Status: Superseded by ADR-282 — its D1-D3 are D18, D19 and D15 there
Date: September 26, 2026
Target Version: Nikaia 0.0.208
Answers: #260’s a view pushed into a list a published
function handed back reaches rustc, found probing ADR-224 §3
Refines: ADR-208 D2, whose refusal now reaches a view the
checker could not see before; ADR-223 §1, whose the checker
typed a method’s view of a String it owns as String this corrects
Related: ADR-107 D3 (a copy is written, never inserted),
ADR-031 (the receiver binds the signature’s names),
ADR-105 (Seq)
pub fn names() -> Vec[String] { … }
let mut c = names()
for line in text.lines() { c.push(line.trim()) } // passed the checker; rustc: mismatched typesA published result is never both kinds (ADR-223 D4), so c is a list of text
of its own, and the view should be refused with ADR-208 D2’s explanation.
Nothing asked. Two gaps lined up:
str::trim was the only method of text that
cuts a view that the ledger described, and only for a view receiver.
text.trim() on text of its own, text.lines(), line.split(" ") were ?
to the checker, and ? fits anything.?. Vec::push said value: ?, so
even a typed view fit. HashMap::insert already said key: $K, value: $V,
but the per-argument check reads the signature before the receiver binds
$K, and a view fits an unbound name.ADR-223 §1 described the first gap as the checker typing the view as String.
It was ?, which is worse: nothing about the value was asked at all.
std.contracts describes trim_start, trim_end (-> ref String), lines,
split, split_whitespace (-> Seq[ref String] sync ends), each
returns = "borrows(self)", beside trim. A method looked up on a String
receiver that String has no entry for is looked up on str: text of its own
lends itself as a view, as the language below has it.
Where a signature writes $T for an argument the callee keeps, and the
receiver binds $T to String, a view there is the question ADR-208 D2
answers for a parameter that says String itself: NK1102, the view is kept,
.clone() is the copy. Vec::push says value: $T. A literal is built where
it is kept (ADR-207 D2), as it is for any other argument.
The tier pass has already decided every position the package can decide: a
list only views go into is Vec[ref String] by then and fits. So what this
refuses is only what that pass could not make a view — a published position,
a push inside a hole — which is exactly where the refusal belongs.
value.into_either() is EitherText, which the checker reads as String
(ADR-223 D3); so the conversion now reads as text of its own too, rather than
as the view it wraps, and either_items() makes a sequence of views one of
text. A view handed to a parameter both kinds flow into is let through, as one
into a mixed field or result already was: the emitter hands it over.
#260’s entry closes. Programs that compiled before still compile
and do the same; where a value’s type is now known, the Rust may say Some(…)
where it said .into() (ADR-068). The corpus refused nothing new: every view the ledger now types
went into a position the tier pass had already made a view or mixed. Tests
that used repeat as their example of a method nothing describes use
to_ascii_uppercase, because a String receiver now finds str::repeat.
All of it, in 0.0.208: the five ledger entries and Vec::push’s $T; the
str fallback in Checker::call_on; the substituted kept-argument check
(a_view_kept_where_the_receiver_says_text); the conversions read as text of
their own; Checker::either_param. crates/nikaia/tests/text_tiers.rs: the
program from §1 refused with .clone() named, and views from lines, split
and trim handed to a mixed parameter, run at both settings of
user_parallelism.