M2-T06: exceptions — throw/try/catch/finally with value propagation

[ncdevshiv]

Closes#32.

What

• Full stack: throw/try/catch/finally as expression forms (matching the expression-oriented IR): AST Throw/Try → both parser twins (strict + recovery, in parity) → JsExpr::Throw/Try → lowering (subst_expr/free-vars honor catch-param shadowing) → eval.
• Value-carrying exceptions: RuntimeError now carries the thrown JS value. catch (e) binds the thrown value verbatim (strings, numbers, new Error objects); internal runtime errors (e.g. unbound variables — ECMA ReferenceError) bind their message string.
• eval Try semantics: catch runs in a fresh scope (optional catch binding catch { } supported per ES2019); finally runs on every path (success, after catch, uncaught); an error raised in finally replaces the pending outcome.
• Error builtin: Error(msg) / new Error(msg) → Error-shaped object {name: "Error", message}; e.message reads back through member access.
• Propagation across calls: a throw two call frames deep unwinds into the component's try (pinned by test); uncaught throws surface at flush/dispatch; error boundaries (M1-T13) still capture render-time throws — thrown messages flow through getDerivedStateFromError into the fallback.
• Latent bug fixed while testing: Env::assign — assignments used define (current-scope insert), so assigning from a nested scope (catch block, closure body) shadowed the outer binding instead of updating it. Assignment now walks to the nearest existing binding (JS semantics); define remains the declaration path.

Documented scoping

• No return-completion exists in the expression IR, so the finally-return-override case has no form (documented in js.rs + JOURNAL).
• Internal errors bind as message strings until the full Error-class work; throw new Error(msg) already produces a real Error object.

Tests

crates/r2n-runtime/tests/exceptions.rs — 12 acceptance tests: catch binding (string/number/Error.message), internal-error catchability, finally on all three paths + finally-error override, uncaught propagation at flush, cross-call propagation, nested try + rethrow, optional catch binding, handler-throw at dispatch, boundary interplay.

Suite: 208 tests green; clippy -D warnings; fmt; verify-audit-claims OK. Records updated (CHECKLIST/README/ROADMAP/yaml/toml, M2 6/15 · 60/106; JOURNAL entry 28).

[ncdevshiv]

Closes#32.

What

• Full stack: throw/try/catch/finally as expression forms (matching the expression-oriented IR): AST Throw/Try → both parser twins (strict + recovery, in parity) → JsExpr::Throw/Try → lowering (subst_expr/free-vars honor catch-param shadowing) → eval.
• Value-carrying exceptions: RuntimeError now carries the thrown JS value. catch (e) binds the thrown value verbatim (strings, numbers, new Error objects); internal runtime errors (e.g. unbound variables — ECMA ReferenceError) bind their message string.
• eval Try semantics: catch runs in a fresh scope (optional catch binding catch { } supported per ES2019); finally runs on every path (success, after catch, uncaught); an error raised in finally replaces the pending outcome.
• Error builtin: Error(msg) / new Error(msg) → Error-shaped object {name: "Error", message}; e.message reads back through member access.
• Propagation across calls: a throw two call frames deep unwinds into the component's try (pinned by test); uncaught throws surface at flush/dispatch; error boundaries (M1-T13) still capture render-time throws — thrown messages flow through getDerivedStateFromError into the fallback.
• Latent bug fixed while testing: Env::assign — assignments used define (current-scope insert), so assigning from a nested scope (catch block, closure body) shadowed the outer binding instead of updating it. Assignment now walks to the nearest existing binding (JS semantics); define remains the declaration path.

Documented scoping

• No return-completion exists in the expression IR, so the finally-return-override case has no form (documented in js.rs + JOURNAL).
• Internal errors bind as message strings until the full Error-class work; throw new Error(msg) already produces a real Error object.

Tests

crates/r2n-runtime/tests/exceptions.rs — 12 acceptance tests: catch binding (string/number/Error.message), internal-error catchability, finally on all three paths + finally-error override, uncaught propagation at flush, cross-call propagation, nested try + rethrow, optional catch binding, handler-throw at dispatch, boundary interplay.

Suite: 208 tests green; clippy -D warnings; fmt; verify-audit-claims OK. Records updated (CHECKLIST/README/ROADMAP/yaml/toml, M2 6/15 · 60/106; JOURNAL entry 28).

