M2-T03: closures & lexical environments (closes #29)

[ncdevshiv]

What

Closes#29. Correct JS closure semantics — not a value snapshot:

letfactory=()=>{letbase="lexical";letread=()=>base;returnread;};letr=factory();letbase="caller";r();// "lexical" — closure's lexical env, NOT the caller's shadowing

• Env frames are Rc<RefCell<...>>: a closure captures its lexical environment by reference (a clone of the shared frame vector). Later writes to captured bindings are visible (n = n + 1 across calls works); the counter pattern is test-pinned.
• Value::Function { params, body, captured }: calls bind params in a child scope of the captured env — lexical scope, not dynamic (a caller's shadowing doesn't leak in).
• Parser gap closures exposed: let/const inside block-bodied arrows was parsed as expression statements — an unbound let at eval time. Real JS closures routinely declare locals; both parsers now lower them to scoped assignments.
• Identity semantics: PartialEq is manual — Function equal by captured-env pointer, Object by Rc::ptr_eq (two closures/objects aren't equal unless the same value).

Verification

5 tests in tests/closures.rs: lexical vs caller shadowing, live writes across calls, nested closures chaining to outer params, cross-scope use, identity distinctness. Suite 181 green; clippy -D warnings clean; fmt clean; audit green. Records: M2 3/15 in progress, overall 57/106.

[ncdevshiv]

What

Closes#29. Correct JS closure semantics — not a value snapshot:

letfactory=()=>{letbase="lexical";letread=()=>base;returnread;};letr=factory();letbase="caller";r();// "lexical" — closure's lexical env, NOT the caller's shadowing

• Env frames are Rc<RefCell<...>>: a closure captures its lexical environment by reference (a clone of the shared frame vector). Later writes to captured bindings are visible (n = n + 1 across calls works); the counter pattern is test-pinned.
• Value::Function { params, body, captured }: calls bind params in a child scope of the captured env — lexical scope, not dynamic (a caller's shadowing doesn't leak in).
• Parser gap closures exposed: let/const inside block-bodied arrows was parsed as expression statements — an unbound let at eval time. Real JS closures routinely declare locals; both parsers now lower them to scoped assignments.
• Identity semantics: PartialEq is manual — Function equal by captured-env pointer, Object by Rc::ptr_eq (two closures/objects aren't equal unless the same value).

Verification

5 tests in tests/closures.rs: lexical vs caller shadowing, live writes across calls, nested closures chaining to outer params, cross-scope use, identity distinctness. Suite 181 green; clippy -D warnings clean; fmt clean; audit green. Records: M2 3/15 in progress, overall 57/106.

[ncdevshiv]

What

Closes#29. Correct JS closure semantics — not a value snapshot:

letfactory=()=>{letbase="lexical";letread=()=>base;returnread;};letr=factory();letbase="caller";r();// "lexical" — closure's lexical env, NOT the caller's shadowing

• Env frames are Rc<RefCell<...>>: a closure captures its lexical environment by reference (a clone of the shared frame vector). Later writes to captured bindings are visible (n = n + 1 across calls works); the counter pattern is test-pinned.
• Value::Function { params, body, captured }: calls bind params in a child scope of the captured env — lexical scope, not dynamic (a caller's shadowing doesn't leak in).
• Parser gap closures exposed: let/const inside block-bodied arrows was parsed as expression statements — an unbound let at eval time. Real JS closures routinely declare locals; both parsers now lower them to scoped assignments.
• Identity semantics: PartialEq is manual — Function equal by captured-env pointer, Object by Rc::ptr_eq (two closures/objects aren't equal unless the same value).

Verification

5 tests in tests/closures.rs: lexical vs caller shadowing, live writes across calls, nested closures chaining to outer params, cross-scope use, identity distinctness. Suite 181 green; clippy -D warnings clean; fmt clean; audit green. Records: M2 3/15 in progress, overall 57/106.

[ncdevshiv]

What

Closes#29. Correct JS closure semantics — not a value snapshot:

letfactory=()=>{letbase="lexical";letread=()=>base;returnread;};letr=factory();letbase="caller";r();// "lexical" — closure's lexical env, NOT the caller's shadowing

• Env frames are Rc<RefCell<...>>: a closure captures its lexical environment by reference (a clone of the shared frame vector). Later writes to captured bindings are visible (n = n + 1 across calls works); the counter pattern is test-pinned.
• Value::Function { params, body, captured }: calls bind params in a child scope of the captured env — lexical scope, not dynamic (a caller's shadowing doesn't leak in).
• Parser gap closures exposed: let/const inside block-bodied arrows was parsed as expression statements — an unbound let at eval time. Real JS closures routinely declare locals; both parsers now lower them to scoped assignments.
• Identity semantics: PartialEq is manual — Function equal by captured-env pointer, Object by Rc::ptr_eq (two closures/objects aren't equal unless the same value).

Verification

5 tests in tests/closures.rs: lexical vs caller shadowing, live writes across calls, nested closures chaining to outer params, cross-scope use, identity distinctness. Suite 181 green; clippy -D warnings clean; fmt clean; audit green. Records: M2 3/15 in progress, overall 57/106.

