diff --git a/test/async/jvm/toughtype.scala b/test/async/jvm/toughtype.scala
index 939d0647e985..9587afa35f19 100644
--- a/test/async/jvm/toughtype.scala
+++ b/test/async/jvm/toughtype.scala
@@ -199,7 +199,7 @@ package scala.async.run.toughtype {
       }
 
       object FunDep {
-        implicit def `Something to do with List`[W, S, R](implicit funDep: FunDep[W, S, R]) =
+        implicit def `Something to do with List`[W, S, R](implicit funDep: FunDep[W, S, R]): FunDep[W,List[S],W] =
           new FunDep[W, List[S], W] {
             def method(w: W, l: List[S]) = async {
               val it = l.iterator
diff --git a/test/files/jvm/future-spec/main.scala b/test/files/jvm/future-spec/main.scala
index 411a6333992f..dda7cfbb4e47 100644
--- a/test/files/jvm/future-spec/main.scala
+++ b/test/files/jvm/future-spec/main.scala
@@ -17,9 +17,10 @@ object Test {
 }
 
 trait Features {
-  implicit def implicitously = scala.language.implicitConversions
-  implicit def reflectively  = scala.language.reflectiveCalls
-  implicit def postulously   = scala.language.postfixOps
+  import languageFeature._
+  implicit def implicitously: implicitConversions = scala.language.implicitConversions
+  implicit def reflectively: reflectiveCalls      = scala.language.reflectiveCalls
+  implicit def postulously: postfixOps            = scala.language.postfixOps
 }
 
 
@@ -40,7 +41,9 @@ trait MinimalScalaTest extends Output with Features with Vigil {
     if (throwables.nonEmpty) println(buffer.toString)
   }
 
-  implicit def stringops(s: String) = new {
+  type Ops = AnyRef{def should[U](snippets: => U): U; def in[U](snippet: => U): scala.collection.mutable.IndexedSeq[_ >: Char with Throwable] with scala.collection.mutable.AbstractSeq[_ >: Char with Throwable] with scala.collection.mutable.Growable[Char with Throwable] with java.io.Serializable}
+
+  implicit def stringops(s: String): Ops = new {
 
     def should[U](snippets: => U) = {
       bufferPrintln(s + " should:")
@@ -62,7 +65,8 @@ trait MinimalScalaTest extends Output with Features with Vigil {
 
   }
 
-  implicit def objectops(obj: Any) = new {
+  type OOps = AnyRef{def mustBe(other: Any): Unit; def mustEqual(other: Any): Unit}
+  implicit def objectops(obj: Any): OOps = new {
 
     def mustBe(other: Any) = assert(obj == other, s"$obj is not $other")
     def mustEqual(other: Any) = mustBe(other)
diff --git a/test/files/jvm/interpreter.check b/test/files/jvm/interpreter.check
index 3acf90e25db0..2e9430f729c4 100644
--- a/test/files/jvm/interpreter.check
+++ b/test/files/jvm/interpreter.check
@@ -87,6 +87,8 @@ scala> case class Bar(n: Int)
 class Bar
 
 scala> implicit def foo2bar(foo: Foo) = Bar(foo.n)
+                    ^
+       warning: Implicit definition should have explicit type (inferred Bar)
 warning: 1 feature warning; for details, enable `:setting -feature` or `:replay -feature`
 def foo2bar(foo: Foo): Bar
 
diff --git a/test/files/jvm/scala-concurrent-tck.scala b/test/files/jvm/scala-concurrent-tck.scala
index d8eafde41b16..3633582cb376 100644
--- a/test/files/jvm/scala-concurrent-tck.scala
+++ b/test/files/jvm/scala-concurrent-tck.scala
@@ -1055,7 +1055,7 @@ class ExecutionContextPrepare extends TestBase {
       delegate.reportFailure(t)
   }
 
-  implicit val ec = new PreparingExecutionContext
+  implicit val ec: ExecutionContext = new PreparingExecutionContext
 
   def testOnComplete(): Unit = once {
     done =>
diff --git a/test/files/neg/implicit-log.scala b/test/files/neg/implicit-log.scala
index f77085e3c2af..7af20610f64d 100644
--- a/test/files/neg/implicit-log.scala
+++ b/test/files/neg/implicit-log.scala
@@ -37,8 +37,8 @@ object Test1579 {
   class Query[E](val value: E)
   class Invoker(q: Any) { val foo = null }
 
-  implicit def unwrap[C](q: Query[C]) = q.value
-  implicit def invoker(q: Query[Column]) = new Invoker(q)
+  implicit def unwrap[C](q: Query[C]): C = q.value
+  implicit def invoker(q: Query[Column]): Invoker = new Invoker(q)
 
   val q = new Query(new Column)
   q.foo
@@ -50,9 +50,9 @@ object Test1625 {
     def unwrap() = x
   }
 
-  implicit def byName[A](x: => A) = new Wrapped(x)
+  implicit def byName[A](x: => A): Wrapped = new Wrapped(x)
 
-  implicit def byVal[A](x: A) = x
+  implicit def byVal[A](x: A): A = x
 
   def main(args: Array[String]) = {
 
diff --git a/test/files/neg/implicits.check b/test/files/neg/implicits.check
index 2eb03eb5f3db..6bcdf6c81285 100644
--- a/test/files/neg/implicits.check
+++ b/test/files/neg/implicits.check
@@ -16,4 +16,11 @@ implicits.scala:47: error: type mismatch;
 implicits.scala:59: error: could not find implicit value for parameter x: Nothing
   foo {
       ^
+implicits.scala:34: warning: Implicit definition should have explicit type (inferred T)
+  implicit def select[T](t: HSome[T,_]) = t.head
+               ^
+implicits.scala:35: warning: Implicit definition should have explicit type (inferred L)
+  implicit def selectTail[L](t: HSome[_,L]) = t.tail
+               ^
+2 warnings
 4 errors
diff --git a/test/files/neg/override-final-implicit.check b/test/files/neg/override-final-implicit.check
index d46efa1acb52..d5e546078794 100644
--- a/test/files/neg/override-final-implicit.check
+++ b/test/files/neg/override-final-implicit.check
@@ -1,5 +1,9 @@
+override-final-implicit.scala:6: warning: Implicit definition should have explicit type (inferred Test.this.FooExtender)
+  override implicit def FooExtender(foo: String) = super.FooExtender(foo)
+                        ^
 override-final-implicit.scala:6: error: cannot override final member:
 final implicit def FooExtender(foo: String): Test.this.FooExtender (defined in class Implicits)
   override implicit def FooExtender(foo: String) = super.FooExtender(foo)
                         ^
+1 warning
 1 error
diff --git a/test/files/neg/private-implicit-class.check b/test/files/neg/private-implicit-class.check
index 31ddc9a023ab..1578f9102325 100644
--- a/test/files/neg/private-implicit-class.check
+++ b/test/files/neg/private-implicit-class.check
@@ -1,4 +1,8 @@
 private-implicit-class.scala:6: error: method BarExtender in class ImplicitsPrivate cannot be accessed as a member of ImplicitsPrivate from class TestPrivate
   override implicit def BarExtender(bar: Int) = super.BarExtender(bar) // error
                                                       ^
+private-implicit-class.scala:6: warning: Implicit definition should have explicit type
+  override implicit def BarExtender(bar: Int) = super.BarExtender(bar) // error
+                        ^
+1 warning
 1 error
diff --git a/test/files/neg/t1038.scala b/test/files/neg/t1038.scala
index 367022965b99..2cc45a190eea 100644
--- a/test/files/neg/t1038.scala
+++ b/test/files/neg/t1038.scala
@@ -4,5 +4,6 @@ object Y {
   val a = new X
   import a._
   implicit val b : Int = 1
+  @annotation.nowarn
   implicit val c = 2
 }
diff --git a/test/files/neg/t2206.check b/test/files/neg/t2206.check
index 5ea5570f9a90..75c5e19c58e5 100644
--- a/test/files/neg/t2206.check
+++ b/test/files/neg/t2206.check
@@ -2,4 +2,8 @@ t2206.scala:10: error: value f is not a member of o.A
  Note: implicit method ax is not applicable here because it comes after the application point and it lacks an explicit result type
   a.f()
     ^
+t2206.scala:13: warning: Implicit definition should have explicit type (inferred o.AX)
+      implicit def ax(a: A) = new AX
+                   ^
+1 warning
 1 error
diff --git a/test/files/neg/t2421b.check b/test/files/neg/t2421b.check
index 7c714f1c9bd7..644395fc6a12 100644
--- a/test/files/neg/t2421b.check
+++ b/test/files/neg/t2421b.check
@@ -1,4 +1,8 @@
 t2421b.scala:12: error: could not find implicit value for parameter aa: Test.F[Test.A]
   f
   ^
+t2421b.scala:10: warning: Implicit definition should have explicit type (inferred Test.F[X])
+  implicit def b[X <: B] = new F[X]()
+               ^
+1 warning
 1 error
diff --git a/test/files/neg/t2866.scala b/test/files/neg/t2866.scala
index 2f464593d30c..d80822349244 100644
--- a/test/files/neg/t2866.scala
+++ b/test/files/neg/t2866.scala
@@ -1,7 +1,7 @@
 // for 2.7.x compatibility
 
