Parser hk-parse-parens gains a `::` arm after the first inner expression:
consume `::`, parse a type via the existing hk-parse-type, expect `)`,
emit (:type-ann EXPR TYPE). Sections, tuples, parenthesised expressions
and unit `()` are unchanged.
Desugar drops the annotation — :type-ann E _ → (hk-desugar E) — since
the existing eval path has no type-directed dispatch. Phase 20 will
extend infer.sx to consume the annotation and unify against the
inferred type.
tests/parse-extras.sx (12/12) covers literal, arithmetic, function arg,
string, bool, tuple, nested annotation, function-typed annotation, and
no-regression checks for plain parens / 3-tuples / left+right sections.
eval (66/0), exceptions (14/0), typecheck (15/0), records (14/0), ioref
(13/0) all still clean.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
