From 30fa1ad3b0fd9a47f63382d1213268d77bd88ad6 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Wed, 8 Jan 2020 11:40:47 +0100
Subject: [PATCH] Fix #7863: Handle type lambda trees in inlined code

---
 compiler/src/dotty/tools/dotc/typer/Inliner.scala | 4 +++-
 tests/pos/i7863.scala                             | 5 +++++
 2 files changed, 8 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i7863.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Inliner.scala b/compiler/src/dotty/tools/dotc/typer/Inliner.scala
index 70861d4be87c..a1315dcc0d16 100644
--- a/compiler/src/dotty/tools/dotc/typer/Inliner.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Inliner.scala
@@ -439,7 +439,9 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
         paramProxy(param.typeRef) = adaptToPrefix(param.typeRef)
     case tpe: NamedType
     if tpe.symbol.is(Param) && tpe.symbol.owner == inlinedMethod && !paramProxy.contains(tpe) =>
-      paramProxy(tpe) = paramBinding(tpe.name)
+      paramBinding.get(tpe.name) match
+        case Some(bound) => paramProxy(tpe) = bound
+        case _ =>  // can happen for params bound by type-lambda trees.
     case _ =>
   }
 
diff --git a/tests/pos/i7863.scala b/tests/pos/i7863.scala
new file mode 100644
index 000000000000..bd33979ef6b2
--- /dev/null
+++ b/tests/pos/i7863.scala
@@ -0,0 +1,5 @@
+def f[F[_]] = ()
+
+inline def g = f[[R] =>> Int => R]
+
+val a = g
\ No newline at end of file