 object A {
-  implicit val one = 1
+  implicit val one: Int = 1
 }
 
 object Test {
diff --git a/test/files/neg/t3006.check b/test/files/neg/t3006.check
index b8dea080a766..e2358b0f0dd9 100644
--- a/test/files/neg/t3006.check
+++ b/test/files/neg/t3006.check
@@ -3,4 +3,8 @@ t3006.scala:8: error: type mismatch;
  required: Int
   println(A(3) + "H")
                  ^
+t3006.scala:6: warning: Implicit definition should have explicit type (inferred Test.Foo)
+  implicit def aToFoo(x: A) = new Foo(x);
+               ^
+1 warning
 1 error
diff --git a/test/files/neg/t3346c.check b/test/files/neg/t3346c.check
index 10c96eeb6cdb..4b18680e493d 100644
--- a/test/files/neg/t3346c.check
+++ b/test/files/neg/t3346c.check
@@ -1,4 +1,4 @@
-t3346c.scala:60: error: value bar is not a member of Either[Int,String]
+t3346c.scala:65: error: value bar is not a member of Either[Int,String]
 did you mean map?
   eii.bar
       ^
diff --git a/test/files/neg/t3346c.scala b/test/files/neg/t3346c.scala
index 59584e0a6168..287c91bdf2ca 100644
--- a/test/files/neg/t3346c.scala
+++ b/test/files/neg/t3346c.scala
@@ -1,3 +1,5 @@
+import annotation._
+
 object Test extends App {
   //
   // An attempt to workaround scala/bug#2712, foiled by scala/bug#3346
@@ -32,15 +34,18 @@ object Test extends App {
   }
 
