Merge pull request #10305 from som-snytt/issue/10314-unused-from-self…

…type

Unused warning checks self-type for overrides

src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala

@@ -41,7 +41,7 @@ import scala.tools.nsc.Reporting.WarningCategory
  *  @author Paul Phillips
  */
 trait TypeDiagnostics extends splain.SplainDiagnostics {
-  self: Analyzer with StdAttachments =>
+  _: Analyzer with StdAttachments =>
 
   import global._
   import definitions._
@@ -738,8 +738,11 @@ trait TypeDiagnostics extends splain.SplainDiagnostics {
       if (settings.warnUnusedParams) {
         def isImplementation(m: Symbol): Boolean = {
           def classOf(s: Symbol): Symbol = if (s.isClass || s == NoSymbol) s else classOf(s.owner)
-          val opc = new overridingPairs.PairsCursor(classOf(m))
-          opc.iterator.exists(pair => pair.low == m)
+          val opc = new overridingPairs.PairsCursor(classOf(m)) {
+            override protected def bases: List[Symbol] = self.baseClasses
+            override protected def exclude(sym: Symbol) = super.exclude(sym) || sym.name != m.name || sym.paramLists.isEmpty || sym.paramLists.head.isEmpty
+          }
+          opc.iterator.exists(pair => pair.low == m || pair.high == m)
         }
         import PartialFunction._
         def isConvention(p: Symbol): Boolean = (
@@ -780,7 +783,7 @@ trait TypeDiagnostics extends splain.SplainDiagnostics {
 
 
   trait TyperDiagnostics {
-    self: Typer =>
+    _: Typer =>
 
     def permanentlyHiddenWarning(pos: Position, hidden: Name, defn: Symbol) =
       context.warning(pos, "imported `%s` is permanently hidden by definition of %s".format(hidden, defn.fullLocationString), WarningCategory.OtherShadowing)

test/files/neg/warn-unused-params.check

@@ -37,6 +37,12 @@ warn-unused-params.scala:102: warning: evidence parameter evidence$1 of type Con
 warn-unused-params.scala:104: warning: evidence parameter evidence$2 of type Context[A] in class Bound is never used
 class Bound[A: Context]
                ^
+warn-unused-params.scala:111: warning: parameter b in method f is never used
+        b: String,               // warn
+        ^
+warn-unused-params.scala:134: warning: parameter s in method i is never used
+  def i(implicit s: String) = answer           // yes, warn
+                 ^
 error: No warnings can be incurred under -Werror.
-13 warnings
+15 warnings
 1 error

test/files/neg/warn-unused-params.scala

@@ -105,3 +105,35 @@ class Bound[A: Context]
 object Answers {
   def answer: Int = 42
 }
+
+trait BadMix { _: 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) = answer           // yes, warn
+}
+
+class Unequal {
+  override def equals(other: Any) = toString.nonEmpty   // no warn non-trivial RHS, required by universal method
+}

test/files/pos/t12520.scala

@@ -13,4 +13,4 @@ trait TimeLimitedTests extends TestSuiteMixin { this: TestSuite =>
 }
 
 trait AnyFunSuiteLike extends TestSuite
-abstract class Test[C] extends AnyFunSuiteLike with TimeLimitedTests
+abstract class Test[C] extends AnyFunSuiteLike with TimeLimitedTests