Improve type inference for vector-of-enum constructor

testing/btest/language/vector-of-enum.zeek

@@ -0,0 +1,9 @@
+# @TEST-EXEC: zeek -b %INPUT >out
+# @TEST-EXEC: btest-diff out
+
+# Type inference for vector constructor comprised of enums should work fine
+# (previously the internal merge_types code did not handle enums).
+
+type color: enum { Red, Green, Blue };
+global v = vector(Red, Green, Blue);
+print type_name(v), v;