Make a function's locally abstract types part of the function node - #8574
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Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## master #8574 +/- ##
==========================================
- Coverage 75.89% 75.85% -0.04%
==========================================
Files 474 474
Lines 62772 62835 +63
==========================================
+ Hits 47640 47665 +25
- Misses 15132 15170 +38
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Replace the Pexp_newtype wrapper chains that the parser built for (type t, x) => ... arrow syntax with a structural field on the function node: Pexp_fun.newtypes carries each newtype name with its own attributes, hoisted in front of the value parameters as before. Pexp_newtype remains solely as the desugaring of [let f: type a. ...] annotations and for PPX-authored trees. Fidelity fixes visible in the formatter: - Attributes keep their association with their type parameter group: (@attr type t, x, @attr2 type s, y) round-trips as written instead of printing @attr @attr2 on the function. - Comments written next to a type parameter travel with it to the hoisted group instead of migrating onto the following value parameter. - Attributes written in front of the arrow now live on the function node, so built-in attribute processing (e.g. @this) sees them on type-first functions; previously they sat inert on the wrapper node. Typing follows the upstream OCaml 5.x design: the newtype machinery is extracted into a reusable type_newtype helper (mirroring OCaml's helper of the same name) and the function case peels one newtype at a time, mimicking the typing of the former wrapper chain; the typedtree output is bit-identical to before. The v0 PPX bridge expands the field back into a wrapper chain around Function$: each wrapper carries its own newtype's attributes, and the outermost wrapper separates function-node attributes from the first newtype's attributes with an internal _res.newtype_attrs marker (no marker means node attributes only, matching the historical wire). Newtype-free programs are wire byte-identical; for functions with newtypes the deltas are confined to wrapper-node locations and, for the rare attributed groups, per-wrapper attribute placement. Identity-PPX round-trips are AST-exact, verified against the previous compiler. Also: jsx_v4 and bs_builtin_ppx now carry newtypes (and their attributes) through their function rebuilds instead of dropping them, the sexp AST debugger emits the field, and dead parser plumbing (fundef param attrs/p_pos, arrow_start_pos, make_newtypes ~attrs) is removed. Signed-Off-By: Cristiano Calcagno <cristianoc@users.noreply.github.com> Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Part of the n-ary functions series tracked in #8557 (item 8 of 10; items 1–7 are merged).
What
Replace the Pexp_newtype wrapper chains that the parser built for
(type t, x) => ... arrow syntax with a structural field on the function
node: Pexp_fun.newtypes carries each newtype name with its own
attributes, hoisted in front of the value parameters as before.
Pexp_newtype remains solely as the desugaring of [let f: type a. ...]
annotations and for PPX-authored trees.
Fidelity fixes visible in the formatter:
(@attr type t, x, @attr2 type s, y) round-trips as written instead of
printing @attr @attr2 on the function.
hoisted group instead of migrating onto the following value parameter.
node, so built-in attribute processing (e.g. @this) sees them on
type-first functions; previously they sat inert on the wrapper node.
Typing follows the upstream OCaml 5.x design: the newtype machinery is
extracted into a reusable type_newtype helper (mirroring OCaml's helper
of the same name) and the function case peels one newtype at a time,
mimicking the typing of the former wrapper chain; the typedtree output
is bit-identical to before.
The v0 PPX bridge expands the field back into a wrapper chain around
Function$: each wrapper carries its own newtype's attributes, and the
outermost wrapper separates function-node attributes from the first
newtype's attributes with an internal _res.newtype_attrs marker (no
marker means node attributes only, matching the historical wire).
Newtype-free programs are wire byte-identical; for functions with
newtypes the deltas are confined to wrapper-node locations and, for the
rare attributed groups, per-wrapper attribute placement. Identity-PPX
round-trips are AST-exact, verified against the previous compiler.
Also: jsx_v4 and bs_builtin_ppx now carry newtypes (and their
attributes) through their function rebuilds instead of dropping them,
the sexp AST debugger emits the field, and dead parser plumbing
(fundef param attrs/p_pos, arrow_start_pos, make_newtypes ~attrs) is
removed.
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