fix: give catch, catch_all, catch_all_panics consistent semantics by sxlijin · Pull Request #5317 · BoundaryML/baml

sxlijin · 2026-10-19T20:47:49Z

Fix the behavior of catch, catch_all, and catch_all_panics across type checking and executable control flow. Canary accepted incomplete exhaustive catches, mishandled panic coverage and wildcard typing, and emitted panic dispatch that could skip an explicitly named panic arm. Flattening chained catches also made panic policy depend on other clauses and prevented later clauses from handling failures in earlier handlers.

The changes repair both individual catch blocks and chains. They reuse the existing exception-table, unwinding, and error-context machinery while correcting syntax-to-AST lowering, effect inference, MIR dispatch, and the handlers emitted into bytecode.

BAML behavior changes

Enforce exhaustive coverage

Previously, all three keywords were treated as partial handlers for ordinary error coverage. Missing cases could propagate silently or produce a downstream throws-contract error. catch_all_panics also accepted incomplete panic coverage.

Clause	Ordinary error coverage	Untyped wildcard (`_` or bare `let x`) receives	Panic coverage
`catch`	Partial; residual errors propagate	Remaining ordinary errors	Optional explicit panic arms
`catch_all`	Exhaustive; missing cases produce E0062	Remaining ordinary errors	Optional explicit panic arms
`catch_all_panics`	Exhaustive; missing cases produce E0062	Remaining ordinary errors and panics	Exhaustive; missing cases produce E0062

For example, if lookup() can throw NotFound | string, this now reports E0062 for missing string:

lookup() catch_all (e) {
    NotFound => "missing",
}

Add the missing arm or a wildcard, or use catch when propagation is intentional. The diagnostic applies with or without a surrounding throws declaration. It is localized to the exhaustive catch instead of also propagating the same missing input into caller contracts.

catch_all_panics must cover every ordinary error and the complete panic family. A wildcard covers both; without one, handle the ordinary errors and name baml.panics.Panic (or cover each panic class). A field-restricted pattern such as Greeting { text: "hi" } or baml.panics.IndexOutOfBounds { index: 0 } does not cover the entire type.

Panics remain outside ordinary throws contracts. throws never does not establish that a function cannot panic. An exhaustive catch covers incoming failures; errors thrown by its own recovery code can still propagate.

Correct wildcard panic dispatch

An ordinary wildcard must skip a panic while leaving later typed panic arms eligible:

function recover_index() -> string {
    let xs = [1];
    xs[5].to_string() catch (e) {
        _ => "ordinary error",
        baml.panics.IndexOutOfBounds => "named panic",
    }
}

This returns "named panic". Previously, the wildcard's panic guard immediately rethrew, escaping the handler before the named arm could run. If no arm takes the panic, it still propagates to a later or enclosing handler. Filtering also follows each Or-pattern alternative: PanicType | _ and _ | PanicType retain explicitly named panic matches while their wildcard alternatives reject other panics.

Wildcard policy now belongs to each clause. A later catch_all_panics no longer makes an earlier catch or catch_all wildcard swallow panics. A catch_all_panics wildcard remains live and receives an appropriate panic type even after preceding arms have consumed all ordinary errors.

Compose chained catches as successive recovery stages

expr catch A catch B means (expr catch A) catch B. B receives both residual errors from the protected expression and new errors or panics raised while A handles a failure:

function recover() -> int throws never {
    {
        throw "original"
    } catch (first) {
        string => throw 42,
    } catch_all (second) {
        int => 7,
    }
}

This returns 7; the later clause handles the replacement int error. The behavior applies to all nine pairings of the three keywords. A later exhaustive clause must cover errors produced by preceding handlers as well as their residual input errors.

Arms within one block remain alternatives: a throw from an arm bypasses its siblings. Normal completion of the operation or a handler supplies the result and skips later handlers. Direct rethrows preserve the original context; new failures during handling retain the earlier error as their cause. Pending defers run before the next handler, and captured earlier bindings survive later landings.

Preserve bare catch operands

Bare identifiers and literals are preserved during AST lowering instead of becoming missing expressions. let x = 1; x catch (e) { _ => 2 } returns 1. Catch precedence is unchanged: 1 + 1 catch ... protects the right-hand operand; (1 + 1) catch ... protects the whole sum.

