From e3d91dcef2bae94463ecca14a0600e662063d130 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Wed, 5 Feb 2020 10:29:54 +0100
Subject: [PATCH] Fix #8181: Fix isExprIntro predicate to exclude `extension
 on`

---
 compiler/src/dotty/tools/dotc/parsing/Parsers.scala | 4 +++-
 tests/pos/i8181.scala                               | 6 ++++++
 2 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i8181.scala

diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
index 166d44ecb4ff..ef68c570f3f0 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -213,7 +213,9 @@ object Parsers {
     } && !in.isSoftModifierInModifierPosition
 
     def isExprIntro: Boolean =
-      in.canStartExprTokens.contains(in.token) && !in.isSoftModifierInModifierPosition
+      in.canStartExprTokens.contains(in.token)
+      && !in.isSoftModifierInModifierPosition
+      && !(isIdent(nme.extension) && followingIsExtension())
 
     def isDefIntro(allowedMods: BitSet, excludedSoftModifiers: Set[TermName] = Set.empty): Boolean =
       in.token == AT
diff --git a/tests/pos/i8181.scala b/tests/pos/i8181.scala
new file mode 100644
index 000000000000..6dbf2b74660f
--- /dev/null
+++ b/tests/pos/i8181.scala
@@ -0,0 +1,6 @@
+object Main:
+  def main(args: Array[String]): Unit =
+    extension on (a: AnyRef):
+      def putout(): Unit = println(a)
+
+    "blub".putout()