From 59ea176b30fbb7af725707a64fe90574c8f47f33 Mon Sep 17 00:00:00 2001
From: Guillaume Martres <smarter@ubuntu.com>
Date: Mon, 2 Dec 2019 18:47:26 +0100
Subject: [PATCH] Fix #7602: Avoid infinite loop with anonymous projection

`Type#findMember` has very careful logic for doing prefix substitution
with a recursive type, but it turns out we don't need to run any of that
if the prefix is already correct, and it avoids infinite loops in the
added testcase.
---
 compiler/src/dotty/tools/dotc/core/Types.scala | 1 +
 tests/pos/i7602.scala                          | 7 +++++++
 2 files changed, 8 insertions(+)
 create mode 100644 tests/pos/i7602.scala

diff --git a/compiler/src/dotty/tools/dotc/core/Types.scala b/compiler/src/dotty/tools/dotc/core/Types.scala
index 7f1554c3dbec..25289c455127 100644
--- a/compiler/src/dotty/tools/dotc/core/Types.scala
+++ b/compiler/src/dotty/tools/dotc/core/Types.scala
@@ -614,6 +614,7 @@ object Types {
       }
       def goRec(tp: RecType) =
         if (tp.parent == null) NoDenotation
+        else if (tp eq pre) go(tp.parent)
         else {
           //println(s"find member $pre . $name in $tp")
 
diff --git a/tests/pos/i7602.scala b/tests/pos/i7602.scala
new file mode 100644
index 000000000000..0a380efc9d79
--- /dev/null
+++ b/tests/pos/i7602.scala
@@ -0,0 +1,7 @@
+object Test {
+  type X[T] = ({ type F[_]; type R = F[T]})#R
+
+  trait Monad[F[_]]
+  type of[M[_[_]], T] = ({ type F[_]; type R = (given M[F]) => F[T]})#R
+  def foo(a: of[Monad, String]) = ???
+}