dart: func_start recall gaps (supersedes closed #2072) — dotted return types, bodyless constructors, extension

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Summary

Fresh, concrete list from the 2026-08-29 tri-comparison recall audit. #2072 tracked this class
but was closed before the residual was resolved; these 9 occurrences still reproduce (dart func
recall 99.5%).

language-crucible/data/dart/flutter/:

file:line	name	form
editable_text.dart	_EditableTextTapOutsideAction	bodyless default constructor _Foo();
editable_text.dart	_EditableTextTapUpOutsideAction	same
editable_text.dart	_characterBoundary / _linebreak / _nextWordBoundary	local function / closure form
framework.dart	findAncestorStateOfType / findRootAncestorStateOfType	generic method T? findAncestorStateOfType<T extends State<StatefulWidget>>()
semantics.dart	ChildSemanticsConfigurationsResultBuilder	bodyless constructor
theme_data.dart	extension	extension is a real Dart 2.7+ top-level keyword, not matched

Fix direction

Per #2072's own analysis: item 1 (bodyless constructors) mirrors the rust #1319 / objc #1336
bodyless handling dart doesn't fully replicate; extension needs a dedicated func_start
branch; the generic-method ones need the return-type-prefix charclass to admit <... extends ...>. Each needs its own regression check — a naive charclass widening breaks generic method
type-parameter bounds (confirmed in #2072).

Found by

tri-comparison-ledger-sweep step 2.6 recall audit, 2026-08-29. Supersedes #2072.

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PR #2467 fixes 8 of the 9 occurrences:

• ✅ multi-line arrow methods (TextBoundary _characterBoundary() =>\n cond ? _A(x) : _B(y);, ×3) — the ternary on the continuation line was false-matching func_start, capping the terminator search at that phantom. The dart arrow-terminator scan now walks past such phantoms to the first genuine top-level ; and marks the span covered.
• ✅ <T extends State<StatefulWidget>> generic methods (findAncestorStateOfType, findRootAncestorStateOfType) — one level of generic-argument nesting added to the three name-following lookaheads in dart func_start.
• ✅ bodyless default/named constructors (_EditableTextTapOutsideAction();, _EditableTextTapUpOutsideAction();, ChildSemanticsConfigurationsResultBuilder();) — branch D now accepts empty parens; detector.py gates the shape on real brace-depth tracking (kept only when the name's leading segment is the nearest enclosing class/mixin/enum), so it can't fire on a bare zero-arg call statement.

dart func recall 99.5% → 99.9%, no precision loss.

Residual (still open)

flutter/theme_data.dart:993 — T? extension<T>() => extensions[T] as T?;, a method literally named extension. extension is a semi-reserved built-in identifier and appears in every keyword-exclusion list in dart func_start (to reject real extension Foo on Bar { declarations). 1 occurrence in the corpus; deferred rather than risk destabilizing extension-declaration detection for it.