Merge pull request #5402 from som-snytt/issue/8040-unused

SI-8040 Improve unused warnings

31 files changed, 493 insertions, 36 deletions

diff --git a/test/files/neg/abstract-inaccessible.check b/test/files/neg/abstract-inaccessible.check
index d56f5691be..739620a4ce 100644
--- a/test/files/neg/abstract-inaccessible.check
+++ b/test/files/neg/abstract-inaccessible.check
@@ -8,7 +8,7 @@ Classes which cannot access Bippy may be unable to override overrideMe.
         ^
 abstract-inaccessible.scala:7: warning: method overrideMeAlso in trait YourTrait references private[foo] trait Bippy.
 Classes which cannot access Bippy may be unable to override overrideMeAlso.
-    def overrideMeAlso(x: Map[Int, Set[Bippy]]) = 5
+    def overrideMeAlso(x: Map[Int, Set[Bippy]]) = x.keys.head
         ^
 error: No warnings can be incurred under -Xfatal-warnings.
 three warnings found
diff --git a/test/files/neg/abstract-inaccessible.flags b/test/files/neg/abstract-inaccessible.flags
index 6c1dd108ae..ea7773e255 100644
--- a/test/files/neg/abstract-inaccessible.flags
+++ b/test/files/neg/abstract-inaccessible.flags
@@ -1 +1 @@
--Xfatal-warnings -Xlint
\ No newline at end of file
+-Xfatal-warnings -Xlint:inaccessible
diff --git a/test/files/neg/abstract-inaccessible.scala b/test/files/neg/abstract-inaccessible.scala
index 3c80f30522..02b458016f 100644
--- a/test/files/neg/abstract-inaccessible.scala
+++ b/test/files/neg/abstract-inaccessible.scala
@@ -4,6 +4,6 @@ package foo {
   trait YourTrait {
     def implementMe(f: Int => (String, Bippy)): Unit
     def overrideMe[T <: Bippy](x: T): T = x
-    def overrideMeAlso(x: Map[Int, Set[Bippy]]) = 5
+    def overrideMeAlso(x: Map[Int, Set[Bippy]]) = x.keys.head
   }
 }
diff --git a/test/files/neg/forgot-interpolator.flags b/test/files/neg/forgot-interpolator.flags
index 7949c2afa2..b0d7bc25cb 100644
--- a/test/files/neg/forgot-interpolator.flags
+++ b/test/files/neg/forgot-interpolator.flags
@@ -1 +1 @@
--Xlint -Xfatal-warnings
+-Xlint:missing-interpolator -Xfatal-warnings
diff --git a/test/files/neg/overloaded-implicit.flags b/test/files/neg/overloaded-implicit.flags
index 9c1e74e4ef..e04a4228ba 100644
--- a/test/files/neg/overloaded-implicit.flags
+++ b/test/files/neg/overloaded-implicit.flags
@@ -1 +1 @@
--Xlint -Xfatal-warnings -Xdev
+-Xlint:poly-implicit-overload -Xfatal-warnings -Xdev
diff --git a/test/files/neg/t1980.flags b/test/files/neg/t1980.flags
index 7949c2afa2..cdc464a47d 100644
--- a/test/files/neg/t1980.flags
+++ b/test/files/neg/t1980.flags
@@ -1 +1 @@
--Xlint -Xfatal-warnings
+-Xlint:by-name-right-associative -Xfatal-warnings
diff --git a/test/files/neg/t4877.flags b/test/files/neg/t4877.flags
deleted file mode 100644
index 7ccd56103a..0000000000
--- a/test/files/neg/t4877.flags
+++ /dev/null
@@ -1 +0,0 @@
--Xlint
\ No newline at end of file
diff --git a/test/files/neg/t6567.flags b/test/files/neg/t6567.flags
index e93641e931..076333a011 100644
--- a/test/files/neg/t6567.flags
+++ b/test/files/neg/t6567.flags
@@ -1 +1 @@
--Xlint -Xfatal-warnings
\ No newline at end of file
+-Xlint:option-implicit -Xfatal-warnings
diff --git a/test/files/neg/t6675.flags b/test/files/neg/t6675.flags
index 2843ea9efc..c6bfaf1f64 100644
--- a/test/files/neg/t6675.flags
+++ b/test/files/neg/t6675.flags
@@ -1 +1 @@
--deprecation -Xlint -Xfatal-warnings
\ No newline at end of file
+-deprecation -Xfatal-warnings
diff --git a/test/files/neg/t7860.check b/test/files/neg/t7860.check
new file mode 100644
index 0000000000..9b9d86c89d
--- /dev/null
+++ b/test/files/neg/t7860.check
@@ -0,0 +1,9 @@
+t7860.scala:5: warning: private class for your eyes only in object Test is never used
+  private implicit class `for your eyes only`(i: Int) {       // warn
+                         ^
+t7860.scala:31: warning: private class C in object Test3 is never used
+  private implicit class C(val i: Int) extends AnyVal {       // warn
+                         ^
+error: No warnings can be incurred under -Xfatal-warnings.