[ncdevshiv]

Closes#32.

What

• Full stack: throw/try/catch/finally as expression forms (matching the expression-oriented IR): AST Throw/Try → both parser twins (strict + recovery, in parity) → JsExpr::Throw/Try → lowering (subst_expr/free-vars honor catch-param shadowing) → eval.
• Value-carrying exceptions: RuntimeError now carries the thrown JS value. catch (e) binds the thrown value verbatim (strings, numbers, new Error objects); internal runtime errors (e.g. unbound variables — ECMA ReferenceError) bind their message string.
• eval Try semantics: catch runs in a fresh scope (optional catch binding catch { } supported per ES2019); finally runs on every path (success, after catch, uncaught); an error raised in finally replaces the pending outcome.
• Error builtin: Error(msg) / new Error(msg) → Error-shaped object {name: "Error", message}; e.message reads back through member access.
• Propagation across calls: a throw two call frames deep unwinds into the component's try (pinned by test); uncaught throws surface at flush/dispatch; error boundaries (M1-T13) still capture render-time throws — thrown messages flow through getDerivedStateFromError into the fallback.
• Latent bug fixed while testing: Env::assign — assignments used define (current-scope insert), so assigning from a nested scope (catch block, closure body) shadowed the outer binding instead of updating it. Assignment now walks to the nearest existing binding (JS semantics); define remains the declaration path.

Documented scoping

• No return-completion exists in the expression IR, so the finally-return-override case has no form (documented in js.rs + JOURNAL).
• Internal errors bind as message strings until the full Error-class work; throw new Error(msg) already produces a real Error object.

Tests

crates/r2n-runtime/tests/exceptions.rs — 12 acceptance tests: catch binding (string/number/Error.message), internal-error catchability, finally on all three paths + finally-error override, uncaught propagation at flush, cross-call propagation, nested try + rethrow, optional catch binding, handler-throw at dispatch, boundary interplay.

Suite: 208 tests green; clippy -D warnings; fmt; verify-audit-claims OK. Records updated (CHECKLIST/README/ROADMAP/yaml/toml, M2 6/15 · 60/106; JOURNAL entry 28).

[ncdevshiv]

Closes#32.

What

• Full stack: throw/try/catch/finally as expression forms (matching the expression-oriented IR): AST Throw/Try → both parser twins (strict + recovery, in parity) → JsExpr::Throw/Try → lowering (subst_expr/free-vars honor catch-param shadowing) → eval.
• Value-carrying exceptions: RuntimeError now carries the thrown JS value. catch (e) binds the thrown value verbatim (strings, numbers, new Error objects); internal runtime errors (e.g. unbound variables — ECMA ReferenceError) bind their message string.
• eval Try semantics: catch runs in a fresh scope (optional catch binding catch { } supported per ES2019); finally runs on every path (success, after catch, uncaught); an error raised in finally replaces the pending outcome.
• Error builtin: Error(msg) / new Error(msg) → Error-shaped object {name: "Error", message}; e.message reads back through member access.
• Propagation across calls: a throw two call frames deep unwinds into the component's try (pinned by test); uncaught throws surface at flush/dispatch; error boundaries (M1-T13) still capture render-time throws — thrown messages flow through getDerivedStateFromError into the fallback.
• Latent bug fixed while testing: Env::assign — assignments used define (current-scope insert), so assigning from a nested scope (catch block, closure body) shadowed the outer binding instead of updating it. Assignment now walks to the nearest existing binding (JS semantics); define remains the declaration path.

Documented scoping

• No return-completion exists in the expression IR, so the finally-return-override case has no form (documented in js.rs + JOURNAL).
• Internal errors bind as message strings until the full Error-class work; throw new Error(msg) already produces a real Error object.

Tests

crates/r2n-runtime/tests/exceptions.rs — 12 acceptance tests: catch binding (string/number/Error.message), internal-error catchability, finally on all three paths + finally-error override, uncaught propagation at flush, cross-call propagation, nested try + rethrow, optional catch binding, handler-throw at dispatch, boundary interplay.

Suite: 208 tests green; clippy -D warnings; fmt; verify-audit-claims OK. Records updated (CHECKLIST/README/ROADMAP/yaml/toml, M2 6/15 · 60/106; JOURNAL entry 28).

