Improve type inference for vector-of-enum constructor

src/Type.cc

@@ -1783,6 +1783,39 @@ BroType* merge_types(const BroType* t1, const BroType* t2)
 	case TYPE_ERROR:
 		return base_type(tg1);
 
+	case TYPE_ENUM:
+		{
+		// Could compare pointers t1 == t2, but maybe there's someone out
+		// there creating clones of the type, so safer to compare name.
+		if ( t1->GetName() != t2->GetName() )
+			{
+			std::string msg = fmt("incompatible enum types: '%s' and '%s'",
+			                      t1->GetName().data(), t2->GetName().data());
+
+			t1->Error(msg.data(), t2);
+			return 0;
+			}
+
+		// Doing a lookup here as a roundabout way of ref-ing t1, without
+		// changing the function params which has t1 as const and also
+		// (potentially) avoiding a pitfall mentioned earlier about clones.
+		auto id = global_scope()->Lookup(t1->GetName().data());
+
+		if ( id && id->AsType() && id->AsType()->Tag() == TYPE_ENUM )
+			// It should make most sense to return the real type here rather
+			// than a copy since it may be redef'd later in parsing.  If we
+			// return a copy, then whoever is using this return value won't
+			// actually see those changes from the redef.
+			return id->AsType()->Ref();
+
+		std::string msg = fmt("incompatible enum types: '%s' and '%s'"
+		                      " ('%s' enum type ID is invalid)",
+		                      t1->GetName().data(), t2->GetName().data(),
+		                      t1->GetName().data());
+		t1->Error(msg.data(), t2);
+		return 0;
+		}
+
 	case TYPE_TABLE:
 		{
 		const IndexType* it1 = (const IndexType*) t1;

testing/btest/Baseline/language.vector-of-enum-mismatch/out

@@ -0,0 +1,2 @@
+error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.vector-of-enum-mismatch/vector-of-enum-mismatch.zeek, line 7 and /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.vector-of-enum-mismatch/vector-of-enum-mismatch.zeek, line 8: incompatible enum types: 'color' and 'number' (enum and enum)
+error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.vector-of-enum-mismatch/vector-of-enum-mismatch.zeek, line 9: inconsistent types in list

testing/btest/Baseline/language.vector-of-enum/out

@@ -0,0 +1 @@
+vector of enum, [Red, Green, Blue]

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

@@ -0,0 +1,9 @@
+# @TEST-EXEC-FAIL: zeek -b %INPUT >out 2>&1
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff out
+
+# Type inference for vector constructor comprised of disparate enum types
+# should raise an error message about the types being incompatible.
+
+type color: enum { Red, Green, Blue };
+type number: enum { One, Two, Three, Four};
+global v = vector(Red, Four, Blue);

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;