 
+  @nowarn
   implicit def ToTCValue[M[_], A](ma: M[A])(implicit M0: TC[M]) = new TCValue[M, A] {
-    implicit val M = M0
+    implicit val M: TC[M] = M0
     val self = ma
   }
   implicit def ToTCValueBin1[M[_, _], A, B](ma: M[A, B])(implicit M0: TC[({type λ[α]=M[A, α]})#λ]): TCValue[({type λ[α] = M[A, α]})#λ, B] = new TCValue[({type λ[α]=M[A, α]})#λ, B] {
+    @nowarn
     implicit val M = M0
     val self = ma
   }
   implicit def ToTCValueBin2[M[_, _], A, B](ma: M[A, B])(implicit M0: TC[({type λ[α]=M[α, B]})#λ]): TCValue[({type λ[α]=M[α, B]})#λ, A] = new TCValue[({type λ[α]=M[α, B]})#λ, A] {
+    @nowarn
     implicit val M = M0
     val self = ma
   }
diff --git a/test/files/neg/t3346i.check b/test/files/neg/t3346i.check
index b1b5a140e8f9..dafa0b861e24 100644
--- a/test/files/neg/t3346i.check
+++ b/test/files/neg/t3346i.check
@@ -4,4 +4,20 @@ t3346i.scala:28: error: value a is not a member of Test.A[T]
 t3346i.scala:29: error: value a is not a member of Test.A[Nothing]
   (new A[Nothing]).a
                    ^
+t3346i.scala:16: warning: Implicit definition should have explicit type (inferred Implicit1[T])
+  implicit def implicit1[T <: Intermediate[_, _]](implicit b: Implicit2[T])                = new Implicit1[T](b)
+               ^
+t3346i.scala:18: warning: Implicit definition should have explicit type (inferred Implicit2[T])
+  implicit def implicit2alt1[T <: Intermediate[_ <: String, _]](implicit c: Implicit3[T])  = new Implicit2[T](c)
+               ^
+t3346i.scala:19: warning: Implicit definition should have explicit type (inferred Implicit2[T])
+  implicit def implicit2alt2[T <: Intermediate[_ <: Double, _]](implicit c: Implicit3[T])  = new Implicit2[T](c)
+               ^
+t3346i.scala:21: warning: Implicit definition should have explicit type (inferred Implicit3[T])
+  implicit def implicit3alt1[T <: Intermediate[_, _ <: Int]]                               = new Implicit3[T]()
+               ^
+t3346i.scala:22: warning: Implicit definition should have explicit type (inferred Implicit3[T])
+  implicit def implicit3alt2[T <: Intermediate[_ <: Double, _ <: AnyRef],X]                = new Implicit3[T]()
+               ^
+5 warnings
 2 errors
diff --git a/test/files/neg/t4271.check b/test/files/neg/t4271.check
index 402a7b9b7acb..d89d07f420a7 100644
--- a/test/files/neg/t4271.check
+++ b/test/files/neg/t4271.check
@@ -8,4 +8,23 @@ t4271.scala:11: error: value -> is not a member of Int
 did you mean >>>?
   3 -> 5
     ^
+t4271.scala:3: warning: Implicit definition should have explicit type (inferred foo.Donotuseme.type)
+  implicit def Ensuring[A](x: A) = Donotuseme
+               ^
+t4271.scala:4: warning: Implicit definition should have explicit type (inferred foo.Donotuseme.type)
+  implicit def doubleWrapper(x: Int) = Donotuseme
+               ^
+t4271.scala:5: warning: Implicit definition should have explicit type (inferred foo.Donotuseme.type)
+  implicit def floatWrapper(x: Int) = Donotuseme
+               ^
+t4271.scala:6: warning: Implicit definition should have explicit type (inferred foo.Donotuseme.type)
+  implicit def intWrapper(x: Int) = Donotuseme
+               ^
+t4271.scala:7: warning: Implicit definition should have explicit type (inferred foo.Donotuseme.type)
+  implicit def longWrapper(x: Int) = Donotuseme
+               ^
+t4271.scala:8: warning: Implicit definition should have explicit type (inferred foo.Donotuseme.type)
+  implicit def ArrowAssoc[A](x: A) = Donotuseme
+               ^
+6 warnings
 3 errors
diff --git a/test/files/neg/t4457_1.check b/test/files/neg/t4457_1.check
index a16bb1ff8b1b..4d65bc39c1e0 100644
--- a/test/files/neg/t4457_1.check
+++ b/test/files/neg/t4457_1.check
@@ -4,4 +4,20 @@ and  method aFunc in object ImplicitConvAmbiguity2 of type [A](a: ImplicitConvAm
 match argument types (Float)
     val x = aFunc(4F)
             ^
+t4457_1.scala:11: warning: Implicit definition should have explicit type (inferred ImplicitConvAmbiguity2.NE[Float])
+  implicit def conv1(i: Float) = new NE[Float]
+               ^
+t4457_1.scala:12: warning: Implicit definition should have explicit type (inferred ImplicitConvAmbiguity2.N[java.util.TooManyListenersException])
+  implicit def conv3(op: AA[java.util.TooManyListenersException]) = new N[java.util.TooManyListenersException]
+               ^
+t4457_1.scala:13: warning: Implicit definition should have explicit type (inferred ImplicitConvAmbiguity2.N[Float])
+  implicit def conv4(op: AA[Float]) = new N[Float]
+               ^
+t4457_1.scala:14: warning: Implicit definition should have explicit type (inferred ImplicitConvAmbiguity2.NZ[Float])
+  implicit def conv7(i: Float) = new NZ[Float]
+               ^
+t4457_1.scala:15: warning: Implicit definition should have explicit type (inferred ImplicitConvAmbiguity2.N[java.util.GregorianCalendar])
+  implicit def conv5(e: BB[java.util.GregorianCalendar]) = new N[java.util.GregorianCalendar]
+               ^
+5 warnings
 1 error
diff --git a/test/files/neg/t4457_2.check b/test/files/neg/t4457_2.check
index b1310f74ed50..d0be6d48ef38 100644
--- a/test/files/neg/t4457_2.check
+++ b/test/files/neg/t4457_2.check
@@ -10,4 +10,20 @@ and  method aFunc in object ImplicitConvAmbiguity2 of type [A](a: ImplicitConvAm
 match argument types (Float)
     bFunc(aFunc(4F))
           ^
+t4457_2.scala:11: warning: Implicit definition should have explicit type (inferred ImplicitConvAmbiguity2.NE[Float])
+  implicit def conv1(i: Float) = new NE[Float]
+               ^
+t4457_2.scala:12: warning: Implicit definition should have explicit type (inferred ImplicitConvAmbiguity2.N[java.util.TooManyListenersException])
+  implicit def conv3(op: AA[java.util.TooManyListenersException]) = new N[java.util.TooManyListenersException]
+               ^
+t4457_2.scala:13: warning: Implicit definition should have explicit type (inferred ImplicitConvAmbiguity2.N[Float])
+  implicit def conv4(op: AA[Float]) = new N[Float]
+               ^
+t4457_2.scala:14: warning: Implicit definition should have explicit type (inferred ImplicitConvAmbiguity2.NZ[Float])
+  implicit def conv7(i: Float) = new NZ[Float]
+               ^
+t4457_2.scala:15: warning: Implicit definition should have explicit type (inferred ImplicitConvAmbiguity2.N[java.util.GregorianCalendar])
+  implicit def conv5(e: BB[java.util.GregorianCalendar]) = new N[java.util.GregorianCalendar]
+               ^
+5 warnings
 2 errors
diff --git a/test/files/neg/t4568.check b/test/files/neg/t4568.check
index 3582e24b188a..604948e41b47 100644
--- a/test/files/neg/t4568.check
+++ b/test/files/neg/t4568.check
@@ -1,4 +1,8 @@
 t4568.scala:8: error: recursive method isSubListOf needs result type
         case h :: t => y.contains(h) && (t.isSubListOf(y.drop(y.indexOf(h) + 1)))
                                            ^
+t4568.scala:2: warning: Implicit definition should have explicit type (inferred SubList.SubListable[A])
+  implicit def sublistable[A](x: List[A]) = new SubListable(x)
+               ^
+1 warning
 1 error
diff --git a/test/files/neg/t4889.check b/test/files/neg/t4889.check
index 96e9b7528e67..e643dd1ffc05 100644
--- a/test/files/neg/t4889.check
+++ b/test/files/neg/t4889.check
@@ -1,4 +1,8 @@
 t4889.scala:19: error: could not find implicit value for parameter ma1: t4889.MatrixAdder[Int,[S]t4889.SparseMatrix[S]]
   m1.foo
      ^
+t4889.scala:14: warning: Implicit definition should have explicit type (inferred t4889.MatrixAdder[S,R])
+  implicit def adderImplicit[S, R[s] <: Matrix[s, R]] = new MatrixAdder[S, R] {
+               ^
+1 warning
 1 error
diff --git a/test/files/neg/t5728.check b/test/files/neg/t5728.check
index 7a80af2af06d..72a0c0273005 100644
--- a/test/files/neg/t5728.check
+++ b/test/files/neg/t5728.check
@@ -1,4 +1,8 @@
 t5728.scala:3: error: implicit classes must accept exactly one primary constructor parameter
   implicit class Foo
                  ^
+t5728.scala:5: warning: Implicit definition should have explicit type (inferred Test.Foo)
+  implicit def Foo = new Foo
+               ^
+1 warning
 1 error
diff --git a/test/files/neg/t6436.check b/test/files/neg/t6436.check
index 27f4466572e5..2d74aa8c2a78 100644
--- a/test/files/neg/t6436.check
+++ b/test/files/neg/t6436.check
@@ -7,4 +7,11 @@ Note that implicit conversions are not applicable because they are ambiguous:
  are possible conversion functions from StringContext to ?{def q: ?}
   println(q"a")
           ^
+t6436.scala:2: warning: Implicit definition should have explicit type (inferred AnyRef{def q: Nothing})
+  implicit def foo1(ctx: StringContext) = new { def q = ??? }
+               ^
+t6436.scala:3: warning: Implicit definition should have explicit type (inferred AnyRef{def q: Nothing})
+  implicit def foo2(ctx: StringContext) = new { def q = ??? }
+               ^
+2 warnings
 1 error
diff --git a/test/files/neg/t6436b.check b/test/files/neg/t6436b.check
index be9b17a4e387..8e33d7bb134a 100644
--- a/test/files/neg/t6436b.check
+++ b/test/files/neg/t6436b.check
@@ -7,4 +7,11 @@ Note that implicit conversions are not applicable because they are ambiguous:
  are possible conversion functions from StringContext to ?{def q: ?}
   println(StringContext("a").q())
                        ^
+t6436b.scala:2: warning: Implicit definition should have explicit type (inferred AnyRef{def q: Nothing})
+  implicit def foo1(ctx: StringContext) = new { def q = ??? }
+               ^
+t6436b.scala:3: warning: Implicit definition should have explicit type (inferred AnyRef{def q: Nothing})
+  implicit def foo2(ctx: StringContext) = new { def q = ??? }
+               ^
+2 warnings
 1 error
diff --git a/test/files/neg/t6567.check b/test/files/neg/t6567.check
index 5ae946a4c1ac..552f4cbd48df 100644
--- a/test/files/neg/t6567.check
+++ b/test/files/neg/t6567.check
@@ -1,3 +1,6 @@
+t6567.scala:8: warning: Implicit definition should have explicit type (inferred B)
+  implicit def a2b(a: A) = new B
+               ^
 t6567.scala:10: warning: Suspicious application of an implicit view (Test.this.a2b) in the argument to Option.apply.
   Option[B](a)
            ^
@@ -6,5 +9,5 @@ t6567.scala:12: warning: Suspicious application of an implicit view (Test.this.a
                            ^
 warning: 1 feature warning; re-run with -feature for details
 error: No warnings can be incurred under -Werror.
-3 warnings
+4 warnings
 1 error
diff --git a/test/files/neg/t6667.check b/test/files/neg/t6667.check
index 1fe4a15e593e..dfcad24c4645 100644
--- a/test/files/neg/t6667.check
+++ b/test/files/neg/t6667.check
@@ -10,4 +10,8 @@ t6667.scala:9: error: ambiguous implicit values:
  match expected type C
   implicitly[C]       // ambiguity reported, rather than falling back to C.companion
             ^
+t6667.scala:3: warning: Implicit definition should have explicit type (inferred C)
+  implicit def companion = new C
+               ^
+1 warning
 2 errors
diff --git a/test/files/neg/t6667.scala b/test/files/neg/t6667.scala
index fb857ebd3322..840921f3449d 100644
--- a/test/files/neg/t6667.scala
+++ b/test/files/neg/t6667.scala
@@ -4,7 +4,7 @@ object C {
 }
 