[ncdevshiv]

Closes#32.

What

• Full stack: throw/try/catch/finally as expression forms (matching the expression-oriented IR): AST Throw/Try → both parser twins (strict + recovery, in parity) → JsExpr::Throw/Try → lowering (subst_expr/free-vars honor catch-param shadowing) → eval.
• Value-carrying exceptions: RuntimeError now carries the thrown JS value. catch (e) binds the thrown value verbatim (strings, numbers, new Error objects); internal runtime errors (e.g. unbound variables — ECMA ReferenceError) bind their message string.
• eval Try semantics: catch runs in a fresh scope (optional catch binding catch { } supported per ES2019); finally runs on every path (success, after catch, uncaught); an error raised in finally replaces the pending outcome.
• Error builtin: Error(msg) / new Error(msg) → Error-shaped object {name: "Error", message}; e.message reads back through member access.
• Propagation across calls: a throw two call frames deep unwinds into the component's try (pinned by test); uncaught throws surface at flush/dispatch; error boundaries (M1-T13) still capture render-time throws — thrown messages flow through getDerivedStateFromError into the fallback.
• Latent bug fixed while testing: Env::assign — assignments used define (current-scope insert), so assigning from a nested scope (catch block, closure body) shadowed the outer binding instead of updating it. Assignment now walks to the nearest existing binding (JS semantics); define remains the declaration path.

Documented scoping

• No return-completion exists in the expression IR, so the finally-return-override case has no form (documented in js.rs + JOURNAL).
• Internal errors bind as message strings until the full Error-class work; throw new Error(msg) already produces a real Error object.

Tests

crates/r2n-runtime/tests/exceptions.rs — 12 acceptance tests: catch binding (string/number/Error.message), internal-error catchability, finally on all three paths + finally-error override, uncaught propagation at flush, cross-call propagation, nested try + rethrow, optional catch binding, handler-throw at dispatch, boundary interplay.

Suite: 208 tests green; clippy -D warnings; fmt; verify-audit-claims OK. Records updated (CHECKLIST/README/ROADMAP/yaml/toml, M2 6/15 · 60/106; JOURNAL entry 28).

[ncdevshiv]

Closes#32.

What

• Full stack: throw/try/catch/finally as expression forms (matching the expression-oriented IR): AST Throw/Try → both parser twins (strict + recovery, in parity) → JsExpr::Throw/Try → lowering (subst_expr/free-vars honor catch-param shadowing) → eval.
• Value-carrying exceptions: RuntimeError now carries the thrown JS value. catch (e) binds the thrown value verbatim (strings, numbers, new Error objects); internal runtime errors (e.g. unbound variables — ECMA ReferenceError) bind their message string.
• eval Try semantics: catch runs in a fresh scope (optional catch binding catch { } supported per ES2019); finally runs on every path (success, after catch, uncaught); an error raised in finally replaces the pending outcome.
• Error builtin: Error(msg) / new Error(msg) → Error-shaped object {name: "Error", message}; e.message reads back through member access.
• Propagation across calls: a throw two call frames deep unwinds into the component's try (pinned by test); uncaught throws surface at flush/dispatch; error boundaries (M1-T13) still capture render-time throws — thrown messages flow through getDerivedStateFromError into the fallback.
• Latent bug fixed while testing: Env::assign — assignments used define (current-scope insert), so assigning from a nested scope (catch block, closure body) shadowed the outer binding instead of updating it. Assignment now walks to the nearest existing binding (JS semantics); define remains the declaration path.

Documented scoping

• No return-completion exists in the expression IR, so the finally-return-override case has no form (documented in js.rs + JOURNAL).
• Internal errors bind as message strings until the full Error-class work; throw new Error(msg) already produces a real Error object.

Tests

crates/r2n-runtime/tests/exceptions.rs — 12 acceptance tests: catch binding (string/number/Error.message), internal-error catchability, finally on all three paths + finally-error override, uncaught propagation at flush, cross-call propagation, nested try + rethrow, optional catch binding, handler-throw at dispatch, boundary interplay.

Suite: 208 tests green; clippy -D warnings; fmt; verify-audit-claims OK. Records updated (CHECKLIST/README/ROADMAP/yaml/toml, M2 6/15 · 60/106; JOURNAL entry 28).

