From 1a20c5b51422c3ed13ee5e53367d6fd6e629385a Mon Sep 17 00:00:00 2001
From: liu fengyun <liu@fengy.me>
Date: Thu, 15 Jun 2017 11:19:03 +0200
Subject: [PATCH 1/2] fix #2749: support implicit resolution of implicit
 function types

---
 compiler/src/dotty/tools/dotc/typer/Implicits.scala | 4 +++-
 compiler/src/dotty/tools/dotc/typer/Typer.scala     | 1 +
 tests/pos/i2749.scala                               | 7 +++++++
 3 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i2749.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Implicits.scala b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
index f0788665ca17..17d922023b17 100644
--- a/compiler/src/dotty/tools/dotc/typer/Implicits.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
@@ -123,7 +123,9 @@ object Implicits {
             record("discarded eligible")
             false
           }
-          else NoViewsAllowed.isCompatible(normalize(ref, pt), pt)
+          else
+            NoViewsAllowed.isCompatible(normalize(ref, pt), pt) ||
+              NoViewsAllowed.isCompatible(ref, pt)  // `pt` could be an implicit function type, check i2749
         }
       }
 
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 974c9786799a..632acca1f00d 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1640,6 +1640,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         if (defn.isImplicitFunctionType(pt) &&
             xtree.isTerm &&
             !untpd.isImplicitClosure(xtree) &&
+            !ctx.mode.is(Mode.ImplicitShadowing) &&
             !ctx.isAfterTyper)
           makeImplicitFunction(xtree, pt)
         else xtree match {
diff --git a/tests/pos/i2749.scala b/tests/pos/i2749.scala
new file mode 100644
index 000000000000..946ae94b52eb
--- /dev/null
+++ b/tests/pos/i2749.scala
@@ -0,0 +1,7 @@
+object Test {
+  val f: implicit (implicit Int => Char) => Boolean = ???
+  implicit val n: Int = 3
+  implicit val g: implicit Int => Char = ???
+
+  f : Boolean
+}

From 9ae3a1f69c797543011d4b5a1a0fc83de625cefa Mon Sep 17 00:00:00 2001
From: liu fengyun <liu@fengy.me>
Date: Fri, 16 Jun 2017 11:23:15 +0200
Subject: [PATCH 2/2] improve the fix to support more general cases

---
 .../src/dotty/tools/dotc/typer/Implicits.scala   |  4 ++--
 tests/pos/i2749.scala                            | 16 ++++++++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/Implicits.scala b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
index 17d922023b17..a9a75735c7e0 100644
--- a/compiler/src/dotty/tools/dotc/typer/Implicits.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
@@ -60,6 +60,7 @@ object Implicits {
 
     /** Return those references in `refs` that are compatible with type `pt`. */
     protected def filterMatching(pt: Type)(implicit ctx: Context): List[Candidate] = track("filterMatching") {
+      val ptNorm = normalize(pt, pt) // `pt` could be implicit function types, check i2749
 
       def refMatches(ref: TermRef)(implicit ctx: Context) = /*ctx.traceIndented(i"refMatches $ref $pt")*/ {
 
@@ -124,8 +125,7 @@ object Implicits {
             false
           }
           else
-            NoViewsAllowed.isCompatible(normalize(ref, pt), pt) ||
-              NoViewsAllowed.isCompatible(ref, pt)  // `pt` could be an implicit function type, check i2749
+            NoViewsAllowed.isCompatible(normalize(ref, pt), ptNorm)
         }
       }
 
diff --git a/tests/pos/i2749.scala b/tests/pos/i2749.scala
index 946ae94b52eb..5d4972421ebb 100644
--- a/tests/pos/i2749.scala
+++ b/tests/pos/i2749.scala
@@ -5,3 +5,19 @@ object Test {
 
   f : Boolean
 }
+
+object Test2 {
+  val f: implicit (implicit Int => Char) => Boolean = ???
+  implicit val s: String = null
+  implicit val g: implicit Int => implicit String => Char = ???
+
+  f : Boolean
+}
+
+object Test3 {
+  val f: implicit (implicit Int => implicit String => Char) => Boolean = ???
+  implicit val n: Int = 3
+  implicit val g: implicit Int => Char = ???
+
+  f : Boolean
+}