From 8e99d2ef8f99c9d9c86b33f7e4751a4cf0b32657 Mon Sep 17 00:00:00 2001
From: Suzanne Millstein <smillst@cs.washington.edu>
Date: Mon, 9 Aug 2021 09:32:17 -0700
Subject: [PATCH 1/2] Fix issue.

---
 .../framework/type/AnnotatedTypeFactory.java           |  7 +++++--
 framework/tests/all-systems/Issue4852.java             | 10 ++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)
 create mode 100644 framework/tests/all-systems/Issue4852.java

diff --git a/framework/src/main/java/org/checkerframework/framework/type/AnnotatedTypeFactory.java b/framework/src/main/java/org/checkerframework/framework/type/AnnotatedTypeFactory.java
index 4471cee719e..76e38eef8ef 100644
--- a/framework/src/main/java/org/checkerframework/framework/type/AnnotatedTypeFactory.java
+++ b/framework/src/main/java/org/checkerframework/framework/type/AnnotatedTypeFactory.java
@@ -4998,7 +4998,8 @@ public List<AnnotatedTypeVariable> order(Collection<AnnotatedTypeVariable> colle
 
   /**
    * Returns the first TypeVariable in {@code collection} that does not lexically contain any other
-   * type in the collection.
+   * type in the collection. Or if all the TypeVariables contain another, then it returns the first
+   * TypeVariable in {@code collection}.
    *
    * @param collection a collection of type variables
    * @return the first TypeVariable in {@code collection} that does not contain any other type in
@@ -5007,7 +5008,9 @@ public List<AnnotatedTypeVariable> order(Collection<AnnotatedTypeVariable> colle
   @SuppressWarnings("interning:not.interned") // must be the same object from collection
   private AnnotatedTypeVariable doesNotContainOthers(
       Collection<? extends AnnotatedTypeVariable> collection) {
+    AnnotatedTypeVariable first = null;
     for (AnnotatedTypeVariable candidate : collection) {
+      first = candidate;
       boolean doesNotContain = true;
       for (AnnotatedTypeVariable other : collection) {
         if (candidate != other && captureScanner.visit(candidate, other.getUnderlyingType())) {
@@ -5019,7 +5022,7 @@ private AnnotatedTypeVariable doesNotContainOthers(
         return candidate;
       }
     }
-    throw new BugInCF("Not found: %s", StringsPlume.join(",", collection));
+    return first;
   }
 
   /**
diff --git a/framework/tests/all-systems/Issue4852.java b/framework/tests/all-systems/Issue4852.java
new file mode 100644
index 00000000000..df423761342
--- /dev/null
+++ b/framework/tests/all-systems/Issue4852.java
@@ -0,0 +1,10 @@
+@SuppressWarnings("all") // Just check for crashes.
+public class Issue4852 {
+  interface Class1<E extends Class1<E, B>, B extends Class1.Class2<E, B>> {
+    abstract class Class2<E extends Class1<E, B>, B extends Class2<E, B>> {}
+  }
+
+  class Class3 {
+    private void f(Class1<?, ?> x) {}
+  }
+}

From 1a51dac7e6e050c6db7dcfb56248035f2f1160a8 Mon Sep 17 00:00:00 2001
From: Suzanne Millstein <smillst@cs.washington.edu>
Date: Thu, 12 Aug 2021 11:21:39 -0700
Subject: [PATCH 2/2] Fix.

---
 .../checkerframework/framework/type/AnnotatedTypeFactory.java | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/framework/src/main/java/org/checkerframework/framework/type/AnnotatedTypeFactory.java b/framework/src/main/java/org/checkerframework/framework/type/AnnotatedTypeFactory.java
index 6596d64323e..3285d2af876 100644
--- a/framework/src/main/java/org/checkerframework/framework/type/AnnotatedTypeFactory.java
+++ b/framework/src/main/java/org/checkerframework/framework/type/AnnotatedTypeFactory.java
@@ -5004,7 +5004,9 @@ private AnnotatedTypeVariable doesNotContainOthers(
       Collection<? extends AnnotatedTypeVariable> collection) {
     AnnotatedTypeVariable first = null;
     for (AnnotatedTypeVariable candidate : collection) {
-      first = candidate;
+      if (first == null) {
+        first = candidate;
+      }
       boolean doesNotContain = true;
       for (AnnotatedTypeVariable other : collection) {
         if (candidate != other && captureScanner.visit(candidate, other.getUnderlyingType())) {