Implementation

Internal structures, grouped by responsibility

Group	Representation or use changes
Protected expressions and bindings	`Expr::Catch { base, clauses: Vec<_> }` becomes `Expr::Catch { base, clause }`; chains nest. `CatchClauseKind` exposes shared keyword, error-coverage, panic-coverage, and wildcard policies. Scope and traversal consumers follow the nested representation.
Effects and coverage judgments	Existing `ThrowsChannel` contributions are collected per protected expression. Per-clause facts, total-pattern checks, and panic coverage state feed a new pending coverage diagnostic. `TirTypeError::NonExhaustiveCatchAll` carries the actual keyword.
Exception regions and caught state	Existing MIR landing locals, block unwind/handling metadata, captured-binding cells, rethrow associations, and bytecode exception/context tables are instantiated separately for each clause. Their region/context layouts are unchanged.
Panic dispatch and persisted formats	Remove MIR `ThrowIfPanic` and its bytecode instruction/opcode. Add the `PANIC` predicate tag and use ordinary tests and branches. Update serialized format versions and retire the corresponding telemetry raise kind.

Nested expressions align effect inference with handler regions

AST lowering folds clauses left to right, wrapping the accumulated expression in a new catch node. It now visits tokens as well as syntax nodes, preserving bare operands. Synthesized LLM prompt catches, HIR scopes, AST traversal, default-expression analysis, throw-fact collection, visualization, and test printers follow the same representation. AST lowering

For each clause, infer_catch opens a throws channel around its base and pops it before checking its own arms. Its residual input and its arm-body errors enter the surrounding channel. Consequently, when B protects Catch(expr, A), B receives both A's residual errors and A's new handler errors; A's own sibling arms cannot consume those new errors.

Coverage removes a fact only when the pattern covers it completely (consumes_matched), preventing refutable patterns from discharging whole types. Panic coverage is tracked separately using the stdlib baml.panics.Panic alias. Missing cases are finalized, widened, sorted, deduplicated, and reported as E0062. After reporting an incomplete exhaustive boundary, its input residual is cleared for diagnostic recovery; its own arm-body errors still propagate. Inference and coverage

MIR no longer flattens all clauses' arms into one dispatch. Recursive lowering gives each clause its own landing, error/context locals, handler, and join. For A followed by B:

Execution region	Unwinds to
Original operation	A
A's dispatch and arm bodies	B
B's dispatch and arm bodies	Enclosing handler, or out of the frame

BasicBlock::unwind routes failures; BasicBlock::handling preserves which error is being handled for cause chaining. The existing emitter derives exact exception and context PC ranges from those blocks, producing distinct handler PCs without a new VM catch-chain mechanism. Each clause can independently use switch dispatch when eligible. MIR lowering

Reject a panic at the arm, rethrow only after dispatch fails

The design error in ThrowIfPanic was encoding “this wildcard does not accept panics” as “leave the handler immediately.” The replacement makes arm rejection an ordinary control-flow edge:

ordinary_wildcard_entry:
    is_panic = IsTypeTag(error, PANIC)
    branch is_panic -> next_arm, wildcard_body

next_arm:
    ...test remaining patterns...

no_match:
    Rethrow(error, context)

PANIC = -2 is a predicate tag, not a value's actual type tag. MIR IsTypeTag becomes bytecode IsType against that constant; the VM invokes its existing panic-class identity predicate. A catch_all_panics wildcard needs no guard. In switch dispatch the wildcard is last, so the rejected-panic branch goes directly to a context-preserving rethrow block. Wildcard lowering and VM type test

Rethrow remains at both MIR and bytecode levels: it propagates an existing error and context, whereas a fresh Throw raises a new failure. Removing ThrowIfPanic eliminates its separate VM unwind/PC-update path and its special cases in MIR analysis, optimization, verification, stack simulation, emission, compact encoding, relinking, and debug formatting.

Removing the instruction changes serialized instruction and opcode discriminants. BAML artifact and BEX cache format versions both advance from 21 to 22. New telemetry records a panic rejected by all arms as ordinary Rethrow; PanicRethrow and protobuf value 3 remain decodable for older recordings.