[ncdevshiv]

What

Closes#29. Correct JS closure semantics — not a value snapshot:

letfactory=()=>{letbase="lexical";letread=()=>base;returnread;};letr=factory();letbase="caller";r();// "lexical" — closure's lexical env, NOT the caller's shadowing

• Env frames are Rc<RefCell<...>>: a closure captures its lexical environment by reference (a clone of the shared frame vector). Later writes to captured bindings are visible (n = n + 1 across calls works); the counter pattern is test-pinned.
• Value::Function { params, body, captured }: calls bind params in a child scope of the captured env — lexical scope, not dynamic (a caller's shadowing doesn't leak in).
• Parser gap closures exposed: let/const inside block-bodied arrows was parsed as expression statements — an unbound let at eval time. Real JS closures routinely declare locals; both parsers now lower them to scoped assignments.
• Identity semantics: PartialEq is manual — Function equal by captured-env pointer, Object by Rc::ptr_eq (two closures/objects aren't equal unless the same value).

Verification

5 tests in tests/closures.rs: lexical vs caller shadowing, live writes across calls, nested closures chaining to outer params, cross-scope use, identity distinctness. Suite 181 green; clippy -D warnings clean; fmt clean; audit green. Records: M2 3/15 in progress, overall 57/106.

[ncdevshiv]

What

Closes#29. Correct JS closure semantics — not a value snapshot:

letfactory=()=>{letbase="lexical";letread=()=>base;returnread;};letr=factory();letbase="caller";r();// "lexical" — closure's lexical env, NOT the caller's shadowing

• Env frames are Rc<RefCell<...>>: a closure captures its lexical environment by reference (a clone of the shared frame vector). Later writes to captured bindings are visible (n = n + 1 across calls works); the counter pattern is test-pinned.
• Value::Function { params, body, captured }: calls bind params in a child scope of the captured env — lexical scope, not dynamic (a caller's shadowing doesn't leak in).
• Parser gap closures exposed: let/const inside block-bodied arrows was parsed as expression statements — an unbound let at eval time. Real JS closures routinely declare locals; both parsers now lower them to scoped assignments.
• Identity semantics: PartialEq is manual — Function equal by captured-env pointer, Object by Rc::ptr_eq (two closures/objects aren't equal unless the same value).

Verification

5 tests in tests/closures.rs: lexical vs caller shadowing, live writes across calls, nested closures chaining to outer params, cross-scope use, identity distinctness. Suite 181 green; clippy -D warnings clean; fmt clean; audit green. Records: M2 3/15 in progress, overall 57/106.

[ncdevshiv]

What

Closes#29. Correct JS closure semantics — not a value snapshot:

letfactory=()=>{letbase="lexical";letread=()=>base;returnread;};letr=factory();letbase="caller";r();// "lexical" — closure's lexical env, NOT the caller's shadowing

• Env frames are Rc<RefCell<...>>: a closure captures its lexical environment by reference (a clone of the shared frame vector). Later writes to captured bindings are visible (n = n + 1 across calls works); the counter pattern is test-pinned.
• Value::Function { params, body, captured }: calls bind params in a child scope of the captured env — lexical scope, not dynamic (a caller's shadowing doesn't leak in).
• Parser gap closures exposed: let/const inside block-bodied arrows was parsed as expression statements — an unbound let at eval time. Real JS closures routinely declare locals; both parsers now lower them to scoped assignments.
• Identity semantics: PartialEq is manual — Function equal by captured-env pointer, Object by Rc::ptr_eq (two closures/objects aren't equal unless the same value).

Verification

5 tests in tests/closures.rs: lexical vs caller shadowing, live writes across calls, nested closures chaining to outer params, cross-scope use, identity distinctness. Suite 181 green; clippy -D warnings clean; fmt clean; audit green. Records: M2 3/15 in progress, overall 57/106.

[ncdevshiv]

What

Closes#29. Correct JS closure semantics — not a value snapshot:

letfactory=()=>{letbase="lexical";letread=()=>base;returnread;};letr=factory();letbase="caller";r();// "lexical" — closure's lexical env, NOT the caller's shadowing

• Env frames are Rc<RefCell<...>>: a closure captures its lexical environment by reference (a clone of the shared frame vector). Later writes to captured bindings are visible (n = n + 1 across calls works); the counter pattern is test-pinned.
• Value::Function { params, body, captured }: calls bind params in a child scope of the captured env — lexical scope, not dynamic (a caller's shadowing doesn't leak in).
• Parser gap closures exposed: let/const inside block-bodied arrows was parsed as expression statements — an unbound let at eval time. Real JS closures routinely declare locals; both parsers now lower them to scoped assignments.
• Identity semantics: PartialEq is manual — Function equal by captured-env pointer, Object by Rc::ptr_eq (two closures/objects aren't equal unless the same value).

Verification

5 tests in tests/closures.rs: lexical vs caller shadowing, live writes across calls, nested closures chaining to outer params, cross-scope use, identity distinctness. Suite 181 green; clippy -D warnings clean; fmt clean; audit green. Records: M2 3/15 in progress, overall 57/106.