parser: fix type_only fns starting with varargs

vlib/v/parser/fn.v

@@ -359,7 +359,7 @@ fn (mut p Parser) fn_args() ([]table.Arg, bool) {
 	mut args := []table.Arg{}
 	mut is_variadic := false
 	// `int, int, string` (no names, just types)
-	types_only := p.tok.kind in [.amp, .and] || (p.peek_tok.kind == .comma && p.table.known_type(p.tok.lit)) ||
+	types_only := p.tok.kind in [.amp, .and, .ellipsis] || (p.peek_tok.kind == .comma && p.table.known_type(p.tok.lit)) ||
 		p.peek_tok.kind == .rpar
 	// TODO copy pasta, merge 2 branches
 	if types_only {

vlib/v/tests/interop_test.v

@@ -0,0 +1,16 @@
+// Not real external functions, so we won't call them
+// We just want to make sure they compile
+
+struct Foo {}
+
+fn C.a(a string, b int) f32
+fn C.b(a &voidptr)
+fn C.c(a string, b ...string) string
+fn C.d(a ...int)
+
+fn JS.e(a string, b ...string) int
+fn JS.f(a &Foo) // TODO: Should this be allowed?
+
+fn C.g(string, ...int)
+fn C.h(&int)
+fn JS.i(...string)