 object Test {
-  implicit val inScope1, inScope2 = new C
+  implicit val inScope1, inScope2: C = new C
   implicitly[C]: Unit // C.companion was used; whereas the ambiguity should abort the implicit search.
   implicitly[C]       // ambiguity reported, rather than falling back to C.companion
 }
diff --git a/test/files/neg/t692.check b/test/files/neg/t692.check
index 670495f6467d..42e2a1b8f2c6 100644
--- a/test/files/neg/t692.check
+++ b/test/files/neg/t692.check
@@ -16,4 +16,8 @@ t692.scala:14: error: class Foo takes type parameters
 t692.scala:19: error: class Foo takes type parameters
   class Bar[A <: Foo](implicit tpeA : Type[A]) extends Foo;
                  ^
+t692.scala:11: warning: Implicit definition should have explicit type (inferred test3.this.FooType)
+  implicit def typeOfFoo = FooType();
+               ^
+1 warning
 6 errors
diff --git a/test/files/neg/t712.check b/test/files/neg/t712.check
index fc8f7824f2c7..606e41f04d92 100644
--- a/test/files/neg/t712.check
+++ b/test/files/neg/t712.check
@@ -1,4 +1,11 @@
 t712.scala:10: error: overloaded method coerce needs result type
   implicit def coerce(p : ParentImpl) = p.self;
                                           ^
+t712.scala:3: warning: Implicit definition should have explicit type (inferred A.this.Node)
+  implicit def coerce(n : NodeImpl) = n.self;
+               ^
+t712.scala:10: warning: Implicit definition should have explicit type
+  implicit def coerce(p : ParentImpl) = p.self;
+               ^
+2 warnings
 1 error
diff --git a/test/files/neg/t7131.check b/test/files/neg/t7131.check
index c66f1b4f927c..86df78172b9c 100644
--- a/test/files/neg/t7131.check
+++ b/test/files/neg/t7131.check
@@ -4,4 +4,11 @@ t7131.scala:21: error: type mismatch;
  Note: implicit method convertToSimpleMappable is not applicable here because it comes after the application point and it lacks an explicit result type
         x.value.map(f)
                    ^
+t7131.scala:28: warning: Implicit definition should have explicit type (inferred ObservableValue.TraversableMappable[T,Container])
+  implicit def convertToTraversableMappable[T, Container[X] <: Traversable[X]](x: ObservableValue[Container[T]]) =
+               ^
+t7131.scala:43: warning: Implicit definition should have explicit type (inferred ObservableValue.NestedMappable[T,Container])
+  implicit def convertToSimpleMappable[T, Container[X] <: ObservableValue.HasMap[X, Container]](x: ObservableValue[Container[T]]) =
+               ^
+2 warnings
 1 error
diff --git a/test/files/neg/t729.check b/test/files/neg/t729.check
index 050772cf84b9..7680b2fdfa4b 100644
--- a/test/files/neg/t729.check
+++ b/test/files/neg/t729.check
@@ -3,4 +3,11 @@ t729.scala:20: error: type mismatch;
  required: ScalaParserAutoEdit.this.NodeImpl(in trait ScalaParserAutoEdit)
       val yyy : NodeImpl = link.from;
                                 ^
+t729.scala:3: warning: Implicit definition should have explicit type (inferred Parser.this.Node)
+  implicit def coerce(n : NodeImpl) = n.self;
+               ^
+t729.scala:14: warning: Implicit definition should have explicit type (inferred ScalaParserAutoEdit.this.Node)
+  implicit def coerce(node : NodeImpl) = node.self;
+               ^
+2 warnings
 1 error
diff --git a/test/files/neg/t8322.check b/test/files/neg/t8322.check
index 6c3f9a5e53ce..bc56230cd385 100644
--- a/test/files/neg/t8322.check
+++ b/test/files/neg/t8322.check
@@ -13,4 +13,11 @@ t8322.scala:19: error: type mismatch;
  required: scala.util.Either[?,?]
   Right(0).right.flatMap(_ => new String())
                               ^
+t8322.scala:15: warning: Implicit definition should have explicit type (inferred Writes[Seq[E]])
+  implicit def rw[E] = Writes[Seq[E]] { _ => "" }
+               ^
+t8322.scala:17: warning: Implicit definition should have explicit type
+  implicit def wr[E] = jw(implicitly, implicitly)
+               ^
+2 warnings
 3 errors
diff --git a/test/files/pos/t7212.scala b/test/files/pos/t7212.scala
index 1c1a3f07a2c2..4b53c034ff1f 100644
--- a/test/files/pos/t7212.scala
+++ b/test/files/pos/t7212.scala
@@ -13,3 +13,14 @@ class C extends B {
   override def f: Option[String] = Some("goodbye, cruel world")
   override def remove(): Unit = println("removed! (not really)")
 }
+
+trait T { def f: Object }
+class K extends T { def f = "" }
+object K {
+  val k = new K
+  val s: Any = k.f
+}
+
+trait U extends T { def f = "" }
+trait V { var v: Any }
+trait W extends V { var v = "" }
diff --git a/test/files/run/Meter.scala b/test/files/run/Meter.scala
index 9fa8a7babd7d..7ef9d247e1ba 100644
--- a/test/files/run/Meter.scala
+++ b/test/files/run/Meter.scala
@@ -23,7 +23,7 @@ package a {
 
     def apply(x: Double): Meter = new Meter(x)
 
-    implicit val boxings = new BoxingConversions[Meter, Double] {
+    implicit val boxings: BoxingConversions[Meter, Double] = new BoxingConversions[Meter, Double] {
       def box(x: Double) = new Meter(x)
       def unbox(m: Meter) = m.underlying
     }
@@ -35,7 +35,7 @@ package a {
     override def toString = unbox.toString+"ft"
   }
   object Foot {
-    implicit val boxings = new BoxingConversions[Foot, Double] {
+    implicit val boxings: BoxingConversions[Foot, Double] = new BoxingConversions[Foot, Double] {
       def box(x: Double) = new Foot(x)
       def unbox(m: Foot) = m.unbox
     }
diff --git a/test/files/run/MeterCaseClass.scala b/test/files/run/MeterCaseClass.scala
index 8c15bbb6d30b..1f40dc5e7dbc 100644
--- a/test/files/run/MeterCaseClass.scala
+++ b/test/files/run/MeterCaseClass.scala
@@ -20,7 +20,7 @@ package a {
 
     private[a] trait MeterArg
 
-    implicit val boxings = new BoxingConversions[Meter, Double] {
+    implicit val boxings: BoxingConversions[Meter, Double] = new BoxingConversions[Meter, Double] {
       def box(x: Double) = new Meter(x)
       def unbox(m: Meter) = m.underlying
     }
@@ -32,7 +32,7 @@ package a {
     override def toString = unbox.toString+"ft"
   }
   object Foot {
-    implicit val boxings = new BoxingConversions[Foot, Double] {
+    implicit val boxings: BoxingConversions[Foot, Double] = new BoxingConversions[Foot, Double] {
       def box(x: Double) = new Foot(x)
       def unbox(m: Foot) = m.unbox
     }
diff --git a/test/files/run/idempotency-lazy-vals.scala b/test/files/run/idempotency-lazy-vals.scala
index 8688add3e699..236e1516137c 100644
--- a/test/files/run/idempotency-lazy-vals.scala
+++ b/test/files/run/idempotency-lazy-vals.scala
@@ -7,7 +7,7 @@ object Test extends App {
   val lazee = reify {
     class C {
       lazy val x = 2
-      implicit lazy val y = 3
+      implicit lazy val y: Int = 3
     }
     val c = new C()
     import c._
diff --git a/test/files/run/impconvtimes.scala b/test/files/run/impconvtimes.scala
index 477a16a8903d..d377685a9c77 100644
--- a/test/files/run/impconvtimes.scala
+++ b/test/files/run/impconvtimes.scala
@@ -9,7 +9,7 @@ object Test {
     def *(newUnit: Unit) = Measure(scalar, newUnit)
   }
 
-  implicit def double2Measure(scalar: Double) =
+  implicit def double2Measure(scalar: Double): Measure =
     Measure(scalar, NoUnit)
 
 
diff --git a/test/files/run/implicits.scala b/test/files/run/implicits.scala
index 5681a9d484dc..fbc8536c041b 100644
--- a/test/files/run/implicits.scala
+++ b/test/files/run/implicits.scala
@@ -2,7 +2,7 @@ import scala.language.implicitConversions
 
 object A {
   object B {
-    implicit def int2string(x: Int) = "["+x.toString+"]"
+    implicit def int2string(x: Int): String = "["+x.toString+"]"
   }
 }
 
diff --git a/test/files/run/macro-expand-implicit-macro-has-implicit/Macros_Test_2.scala b/test/files/run/macro-expand-implicit-macro-has-implicit/Macros_Test_2.scala
index 46367cd1a307..a126bd813d46 100644
--- a/test/files/run/macro-expand-implicit-macro-has-implicit/Macros_Test_2.scala
+++ b/test/files/run/macro-expand-implicit-macro-has-implicit/Macros_Test_2.scala
@@ -1,6 +1,6 @@
 import scala.language.experimental.macros
 object Test extends App {
-  implicit val x = 42
+  implicit val x: Int = 42
   def foo(implicit x: Int): Unit = macro Impls.foo
   foo
 }
diff --git a/test/files/run/macro-implicit-decorator/Test_2.scala b/test/files/run/macro-implicit-decorator/Test_2.scala
index bfcb57986997..88c60d91b09f 100644
--- a/test/files/run/macro-implicit-decorator/Test_2.scala
+++ b/test/files/run/macro-implicit-decorator/Test_2.scala
@@ -5,9 +5,9 @@ class CustomClass
 trait MyTC[A]
 
 object MyTC {
-  implicit val forInt = new MyTC[Int] {}
-  implicit def forList[A](implicit a: Derivation[MyTC[A]]) = new MyTC[List[A]] {}
-  implicit def forCustomClass(implicit a: Derivation[MyTC[List[Boolean]]]) = new MyTC[CustomClass] {}
+  implicit val forInt: MyTC[Int] = new MyTC[Int] {}
+  implicit def forList[A](implicit a: Derivation[MyTC[A]]): MyTC[List[A]] = new MyTC[List[A]] {}
+  implicit def forCustomClass(implicit a: Derivation[MyTC[List[Boolean]]]): MyTC[CustomClass] = new MyTC[CustomClass] {}
 }
 
 object Test extends App {
diff --git a/test/files/run/reflection-implicit.scala b/test/files/run/reflection-implicit.scala
index a6e939322ad5..1e104d1e5809 100644
--- a/test/files/run/reflection-implicit.scala
+++ b/test/files/run/reflection-implicit.scala
@@ -3,7 +3,7 @@ import scala.language.implicitConversions
 import scala.reflect.runtime.universe._
 
 class C {
-  implicit val v = new C
+  implicit val v: C = new C
   implicit def d(x: C)(implicit c: C): Int = ???
   implicit class X(val x: Int)
 }
diff --git a/test/files/run/repl-class-based-implicit-import.check b/test/files/run/repl-class-based-implicit-import.check
index 9ad75cba7540..85d97a78c1fd 100644
--- a/test/files/run/repl-class-based-implicit-import.check
+++ b/test/files/run/repl-class-based-implicit-import.check
@@ -2,7 +2,7 @@
 scala> def showInt(implicit x: Int) = println(x)
 def showInt(implicit x: Int): Unit
 