Regression coverage

BAML catch-clause tests cover all nine keyword pairings, replacement errors, direct rethrows and preserved traces, panic cause chains, wildcard policy, lambda calls, captured bindings, successful completion, three-clause chains, defer order, and bare operands.
Coverage diagnostic fixtures cover missing ordinary errors and panics, refutable patterns, errors from preceding handlers, localized E0062, and residual partial-catch E0096.
Bytecode structure tests check all nine pairings at optimization levels Zero and Two: separate handler PCs, A protected by B, B not catching itself, A's throw covered by B, and preserved nesting after compact lowering.
A TIR rendering regression checks that both inner and outer handlers retain their typed block output. Existing catch and generated LLM MIR/bytecode snapshots reflect predicate-and-branch panic filtering with context-preserving rethrows. Keyword, book, and testing documentation is updated to match.

Summary by CodeRabbit

New Features
- Improved error-handling syntax with chained catch, catch_all, and catch_all_panics clauses.
- Panics can now be matched explicitly by type or handled at boundaries with catch_all_panics.
- Unmatched panics continue propagating through ordinary catch handlers.
- Added clearer handling for errors raised during recovery handlers.
Bug Fixes
- Improved diagnostics for incomplete error and panic coverage.
Documentation
- Updated language guidance and examples for catch behavior, chaining, and panic handling.

…stiveness All three catch clause kinds now share one control path in each compiler phase; a kind only selects policy (CatchClauseKind::requires_error_coverage, wildcard_traps_panics, requires_panic_coverage). - hir_ty: restore E0062 for a catch_all that leaves a thrown type unhandled (B-1787; lost in the TIR -> hir_ty cutover). Each clause is judged against the residual it receives, and nothing a catch_all receives propagates. catch_all_panics must also cover every panic. - MIR: one dispatch for every clause kind. A wildcard arm whose clause does not trap panics is entered after an IsTypeTag(PANIC) test that passes a panic on to the next arm, so a later clause in a chain can still catch it (previously a later catch_all_panics disabled the guard for every clause, and the guard rethrew instead of trying later arms). - Remove the ThrowIfPanic terminator/opcode end to end; bump bex_cache and baml_artifact format versions for the shifted opcode discriminants. - AST: lower a bare-token catch base (`x catch ...`, `1 catch ...`) instead of Expr::Missing, which passed check and then failed MIR lowering. - Docs: keyword docs, TEST_INSTRUCTIONS, errors.mdx. Co-Authored-By: Claude Opus 5.5 <[email protected]>

- A refutable catch arm (`Foo { x: 1 }`, `IndexOutOfBounds { index: 0 }`) handles only some values of its type, so it no longer discharges an error fact or counts toward catch_all_panics panic coverage (the B-1069 rule match already applies). - A catch_all_panics wildcard arm's binding includes the panics no earlier arm trapped, instead of `never` once the errors are drained. Co-Authored-By: Claude Opus 5.5 <[email protected]>

vercel · 2026-10-19T20:47:51Z

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chatgpt-codex-connector · 2026-10-19T20:48:02Z

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-19T20:50:57.809723Z	`b053d3d`	PR opened

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github-actions · 2026-10-19T20:48:32Z

⏭️ Performance benchmarks were skipped

Perf benchmarks (CodSpeed) are opt-in on pull requests — they no longer run on every push. They always run automatically after merge to canary/main.

To run them on this PR, do any of the following, then push a commit (or re-run CI):

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coderabbitai · 2026-10-19T20:50:30Z

No actionable comments were generated in the recent review. 🎉

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📒 Files selected for processing: 6

.github/workflows/kiln-shadow.yml
baml_language/crates/baml_compiler2_hir_ty/src/infer.rs
baml_language/crates/baml_compiler2_mir/src/lower.rs
baml_language/crates/baml_tests/baml_src/ns_catch_clauses/catch_clauses.baml
baml_language/crates/baml_tests/src/compiler2_tir/mod.rs
baml_language/crates/baml_tests/src/compiler2_tir/phase8_exceptions.rs

🚧 Files skipped from review as they are similar to previous changes: 4

baml_language/crates/baml_tests/src/compiler2_tir/mod.rs
baml_language/crates/baml_tests/baml_src/ns_catch_clauses/catch_clauses.baml
baml_language/crates/baml_compiler2_mir/src/lower.rs
baml_language/crates/baml_compiler2_hir_ty/src/infer.rs

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📝 Walkthrough

Catch clauses now dispatch errors and panics according to clause and pattern coverage. Catch-all clauses report missing error or panic cases. The compiler and VM remove the ThrowIfPanic instruction path, and artifact and cache format versions advance to 22.

