fix: #740 — Effect TaggedError class-extends-factory(captured) pattern#783
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Root cause: a class declared inside a factory function (`class Inner {
_tag = tag }` where `tag` is the factory's param) participates in two
broken seams:
- lower_class_decl synthesizes the capture machinery (__perry_cap_<id>
ctor params + matching fields + field-init rewrite), but
lower_class_from_ast (used for class EXPRESSIONS like
`class extends Error { ... }`) did not, so anon-class-expr
captures were silently dropped.
- When the factory function returns the class (`return Inner` or
`return O.BaseEffectError`), the inliner replaces the call with
`ClassRef(...)` and discards the parameter bindings — so even the
named-class path lost the captured value at the call site.
Fix has two parts:
1. crates/perry-hir/src/lower_decl.rs — extract the Issue #212 capture
machinery into a shared `synthesize_class_captures` helper and call
it from BOTH `lower_class_decl` and `lower_class_from_ast`, so
anon class expressions get the same __perry_cap_<outer_id> ctor
params + field rewriting as named declarations. Also collect captures
from field initializers / computed keys (not just method bodies)
inside the helper.
2. crates/perry-transform/src/inline.rs — add a pre-pass
`specialize_captured_class_factories` that, for each
`Let { init: Call(FuncRef(f), args) }` where `f` is a single-
expression factory that returns a captured class (three body shapes
supported: direct `Return ClassRef(C)`; `Let X = ClassRef(C); ...; Return LocalGet(X)`;
`Let O = New(__AnonShape, [ClassRef(C),...]); ...; Return O.<field>`):
- Clone C → C__inline_<n> with each __perry_cap_<outer_id> ctor
param's id substituted by the corresponding call arg in
method/getter/setter/field-init/computed-key bodies, then drop
the cap ctor param, the cap field, and the ctor-body assignment.
- If the cloned ctor ends up with no params and an empty body, drop
the ctor entirely so lower_new's parent-walk continues to the
first real ancestor ctor (otherwise the empty middle-class ctor
would short-circuit BaseError's `this.issue = opts.issue`).
- Replace the Call site with `ClassRef(C__inline_<n>)`.
- When the rewrite lands inside `RegisterClassParentDynamic`'s
parent_expr, hoist the resolved `extends_name` (and `extends`
class-id) onto the child class statically so codegen's field-
initializer-recursive walk and parent-ctor inlining find the
specialized class.
3. crates/perry-codegen/src/lower_call.rs — bind ctor params BEFORE the
`apply_field_initializers_recursive` call (saving/restoring locals
around the whole block), so field initializers rewritten to read
`LocalGet(__perry_cap_<n>)` see the actual ctor param value instead
of falling through to the 0.0 soft-fallback.
4. crates/perry-hir/src/lower.rs + destructuring.rs + lower/expr_new.rs —
register let-binding aliases at HIR-lowering time
(`const Cls = Inner` style direct-ClassRef bindings) and follow
LocalGet alias chains, so `Expr::New { class_name: <alias> }` can
resolve through to the underlying class's captures. (Useful for
intra-module rebinds that never went through a factory.)
5. crates/perry-hir/src/analysis.rs — make `remap_local_ids_in_expr`
pub(crate) so the capture-machinery extraction can reach it from
`lower_decl`.
Standalone repro from issue text matches node byte-for-byte:
[3] ParseError defined
[4] pe._tag: ParseError
[5] pe.message: parse error: {"kind":"bad","detail":42}
Three smaller probes (factory returning class via direct return / local-
binding / object-literal-wrapping) all match node.
Gap suite: 33/35 pass — no regression from main (same two pre-existing
failures: test_gap_console_methods, test_gap_regexp_advanced).
Targeted cargo test suites (perry-hir, perry-runtime, perry-codegen,
perry-transform) all pass.
Resolves the failing `lint` check on PR #783 (cargo fmt --all --check). Pure rustfmt reflow — no token or logic changes.
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Summary
class ParseError extends TaggedError("ParseError")<...>in Effect'sParseResult.ts__initthrewTypeError: value is not a functionat module init. Two broken seams when a class is declared inside a factory function with captured values:lower_class_from_ast(anonymous class expressions used byclass extends Error<{}> { ... }) silently skipped the__perry_cap_<id>capture-synthesis machinery thatlower_class_declran for named declarations.makeFactory("MyTag")withClassRef("Inner")while discarding the param bindings, so the captured value never reached thenew Cls()site.RegisterClassParentDynamic; even with captures wired, codegen's static parent-ctor walk couldn't find the specialized parent.Fix:
synthesize_class_captureshelper inperry-hir/src/lower_decl.rsand call it from bothlower_class_declandlower_class_from_astso anon class expressions get the same__perry_cap_*field/param synthesis. (Also covers field initializers like_tag = tagand computed-key expressions, which previously read garbage at runtime.)specialize_captured_class_factoriespre-pass inperry-transform/src/inline.rsthat clones the captured class per call site with captures baked in as constants; recurses intoRegisterClassParentDynamic.parent_exprand hoists the resolved parent onto the child's staticextends_name; drops empty synthesized middle ctors so the real ancestor ctor runs.perry-codegen/src/lower_call.rs: bind ctor params beforeapply_field_initializers_recursiveso field-init expressions see the captured value at construction time.lower.rs,destructuring.rs,lower/expr_new.rs,analysis.rs(let-binding class-alias chain at HIR-lower time + helper visibility bump).Refs #321 (Effect end-to-end blocker post-#711).
Test plan
ParseError extends TaggedError("ParseError")<...>) matchesnode --experimental-strip-typesbyte-for-byte:cargo test --release -p perry-hir --lib— 41/41 passcargo build --release -p perry-hir -p perry-transform -p perry-codegen -p perrygreentest_gap_console_methods,test_gap_regexp_advanced)bun add effect@3.21.2 && perry compile test_bare.ts -o /tmp/out && /tmp/out) — not validated in this PR; the standalone repro from the issue is the validation gate. Worth verifying before closing Tracking: Effect framework end-to-end compat (post-#309 / #310) #321.