-scala> object IntHolder { implicit val myInt = 5 }
+scala> object IntHolder { implicit val myInt: Int = 5 }
 object IntHolder
 
 scala> import IntHolder.myInt
diff --git a/test/files/run/repl-class-based-implicit-import.scala b/test/files/run/repl-class-based-implicit-import.scala
index 9153c8e08f7f..133c99969f66 100644
--- a/test/files/run/repl-class-based-implicit-import.scala
+++ b/test/files/run/repl-class-based-implicit-import.scala
@@ -11,7 +11,7 @@ object Test extends ReplTest {
 
   def code = """
     |def showInt(implicit x: Int) = println(x)
-    |object IntHolder { implicit val myInt = 5 }
+    |object IntHolder { implicit val myInt: Int = 5 }
     |import IntHolder.myInt
     |showInt
     |class A; showInt
diff --git a/test/files/run/repl-no-imports-no-predef-power.check b/test/files/run/repl-no-imports-no-predef-power.check
index 64c4b37b92e2..52140e1b5c2c 100644
--- a/test/files/run/repl-no-imports-no-predef-power.check
+++ b/test/files/run/repl-no-imports-no-predef-power.check
@@ -11,7 +11,6 @@ warning: 1 deprecation (since 2.11.0); for details, enable `:setting -deprecatio
 val res0: $r.global.noSelfType.type = private val _ = _
 
 scala> val tp = ArrayClass[scala.util.Random]    // magic with tags
-warning: 1 feature warning; for details, enable `:setting -feature` or `:replay -feature`
 val tp: $r.global.Type = Array[scala.util.Random]
 
 scala> tp.memberType(Array_apply)                // evidence
diff --git a/test/files/run/repl-power.check b/test/files/run/repl-power.check
index 64c4b37b92e2..52140e1b5c2c 100644
--- a/test/files/run/repl-power.check
+++ b/test/files/run/repl-power.check
@@ -11,7 +11,6 @@ warning: 1 deprecation (since 2.11.0); for details, enable `:setting -deprecatio
 val res0: $r.global.noSelfType.type = private val _ = _
 
 scala> val tp = ArrayClass[scala.util.Random]    // magic with tags
-warning: 1 feature warning; for details, enable `:setting -feature` or `:replay -feature`
 val tp: $r.global.Type = Array[scala.util.Random]
 
 scala> tp.memberType(Array_apply)                // evidence
diff --git a/test/files/run/sip23-implicit-resolution.scala b/test/files/run/sip23-implicit-resolution.scala
index 5d83f89c43b1..beef7ae73e9f 100644
--- a/test/files/run/sip23-implicit-resolution.scala
+++ b/test/files/run/sip23-implicit-resolution.scala
@@ -4,11 +4,11 @@ object Test extends App {
   def mkAssoc[K, V0](k: K, v0: V0): Assoc[k.type] { type V = V0 } = new Assoc[k.type] {type V = V0 ; val v = v0}
   def lookup[K](k: K)(implicit a: Assoc[k.type]): a.V = a.v
 
-  implicit def firstAssoc = mkAssoc(1, "Panda!")
-  implicit def secondAssoc = mkAssoc(2, "Kitty!")
+  implicit def firstAssoc: Assoc[1] { type V = String } = mkAssoc(1, "Panda!")
+  implicit def secondAssoc: Assoc[2] { type V = String } = mkAssoc(2, "Kitty!")
 
-  implicit def ageAssoc = mkAssoc("Age", 3)
-  implicit def nmAssoc = mkAssoc("Name", "Jane")
+  implicit def ageAssoc: Assoc["Age"] { type V = Int } = mkAssoc("Age", 3)
+  implicit def nmAssoc: Assoc["Name"] { type V = String } = mkAssoc("Name", "Jane")
 
   assert(lookup(1) == "Panda!")
   assert(lookup(2) == "Kitty!")
diff --git a/test/files/run/t2316_run.scala b/test/files/run/t2316_run.scala
index 19d326f57f1a..2a17886aea46 100644
--- a/test/files/run/t2316_run.scala
+++ b/test/files/run/t2316_run.scala
@@ -1,7 +1,7 @@
 case class T1(source: String)
 
 object T1 {
-  implicit def T1FromT2(implicit t2: T2) = new T1(t2.source)
+  implicit def T1FromT2(implicit t2: T2): T1 = new T1(t2.source)
 }
 
 case class T2(source: String)
@@ -10,7 +10,7 @@ object A {
   def requireT1(implicit t1: T1) = t1
 
   object B1 {
-    implicit val t2_b1 = new T2("from B1")
+    implicit val t2_b1: T2 = new T2("from B1")
     requireT1
   }
 
diff --git a/test/files/run/t2514.scala b/test/files/run/t2514.scala
index 0bf716e8bbf6..6a58c8f63c36 100644
--- a/test/files/run/t2514.scala
+++ b/test/files/run/t2514.scala
@@ -2,9 +2,8 @@
 
 import scala.language.{ implicitConversions, postfixOps, reflectiveCalls }
 
-object Test
-{
-  implicit def x[A](a: A) = new { def xx = a }
+object Test {
+  implicit def x[A](a: A): AnyRef{def xx: A} = new { def xx = a }
 
   def main(args: Array[String]): Unit = {
     val r1 = 12 xx;
diff --git a/test/files/run/t2866.scala b/test/files/run/t2866.scala
index c1583e91ace9..7c65e3c406bd 100644
--- a/test/files/run/t2866.scala
+++ b/test/files/run/t2866.scala
@@ -1,7 +1,7 @@
 // for 2.7.x compatibility
 
 object A {
-  implicit val one = 1
+  implicit val one: Int = 1
 }
 
 object Test extends App {
diff --git a/test/files/run/t3346d.scala b/test/files/run/t3346d.scala
index 118318dee67d..261028dea3a9 100644
--- a/test/files/run/t3346d.scala
+++ b/test/files/run/t3346d.scala
@@ -11,7 +11,7 @@ object Test extends App {
     def create(v: A): Basket[A,B]
   }
 
-  implicit val bf = new BasketFactory[Int,TARInt] {
+  implicit val bf: BasketFactory[Int,TARInt] = new BasketFactory[Int,TARInt] {
     def create(v: Int): Basket[Int,TARInt] = new Basket[Int, TARInt]{}
   }
 
diff --git a/test/files/run/t3346e.scala b/test/files/run/t3346e.scala
index 8f75eb97edd3..66bba85818f6 100644
--- a/test/files/run/t3346e.scala
+++ b/test/files/run/t3346e.scala
@@ -47,9 +47,9 @@ class FilterMapFixed[A, Repr <% IterableOps[A, Iterable, _]](a: Repr) {
 }
 
 object MyEnhancements {
-  implicit def toQS[Coll](a: Coll) = new QuickSort(a)
-  implicit def toFM[Coll](a: Coll) = new FilterMap(a)
-  implicit def toFM2[A, Repr <% IterableOps[A, Iterable, _]](a: Repr) = new FilterMapFixed(a)
+  implicit def toQS[Coll](a: Coll): QuickSort[Coll] = new QuickSort(a)
+  implicit def toFM[Coll](a: Coll): FilterMap[Coll] = new FilterMap(a)
+  implicit def toFM2[A, Repr <% IterableOps[A, Iterable, _]](a: Repr): FilterMapFixed[A,Repr] = new FilterMapFixed(a)
 }
 
 object Test extends App {
diff --git a/test/files/run/t3346f.scala b/test/files/run/t3346f.scala
index 4799ca2ca9a5..b2dc16de5bfd 100644
--- a/test/files/run/t3346f.scala
+++ b/test/files/run/t3346f.scala
@@ -4,11 +4,11 @@ import scala.language.reflectiveCalls
 object Test extends App {
   trait Foo[A]
   implicit def fooString: Foo[String] = null
-  implicit def value[A](implicit foo: Foo[A]) = 5
+  implicit def value[A](implicit foo: Foo[A]): Int = 5
 
   println(implicitly[Int])
 