+two warnings found
+one error found
diff --git a/test/files/neg/t7860.flags b/test/files/neg/t7860.flags
new file mode 100644
index 0000000000..6ff0dea0b2
--- /dev/null
+++ b/test/files/neg/t7860.flags
@@ -0,0 +1 @@
+-Xfatal-warnings -Ywarn-unused:privates
diff --git a/test/files/neg/t7860.scala b/test/files/neg/t7860.scala
new file mode 100644
index 0000000000..6cc0d3e7f5
--- /dev/null
+++ b/test/files/neg/t7860.scala
@@ -0,0 +1,42 @@
+
+class Test
+
+object Test {
+  private implicit class `for your eyes only`(i: Int) {       // warn
+    def f = i
+  }
+}
+
+class Test2 {
+  import Test2._
+  println(5.toStr)
+}
+ 
+object Test2 {
+  // was: warning: private object in object Test2 is never used
+  // i.e. synthetic object C
+  private implicit class C(val i: Int) extends AnyVal {       // no warn
+    def toStr = i.toString
+  }
+}
+
+class Test3 {
+  import Test3._
+  //println(5.toStr)
+}
+ 
+object Test3 {
+  // was: warning: private object in object Test2 is never used
+  // i.e. synthetic object C
+  private implicit class C(val i: Int) extends AnyVal {       // warn
+    def toStr = i.toString
+  }
+}
+
+object Test4 {
+  class A { class B }
+
+  private val a: A = new A
+
+  def b = (new a.B).##
+}
diff --git a/test/files/neg/warn-unused-implicits.check b/test/files/neg/warn-unused-implicits.check
new file mode 100644
index 0000000000..4cc5836800
--- /dev/null
+++ b/test/files/neg/warn-unused-implicits.check
@@ -0,0 +1,9 @@
+warn-unused-implicits.scala:11: warning: parameter value s in method f is never used
+       )(implicit s: String): Int = {  // warn
+                  ^
+warn-unused-implicits.scala:31: warning: parameter value s in method i is never used
+  def i(implicit s: String, t: Int) = t           // yes, warn
+                 ^
+error: No warnings can be incurred under -Xfatal-warnings.
