From 7c4793f23c971f5305c63f1b343e7f8576f32781 Mon Sep 17 00:00:00 2001
From: mlugg <mlugg@mlugg.co.uk>
Date: Fri, 8 Mar 2024 10:59:32 +0000
Subject: [PATCH] Zcu: remove old decls after scanning namespace

---
 src/Module.zig | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/Module.zig b/src/Module.zig
index 01aa6702e0..f17232c674 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -4103,6 +4103,21 @@ pub fn scanNamespace(
     for (decls) |decl_inst| {
         try scanDecl(&scan_decl_iter, decl_inst);
     }
+
+    if (seen_decls.count() != namespace.decls.count()) {
+        // Do a pass over the namespace contents and remove any decls from the last update
+        // which were removed in this one.
+        var i: usize = 0;
+        while (i < namespace.decls.count()) {
+            const decl_index = namespace.decls.keys()[i];
+            const decl = zcu.declPtr(decl_index);
+            if (!seen_decls.contains(decl.name)) {
+                // We must preserve namespace ordering for @typeInfo.
+                namespace.decls.orderedRemoveAt(i);
+                i -= 1;
+            }
+        }
+    }
 }
 
 const ScanDeclIter = struct {