SI-8040 Xlint enables unused warnings

`-Ywarn-unused-import` is deprecated in favor of `-Ywarn-unused:imports`.

`-Xlint` does not yet enable `-Ywarn-unused:patvars`.

But the default for `-Ywarn-unused` is everything, including `patvars`.

So `-Xlint:unused` is the populist option, `-Ywarn-unused` more exclusive.

Tests are fixed by narrowing scope of `-Xlint` when specified.

15 files changed, 23 insertions, 19 deletions

diff --git a/src/compiler/scala/tools/nsc/settings/Warnings.scala b/src/compiler/scala/tools/nsc/settings/Warnings.scala
index 29138c78d1..eb78064155 100644
--- a/src/compiler/scala/tools/nsc/settings/Warnings.scala
+++ b/src/compiler/scala/tools/nsc/settings/Warnings.scala
@@ -48,7 +48,7 @@ trait Warnings {
 
   BooleanSetting("-Ywarn-unused-import", "Warn when imports are unused.") withPostSetHook { s =>
     warnUnused.add(s"${if (s) "" else "-"}imports")
-  } // withDeprecationMessage s"Enable -Ywarn-unused:imports"
+  } withDeprecationMessage s"Enable -Ywarn-unused:imports"
 
   val warnExtraImplicit    = BooleanSetting("-Ywarn-extra-implicit", "Warn when more than one implicit parameter section is defined.")
 
@@ -85,8 +85,7 @@ trait Warnings {
     val UnsoundMatch           = LintWarning("unsound-match",             "Pattern match may not be typesafe.")
     val StarsAlign             = LintWarning("stars-align",               "Pattern sequence wildcard must align with sequence component.")
     val Constant               = LintWarning("constant",                  "Evaluation of a constant arithmetic expression results in an error.")
-    //val Unused                 = LintWarning("unused",                    "Warn when private and local definitions are unused.")
-    val Unused                 = LintWarning("unused",                    "Use -Ywarn-unused to warn when private and local definitions are unused.")
+    val Unused                 = LintWarning("unused",                    "Enable -Ywarn-unused:-patvars,_.")
 
     def allLintWarnings = values.toSeq.asInstanceOf[Seq[LintWarning]]
   }
@@ -129,9 +128,8 @@ trait Warnings {
     helpArg = "warning",
     descr   = "Enable or disable specific warnings",
     domain  = LintWarnings,
-    default = Some(List("_"))) //.withPostSetHook (s => if (s contains Unused) warnUnused.add("_"))
-
-  // restore -Xlint:unused hook when SI-8040 is complete
+    default = Some(List("_"))
+  ).withPostSetHook { s => if (s contains Unused) List("-patvars","_").foreach(warnUnused.add) }
 
   allLintWarnings foreach {
     case w if w.yAliased =>
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/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/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..b067f36b0b
--- /dev/null
+++ b/test/files/pos/t8040.scala
@@ -0,0 +1,6 @@
+
+object Test {
+  implicit class C(val sc: StringContext) {                 // no warn unused sc
+    def c(args: Any*): String = "c?" + args.mkString(",")   // would warn unused args
+  }
+}