[ncdevshiv]

Closes#32.

What

• Full stack: throw/try/catch/finally as expression forms (matching the expression-oriented IR): AST Throw/Try → both parser twins (strict + recovery, in parity) → JsExpr::Throw/Try → lowering (subst_expr/free-vars honor catch-param shadowing) → eval.
• Value-carrying exceptions: RuntimeError now carries the thrown JS value. catch (e) binds the thrown value verbatim (strings, numbers, new Error objects); internal runtime errors (e.g. unbound variables — ECMA ReferenceError) bind their message string.
• eval Try semantics: catch runs in a fresh scope (optional catch binding catch { } supported per ES2019); finally runs on every path (success, after catch, uncaught); an error raised in finally replaces the pending outcome.
• Error builtin: Error(msg) / new Error(msg) → Error-shaped object {name: "Error", message}; e.message reads back through member access.
• Propagation across calls: a throw two call frames deep unwinds into the component's try (pinned by test); uncaught throws surface at flush/dispatch; error boundaries (M1-T13) still capture render-time throws — thrown messages flow through getDerivedStateFromError into the fallback.
• Latent bug fixed while testing: Env::assign — assignments used define (current-scope insert), so assigning from a nested scope (catch block, closure body) shadowed the outer binding instead of updating it. Assignment now walks to the nearest existing binding (JS semantics); define remains the declaration path.

Documented scoping

• No return-completion exists in the expression IR, so the finally-return-override case has no form (documented in js.rs + JOURNAL).
• Internal errors bind as message strings until the full Error-class work; throw new Error(msg) already produces a real Error object.

Tests

crates/r2n-runtime/tests/exceptions.rs — 12 acceptance tests: catch binding (string/number/Error.message), internal-error catchability, finally on all three paths + finally-error override, uncaught propagation at flush, cross-call propagation, nested try + rethrow, optional catch binding, handler-throw at dispatch, boundary interplay.

Suite: 208 tests green; clippy -D warnings; fmt; verify-audit-claims OK. Records updated (CHECKLIST/README/ROADMAP/yaml/toml, M2 6/15 · 60/106; JOURNAL entry 28).

[ncdevshiv]

Closes#32.

What

• Full stack: throw/try/catch/finally as expression forms (matching the expression-oriented IR): AST Throw/Try → both parser twins (strict + recovery, in parity) → JsExpr::Throw/Try → lowering (subst_expr/free-vars honor catch-param shadowing) → eval.
• Value-carrying exceptions: RuntimeError now carries the thrown JS value. catch (e) binds the thrown value verbatim (strings, numbers, new Error objects); internal runtime errors (e.g. unbound variables — ECMA ReferenceError) bind their message string.
• eval Try semantics: catch runs in a fresh scope (optional catch binding catch { } supported per ES2019); finally runs on every path (success, after catch, uncaught); an error raised in finally replaces the pending outcome.
• Error builtin: Error(msg) / new Error(msg) → Error-shaped object {name: "Error", message}; e.message reads back through member access.
• Propagation across calls: a throw two call frames deep unwinds into the component's try (pinned by test); uncaught throws surface at flush/dispatch; error boundaries (M1-T13) still capture render-time throws — thrown messages flow through getDerivedStateFromError into the fallback.
• Latent bug fixed while testing: Env::assign — assignments used define (current-scope insert), so assigning from a nested scope (catch block, closure body) shadowed the outer binding instead of updating it. Assignment now walks to the nearest existing binding (JS semantics); define remains the declaration path.

Documented scoping

• No return-completion exists in the expression IR, so the finally-return-override case has no form (documented in js.rs + JOURNAL).
• Internal errors bind as message strings until the full Error-class work; throw new Error(msg) already produces a real Error object.

Tests

crates/r2n-runtime/tests/exceptions.rs — 12 acceptance tests: catch binding (string/number/Error.message), internal-error catchability, finally on all three paths + finally-error override, uncaught propagation at flush, cross-call propagation, nested try + rethrow, optional catch binding, handler-throw at dispatch, boundary interplay.

Suite: 208 tests green; clippy -D warnings; fmt; verify-audit-claims OK. Records updated (CHECKLIST/README/ROADMAP/yaml/toml, M2 6/15 · 60/106; JOURNAL entry 28).