006 subflow in effect branch

○ Planned This feature is planned but not yet implemented.

OWED: string uppercase (string-ops gap) works as a subflow under an effect branch.

Failure Output

error[KORU021]: continuation branch 'upped' on tor 'input:upper-stub' — a bare return has no tags
  --> tests/regression/600_STDLIB/650_FS/650_006_subflow_in_effect_branch/input.k:12:0
  hint: bind the value with `: name`, not `| upped`

❌ Compiler coordination error: Incomplete branch coverage
   (set KORU_BACKEND_TRACE=1 for the backend return trace)

Code

// EXPLICIT PIN (Lars 2026-06-13): a SUBFLOW call inside an effect branch is
// legal and exercised on its own — the ! line handler invokes a subflow
// (which itself dispatches a branched event) and handles its terminal.
// Inline lowering must keep subflow invocation + branch dispatch working
// from inside a spliced handler body.

import std/io
import std/fs

pub tor shout { s: string } -> string

shout = upper-stub(s)
| upped u -> u

pub tor upper-stub { s: string } -> string

capture { seen: 0[i64] }
! as acc |> std/fs:read-lines(path: "tests/regression/600_STDLIB/650_FS/650_006_subflow_in_effect_branch/input.txt")
    ! line l |> shout(s: l)
        | shouted u |> captured { seen: acc.seen + 1 } |> std/io:print.ln("shout: {{ u:s }}")
    | done _ |> _
    | failed e |> std/io:print.ln("FAILED {{ e:s }}")
| captured total |> std/io:print.ln("{{ total.seen:d }} lines")

input.k

Supporting Files

first
second

input.txt

Expected output

shout: FIRST
shout: SECOND
2 lines

Test Configuration

MUST_RUN

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