From 5c36cb810967bf20f1a75d91d4505b660365cd8b Mon Sep 17 00:00:00 2001
From: Fengyun Liu <liu@fengy.me>
Date: Mon, 23 Oct 2017 17:24:33 +0200
Subject: [PATCH 1/2] Revert "Fix #3348: use a new typeState in inferView"

---
 compiler/src/dotty/tools/dotc/typer/Typer.scala |  7 ++-----
 tests/neg/i3348.scala                           | 10 ----------
 2 files changed, 2 insertions(+), 15 deletions(-)
 delete mode 100644 tests/neg/i3348.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 5757facc0029..095ccd29bdfe 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -2224,11 +2224,9 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         if (isFullyDefined(wtp, force = ForceDegree.all) &&
             ctx.typerState.constraint.ne(prevConstraint)) adapt(tree, pt)
         else err.typeMismatch(tree, pt, failure)
-      if (ctx.mode.is(Mode.ImplicitsEnabled)) {
-        val nestedCtx = ctx.fresh.setNewTyperState()
-        inferView(tree, pt)(nestedCtx) match {
+      if (ctx.mode.is(Mode.ImplicitsEnabled))
+        inferView(tree, pt) match {
           case SearchSuccess(inferred, _, _, _) =>
-            nestedCtx.typerState.commit()
             adapt(inferred, pt)(ctx.retractMode(Mode.ImplicitsEnabled))
           case failure: SearchFailure =>
             if (pt.isInstanceOf[ProtoType] && !failure.isInstanceOf[AmbiguousImplicits])
@@ -2238,7 +2236,6 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
               tree
             else recover(failure)
         }
-      }
       else recover(NoImplicitMatches)
     }
 
diff --git a/tests/neg/i3348.scala b/tests/neg/i3348.scala
deleted file mode 100644
index d5a9c0566938..000000000000
--- a/tests/neg/i3348.scala
+++ /dev/null
@@ -1,10 +0,0 @@
-class Test {
-  import Test.test
-  "Hello".toto     // error
-}
-
-object Test {
-  def test = {
-    implicitly[collection.generic.CanBuildFrom[List[Int], Int, List[Int]]]
-  }
-}

From 97ea776dcf4688b48f387f1a8839a25c2768fc8b Mon Sep 17 00:00:00 2001
From: liu fengyun <liu@fengy.me>
Date: Tue, 24 Oct 2017 11:18:02 +0200
Subject: [PATCH 2/2] Fix #3348: remove assertion as completion can happen in
 inferImplicit

---
 compiler/src/dotty/tools/dotc/typer/Implicits.scala |  2 --
 tests/neg/i3348.scala                               | 10 ++++++++++
 2 files changed, 10 insertions(+), 2 deletions(-)
 create mode 100644 tests/neg/i3348.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Implicits.scala b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
index 14da2a95a23a..657f10564787 100644
--- a/compiler/src/dotty/tools/dotc/typer/Implicits.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
@@ -708,7 +708,6 @@ trait Implicits { self: Typer =>
     assert(!ctx.isAfterTyper,
       if (argument.isEmpty) i"missing implicit parameter of type $pt after typer"
       else i"type error: ${argument.tpe} does not conform to $pt${err.whyNoMatchStr(argument.tpe, pt)}")
-    val prevConstr = ctx.typerState.constraint
     trace(s"search implicit ${pt.show}, arg = ${argument.show}: ${argument.tpe.show}", implicits, show = true) {
       assert(!pt.isInstanceOf[ExprType])
       val isearch =
@@ -737,7 +736,6 @@ trait Implicits { self: Typer =>
           }
           else result
         case _ =>
-          assert(prevConstr eq ctx.typerState.constraint)
           result
       }
     }
diff --git a/tests/neg/i3348.scala b/tests/neg/i3348.scala
new file mode 100644
index 000000000000..34ae282074f6
--- /dev/null
+++ b/tests/neg/i3348.scala
@@ -0,0 +1,10 @@
+class Test {
+  import Test.test
+  "Hello".toto
+}
+
+object Test {
+  def test = {
+    implicitly[collection.generic.CanBuildFrom[List[Int], Int, List[Int]]]
+  }
+}