-  implicit def conversion[A](x: Int)(implicit foo: Foo[A]) = new {
+  implicit def conversion[A](x: Int)(implicit foo: Foo[A]): AnyRef{def aMethod: Int} = new {
     def aMethod = 5
   }
   println(1.aMethod)
diff --git a/test/files/run/t3346h.check b/test/files/run/t3346h.check
deleted file mode 100644
index 587be6b4c3f9..000000000000
--- a/test/files/run/t3346h.check
+++ /dev/null
@@ -1 +0,0 @@
-x
diff --git a/test/files/run/t3346h.scala b/test/files/run/t3346h.scala
index 642b7cf58505..3e94e25df7ed 100644
--- a/test/files/run/t3346h.scala
+++ b/test/files/run/t3346h.scala
@@ -3,7 +3,7 @@ import scala.language.implicitConversions
 object Test extends App {
   trait Fundep[T, U] { def u(t: T): U }
   class C { def y = "x" }
-  implicit val FundepStringC = new Fundep[String, C]{ def u(t: String) = new C }
+  implicit val FundepStringC: Fundep[String,C] = new Fundep[String, C]{ def u(t: String) = new C }
   implicit def foo[T, U](x: T)(implicit y: Fundep[T, U]): U = y.u(x)
-  println("x".y)
+  assert("x".y == "x")
 }
diff --git a/test/files/run/t3346j.scala b/test/files/run/t3346j.scala
index 719d11819af4..bfacb6d0e17a 100644
--- a/test/files/run/t3346j.scala
+++ b/test/files/run/t3346j.scala
@@ -5,7 +5,7 @@ import scala.reflect.runtime.universe._
 object Test extends App {
   class A[T]
   class B[T]
-  implicit def foo[T: TypeTag](a: A[T])(implicit b: B[T]) = new { def baz = typeOf[T] }
+  implicit def foo[T: TypeTag](a: A[T])(implicit b: B[T]): AnyRef{def baz: reflect.runtime.universe.Type} = new { def baz = typeOf[T] }
   implicit def bar[T <: Int]: B[T] = new B[T]()
   println(new A[Int]().baz)
 }
diff --git a/test/files/run/t5080.scala b/test/files/run/t5080.scala
index acb6167f4652..8d0d04fd60ec 100644
--- a/test/files/run/t5080.scala
+++ b/test/files/run/t5080.scala
@@ -11,7 +11,7 @@ object Test extends App {
     override def toString = value.toString;
   }
 
-  implicit def conversions(x: Value) = new {
+  implicit def conversions(x: Value): AnyRef { def toInt: Int } = new {
     def toInt =
       x match {
         case Num(n) => n
diff --git a/test/files/run/t5276_2b.scala b/test/files/run/t5276_2b.scala
index 9cc789ec22c8..eb3d744befa4 100644
--- a/test/files/run/t5276_2b.scala
+++ b/test/files/run/t5276_2b.scala
@@ -4,7 +4,7 @@ import scala.tools.reflect.Eval
 object Test extends App {
   reify {
     class C {
-      implicit lazy val x = 2
+      implicit lazy val x: Int = 2
       def y = implicitly[Int]
     }
 
diff --git a/test/files/run/t5565.scala b/test/files/run/t5565.scala
index 9ced87ca21a7..3c9ed24003af 100644
--- a/test/files/run/t5565.scala
+++ b/test/files/run/t5565.scala
@@ -1,7 +1,9 @@
+import scala.annotation.nowarn
 import scala.language.reflectiveCalls
 import scala.language.implicitConversions
 
 object Test extends App {
+  @nowarn  // the inferred type includes the default arg, which can't be written explicitly
   implicit def doubleWithApproxEquals(d: Double) = new {
     def ~==(v: Double, margin: Double = 0.001): Boolean =
       math.abs(d - v) < margin
@@ -10,3 +12,11 @@ object Test extends App {
   assert(math.abs(-4.0) ~== (4.0, 0.001))
   assert(math.abs(-4.0) ~== 4.0)
 }
+/*
+was:
+Exception in thread "main" java.lang.IllegalAccessError: tried to access field illegal_access_error_test_case$.reflParams$Cache2 from class illegal_access_error_test_case$delayedInit$body
+  at illegal_access_error_test_case$delayedInit$body.<clinit>(illegal_access_error_test_case.scala:8)
+  at illegal_access_error_test_case$.<init>(illegal_access_error_test_case.scala:1)
+  at illegal_access_error_test_case$.<clinit>(illegal_access_error_test_case.scala)
+  at illegal_access_error_test_case.main(illegal_access_error_test_case.scala)
+ */
diff --git a/test/files/run/t6290.scala b/test/files/run/t6290.scala
index 9d05db0d1885..4a5ac1cf4d14 100644
--- a/test/files/run/t6290.scala
+++ b/test/files/run/t6290.scala
@@ -1,4 +1,5 @@
 object Test {
-  implicit val foo = language.dynamics
+  import languageFeature._
+  implicit val foo: dynamics = language.dynamics
   def main(args: Array[String]): Unit = ()
 }
diff --git a/test/files/run/t6327.scala b/test/files/run/t6327.scala
index 4a2f6c3ee88f..7ebba247b871 100644
--- a/test/files/run/t6327.scala
+++ b/test/files/run/t6327.scala
@@ -7,8 +7,8 @@ object Test extends App {
   case class R[+T](s: String) { def x() = println(s) }
 
   // Implicits in contention; StringR is nested to avoid ambiguity
-  object R { implicit val StringR = R[String]("A") }
-  implicit val Default = R[Any]("B")
+  object R { implicit val StringR: R[String] = R[String]("A") }
+  implicit val Default: R[Any] = R[Any]("B")
 
   class B() extends Dynamic {
     def selectDynamic[T](f: String)(implicit r: R[T]): Unit = r.x()
diff --git a/test/files/run/t657.scala b/test/files/run/t657.scala
index d7f882b4342a..882c9bf3fb71 100644
--- a/test/files/run/t657.scala
+++ b/test/files/run/t657.scala
@@ -4,7 +4,7 @@
 import scala.language.{ implicitConversions }
 abstract class BaseList {
   type Node <: BaseNodeImpl
-  implicit def convertNode(ni : BaseNodeImpl) = ni.asInstanceOf[Node];
+  implicit def convertNode(ni : BaseNodeImpl): Node = ni.asInstanceOf[Node];
   abstract class BaseNodeImpl
 }
 abstract class LinkedList extends BaseList {
@@ -33,7 +33,7 @@ trait Matcher extends PrecedenceParser {
   trait NodeImpl4 extends super.NodeImpl3
 
   type Matchable <: Node with MatchableImpl0
-  implicit def convertMatchable(m : MatchableImpl0) = m.asInstanceOf[Matchable]
+  implicit def convertMatchable(m : MatchableImpl0): Matchable = m.asInstanceOf[Matchable]
   trait MatchableImpl0 extends NodeImpl4 {
     override def chop : Node = {
       Console.println("passed"); super.chop;
diff --git a/test/files/run/t8564.scala b/test/files/run/t8564.scala
index 6d7d1178c4a0..6ffaa75938e2 100644
--- a/test/files/run/t8564.scala
+++ b/test/files/run/t8564.scala
@@ -13,8 +13,8 @@ object Test extends App {
 
   def lookup(k: String)(implicit assoc: Assoc[k.type]): assoc.V = assoc.value
 
-  implicit def nameAssoc = mkAssoc("Name", "Mary")
-  implicit def ageAssoc = mkAssoc("Age", 23)
+  implicit def nameAssoc: Assoc["Name"] { type V = String } = mkAssoc("Name", "Mary")
+  implicit def ageAssoc: Assoc["Age"] { type V = Int } = mkAssoc("Age", 23)
 
   assert((lookup("Name"): String) == "Mary")
   assert((lookup("Age"): Int) == 23)
diff --git a/test/files/run/tcpoly_parseridioms.scala b/test/files/run/tcpoly_parseridioms.scala
index 38455f05eebb..6144fb30dba0 100644
--- a/test/files/run/tcpoly_parseridioms.scala
+++ b/test/files/run/tcpoly_parseridioms.scala
@@ -103,8 +103,8 @@ trait ParserIdioms extends Parsers with Idioms {
   // TODO: how can parserIdiom(curry2(_)) be omitted?
   def expr: Parser[Expr] = parserIdiomFun(curry2(Plus)) <| num <> num |>
 