Changes: Catch dispatch and panic coverage

Layer / File(s)	Summary
Catch clause contracts and parsing `baml_language/crates/baml_compiler2_ast/src/*`, `baml_language/crates/baml_compiler2_hir/src/builder.rs`, `baml_language/crates/baml_compiler2_hir_ty/src/{defaults.rs,throw_facts.rs}`, `baml_language/crates/baml_compiler2_visualization/src/control_flow/from_ast.rs`, `baml_language/crates/baml_tests/src/compiler2_tir/mod.rs`, `baml_language/crates/baml_builtins2/keyword_docs/baml_keywords.yaml`, `baml_language/TEST_INSTRUCTIONS.md`, `typescript2/app-developer-docs/content/baml/book/errors.mdx`	Catch expressions now contain one clause, with chained catches represented as nested expressions. AST traversal and rendering handle the single-clause structure. Documentation describes chaining and panic behavior.
Catch coverage inference and diagnostics `baml_language/crates/baml_compiler2_hir_ty/src/{infer.rs,diagnostics.rs}`, `baml_language/crates/baml_db/src/check.rs`, `baml_language/crates/baml_tests/projects/diagnostic_errors/catch_all_coverage/catch_all_coverage.baml`, `baml_language/crates/baml_tests/baml_src/ns_fixtures/ns_catch_all_panics/catch_all_panics.baml`	Type inference tracks handled errors and panics and checks catch-all coverage. Non-exhaustive diagnostics include the clause keyword. Test cases cover missing and exhaustive coverage.
Per-arm panic dispatch `baml_language/crates/baml_compiler2_mir/src/`, `baml_language/crates/baml_compiler2_emit/src/`, `baml_language/crates/baml_tests/baml_src/ns_catch_clauses/catch_clauses.baml`, `baml_language/crates/baml_tests/src/{compiler2_emit/mod.rs,compiler2_tir/phase8_exceptions.rs}`	MIR lowering applies panic behavior per arm and routes unmatched panics onward. `ThrowIfPanic` terminator handling is removed. Tests cover chained dispatch, panic propagation, and handler failures.
PANIC matching and bytecode update `baml_language/crates/baml_type/src/typetag.rs`, `baml_language/crates/bex_vm_types/src/`, `baml_language/crates/bex_vm/src/`, `baml_language/crates/baml_artifact/src/lib.rs`, `baml_language/crates/bex_cache/src/lib.rs`, `baml_language/crates/btel_recorder/proto/recording.proto`, `baml_language/crates/btel_records/src/lib.rs`	The VM matches the PANIC pseudo-tag with `is_panic`. `ThrowIfPanic` is removed from bytecode definitions and VM support. Artifact and cache format versions change to 22. Recording documentation marks `PanicRethrow` as retired.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~50 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant CatchLowering
  participant WildcardEntry
  participant BytecodeEmitter
  participant VM
  CatchLowering->>WildcardEntry: Pass per-arm skips_panics policy
  WildcardEntry->>BytecodeEmitter: Emit PANIC type test and rethrow path
  BytecodeEmitter->>VM: Execute emitted type test
  VM-->>WildcardEntry: Match or pass through panic

Suggested reviewers: 2kai2kai2, codeshaunted

Merge Risk: ⚪ Minimal · up to 5fd94

No actionable merge-blocking issue remains from the assessed catch coverage and panic dispatch paths. The change is ready to merge after normal checks.

Security architecture risk: 🔵 Low · up to 5fd94

The inspected changes preserve clause-specific panic handling and reject incompatible saved programs rather than silently executing them. No security bypass was established. Compatibility and exposure through external consumers remain incompletely verified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

inferred — The demonstrated exposure is program-controlled exception routing within compiled BAML execution and acceptance of persisted bytecode. The supplied evidence does not establish tenant, credential, network or hosting-level exposure, or whether external embeddings consume raw bytecode without the inspected version checks.

Trust Boundaries and Controls

observed — The inspected enforcement path keeps panic recognition in the VM and applies clause-specific filtering in generated control flow. Persisted-format readers separately enforce version equality before accepting changed opcode encodings.