+two warnings found
+one error found
diff --git a/test/files/neg/warn-unused-implicits.flags b/test/files/neg/warn-unused-implicits.flags
new file mode 100644
index 0000000000..18169f3218
--- /dev/null
+++ b/test/files/neg/warn-unused-implicits.flags
@@ -0,0 +1 @@
+-Ywarn-unused:implicits -Xfatal-warnings
diff --git a/test/files/neg/warn-unused-implicits.scala b/test/files/neg/warn-unused-implicits.scala
new file mode 100644
index 0000000000..54f924eac0
--- /dev/null
+++ b/test/files/neg/warn-unused-implicits.scala
@@ -0,0 +1,32 @@
+
+trait InterFace {
+  /** Call something. */
+  def call(a: Int, b: String, c: Double)(implicit s: String): Int
+}
+
+trait BadAPI extends InterFace {
+  def f(a: Int,
+        b: String,
+        c: Double
+       )(implicit s: String): Int = {  // warn
+    println(b + c)
+    a
+  }
+  @deprecated ("no warn in deprecated API", since="yesterday")
+  def g(a: Int,
+        b: String,
+        c: Double
+       )(implicit s: String): Int = {  // no warn
+    println(b + c)
+    a
+  }
+  override def call(a: Int,
+                    b: String,
+                    c: Double
+                   )(implicit s: String): Int = {  // no warn, required by superclass
+    println(b + c)
+    a
+  }
+
+  def i(implicit s: String, t: Int) = t           // yes, warn
+}
diff --git a/test/files/neg/warn-unused-imports.check b/test/files/neg/warn-unused-imports.check
index 0a53d7a9cd..29d73a6264 100644
--- a/test/files/neg/warn-unused-imports.check
+++ b/test/files/neg/warn-unused-imports.check
@@ -51,5 +51,8 @@ warn-unused-imports_2.scala:149: warning: Unused import
 warn-unused-imports_2.scala:150: warning: Unused import
     import p1.A                         // warn
               ^
-16 warnings found
+warn-unused-imports_2.scala:158: warning: Unused import
+  def x = Macro.f  // warn, not crash
+                ^
+17 warnings found
 one error found
diff --git a/test/files/neg/warn-unused-imports.flags b/test/files/neg/warn-unused-imports.flags
index 24db705df1..c4e11e7fe7 100644
--- a/test/files/neg/warn-unused-imports.flags
+++ b/test/files/neg/warn-unused-imports.flags
@@ -1 +1 @@
--Xfatal-warnings -Ywarn-unused-import
+-Xfatal-warnings -Ywarn-unused:imports
diff --git a/test/files/neg/warn-unused-imports/sample_1.scala b/test/files/neg/warn-unused-imports/sample_1.scala
index d2f86239db..eea4d0eb4c 100644
--- a/test/files/neg/warn-unused-imports/sample_1.scala
+++ b/test/files/neg/warn-unused-imports/sample_1.scala
@@ -15,3 +15,18 @@ object Sample {
   def f(x: X) = ???
   def g(y: Y) = ???
 }
+
+import scala.language.experimental.macros
+import scala.reflect.macros.blackbox.Context
+ 
+object Macro {
+  def f: Int = macro fImpl
+  def fImpl(c: Context): c.Tree = {
+    import c.universe._
+ 
+    q"""
+     import scala.util.Random
+     42 // TODO randomize
+    """
+  }
+}
diff --git a/test/files/neg/warn-unused-imports/warn-unused-imports_2.scala b/test/files/neg/warn-unused-imports/warn-unused-imports_2.scala
index ded1186209..58fe0131d9 100644
--- a/test/files/neg/warn-unused-imports/warn-unused-imports_2.scala
+++ b/test/files/neg/warn-unused-imports/warn-unused-imports_2.scala
@@ -96,7 +96,7 @@ trait Warn {
 trait Nested {
   {
     import p1._   // warn
-    trait Warn {  // warn about unused local trait for good measure
+    trait Warn {  // don't warn about unused local trait with -Ywarn-unused:imports
       import p2._
       println(new A)
       println("abc".bippy)
@@ -153,3 +153,7 @@ trait Outsiders {
     //Future("abc".bippy)
   }
 }
+
+class MacroClient {
+  def x = Macro.f  // warn, not crash
+}
diff --git a/test/files/neg/warn-unused-params.check b/test/files/neg/warn-unused-params.check
new file mode 100644
index 0000000000..373417ce08
--- /dev/null
+++ b/test/files/neg/warn-unused-params.check
@@ -0,0 +1,18 @@
+warn-unused-params.scala:9: warning: parameter value b in method f is never used
+        b: String,               // warn
+        ^
+warn-unused-params.scala:32: warning: parameter value s in method i is never used
+  def i(implicit s: String) = 42           // yes, warn
+                 ^
+warn-unused-params.scala:49: warning: parameter value u in class Unusing is never used
+class Unusing(u: Int) {       // warn
+              ^
+warn-unused-params.scala:59: warning: parameter value s in class CaseyAtTheBat is never used
+case class CaseyAtTheBat(k: Int)(s: String)        // warn
+                                 ^
+warn-unused-params.scala:62: warning: parameter value readResolve in method f is never used
+  def f(readResolve: Int) = 42           // warn
+        ^
+error: No warnings can be incurred under -Xfatal-warnings.
