5 files changed, 19 insertions, 0 deletions
diff --git a/test/Modules/Inputs/PR20786/TBranchProxy.h b/test/Modules/Inputs/PR20786/TBranchProxy.h
new file mode 100644
index 000000000000..91f3730c3b88
--- /dev/null
+++ b/test/Modules/Inputs/PR20786/TBranchProxy.h
@@ -0,0 +1,2 @@
+#include "random.h"
+#include "TFormula.h"
diff --git a/test/Modules/Inputs/PR20786/TFormula.h b/test/Modules/Inputs/PR20786/TFormula.h
new file mode 100644
index 000000000000..316e3ad7222b
--- /dev/null
+++ b/test/Modules/Inputs/PR20786/TFormula.h
@@ -0,0 +1 @@
+#include "TMath.h"
diff --git a/test/Modules/Inputs/PR20786/TMath.h b/test/Modules/Inputs/PR20786/TMath.h
new file mode 100644
index 000000000000..b7dba620f7d1
--- /dev/null
+++ b/test/Modules/Inputs/PR20786/TMath.h
@@ -0,0 +1 @@
+#include "random.h"
diff --git a/test/Modules/Inputs/PR20786/module.modulemap b/test/Modules/Inputs/PR20786/module.modulemap
new file mode 100644
index 000000000000..daf78cd0cd3f
--- /dev/null
+++ b/test/Modules/Inputs/PR20786/module.modulemap
@@ -0,0 +1,3 @@
+module TMath { header "TMath.h" }
+module TFormula { header "TFormula.h" }
+module TBranchProxy { header "TBranchProxy.h" }
diff --git a/test/Modules/Inputs/PR20786/random.h b/test/Modules/Inputs/PR20786/random.h
new file mode 100644
index 000000000000..86a7d83c19c0
--- /dev/null
+++ b/test/Modules/Inputs/PR20786/random.h
@@ -0,0 +1,12 @@
+namespace std {
+  template<typename> struct mersenne_twister_engine {
+    friend bool operator==(const mersenne_twister_engine &,
+                           const mersenne_twister_engine &) {
+      return false;
+    }
+  };
+  struct random_device {
+    mersenne_twister_engine<int> mt; // require complete type
+  };
+}
+