-  implicit def curry2[s, t, u](fun: (s, t) => u)(a: s)(b: t) = fun(a, b)
-  implicit def curry3[r, s, t, u](fun: (r, s, t) => u)(a: r)(b: s)(c: t) = fun(a, b, c)
+  implicit def curry2[s, t, u](fun: (s, t) => u)(a: s)(b: t): u = fun(a, b)
+  implicit def curry3[r, s, t, u](fun: (r, s, t) => u)(a: r)(b: s)(c: t): u = fun(a, b, c)
 }
 
 object Test extends ParserIdioms with App {
diff --git a/test/junit/scala/io/SourceTest.scala b/test/junit/scala/io/SourceTest.scala
index 0c4a996d1c9f..593b990d0413 100644
--- a/test/junit/scala/io/SourceTest.scala
+++ b/test/junit/scala/io/SourceTest.scala
@@ -10,7 +10,7 @@ import java.io.{Console => _, _}
 
 class SourceTest {
 
-  private implicit val `our codec` = Codec.UTF8
+  private implicit val `our codec`: Codec = Codec.UTF8
   private val charSet = Codec.UTF8.charSet.name
 
   private def sampler = """
diff --git a/test/junit/scala/reflect/internal/util/AbstractFileClassLoaderTest.scala b/test/junit/scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
index c57ca039a144..0248aebdb990 100644
--- a/test/junit/scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
+++ b/test/junit/scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
@@ -10,11 +10,11 @@ class AbstractFileClassLoaderTest {
 
   import scala.reflect.io._
   import scala.io.Source
-  import scala.io.Codec.UTF8
+  import scala.io.Codec, Codec.UTF8
   import scala.reflect.io.Streamable
   import java.net.{ URLClassLoader, URL }
 
-  implicit def `we love utf8` = UTF8
+  implicit def `we love utf8`: Codec = UTF8
   implicit class `abs file ops`(f: AbstractFile) {
     def writeContent(s: String): Unit = Streamable.closing(f.bufferedOutput)(os => os write s.getBytes(UTF8.charSet))
   }
diff --git a/test/macro-annot/run/scopes/scopes_2.scala b/test/macro-annot/run/scopes/scopes_2.scala
index 451931c14ee8..783c729aef1f 100644
--- a/test/macro-annot/run/scopes/scopes_2.scala
+++ b/test/macro-annot/run/scopes/scopes_2.scala
@@ -2,7 +2,7 @@
 object Test extends App {
   def assertEquals(a: Any, b: Any): Unit = { assert(a == b, s"$a != $b") }
 
-  implicit val x = 42
+  implicit val x: Int = 42
   @explorer object C
 
   // @Test def toplevel: Unit =
diff --git a/test/scalacheck/scala/collection/mutable/MutableTreeMap.scala b/test/scalacheck/scala/collection/mutable/MutableTreeMap.scala
index 5b06a35725be..adae13349733 100644
--- a/test/scalacheck/scala/collection/mutable/MutableTreeMap.scala
+++ b/test/scalacheck/scala/collection/mutable/MutableTreeMap.scala
@@ -31,8 +31,8 @@ trait Generators {
     } yield mutable.TreeMap(keys zip values: _*)
   }
 
-  implicit def arbRedBlackTree[A: Arbitrary: Ordering, B: Arbitrary] = Arbitrary(genRedBlackTree[A, B])
-  implicit def arbTreeMap[A: Arbitrary: Ordering, B: Arbitrary] = Arbitrary(genTreeMap[A, B])
+  implicit def arbRedBlackTree[A: Arbitrary: Ordering, B: Arbitrary]: Arbitrary[RB.Tree[A,B]] = Arbitrary(genRedBlackTree[A, B])
+  implicit def arbTreeMap[A: Arbitrary: Ordering, B: Arbitrary]: Arbitrary[mutable.TreeMap[A,B]] = Arbitrary(genTreeMap[A, B])
 }
 
 object RedBlackTreeProperties extends Properties("mutable.RedBlackTree") with Generators {
@@ -218,7 +218,7 @@ object MutableTreeMapProjectionProperties extends Properties("mutable.TreeMapPro
   type K = String
   type V = Int
 
-  implicit val ord = implicitly[Ordering[K]]
+  private val ord = implicitly[Ordering[K]]
 
   def in(key: K, from: Option[K], until: Option[K]) =
     from.fold(true)(_ <= key) && until.fold(true)(_ > key)
diff --git a/test/scalacheck/scala/collection/mutable/MutableTreeSet.scala b/test/scalacheck/scala/collection/mutable/MutableTreeSet.scala
index 39a44ae453e7..68ee90462935 100644
--- a/test/scalacheck/scala/collection/mutable/MutableTreeSet.scala
+++ b/test/scalacheck/scala/collection/mutable/MutableTreeSet.scala
@@ -117,7 +117,7 @@ object MutableTreeSetProperties extends Properties("mutable.TreeSet") {
 object MutableTreeSetProjectionProperties extends Properties("mutable.TreeSetProjection") {
   type K = String
 
-  implicit val ord = implicitly[Ordering[K]]
+  private val ord = implicitly[Ordering[K]]
 
   def in(key: K, from: Option[K], until: Option[K]) =
     from.fold(true)(_ <= key) && until.fold(true)(_ > key)
diff --git a/test/scalacheck/scala/reflect/quasiquotes/ArbitraryTreesAndNames.scala b/test/scalacheck/scala/reflect/quasiquotes/ArbitraryTreesAndNames.scala
index 19032a2d0fb7..bc6e6089c231 100644
--- a/test/scalacheck/scala/reflect/quasiquotes/ArbitraryTreesAndNames.scala
+++ b/test/scalacheck/scala/reflect/quasiquotes/ArbitraryTreesAndNames.scala
@@ -267,8 +267,8 @@ trait ArbitraryTreesAndNames {
   def genTreeIsTypeWrapped(size: Int) =
     for(tit <- genTreeIsType(size)) yield TreeIsType(tit)
 
-  implicit val liftTreeIsTerm = Liftable[TreeIsTerm] { _.tree }
-  implicit val liftTreeIsType = Liftable[TreeIsType] { _.tree }
+  implicit val liftTreeIsTerm: Liftable[TreeIsTerm] = Liftable[TreeIsTerm] { _.tree }
+  implicit val liftTreeIsType: Liftable[TreeIsType] = Liftable[TreeIsType] { _.tree }
   implicit def treeIsTerm2tree(tit: TreeIsTerm): Tree = tit.tree
   implicit def treeIsType2tree(tit: TreeIsType): Tree = tit.tree
 
diff --git a/test/scalacheck/treemap.scala b/test/scalacheck/treemap.scala
index 83fb586b5192..1df3424c2064 100644
--- a/test/scalacheck/treemap.scala
+++ b/test/scalacheck/treemap.scala
@@ -12,7 +12,7 @@ object TreeMapTest extends Properties("TreeMap") {
       keys <- listOf(arbitrary[A])
       values <- listOfN(keys.size, arbitrary[B])
     } yield TreeMap(keys zip values: _*)
-  implicit def arbTreeMap[A : Arbitrary : Ordering, B : Arbitrary] = Arbitrary(genTreeMap[A, B])
+  implicit def arbTreeMap[A : Arbitrary : Ordering, B : Arbitrary]: Arbitrary[TreeMap[A, B]] = Arbitrary(genTreeMap[A, B])
 
