fix: object patterns no longer match array values

[chatman-media]

Problem

Arrays are objects in JavaScript, which means typeof [] === 'object'. Because of this, when matching an array value against an object pattern like {}, the runtime matcher entered the object-pattern branch and called Reflect.ownKeys({}).every(…). Since every on an empty iterable always returns true, any array — including [] — matched the empty object pattern {}.

match([]).with({}, () => 'matched').otherwise(() => 'not matched')
// Expected: 'not matched'
// Actual:   'matched'  ← bug

Reported in #309.

Root cause

In src/internals/helpers.ts, matchPattern checks isObject(pattern) first, which is true for plain objects. Inside that block it checks Array.isArray(pattern) to handle tuple patterns, but it did not check whether value is an array before falling through to the plain-object key iteration:

// Before fix — no guard against array values here:
return Reflect.ownKeys(pattern).every((k) => …);

Fix

Add a single Array.isArray(value) guard immediately before the Reflect.ownKeys iteration so that a non-array pattern is rejected when the value happens to be an array:

// After fix:
if (Array.isArray(value)) return false;
return Reflect.ownKeys(pattern).every((k) => …);

Test evidence

New test in tests/objects.test.ts under issue #309:

case	before fix	after fix
match<any>([]).with({}, …)	'matched object pattern'	'no match'
match<any>([1,2,3]).with({}, …)	'matched object pattern'	'no match'
match<any>([1,2,3]).with({ length: 3 }, …)	'matched object pattern'	'no match'
match<any>({}).with({}, …)	'matched' (correct)	'matched' (still correct)
match<any>({ a:1 }).with({ a:1 }, …)	'matched' (correct)	'matched' (still correct)

Full suite: 454/454 tests pass after the fix.

Closes #309