From 4271677e154ed330445117b8e5e2aec43820cec0 Mon Sep 17 00:00:00 2001
From: William Roy <wroy@proton.me>
Date: Sat, 31 Oct 2026 04:54:46 -0400
Subject: [PATCH] fix: Paste tokens in arguments of nested macros (#1062)

---
 .../Parsing/Impl/DefinesStreamProxy.cpp       | 20 ++++++++++++++++++-
 .../Parsing/Impl/DefinesStreamProxyTests.cpp  | 20 +++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/src/Parser/Parsing/Impl/DefinesStreamProxy.cpp b/src/Parser/Parsing/Impl/DefinesStreamProxy.cpp
index c2e20fb29..db3244476 100644
--- a/src/Parser/Parsing/Impl/DefinesStreamProxy.cpp
+++ b/src/Parser/Parsing/Impl/DefinesStreamProxy.cpp
@@ -7,6 +7,7 @@
 #include "Parsing/Simple/SimpleExpressionInterpreter.h"
 #include "Utils/StringUtils.h"
 
+#include <algorithm>
 #include <regex>
 #include <sstream>
 #include <utility>
@@ -879,8 +880,25 @@ void DefinesStreamProxy::ExpandMacro(ParserLine& line,
                                      const Define* macro,
                                      const std::vector<std::string>& parameterValues)
 {
+    std::vector<std::string> pastedValues;
+    const auto* values = &parameterValues;
+    if (std::ranges::any_of(parameterValues,
+                            [](const std::string& value)
+                            {
+                                return value.find("##") != std::string::npos;
+                            }))
+    {
+        pastedValues = parameterValues;
+        for (auto& value : pastedValues)
+        {
+            if (value.find("##") != std::string::npos)
+                ProcessTokenPastingOperators(line, linePos, value);
+        }
+        values = &pastedValues;
+    }
+
     std::ostringstream rawOutput;
-    InsertMacroParameters(rawOutput, macro, parameterValues);
+    InsertMacroParameters(rawOutput, macro, *values);
 
     std::string str = rawOutput.str();
     ProcessNestedMacros(line, linePos, callstack, str);
diff --git a/test/ParserTests/Parsing/Impl/DefinesStreamProxyTests.cpp b/test/ParserTests/Parsing/Impl/DefinesStreamProxyTests.cpp
index a3a776467..be5e48636 100644
--- a/test/ParserTests/Parsing/Impl/DefinesStreamProxyTests.cpp
+++ b/test/ParserTests/Parsing/Impl/DefinesStreamProxyTests.cpp
@@ -1127,6 +1127,26 @@ namespace test::parsing::impl::defines_stream_proxy
         REQUIRE(proxy.Eof());
     }
 
+    TEST_CASE("DefinesStreamProxy: Can use token-pasting operator in arguments of nested macros", "[parsing][parsingstream]")
+    {
+        const std::vector<std::string> lines{
+            "#define s(t) #t",
+            "#define tag(id) s(id##_tag)",
+            "#define outer(list) tag(list##_member0)",
+            "outer(party)",
+        };
+
+        MockParserLineStream mockStream(lines);
+        DefinesStreamProxy proxy(&mockStream);
+
+        ExpectLine(&proxy, 1, "");
+        ExpectLine(&proxy, 2, "");
+        ExpectLine(&proxy, 3, "");
+        ExpectLine(&proxy, 4, "\"party_member0_tag\"");
+
+        REQUIRE(proxy.Eof());
+    }
+
     TEST_CASE("DefinesStreamProxy: Can use token-pasting operator with string and stringization outside macro", "[parsing][parsingstream]")
     {
         const std::vector<std::string> lines{