From a519333ebdce3829a593529ff0ffbac413f95362 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Wed, 27 Sep 2017 21:21:47 +0200
Subject: [PATCH 1/4] Fix #3168 Don't insert apply if tree has method type

It would be simply an eta-expansion followed by an application.
As #3168 shows, overloading resolution gets confused by this.
---
 compiler/src/dotty/tools/dotc/typer/Typer.scala | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index a4fe66b932b2..099630757590 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1799,6 +1799,11 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
    */
   def tryInsertApplyOrImplicit(tree: Tree, pt: ProtoType)(fallBack: => Tree)(implicit ctx: Context): Tree = {
 
+    def isMethod(tree: Tree) = tree.tpe match {
+      case ref: TermRef => ref.denot.alternatives.forall(_.info.widen.isInstanceOf[MethodicType])
+      case _ => false
+    }
+
     def isSyntheticApply(tree: Tree): Boolean = tree match {
       case tree: Select => tree.getAttachment(InsertedApply).isDefined
       case Apply(fn, _) => fn.getAttachment(InsertedApply).isDefined
@@ -1821,7 +1826,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         pt.markAsDropped()
         tree
       case _ =>
-        if (isApplyProto(pt) || isSyntheticApply(tree)) tryImplicit
+        if (isApplyProto(pt) || isMethod(tree) || isSyntheticApply(tree)) tryImplicit
         else tryEither(tryApply(_))((_, _) => tryImplicit)
      }
   }

From 9d4e8fd02efe20b029b93379a854e0ed3143a40e Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Wed, 27 Sep 2017 21:23:30 +0200
Subject: [PATCH 2/4] Add test case

 - also rework previous test of #3189 to be a run test, just to make
   sure the problem is solved.
---
 tests/pos/i3168.scala | 14 ++++++++++++++
 tests/pos/i3189.scala |  3 ---
 tests/run/i3189.scala |  9 +++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)
 create mode 100644 tests/pos/i3168.scala
 delete mode 100644 tests/pos/i3189.scala
 create mode 100644 tests/run/i3189.scala

diff --git a/tests/pos/i3168.scala b/tests/pos/i3168.scala
new file mode 100644
index 000000000000..aa4c2e812a75
--- /dev/null
+++ b/tests/pos/i3168.scala
@@ -0,0 +1,14 @@
+object Test {
+  class C {
+    def foo(x: Int) = 1
+    def foo(x: Double) = 2
+  }
+
+  implicit class COps(val x: C) {
+    def foo(x: String) = 3
+  }
+
+  def test: Unit = {
+    (new C).foo("Hello")
+  }
+}
diff --git a/tests/pos/i3189.scala b/tests/pos/i3189.scala
deleted file mode 100644
index ca06bc54af99..000000000000
--- a/tests/pos/i3189.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-class Test[A](action: A => A) {
-  def this() = this(a => a)
-}
\ No newline at end of file
diff --git a/tests/run/i3189.scala b/tests/run/i3189.scala
new file mode 100644
index 000000000000..f74fe7bfc115
--- /dev/null
+++ b/tests/run/i3189.scala
@@ -0,0 +1,9 @@
+class Test[A](action: A => A) {
+  def this() = this(a => a)
+  def go(x: A) = action(x)
+}
+
+object Test extends App {
+  assert(new Test[Int]().go(3) == 3)
+}
+

From a02cbe424e72736b036286c0db2a65c2dee876b4 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Wed, 27 Sep 2017 21:38:43 +0200
Subject: [PATCH 3/4] Another test

This one verifies that we still need the `isSyntheticApply` condition
in the test whether to elide an `apply` insertion attempt.
---
 tests/pos/insertapply.scala | 6 ++++++
 1 file changed, 6 insertions(+)
 create mode 100644 tests/pos/insertapply.scala

diff --git a/tests/pos/insertapply.scala b/tests/pos/insertapply.scala
new file mode 100644
index 000000000000..0a692865c1a7
--- /dev/null
+++ b/tests/pos/insertapply.scala
@@ -0,0 +1,6 @@
+class C {
+  def apply: C
+}
+object Test {
+  (new C)(22)
+}

From c6b65cd846eed415dc6a4b45e5a1d78259799a62 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Thu, 28 Sep 2017 16:02:50 +0200
Subject: [PATCH 4/4] Fix test

---
 tests/neg/insertapply.scala | 6 ++++++
 tests/pos/insertapply.scala | 6 ------
 2 files changed, 6 insertions(+), 6 deletions(-)
 create mode 100644 tests/neg/insertapply.scala
 delete mode 100644 tests/pos/insertapply.scala

diff --git a/tests/neg/insertapply.scala b/tests/neg/insertapply.scala
new file mode 100644
index 000000000000..470e950a7863
--- /dev/null
+++ b/tests/neg/insertapply.scala
@@ -0,0 +1,6 @@
+class C {
+  def apply: C
+}
+object Test {
+  (new C)(22) // error: does not take parameters
+}
diff --git a/tests/pos/insertapply.scala b/tests/pos/insertapply.scala
deleted file mode 100644
index 0a692865c1a7..000000000000
--- a/tests/pos/insertapply.scala
+++ /dev/null
@@ -1,6 +0,0 @@
-class C {
-  def apply: C
-}
-object Test {
-  (new C)(22)
-}