+5 warnings found
+one error found
diff --git a/test/files/neg/warn-unused-params.flags b/test/files/neg/warn-unused-params.flags
new file mode 100644
index 0000000000..795fb74272
--- /dev/null
+++ b/test/files/neg/warn-unused-params.flags
@@ -0,0 +1 @@
+-Ywarn-unused:params -Xfatal-warnings
diff --git a/test/files/neg/warn-unused-params.scala b/test/files/neg/warn-unused-params.scala
new file mode 100644
index 0000000000..b166e8fae6
--- /dev/null
+++ b/test/files/neg/warn-unused-params.scala
@@ -0,0 +1,69 @@
+
+trait InterFace {
+  /** Call something. */
+  def call(a: Int, b: String, c: Double): Int
+}
+
+trait BadAPI extends InterFace {
+  def f(a: Int,
+        b: String,               // warn
+        c: Double): Int = {
+    println(c)
+    a
+  }
+  @deprecated ("no warn in deprecated API", since="yesterday")
+  def g(a: Int,
+        b: String,               // no warn
+        c: Double): Int = {
+    println(c)
+    a
+  }
+  override def call(a: Int,
+                    b: String,               // no warn, required by superclass
+                    c: Double): Int = {
+    println(c)
+    a
+  }
+
+  def meth(x: Int) = x
+
+  override def equals(other: Any): Boolean = true  // no warn
+
+  def i(implicit s: String) = 42           // yes, warn
+
+  /*
+  def future(x: Int): Int = {
+    val y = 42
+    val x = y               // maybe option to warn only if shadowed
+    x
+  }
+  */
+}
+
+// mustn't alter warnings in super
+trait PoorClient extends BadAPI {
+  override def meth(x: Int) = ???       // no warn
+  override def f(a: Int, b: String, c: Double): Int = a + b.toInt + c.toInt
+}
+
+class Unusing(u: Int) {       // warn
+  def f = ???
+}
+
+class Valuing(val u: Int)        // no warn
+
+class Revaluing(u: Int) { def f = u } // no warn
+
+case class CaseyKasem(k: Int)        // no warn
+
+case class CaseyAtTheBat(k: Int)(s: String)        // warn
+
+trait Ignorance {
+  def f(readResolve: Int) = 42           // warn
+}
+
+class Reusing(u: Int) extends Unusing(u)   // no warn
+
+class Main {
+  def main(args: Array[String]): Unit = println("hello, args")  // no warn
+}
diff --git a/test/files/neg/warn-unused-patvars.check b/test/files/neg/warn-unused-patvars.check
new file mode 100644
index 0000000000..2665126a36
--- /dev/null
+++ b/test/files/neg/warn-unused-patvars.check
@@ -0,0 +1,12 @@
+warn-unused-patvars.scala:9: warning: private val x in trait Boundings is never used
+  private val x = 42                      // warn, sanity check
+              ^
+warn-unused-patvars.scala:28: warning: local val x in method v is never used
+    val D(x) = d                          // warn, fixme
+         ^
+warn-unused-patvars.scala:32: warning: local val x in method w is never used
+    val D(x @ _) = d                      // warn, fixme (valdef pos is different)
+         ^
+error: No warnings can be incurred under -Xfatal-warnings.
