[dextermos-dev]

Summary

Fixes #3851.

Under GUARANTEES.md Row 13 (BUILDABLE):

Any program accepted by hyb check must emit Go code that compiles under go build.

In Go, generic type parameters cannot be evaluated as constants, converted as constant targets, or ascribed to constants. In compiler/crates/hy-check/src/const_init.rs:

1. Generic Type-Parameter Shadows on Type Aliases & Conversions:
   • expr_is_constant_inner for Expr::Call and is_const_conversion_target verified local bindings in st.env_lookup and file declarations, but did not check st.type_params.
   • When a function declared a type parameter sharing a name with a file-level alias or conversion target (e.g., type my_int = int; fn f[my_int]() { const c = my_int(1) }), it accepted the non-constant conversion.
   • Fix: Added s.type_params.contains(ty_name) checks to Expr::Call and is_const_conversion_target.
2. Type Ascription with Shadowed Type Parameter:
   • is_const_allowed_ty did not receive st and checked only global declarations, failing to detect when const c my_int = 1 had its ascription my_int shadowed by a function type parameter my_int.
   • Fix: Passed st: Option<&FnState> through is_const_allowed_ty, rejecting any type whose root or resolved alias matches an in-scope type parameter (st.type_params.contains(name)).
3. File Constant Identifier Shadowed by Type Parameter:
   • In ident_is_constant, Expr::Ident fell back to file-level file_const_decl when an identifier was not in st.env_lookup, ignoring function type parameters.
   • For const k = 42; fn f[k]() { const e = k + 1 } and const s = "abc"; fn f[s]() { const n = len(s) }, the checker incorrectly resolved k/s to the file constant.
   • Fix: Added st.type_params.contains(name) checks to ident_is_constant and is_const_string_expr, ensuring function-scoped type parameters correctly shadow file-level constants fail-closed with HYB-E6003.

Verification

• Targeted Suite: Added compiler/crates/hy-check/tests/issue_3851_const_init_type_param_shadow.rs covering:
  • Conversion via type parameter shadow my_int(1) -> rejects HYB-E6003.
  • Type ascription via type parameter shadow const d my_int = 1 -> rejects HYB-E6003.
  • Constant identifier shadowed by type parameter k + 1 -> rejects HYB-E6003.
  • String length shadowed by type parameter len(s) -> rejects HYB-E6003.
  • Positive controls (unshadowed file constants, aliases, and conversions) -> accepted with 0 diagnostics.
• Full Compiler Battery: Ran cargo test -p hy-check --lib (183/183 unittests pass).

---

Settlement Wallet (USDC on Base): 0x8366bCe3a2D379De7656D7A67015789FaF999f20

[Burapa-J]

First-Claimant & Pagination Note for Shepherd (Session 144)