   property("foreach/iterator consistency") = forAll { (subject: TreeMap[Int, String]) =>
     val it = subject.iterator
diff --git a/test/scaladoc/run/diagrams-base.check b/test/scaladoc/run/diagrams-base.check
index 619c56180bb9..ec9c6d6a74f2 100644
--- a/test/scaladoc/run/diagrams-base.check
+++ b/test/scaladoc/run/diagrams-base.check
@@ -1 +1,10 @@
+newSource:10: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.diagrams.T)
+      object E { implicit def eToT(e: E) = new T }
+                              ^
+newSource:18: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.diagrams.E)
+      object X { implicit def xToE(x: X) = new E}
+                              ^
+newSource:21: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.diagrams.E)
+      object Z { implicit def zToE(z: Z) = new E}
+                              ^
 Done.
diff --git a/test/scaladoc/run/diagrams-filtering.check b/test/scaladoc/run/diagrams-filtering.check
index 619c56180bb9..6f40b2c32793 100644
--- a/test/scaladoc/run/diagrams-filtering.check
+++ b/test/scaladoc/run/diagrams-filtering.check
@@ -1 +1,7 @@
+newSource:30: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.diagrams.T)
+            implicit def eToT(e: E) = new T
+                         ^
+newSource:31: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.diagrams.A)
+            implicit def eToA(e: E) = new A { }
+                         ^
 Done.
diff --git a/test/scaladoc/run/implicits-ambiguating.check b/test/scaladoc/run/implicits-ambiguating.check
index 619c56180bb9..f716066eb126 100644
--- a/test/scaladoc/run/implicits-ambiguating.check
+++ b/test/scaladoc/run/implicits-ambiguating.check
@@ -1 +1,7 @@
+newSource:70: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.ambiguating.X[T])
+  implicit def AtoX[T](a: A[T]) = new X[T]
+               ^
+newSource:71: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.ambiguating.Z[T])
+  implicit def AtoZ[T](a: A[T]) = new Z[T]
+               ^
 Done.
diff --git a/test/scaladoc/run/implicits-base.check b/test/scaladoc/run/implicits-base.check
index 619c56180bb9..e5f9afca6ebf 100644
--- a/test/scaladoc/run/implicits-base.check
+++ b/test/scaladoc/run/implicits-base.check
@@ -1 +1,19 @@
+newSource:36: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.base.EnrichedA[V])
+  implicit def enrichA0[V](a: A[V]) = new EnrichedA(a)
+               ^
+newSource:37: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.base.NumericA[ZBUR])
+  implicit def enrichA1[ZBUR: Numeric](a: A[ZBUR]) = new NumericA[ZBUR](a)
+               ^
+newSource:38: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.base.IntA)
+  implicit def enrichA2(a: A[Int]) = new IntA(a)
+               ^
+newSource:39: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.base.GtColonDoubleA)
+  implicit def enrichA3(a: A[T] forSome { type T <: Double }) = new GtColonDoubleA(a)
+               ^
+newSource:42: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.base.MyNumericA[Z])
+  implicit def enrichA6[Z: MyNumeric](a: A[Z]) = new MyNumericA[Z](a)
+               ^
+newSource:44: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.base.ManifestA[H] with scala.test.scaladoc.implicits.base.MyTraversableOps[H])
+  implicit def enrichA7[H <: Double : Manifest](a: A[H]) = new ManifestA[H](a) with MyTraversableOps[H] { def convToTraversableOps(x: H): H = sys.error("no") }
+               ^
 Done.
diff --git a/test/scaladoc/run/implicits-chaining.check b/test/scaladoc/run/implicits-chaining.check
index 619c56180bb9..9cbfe46b4ac1 100644
--- a/test/scaladoc/run/implicits-chaining.check
+++ b/test/scaladoc/run/implicits-chaining.check
@@ -1 +1,16 @@
+newSource:22: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.Implicit1[T])
+    implicit def implicit1[T <: Intermediate[_, _]](implicit b: Implicit2[T])                = new Implicit1[T](b)
+                 ^
+newSource:24: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.Implicit2[T])
+    implicit def implicit2alt1[T <: Intermediate[_ <: String, _]](implicit c: Implicit3[T])  = new Implicit2[T](c)
+                 ^
+newSource:25: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.Implicit2[T])
+    implicit def implicit2alt2[T <: Intermediate[_ <: Double, _]](implicit c: Implicit3[T])  = new Implicit2[T](c)
+                 ^
+newSource:27: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.Implicit3[T])
+    implicit def implicit3alt1[T <: Intermediate[_, _ <: Int]]                               = new Implicit3[T]()
+                 ^
+newSource:28: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.Implicit3[T])
+    implicit def implicit3alt2[T <: Intermediate[_ <: Double, _ <: AnyRef],X]                = new Implicit3[T]()
+                 ^
 Done.
diff --git a/test/scaladoc/run/implicits-known-type-classes.check b/test/scaladoc/run/implicits-known-type-classes.check
index 619c56180bb9..225b60e6cfe3 100644
--- a/test/scaladoc/run/implicits-known-type-classes.check
+++ b/test/scaladoc/run/implicits-known-type-classes.check
@@ -1 +1,49 @@
+newSource:13: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[Numeric[T]])
+    implicit def convertNumeric       [T: Numeric]       (a: A[T]) = new B(implicitly[Numeric[T]])
+                 ^
+newSource:14: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[Integral[T]])
+    implicit def convertIntegral      [T: Integral]      (a: A[T]) = new B(implicitly[Integral[T]])
+                 ^
+newSource:15: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[Fractional[T]])
+    implicit def convertFractional    [T: Fractional]    (a: A[T]) = new B(implicitly[Fractional[T]])
+                 ^
+newSource:16: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[Manifest[T]])
+    implicit def convertManifest      [T: Manifest]      (a: A[T]) = new B(implicitly[Manifest[T]])
+                 ^
+newSource:17: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[reflect.ClassManifest[T]])
+    implicit def convertClassManifest [T: ClassManifest] (a: A[T]) = new B(implicitly[ClassManifest[T]])
+                 ^
+newSource:18: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[OptManifest[T]])
+    implicit def convertOptManifest   [T: OptManifest]   (a: A[T]) = new B(implicitly[OptManifest[T]])
+                 ^
+newSource:19: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[scala.reflect.ClassTag[T]])
+    implicit def convertClassTag      [T: ClassTag]      (a: A[T]) = new B(implicitly[ClassTag[T]])
+                 ^
+newSource:20: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[reflect.runtime.universe.TypeTag[T]])
+    implicit def convertTypeTag       [T: TypeTag]       (a: A[T]) = new B(implicitly[TypeTag[T]])
+                 ^
+newSource:29: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[scala.test.scaladoc.implicits.typeclasses.A.K[T]])
+    implicit def convertK [T: K] (a: A[T]) = new B(implicitly[K[T]])
+                 ^
+newSource:30: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[scala.test.scaladoc.implicits.typeclasses.A.L[T]])
+    implicit def convertL [T: L] (a: A[T]) = new B(implicitly[L[T]])
+                 ^
+newSource:31: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[scala.test.scaladoc.implicits.typeclasses.A.M[T]])
+    implicit def convertM [T: M] (a: A[T]) = new B(implicitly[M[T]])
+                 ^
+newSource:32: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[scala.test.scaladoc.implicits.typeclasses.A.N[T]])
+    implicit def convertN [T: N] (a: A[T]) = new B(implicitly[N[T]])
+                 ^
+newSource:33: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[scala.test.scaladoc.implicits.typeclasses.A.O[T]])
+    implicit def convertO [T: O] (a: A[T]) = new B(implicitly[O[T]])
+                 ^
+newSource:34: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[scala.test.scaladoc.implicits.typeclasses.A.P[T]])
+    implicit def convertP [T: P] (a: A[T]) = new B(implicitly[P[T]])
+                 ^
+newSource:35: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[scala.test.scaladoc.implicits.typeclasses.A.Q[T]])
+    implicit def convertQ [T: Q] (a: A[T]) = new B(implicitly[Q[T]])
+                 ^
+newSource:36: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.typeclasses.B[scala.test.scaladoc.implicits.typeclasses.A.R[T]])
+    implicit def convertR [T: R] (a: A[T]) = new B(implicitly[R[T]])
+                 ^
 Done.
diff --git a/test/scaladoc/run/implicits-shadowing.check b/test/scaladoc/run/implicits-shadowing.check
index 619c56180bb9..59ba86b25cef 100644
--- a/test/scaladoc/run/implicits-shadowing.check
+++ b/test/scaladoc/run/implicits-shadowing.check
@@ -1 +1,4 @@
+newSource:63: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.implicits.shadowing.Z[T])
+  implicit def AtoZ[T](a: A[T]) = new Z[T]
+               ^
 Done.
diff --git a/test/scaladoc/run/implicits-var-exp.check b/test/scaladoc/run/implicits-var-exp.check
index 619c56180bb9..9cc519cab9e0 100644
--- a/test/scaladoc/run/implicits-var-exp.check
+++ b/test/scaladoc/run/implicits-var-exp.check
@@ -1 +1,7 @@
+newSource:8: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.variable.expansion.C)
+            implicit def aToC(a: A) = new C
+                         ^
+newSource:9: warning: Implicit definition should have explicit type (inferred scala.test.scaladoc.variable.expansion.E with scala.test.scaladoc.variable.expansion.F)
+            implicit def aToE(a: A) = new E with F
+                         ^
 Done.
diff --git a/test/tasty/neg/src-2/TestCtxFns_fail.scala b/test/tasty/neg/src-2/TestCtxFns_fail.scala
index 150ec4a209bc..c1db5e1d1585 100644
--- a/test/tasty/neg/src-2/TestCtxFns_fail.scala
+++ b/test/tasty/neg/src-2/TestCtxFns_fail.scala
@@ -9,7 +9,7 @@ object TestCtxFns {
     def puts[T](t: T): Unit = logs += t.toString
   }
 
-  implicit val ctx = new TestContext
+  implicit val ctx: TestContext = new TestContext
 
   def test1: Unit = {
     puts(23)(ctx)