+three warnings found
+one error found
diff --git a/test/files/neg/warn-unused-patvars.flags b/test/files/neg/warn-unused-patvars.flags
new file mode 100644
index 0000000000..d5bd86a658
--- /dev/null
+++ b/test/files/neg/warn-unused-patvars.flags
@@ -0,0 +1 @@
+-Ywarn-unused:-patvars,_ -Xfatal-warnings
diff --git a/test/files/neg/warn-unused-patvars.scala b/test/files/neg/warn-unused-patvars.scala
new file mode 100644
index 0000000000..3d35dfedd6
--- /dev/null
+++ b/test/files/neg/warn-unused-patvars.scala
@@ -0,0 +1,53 @@
+
+// verify no warning when -Ywarn-unused:-patvars
+
+case class C(a: Int, b: String, c: Option[String])
+case class D(a: Int)
+
+trait Boundings {
+
+  private val x = 42                      // warn, sanity check
+
+  def c = C(42, "hello", Some("world"))
+  def d = D(42)
+
+  def f() = {
+    val C(x, y, Some(z)) = c              // no warn
+    17
+  }
+  def g() = {
+    val C(x @ _, y @ _, Some(z @ _)) = c  // no warn
+    17
+  }
+  def h() = {
+    val C(x @ _, y @ _, z @ Some(_)) = c  // no warn for z?
+    17
+  }
+
+  def v() = {
+    val D(x) = d                          // warn, fixme
+    17
+  }
+  def w() = {
+    val D(x @ _) = d                      // warn, fixme (valdef pos is different)
+    17
+  }
+
+}
+
+trait Forever {
+  def f = {
+    val t = Option((17, 42))
+    for {
+      ns <- t
+      (i, j) = ns                        // no warn
+    } yield (i + j)
+  }
+  def g = {
+    val t = Option((17, 42))
+    for {
+      ns <- t
+      (i, j) = ns                        // no warn
+    } yield 42
+  }
+}
diff --git a/test/files/neg/warn-unused-privates.check b/test/files/neg/warn-unused-privates.check
index 2e93f338bb..2a88d3e6c3 100644
--- a/test/files/neg/warn-unused-privates.check
+++ b/test/files/neg/warn-unused-privates.check
@@ -1,66 +1,120 @@
 warn-unused-privates.scala:2: warning: private constructor in class Bippy is never used
   private def this(c: Int) = this(c, c)           // warn
               ^
-warn-unused-privates.scala:4: warning: private method in class Bippy is never used
+warn-unused-privates.scala:4: warning: private method boop in class Bippy is never used
   private def boop(x: Int)            = x+a+b     // warn
               ^
-warn-unused-privates.scala:6: warning: private val in class Bippy is never used
+warn-unused-privates.scala:6: warning: private val MILLIS2 in class Bippy is never used
   final private val MILLIS2: Int      = 1000      // warn
                     ^
-warn-unused-privates.scala:13: warning: private val in object Bippy is never used
+warn-unused-privates.scala:13: warning: private val HEY_INSTANCE in object Bippy is never used
   private val HEY_INSTANCE: Int = 1000    // warn
               ^
-warn-unused-privates.scala:14: warning: private val in object Bippy is never used
+warn-unused-privates.scala:14: warning: private val BOOL in object Bippy is never used
   private lazy val BOOL: Boolean = true   // warn
                    ^
-warn-unused-privates.scala:36: warning: private val in class Boppy is never used
+warn-unused-privates.scala:36: warning: private val hummer in class Boppy is never used
   private val hummer = "def" // warn
               ^
-warn-unused-privates.scala:43: warning: private var in trait Accessors is never used
+warn-unused-privates.scala:43: warning: private var v1 in trait Accessors is never used
   private var v1: Int = 0 // warn
               ^
-warn-unused-privates.scala:44: warning: private var in trait Accessors is never used