Resilience and Maintainability Implications

inferred — Independent landing regions, outward handler-failure routing and the shared rethrow contract preserve failure containment in the inspected transitions. No self-catching handler loop or loss of exception-context ownership was established; interruption and concurrent execution were not dynamically validated.

Pre-merge checks: 4 · 1

Failed checks: 1 inconclusive

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 59.62% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 52 functions across 26 files. (4 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Title check		The title clearly and concisely describes the main change: consistent semantics for catch, catch_all, and catch_all_panics.

Full details: Docstring Coverage

Explanation

Docstring coverage is 59.62% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 52 functions across 26 files. (4 skipped: 2 unsupported, 2 too large.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

✨ Finishing Touches: 💡 1

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_{A rabbit hops through catches bright
Panic paths now test the light
Nested clauses safely run
Errors yield when work is done
Old opcodes rest beneath the moon
New tests hum a tidy tune}

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chatgpt-codex-connector · 2026-10-19T20:50:54Z

+            let mut trapped_panics: Vec<Ty> = Vec::new();
+            let mut traps_every_panic = false;


Carry trapped panics across catch clauses

When an earlier clause handles a panic type, this per-clause reset forgets that coverage before checking a later catch_all_panics. For example, f() catch (e) { baml.panics.Panic => ... } catch_all_panics (e2) { <all error arms> } is exhaustive because no panic reaches the second clause, but judge_catch_coverage receives an empty trapped_panics list and incorrectly reports E0062 for baml.panics.Panic. Track the residual panic set across the clause chain, analogous to the existing facts residual for ordinary errors.

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Actionable comments posted: 1

🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @baml_language/crates/baml_compiler2_mir/src/lower.rs:
- Around line 14793-14794: Update the `skips_panics` logic in the arm-lowering
path to apply the panic-skip policy to each Or-pattern alternative rather than
treating the whole pattern as irrefutable when it contains `_`. Ensure named
panic alternatives run their pattern tests and wildcard alternatives still skip
panics.

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⛔ Files ignored due to path filters: 7

baml_language/crates/baml_cli/src/snapshots/baml_cli__describe_command_tests__render_keyword_cleanup.snap is excluded by !**/*.snap
baml_language/crates/baml_tests/snapshots/baml_src/ns_fixtures/ns_catch_throw/bytecode.snap is excluded by !**/*.snap
baml_language/crates/baml_tests/snapshots/baml_src/ns_fixtures/ns_catch_throw/mir.snap is excluded by !**/*.snap
baml_language/crates/baml_tests/snapshots/baml_src/ns_fixtures/ns_llm_quoted_prompt/mir.snap is excluded by !**/*.snap
baml_language/crates/baml_tests/snapshots/diagnostic_errors/catch_all_coverage/baml_tests__diagnostic_errors__catch_all_coverage__05_diagnostics.snap is excluded by !**/*.snap
baml_language/crates/baml_tests/snapshots/diagnostic_errors/catch_all_coverage/baml_tests__diagnostic_errors__catch_all_coverage__10_formatter__catch_all_coverage.snap is excluded by !**/*.snap
baml_language/crates/baml_tests/snapshots/diagnostic_errors/catch_throw_regressions/baml_tests__diagnostic_errors__catch_throw_regressions__05_diagnostics.snap is excluded by !**/*.snap

