderAlternation
    comptime { @compileError("regex: cannot compile pattern `a|(?<x>b)`: GroupUnderAlternation"); }
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
referenced by:
    main_module: output_emitted.zig:9:25
    main: output_emitted.zig:438:5
    4 reference(s) hidden; use '-freference-trace=6' to see all references

Test Configuration

MUST_FAIL

← 008 reject group under quantifier 010 reject groups discarded →