+warn-unused-privates.scala:44: warning: private var v2 in trait Accessors is never used
   private var v2: Int = 0 // warn, never set
               ^
-warn-unused-privates.scala:45: warning: private var in trait Accessors is never used
+warn-unused-privates.scala:45: warning: private var v3 in trait Accessors is never used
   private var v3: Int = 0 // warn, never got
               ^
-warn-unused-privates.scala:57: warning: private default argument in trait DefaultArgs is never used
+warn-unused-privates.scala:56: warning: private var s1 in class StableAccessors is never used
+  private var s1: Int = 0 // warn
+              ^
+warn-unused-privates.scala:57: warning: private setter of s2 in class StableAccessors is never used
+  private var s2: Int = 0 // warn, never set
+              ^
+warn-unused-privates.scala:58: warning: private var s3 in class StableAccessors is never used
+  private var s3: Int = 0 // warn, never got
+              ^
+warn-unused-privates.scala:70: warning: private default argument in trait DefaultArgs is never used
   private def bippy(x1: Int, x2: Int = 10, x3: Int = 15): Int = x1 + x2 + x3
                              ^
-warn-unused-privates.scala:57: warning: private default argument in trait DefaultArgs is never used
+warn-unused-privates.scala:70: warning: private default argument in trait DefaultArgs is never used
   private def bippy(x1: Int, x2: Int = 10, x3: Int = 15): Int = x1 + x2 + x3
                                            ^
-warn-unused-privates.scala:68: warning: local var in method f0 is never used
+warn-unused-privates.scala:86: warning: local var x in method f0 is never used
     var x = 1 // warn
         ^
-warn-unused-privates.scala:75: warning: local val in method f1 is never used
+warn-unused-privates.scala:93: warning: local val b in method f1 is never used
     val b = new Outer // warn
         ^
-warn-unused-privates.scala:85: warning: private object in object Types is never used
+warn-unused-privates.scala:103: warning: private object Dongo in object Types is never used
   private object Dongo { def f = this } // warn
                  ^
-warn-unused-privates.scala:95: warning: local object in method l1 is never used
+warn-unused-privates.scala:113: warning: local object HiObject in method l1 is never used
     object HiObject { def f = this } // warn
            ^
-warn-unused-privates.scala:79: warning: local var x in method f2 is never set - it could be a val
+warn-unused-privates.scala:136: warning: private method x_= in class OtherNames is never used
+  private def x_=(i: Int): Unit = ???
+              ^
+warn-unused-privates.scala:137: warning: private method x in class OtherNames is never used
+  private def x: Int = 42
+              ^
+warn-unused-privates.scala:138: warning: private method y_= in class OtherNames is never used
+  private def y_=(i: Int): Unit = ???
+              ^
+warn-unused-privates.scala:153: warning: local val x in method f is never used
+    val C(x, y, Some(z)) = c              // warn
+          ^
+warn-unused-privates.scala:153: warning: local val y in method f is never used
+    val C(x, y, Some(z)) = c              // warn
+             ^
+warn-unused-privates.scala:153: warning: local val z in method f is never used
+    val C(x, y, Some(z)) = c              // warn
+                     ^
+warn-unused-privates.scala:161: warning: local val z in method h is never used
+    val C(x @ _, y @ _, z @ Some(_)) = c  // warn for z?