📒 Files selected for processing: 33

baml_language/TEST_INSTRUCTIONS.md
baml_language/crates/baml_artifact/src/lib.rs
baml_language/crates/baml_builtins2/keyword_docs/baml_keywords.yaml
baml_language/crates/baml_compiler2_ast/src/ast.rs
baml_language/crates/baml_compiler2_ast/src/lower_expr_body.rs
baml_language/crates/baml_compiler2_emit/src/analysis.rs
baml_language/crates/baml_compiler2_emit/src/emit.rs
baml_language/crates/baml_compiler2_emit/src/stack_carry.rs
baml_language/crates/baml_compiler2_hir_ty/src/diagnostics.rs
baml_language/crates/baml_compiler2_hir_ty/src/infer.rs
baml_language/crates/baml_compiler2_mir/src/builder.rs
baml_language/crates/baml_compiler2_mir/src/ir.rs
baml_language/crates/baml_compiler2_mir/src/lower.rs
baml_language/crates/baml_compiler2_mir/src/memory.rs
baml_language/crates/baml_compiler2_mir/src/optimize.rs
baml_language/crates/baml_compiler2_mir/src/pretty.rs
baml_language/crates/baml_compiler2_visualization/src/control_flow/from_ast.rs
baml_language/crates/baml_db/src/check.rs
baml_language/crates/baml_tests/baml_src/ns_catch_clauses/catch_clauses.baml
baml_language/crates/baml_tests/baml_src/ns_fixtures/ns_catch_all_panics/catch_all_panics.baml
baml_language/crates/baml_tests/projects/diagnostic_errors/catch_all_coverage/catch_all_coverage.baml
baml_language/crates/baml_tests/src/compiler2_tir/mod.rs
baml_language/crates/baml_type/src/typetag.rs
baml_language/crates/bex_cache/src/lib.rs
baml_language/crates/bex_vm/src/debug.rs
baml_language/crates/bex_vm/src/vm.rs
baml_language/crates/bex_vm/src/vm/error_evidence.rs
baml_language/crates/bex_vm_types/src/bytecode.rs
baml_language/crates/bex_vm_types/src/errors.rs
baml_language/crates/bex_vm_types/src/relink.rs
baml_language/crates/btel_recorder/proto/recording.proto
baml_language/crates/btel_records/src/lib.rs
typescript2/app-developer-docs/content/baml/book/errors.mdx

💤 Files with no reviewable changes: 4

baml_language/crates/baml_compiler2_mir/src/builder.rs
baml_language/crates/bex_vm_types/src/relink.rs
baml_language/crates/baml_compiler2_mir/src/ir.rs
baml_language/crates/bex_vm/src/vm/error_evidence.rs

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github-actions · 2026-10-19T21:19:14Z

Binary size checks failed

❌ 2 violations · ✅ 1 passed

⚠️ Please fix the size gate issues or acknowledge them by updating baselines.

	Artifact	Platform	File	Gzip	Gated on	Baseline	Delta	Status
✅	`baml-cli`	Linux	🔒 61.9 MB	26.3 MB	file	73.1 MB	-11.2 MB (-15.3%)	OK
❌	`packed-program`	Linux	🔒 40.1 MB	16.3 MB	file	29.2 MB	+11.0 MB (+37.7%)	FAIL
❌	`bridge_wasm`	WASM	26.2 MB	🔒 7.7 MB	gzip	5.7 MB	+2.0 MB (+35.9%)	FAIL

🔒 = the size this artifact is GATED on (ceiling + delta). Binaries gate on file size (installed binary); WASM gates on gzip (download size). The other size is shown for information only.

Details & how to fix

Violations:

packed-program (Linux) file_bytes: 40.1 MB exceeds limit of 30.1 MB (exceeded by +10.1 MB, policy: max_file_bytes)
packed-program (Linux) file_delta_pct: +37.7% exceeds limit of 3.0% (exceeded by +34.7pp, policy: max_delta_pct)
bridge_wasm (WASM) gzip_bytes: 7.7 MB exceeds limit of 5.9 MB (exceeded by +1.8 MB, policy: max_gzip_bytes)
bridge_wasm (WASM) gzip_delta_pct: +35.9% exceeds limit of 3.0% (exceeded by +32.9pp, policy: max_delta_pct)

Add/update baselines:

.ci/size-gate/wasm32-unknown-unknown.toml:

[artifacts.bridge_wasm]
file_bytes = 26237161
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Review comments at @baml_language/crates/baml_compiler2_hir_ty/src/infer.rs:
- Around line 10829-10832: Update infer_catch so an outer clause’s coverage
check accounts for panic classes totally trapped by its nested base, seeding
trapped_panics or traps_every_panic from those total claims only; refutable arms
must not contribute. Add the chained-catch case to catch_all_coverage.baml as a
passing test.

Review comments at @baml_language/crates/baml_tests/src/compiler2_tir/mod.rs:
- Line 527: Update the Expr::Catch handling in render_expr to recursively render
a catch base when it is another catch clause before rendering the outer clause,
preserving the inner arms’ inferred types and detailed block output.

