add highlight tests for connections

grammar.js

@@ -73,6 +73,8 @@ module.exports = grammar({
         )
       ),
 
+    _dash: ($) => token.immediate("-"),
+
     label: ($) => choice($.string, $._unquoted_string),
 
     attr_value: ($) => seq(spaces, choice($.string, $._unquoted_string)),
@@ -175,8 +177,6 @@ module.exports = grammar({
 
     arrow: ($) => choice(/-+>/, /--+/, /<-+/, /<-+>/),
 
-    _dash: ($) => token.immediate("-"),
-
     dot: ($) => token.immediate("."),
 
     _unquoted_string: ($) => token.immediate(/[^'"`\n;{}]+/),

src/grammar.json

@@ -366,6 +366,13 @@
         }
       ]
     },
+    "_dash": {
+      "type": "IMMEDIATE_TOKEN",
+      "content": {
+        "type": "STRING",
+        "value": "-"
+      }
+    },
     "label": {
       "type": "CHOICE",
       "members": [
@@ -1024,13 +1031,6 @@
         }
       ]
     },
-    "_dash": {
-      "type": "IMMEDIATE_TOKEN",
-      "content": {
-        "type": "STRING",
-        "value": "-"
-      }
-    },
     "dot": {
       "type": "IMMEDIATE_TOKEN",
       "content": {

test/highlight/connection.d2

@@ -0,0 +1,33 @@
+a <- b <-> c -- d -> e
+# <- variable
+# ^ operator
+#    ^ variable
+#      ^ operator
+#          ^ variable
+#            ^ operator
+#               ^ variable
+#                 ^ operator
+#                    ^ variable
+
+a ----- b
+# ^ operator
+
+a ----> b
+# ^ operator
+
+a <---- b
+# ^ operator
+
+a <---> b
+# ^ operator
+
+a.b.c --> d.e
+# <- constant
+# ^ constant
+#   ^ variable
+#     ^ operator
+#         ^ constant
+#           ^ variable
+
+
+