+                        ^
+warn-unused-privates.scala:166: warning: local val x in method v is never used
+    val D(x) = d                          // warn
+         ^
+warn-unused-privates.scala:170: warning: local val x in method w is never used
+    val D(x @ _) = d                      // warn, fixme (valdef pos is different)
+         ^
+warn-unused-privates.scala:97: warning: local var x in method f2 is never set: consider using immutable val
     var x = 100 // warn about it being a var
         ^
-warn-unused-privates.scala:86: warning: private class Bar1 in object Types is never used
+warn-unused-privates.scala:104: warning: private class Bar1 in object Types is never used
   private class Bar1 // warn
                 ^
-warn-unused-privates.scala:88: warning: private type Alias1 in object Types is never used
+warn-unused-privates.scala:106: warning: private type Alias1 in object Types is never used
   private type Alias1 = String // warn
                ^
-warn-unused-privates.scala:96: warning: local class Hi is never used
+warn-unused-privates.scala:114: warning: local class Hi is never used
     class Hi { // warn
           ^
-warn-unused-privates.scala:100: warning: local class DingDongDoobie is never used
+warn-unused-privates.scala:118: warning: local class DingDongDoobie is never used
     class DingDongDoobie // warn
           ^
-warn-unused-privates.scala:103: warning: local type OtherThing is never used
+warn-unused-privates.scala:121: warning: local type OtherThing is never used
     type OtherThing = String // warn
          ^
+warn-unused-privates.scala:216: warning: private class for your eyes only in object not even using companion privates is never used
+  private implicit class `for your eyes only`(i: Int) {  // warn
+                         ^
+warn-unused-privates.scala:201: warning: pattern var z in method f is never used; `z@_' suppresses this warning
+    case z => "warn"
+         ^
+warn-unused-privates.scala:208: warning: pattern var z in method f is never used; `z@_' suppresses this warning
+    case Some(z) => "warn"
+              ^
+warn-unused-privates.scala:20: warning: parameter value msg0 in class B3 is never used
+class B3(msg0: String) extends A("msg")
+         ^
+warn-unused-privates.scala:136: warning: parameter value i in method x_= is never used
+  private def x_=(i: Int): Unit = ???
+                  ^
+warn-unused-privates.scala:138: warning: parameter value i in method y_= is never used
+  private def y_=(i: Int): Unit = ???
+                  ^
 error: No warnings can be incurred under -Xfatal-warnings.
-21 warnings found
+39 warnings found
 one error found
diff --git a/test/files/neg/warn-unused-privates.scala b/test/files/neg/warn-unused-privates.scala
index 2eda280d40..f7640927fb 100644
--- a/test/files/neg/warn-unused-privates.scala
+++ b/test/files/neg/warn-unused-privates.scala
@@ -52,6 +52,19 @@ trait Accessors {
   }
 }
 
+class StableAccessors {
+  private var s1: Int = 0 // warn
+  private var s2: Int = 0 // warn, never set
+  private var s3: Int = 0 // warn, never got
+  private var s4: Int = 0 // no warn
+
+  def bippy(): Int = {
+    s3 = 5
+    s4 = 6
+    s2 + s4
+  }
+}
+
 trait DefaultArgs {
   // warn about default getters for x2 and x3
   private def bippy(x1: Int, x2: Int = 10, x3: Int = 15): Int = x1 + x2 + x3
@@ -59,6 +72,11 @@ trait DefaultArgs {
   def boppy() = bippy(5, 100, 200)
 }
 
+/* SI-7707 Both usages warn default arg because using PrivateRyan.apply, not new.
+case class PrivateRyan private (ryan: Int = 42) { def f = PrivateRyan() }
+object PrivateRyan { def f = PrivateRyan() }
+*/
+
 class Outer {
   class Inner
 }
@@ -104,3 +122,105 @@ object Types {
     (new Bippy): Something
   }
 }
+
+trait Underwarn {
+  def f(): Seq[Int]
+
+  def g() = {
+    val Seq(_, _) = f()  // no warn
+    true
+  }
+}
+
+class OtherNames {
+  private def x_=(i: Int): Unit = ???
+  private def x: Int = 42
+  private def y_=(i: Int): Unit = ???
