Allow 16 arguments, and handle going over that correctly.

test/method/arity.wren

@@ -10,6 +10,12 @@ class Foo {
   method(a, b, c, d, e, f, g, h) { a + b + c + d + e + f + g + h }
   method(a, b, c, d, e, f, g, h, i) { a + b + c + d + e + f + g + h + i }
   method(a, b, c, d, e, f, g, h, i, j) { a + b + c + d + e + f + g + h + i + j }
+  method(a, b, c, d, e, f, g, h, i, j, k) { a + b + c + d + e + f + g + h + i + j + k}
+  method(a, b, c, d, e, f, g, h, i, j, k, l) { a + b + c + d + e + f + g + h + i + j + k + l}
+  method(a, b, c, d, e, f, g, h, i, j, k, l, m) { a + b + c + d + e + f + g + h + i + j + k + l + m}
+  method(a, b, c, d, e, f, g, h, i, j, k, l, m, n) { a + b + c + d + e + f + g + h + i + j + k + l + m + n}
+  method(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) { a + b + c + d + e + f + g + h + i + j + k + l + m + n + o}
+  method(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p) { a + b + c + d + e + f + g + h + i + j + k + l + m + n + o + p}
 }
 
 var foo = Foo.new
@@ -24,3 +30,9 @@ io.write(foo.method(1, 2, 3, 4, 5, 6, 7)) // expect: 28
 io.write(foo.method(1, 2, 3, 4, 5, 6, 7, 8)) // expect: 36
 io.write(foo.method(1, 2, 3, 4, 5, 6, 7, 8, 9)) // expect: 45
 io.write(foo.method(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)) // expect: 55
+io.write(foo.method(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11)) // expect: 66
+io.write(foo.method(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)) // expect: 78
+io.write(foo.method(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)) // expect: 91
+io.write(foo.method(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)) // expect: 105
+io.write(foo.method(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)) // expect: 120
+io.write(foo.method(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)) // expect: 136

test/method/subscript_too_many_arguments.wren

@@ -0,0 +1,2 @@
+var list = []
+list[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] // expect error

test/method/too_many_arguments.wren

@@ -0,0 +1 @@
+io.write(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17) // expect error

test/method/too_many_parameters.wren

@@ -0,0 +1,4 @@
+class Foo {
+  // 17 parameters.
+  method(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q) { "!" } // expect error
+}