Fix dlang#18518 - Add mixin template members to -X json output

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 2 people

compiler/src/dmd/json.d

@@ -806,6 +806,16 @@ public:
     {
         objectStart();
         jsonProperties(d);
+        if (d.members)
+        {
+            propertyStart("members");
+            arrayStart();
+            foreach (member; (*d.members))
+            {
+                member.accept(this);
+            }
+            arrayEnd();
+        }
         objectEnd();
     }
 

compiler/test/compilable/json18518.d

@@ -0,0 +1,77 @@
+/*
+REQUIRED_ARGS: -Xf- -o-
+PERMUTE_ARGS:
+TEST_OUTPUT:
+----
+[
+ {
+  "kind" : "module",
+  "file" : "compilable$?:windows=\\|/$json18518.d",
+  "members" : [
+   {
+    "kind" : "template",
+    "protection" : "public",
+    "line" : $n$,
+    "char" : $n$,
+    "name" : "Mix",
+    "parameters" : [
+     {
+      "name" : "T",
+      "kind" : "type"
+     }
+    ],
+    "members" : [
+     {
+      "name" : "mixmember",
+      "kind" : "variable",
+      "line" : $n$,
+      "char" : $n$,
+      "type" : "T"
+     }
+    ]
+   },
+   {
+    "name" : "S",
+    "kind" : "struct",
+    "protection" : "public",
+    "line" : $n$,
+    "char" : $n$,
+    "members" : [
+     {
+      "name" : "Mix!int",
+      "kind" : "mixin",
+      "protection" : "public",
+      "line" : $n$,
+      "char" : $n$,
+      "members" : [
+       {
+        "name" : "mixmember",
+        "kind" : "variable",
+        "protection" : "public",
+        "line" : $n$,
+        "char" : $n$,
+        "deco" : "i",
+        "originalType" : "T",
+        "offset" : 0
+       }
+      ]
+     }
+    ]
+   }
+  ]
+ }
+]
+----
+
+https://github.com/dlang/dmd/issues/18518
+*/
+
+mixin template Mix(T)
+{
+    T mixmember;
+}
+
+struct S
+{
+    mixin Mix!int;
+}