+  private def y: Int = 42
+
+  def f = y
+}
+
+case class C(a: Int, b: String, c: Option[String])
+case class D(a: Int)
+
+trait Boundings {
+
+  def c = C(42, "hello", Some("world"))
+  def d = D(42)
+
+  def f() = {
+    val C(x, y, Some(z)) = c              // warn
+    17
+  }
+  def g() = {
+    val C(x @ _, y @ _, Some(z @ _)) = c  // no warn
+    17
+  }
+  def h() = {
+    val C(x @ _, y @ _, z @ Some(_)) = c  // warn for z?
+    17
+  }
+
+  def v() = {
+    val D(x) = d                          // warn
+    17
+  }
+  def w() = {
+    val D(x @ _) = d                      // warn, fixme (valdef pos is different)
+    17
+  }
+
+}
+
+trait Forever {
+  def f = {
+    val t = Option((17, 42))
+    for {
+      ns <- t
+      (i, j) = ns                        // no warn
+    } yield (i + j)
+  }
+  def g = {
+    val t = Option((17, 42))
+    for {
+      ns <- t
+      (i, j) = ns                        // warn, fixme
+    } yield 42                           // val emitted only if needed, hence nothing unused
+  }
+}
+
+trait Ignorance {
+  private val readResolve = 42      // ignore
+}
+
+trait CaseyKasem {
+  def f = 42 match {
+    case x if x < 25 => "no warn"
+    case y if toString.nonEmpty => "no warn" + y
+    case z => "warn"
+  }
+}
+trait CaseyAtTheBat {
+  def f = Option(42) match {
+    case Some(x) if x < 25 => "no warn"
+    case Some(y @ _) if toString.nonEmpty => "no warn"
+    case Some(z) => "warn"
+    case None => "no warn"
+  }
+}
+
+class `not even using companion privates`
+
+object `not even using companion privates` {
+  private implicit class `for your eyes only`(i: Int) {  // warn
+    def f = i
+  }
+}
+
+class `no warn in patmat anonfun isDefinedAt` {
+  def f(pf: PartialFunction[String, Int]) = pf("42")
+  def g = f {
+    case s => s.length        // no warn (used to warn case s => true in isDefinedAt)
+  }
+}
diff --git a/test/files/pos/t6091.scala b/test/files/pos/t6091.scala
index 72e663ec3b..0318640e7b 100644
--- a/test/files/pos/t6091.scala
+++ b/test/files/pos/t6091.scala
@@ -1,6 +1,6 @@
-object Foo { def eq(x:Int) = x }
+object Foo { def eq(x: Int) = x }
 
-class X { def ==(other: String) = true }
+class X { def ==(other: String) = other.nonEmpty }
 
 object Test {
   def main(args: Array[String]): Unit = {
diff --git a/test/files/pos/t8013.flags b/test/files/pos/t8013.flags
index 3955bb6710..219723cec9 100644
--- a/test/files/pos/t8013.flags
+++ b/test/files/pos/t8013.flags
@@ -1 +1 @@
--Xfatal-warnings -Xlint:-infer-any,_
+-Xfatal-warnings -Xlint:missing-interpolator
diff --git a/test/files/pos/t8040.flags b/test/files/pos/t8040.flags
new file mode 100644
index 0000000000..3126c059f0
--- /dev/null
+++ b/test/files/pos/t8040.flags
@@ -0,0 +1 @@
+-Xfatal-warnings -Ywarn-unused:params
diff --git a/test/files/pos/t8040.scala b/test/files/pos/t8040.scala
new file mode 100644
index 0000000000..3e01014ab4
--- /dev/null
+++ b/test/files/pos/t8040.scala
@@ -0,0 +1,13 @@
+
+object Test {
+  implicit class C(val sc: StringContext) {                 // no warn unused sc
+    def c(args: Any*): String = "c?" + args.mkString(",")   // would warn unused args
+  }
+
+  def f(implicit x: DummyImplicit) = 42                     // no warn DummyImplicit
+
+
+  def f(x: Int)(y: Int = 1) = x + y                         // no warn default getter
+
+  def g(@deprecated("","") x: Int) = 42                     // no warn deprecated
+}