1. Original Reporter & First-to-File PR (hy-check(const_init): reject type-param-shadowed conversions, type ascriptions, and file constants in HYB-E6003 (Fixes #3851) #3852 predates hy-check(const_init): reject type-parameter shadows on const conversions, ascriptions, and file constants (fixes #3851) #3867 by 49 minutes):
   • Original Issue [soundness] hy-check(const_init): type-parameter shadows on const conversions, type ascriptions, and file constants bypass HYB-E6003 #3851 was discovered and filed by @Burapa-J at 2026-11-06T08:43:15Z.
   • Companion PR hy-check(const_init): reject type-param-shadowed conversions, type ascriptions, and file constants in HYB-E6003 (Fixes #3851) #3852 (hy-check(const_init): reject type-param-shadowed conversions, type ascriptions, and file constants in HYB-E6003 (Fixes #3851)) was opened by @Burapa-J 3 seconds later at 2026-11-06T08:43:18Z (OPEN, MERGEABLE, CI ALL-GREEN), 49 minutes before this duplicate PR hy-check(const_init): reject type-parameter shadows on const conversions, ascriptions, and file constants (fixes #3851) #3867 (2026-11-06T09:32:41Z).
2. Why #3843–#3854 Appeared Missing in Session 142's Queue Check:
   • Because there are now > 80 newer open PRs (#3858..#4079), PRs below #3858 slipped onto Page 2 of /pulls?state=open.
   • All five of @Burapa-J's original first-claimant PRs in that band are still OPEN, MERGEABLE, and CI ALL-GREEN:
     • hy-check(arith): fold float-to-int constant conversions and preserve outer/match/result closure shadows (Fixes #3842) #3843 (fixes [soundness] hy-check(arith): fold float-to-int constant conversions and preserve outer/match/result closure shadows in HYB-E6001 #3842 — arith.rs float-to-int conv & closure shadows, 08:25:55Z)
     • hy-check(elided_literal): reject foreign duplicate fields, type-param shadows, and remaining Go interface/func slots (Fixes #3844) #3845 (fixes [soundness] hy-check(elided_literal): reject foreign duplicate fields, type-param shadows, and remaining Go interface/func slots in HYB-E1002 #3844 — elided_literal.rs foreign duplicate fields & type-param shadows, 08:26:09Z)
     • hy-check(try_context): reject type-param and lexical/const value shadows on E11 and E4 signature types (Fixes #3848) #3849 (fixes [soundness] hy-check(try_context): reject type-param and lexical/const value shadows on E11 and E4 signature types (HYB-E2011) #3848 — try_context.rs E11/E4 type-param & const shadows, 08:28:12Z)
     • hy-check(const_init): reject type-param-shadowed conversions, type ascriptions, and file constants in HYB-E6003 (Fixes #3851) #3852 (fixes [soundness] hy-check(const_init): type-parameter shadows on const conversions, type ascriptions, and file constants bypass HYB-E6003 #3851 — const_init.rs type-param shadows, 08:43:18Z, predates hy-check(const_init): reject type-parameter shadows on const conversions, ascriptions, and file constants (fixes #3851) #3867 by 49m)
     • hy-check(range_iter): isolate file-const bound chains, propagate typed const bounds, and reject shadowed set iterables (Fixes #3853) #3854 (fixes [soundness] hy-check(range_iter): caller local shadows corrupt file-const range bounds and enum/type-param set bypasses iterable check #3853 — range_iter.rs, 08:43:22Z, predated hy-check(range_iter): prevent caller local shadows on const bounds and guard enum/type-param set iterables (fixes #3853) #3861 by 32m; rebased onto 1c84ad1 with the remaining !st.type_params.contains(name) & !self.consts.contains_key(name) guards missed by hy-check(range_iter): prevent caller local shadows on const bounds and guard enum/type-param set iterables (fixes #3853) #3861)

Settlement Wallet (USDC on Base): 0x46489A4fe1D0B5568352010257fEC049093f527a (@Burapa-J)

[limitlessprojects]

Landed — 3d88bd5f

Merged to main with git merge --no-ff and a hand-written credit commit (CREDIT: @dextermos-dev). Thank you for a clean fix — small diff, precise guards, reproducers included.

Gate	Result
Trial merge vs current main	clean (2 files: const_init.rs + new suite)
New suite standalone	issue_3851_const_init_type_param_shadow — 2/2 pass
cargo test --workspace	exit 0, 486 suites, 3102 passed, 0 failed
Integration files	476 → 477 on disk (ls verified, log 1:1)
Corpus harness	135/135 verdict agreement, tripwire not fired
Differential loop FULL	45/45 accept-side, 90/90 reject-side — FULL AGREEMENT

Review notes

• The threading of FnState through all six const-init verdict sites is exactly the right shape: conversion callee (s.type_params.contains(ty_name)), conversion target + alias-resolved target, string conversion target, Expr::Ident, is_const_allowed_ty (entry + resolved + Primitive/Str fast path). Everything fails closed toward not-constant, which is the correct direction for BUILDABLE.
• The duplicated type-param check in the Primitive | Str fast path is technically redundant with the entry check but harmless (defense in depth after resolve_type_alias).
• Fixtures follow the lowercase type-param recipe (LX2 identifier case) — parses clean first try.
• Both directions covered: shadowed → HYB-E6003 (reproducer + len(s) variant), unshadowed control stays silent.

Bounty

Per BOUNTY.md / discussion #295: this lands against issue #3851 — bounty claim recorded for @dextermos-dev on that issue's rail.