Handle Array.with_capacity with negative sizes

This adds an explicit check in Array.with_capacity to disallow negative
sizes, instead of relying on the raw allocation failing.

Changelog: fixed

std/src/std/array.inko

@@ -117,11 +117,17 @@ class builtin Array[T] {
   # Returns a new `Array` with enough space for at least `amount` values.
   #
   # The actual capacity may be greater than the given value.
-  fn pub static with_capacity(amount: Int) -> Array[T] {
+  #
+  # # Panics
+  #
+  # This method panics of `size` if less than zero.
+  fn pub static with_capacity(size: Int) -> Array[T] {
+    if size < 0 { panic('The capacity must be greater than or equal to zero') }
+
     let buffer = alloc_imp
-      .resize(0x0 as Pointer[UInt8], size: amount * VALUE_SIZE)
+      .resize(0x0 as Pointer[UInt8], size: size * VALUE_SIZE)
 
-    Array { @size = 0, @capacity = amount, @buffer = buffer }
+    Array { @size = 0, @capacity = size, @buffer = buffer }
   }
 
   # Returns an array filled with a certain amount of values.

std/test/std/test_array.inko

@@ -46,6 +46,10 @@ fn pub tests(t: mut Tests) {
     t.equal(ary2.capacity, 2)
   }
 
+  t.panic('Array.with_capacity with an invalid size') fn {
+    Array.with_capacity(-4) as Array[Int]
+  }
+
   t.test('Array.filled') fn (t) {
     t.equal(Array.filled(with: 1, times: 0), [])
     t.equal(Array.filled(with: 1, times: 1), [1])