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agent: builder model: opus max_turns: 80 budget_usd: 20 —

Brief: a call with type arguments in brackets is named in the effect walk (#1095; unblocks #1087 step 2, #1019 step 3b’)

Facts: Traps already met

Score: blocks j5’s step 2 (comptime c = wire(f) through a generic value function in the build-time sub-program), so #1019 step 3c; S=A, O=~0.6M tokens, C=~0.5M tokens; one walk in foreign.nika. A defect (kind 3): sync and comptime are specified over any call the checker resolves.

Problem (probe both with target/fast/nikaia run at your start, in your scratchpad)

fn id[T](x: T) -> T sync {
	return x
}

fn v() -> i64 sync {
	return id[i64](3)
}

fn main() {
	println(f"{v()}")
}

Today (architect’s probe on 417abcf): error[NK2202]: v is sync, but it calls something this compiler cannot resolve, which can pause. at 6:2 (an NK1233 warning comes first, #514, not yours). Wanted: 3.

struct Contact {
	name: String,
	age: i64 = 7,
}

fn turn[T: Struct]() -> String sync {
	for f in T::fields {
		if f.name == "age" { return f.name.clone() }
	}
	return ""
}

fn v() -> String sync {
	return turn[Contact]()
}

comptime W: String = turn[Contact]()

fn main() {
	println(v())
	println(W)
}

Today: NK1152 “You can’t call W while the program is built.” and the same NK2202. Wanted: age twice.

Decision (no owner decision needed)

A call f[A](...) is a call of f (Part I 4.7, ADR-288: the callee is named and resolved before its arguments). The effect walk names it by its base and takes the generic function’s promise, as for f(...). A bracket call of a function that can pause stays refused in a sync caller.

Locations

To build

  1. The effect walk names a bracket call by its base. Test tests/compiler/tests/a_sync_function_calls_a_generic_by_brackets.nika + .stdout (both probes in one program); test tests/compiler/tests/a_sync_function_calls_a_pausing_generic_by_brackets.nika + .stderr: a generic function without sync that calls sleep (or another pausing std call; probe which one the checker counts) called as g[i64](1) from a sync function stays NK2202, now naming g. The commit says Fixes #1095, Part: #1019.

Done when

The new tests pass through nikaia test (one program alone: docs/builder-facts.md, Traps already met) with --both-settings, the first failed once on the compiler without your change (say so under Tests:); every sync_* and *sync* test and every comptime_* test still pass; lower-std fixpoint clean; the cheap checks of Rules. Changelog: one line.

Stop and report if

an edit outside foreign.nika, sync.nika, their lowered files and the new tests; an error in another agent’s file. Stop about 15 turns before max_turns, commit what is finished and report partial.

Not yours, never stage: every file git status shows modified or untracked at your start, and every docs/briefs/* file except your report.

Rules (CLAUDE.md; this block is pasted into every brief, also a fix-forward)

Report (at most 15 lines, to exactly /home/user/Nikaia/docs/briefs/tools/j7-1095-sync-bracket-call.md.report.md)

Fields of docs/architect.md, Briefs and reports: Result: done|noop|partial|blocked (the bare word alone on that line: Result: done, never a summary after it, which cuts the batch, b869a 2026-10-27; Owner: is a question for the owner or none, never a role), Files, Commit, Body (optional, one paragraph for the commit message), Fixes, Pushed, Tests, Gate (green or red <check>: your cheap checks, never none, which cuts the batch, j4 2026-10-31), Deviation, Found, Needs, Changelog, Owner, Disk freed, and for a move Rs2nika: (the kept N of M lines of rs2nika --score, then the three costliest hand edits; none for a task that moves no Rust, none (redesign) for a brief with Shape: redesign and no Convert: line). none where nothing, and then the bare word: Deviation: none (a note) cuts the batch (batch.nika compares exactly); a note goes into the commit message. Found: is only for a defect outside your change (it cuts the batch); a process event such as another session resetting or rewriting your files is no Found:, it goes under Needs: (m3a 2026-10-28); a converter draft that came out wrong is no Found:, it is one of the costliest edits under Rs2nika:, which the converter lane reads (e12-4b 2026-10-27); how you solved your own step goes into the commit message. Deviation: is only a step of the brief built otherwise than written or not built (a choice the brief left to you, such as keep what X needs and say so, is no deviation: it goes into the commit message; nor is building two steps in one commit when every step is built, e12-3a 2026-10-27, nor a step another commit on develop already built, shown by your test failing with that commit’s change reverted, b889 2026-10-27: name the commit in Body:, nor a test’s expected .stdout/.stderr taken from what the program really prints where the brief’s sketch of it was short or wrong, b934 2026-10-29: say so in Body:, nor a lowering that follows the ADR governing it where the brief’s expected lowering contradicts that ADR, b933 2026-10-29: name the ADR in Body:, nor a lowering other than the brief’s where rustc cannot take the brief’s, b1029 2026-10-31: say why in Body:, nor re-keying an allow-list entry (KNOWN) whose hash changed for the same program and the same reason, b-fixforward-sweep2 2026-10-28: say so in Body:, nor an existing test’s expected .stdout/.stderr updated because your change rightly changes the message it prints, b1012b 2026-10-31: name the test in Body:); how you verified (e.g. a test not run against the unfixed compiler) goes under Tests:. A noop says why under Tests: (what was probed), not under Deviation:. Final answer, one line: done <sha>, report <path> (or BLOCKED: ... / PUSH REJECTED ...).

Attribution: Co-Authored-By: Claude Opus 5.5 noreply@anthropic.com Claude-Session: https://claude.ai/code/session_01UVxJDvLe1uS47UcqA9y1U2

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