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baml_language/crates/baml_tests/snapshots/baml_src/ns_fixtures/ns_catch_throw/bytecode.snap is excluded by !**/*.snap
baml_language/crates/baml_tests/snapshots/baml_src/ns_fixtures/ns_catch_throw/mir.snap is excluded by !**/*.snap
baml_language/crates/baml_tests/snapshots/diagnostic_errors/catch_all_coverage/baml_tests__diagnostic_errors__catch_all_coverage__05_diagnostics.snap is excluded by !**/*.snap
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📒 Files selected for processing: 17

baml_language/crates/baml_builtins2/keyword_docs/baml_keywords.yaml
baml_language/crates/baml_compiler2_ast/src/ast.rs
baml_language/crates/baml_compiler2_ast/src/lib.rs
baml_language/crates/baml_compiler2_ast/src/lower_expr_body.rs
baml_language/crates/baml_compiler2_ast/src/traverse.rs
baml_language/crates/baml_compiler2_hir/src/builder.rs
baml_language/crates/baml_compiler2_hir_ty/src/defaults.rs
baml_language/crates/baml_compiler2_hir_ty/src/infer.rs
baml_language/crates/baml_compiler2_hir_ty/src/throw_facts.rs
baml_language/crates/baml_compiler2_mir/src/lower.rs
baml_language/crates/baml_compiler2_visualization/src/control_flow/from_ast.rs
baml_language/crates/baml_tests/baml_src/ns_catch_clauses/catch_clauses.baml
baml_language/crates/baml_tests/projects/diagnostic_errors/catch_all_coverage/catch_all_coverage.baml
baml_language/crates/baml_tests/src/compiler2_emit/mod.rs
baml_language/crates/baml_tests/src/compiler2_tir/mod.rs
baml_language/crates/bex_vm_types/src/bytecode.rs
typescript2/app-developer-docs/content/baml/book/errors.mdx

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linear · 2026-10-21T00:45:01Z

B-1787

Conflicts: baml_pack_host's binary moved into lib.rs on this branch while canary reworked it to parse argv before engine init and accept BAML_CONTEXT (#5319); lib.rs takes canary's host with the compiled-body table, BAML_COMPILED_BODIES and the 8 MiB worker stacks threaded through. canary removed MIR's ThrowIfPanic (#5317, panics are now ordinary type tests), so the Rust backend drops its arms in analysis, reach and codegen. The Recursion probe catches only StackOverflow, which #5317 makes an error under catch_all_panics; it uses catch with the named panic arm instead. rust_differential passes: every probe agrees as bytecode, compiled, and compiled under GC stress.

sxlijin and others added 2 commits October 19, 2026 13:44

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Comment thread baml_language/crates/baml_compiler2_mir/src/lower.rs Resolved

Nest chained catches into independent exception handlers

afc3a13

sxlijin changed the title ~~Restore exhaustive catch checking and clause-local panic dispatch on canary~~ Compose chained catches through nested exception handlers Oct 19, 2026

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Comment thread baml_language/crates/baml_compiler2_hir_ty/src/infer.rs Resolved

Comment thread baml_language/crates/baml_tests/src/compiler2_tir/mod.rs Resolved

sxlijin added 2 commits October 19, 2026 18:04

Use a supported Ruby 3.2 patch on Kiln runners

7f01deb

Filter catch wildcards per pattern alternative

5fd94c1

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sxlijin changed the title ~~Compose chained catches through nested exception handlers~~ fix: give catch, catch_all, catch_all_panics consistent semantics Oct 20, 2026

sxlijin added this pull request to the merge queue Oct 20, 2026

Merged via the queue into canary with commit 1720f0d Oct 20, 2026
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sxlijin deleted the sxlijin/catch_all-v2 branch October 20, 2026 01:44

sxlijin mentioned this pull request Oct 21, 2026

[bug] catch_all does not catch an assert.* failure raised inside the called function #4967

Open

		let mut trapped_panics: Vec<Ty> = Vec::new();
		let mut traps_every_panic = false;

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sxlijin commented Oct 19, 2026 • edited by coderabbitai Bot Loading Uh oh! There was an error while loading. Please reload this page.

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BAML behavior changes

Enforce exhaustive coverage

Correct wildcard panic dispatch

Compose chained catches as successive recovery stages

Preserve bare catch operands

Implementation

Internal structures, grouped by responsibility

Nested expressions align effect inference with handler regions

Reject a panic at the arm, rethrow only after dispatch fails

Regression coverage

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⏭️ Performance benchmarks were skipped

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sxlijin commented Oct 19, 2026 •

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