Consider superclass context

Filter member of refinement, handle Annotated
TypeTree is usage of simple name
Handle quotes and splices
Tighten allowance for serialization methods
Restore inferred type is not a usage, noprefix is in import
Warn for top level private
Import given takes NoPrefix usage
Don't ignore params of public methods
Accept updated semanticdb output

Author: som-snytt

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -48,10 +48,10 @@ class Compiler {
     List(new sbt.ExtractAPI) ::     // Sends a representation of the API of classes to sbt via callbacks
     List(new Inlining) ::           // Inline and execute macros
     List(new PostInlining) ::       // Add mirror support for inlined code
-    List(new CheckUnused.PostInlining) ::  // Check for unused elements
     List(new Staging) ::            // Check staging levels and heal staged types
     List(new Splicing) ::           // Replace level 1 splices with holes
     List(new PickleQuotes) ::       // Turn quoted trees into explicit run-time data structures
+    List(new CheckUnused.PostInlining) ::  // Check for unused elements
     Nil
 
   /** Phases dealing with the transformation from pickled trees to backend trees */

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -494,6 +494,8 @@ class Definitions {
     @tu lazy val Predef_undefined: Symbol = ScalaPredefModule.requiredMethod(nme.???)
   @tu lazy val ScalaPredefModuleClass: ClassSymbol = ScalaPredefModule.moduleClass.asClass
 
+  @tu lazy val SameTypeClass: ClassSymbol = requiredClass("scala.=:=")
+  @tu lazy val SameType_refl: Symbol = SameTypeClass.companionModule.requiredMethod(nme.refl)
   @tu lazy val SubTypeClass: ClassSymbol = requiredClass("scala.<:<")
   @tu lazy val SubType_refl: Symbol = SubTypeClass.companionModule.requiredMethod(nme.refl)
 

compiler/src/dotty/tools/dotc/transform/CheckUnused.scala

@@ -1,4 +1,4 @@
-//> using options -Xfatal-warnings -Wunused:all -deprecation -feature
+//> using options -Werror -Wunused:all -deprecation -feature
 
 object foo {
   type Bar
@@ -32,3 +32,23 @@ object Main {
     (bad1, bad2)
   }
 }
+
+def `i18388`: Unit =
+  def func(pred: [A] => A => Boolean): Unit =
+    val _ = pred
+    ()
+  val _ = func
+
+trait L[T]:
+  type E
+
+def `i19748` =
+  type Warn1 = [T] => (l: L[T]) => T => l.E
+  type Warn2 = [T] => L[T] => T
+  type Warn3 = [T] => T => T
+  def use(x: (Warn1, Warn2, Warn3)) = x
+  use
+
+type NoWarning1 = [T] => (l: L[T]) => T => l.E
+type NoWarning2 = [T] => L[T] => T
+type NoWarning3 = [T] => T => T

tests/pos/i17631.scala

@@ -1,10 +1,19 @@
-//> using options -Xfatal-warnings -Wunused:all
+//> using options -Werror -Wunused:all
 
 trait Builder {
   def foo(): Unit
 }
 
-def repro =
+def `i18366` =
   val builder: Builder = ???
   import builder.{foo => bar}
-  bar()
+  bar()
+
+import java.io.DataOutputStream
+
+val buffer: DataOutputStream = ???
+
+import buffer.{write => put}
+
+def `i17315` =
+  put(0: Byte)

tests/pos/i18366.scala

@@ -575,7 +575,7 @@ Text => empty
 Language => Scala
 Symbols => 108 entries
 Occurrences => 127 entries
-Diagnostics => 6 entries
+Diagnostics => 10 entries
 Synthetics => 2 entries
 
 Symbols:
@@ -830,6 +830,10 @@ See: https://docs.scala-lang.org/scala3/reference/dropped-features/this-qualifie
 This construct can be rewritten automatically under -rewrite -source 3.4-migration.
 [22:27..22:28): [warning] unused explicit parameter
 [24:10..24:11): [warning] unused explicit parameter
+[36:11..36:12): [warning] unused explicit parameter
+[39:11..39:12): [warning] unused explicit parameter
+[39:19..39:20): [warning] unused explicit parameter
+[51:30..51:31): [warning] unused explicit parameter
 
 Synthetics:
 [51:16..51:27):List(1).map => *[Int]
@@ -3533,6 +3537,7 @@ Text => empty
 Language => Scala
 Symbols => 62 entries
 Occurrences => 165 entries
+Diagnostics => 2 entries
 Synthetics => 39 entries
 
 Symbols:
@@ -3766,6 +3771,10 @@ Occurrences:
 [68:18..68:24): impure -> local20
 [68:30..68:31): s -> local16
 
+Diagnostics:
+[19:21..19:22): [warning] unused explicit parameter
+[41:4..41:5): [warning] unused explicit parameter
+
 Synthetics:
 [5:2..5:13):List(1).map => *[Int]
 [5:2..5:6):List => *.apply[Int]
@@ -4235,6 +4244,7 @@ Text => empty
 Language => Scala
 Symbols => 6 entries
 Occurrences => 11 entries
+Diagnostics => 2 entries
 
 Symbols:
 example/Vararg# => class Vararg extends Object { self: Vararg => +3 decls }
@@ -4257,6 +4267,10 @@ Occurrences:
 [4:18..4:21): Int -> scala/Int#
 [4:26..4:30): Unit -> scala/Unit#
 
+Diagnostics:
+[3:11..3:12): [warning] unused explicit parameter
+[4:11..4:12): [warning] unused explicit parameter
+
 expect/dep-match.scala
 ----------------------
 
@@ -4873,6 +4887,7 @@ Text => empty
 Language => Scala
 Symbols => 36 entries
 Occurrences => 48 entries
+Diagnostics => 5 entries
 
 Symbols:
 local0 => type N$1  <: Nat
@@ -4962,6 +4977,13 @@ Occurrences:
 [23:35..23:39): Zero -> recursion/Nats.Zero.
 [23:40..23:42): ++ -> recursion/Nats.Nat#`++`().
 
+Diagnostics:
+[10:24..10:24): [warning] unused local definition
+[10:33..11:5): [warning] unused local definition
+[23:19..23:19): [warning] unused local definition
+[23:24..23:32): [warning] unused local definition
+[23:40..25:2): [warning] unused local definition
+
 expect/semanticdb-Definitions.scala
 -----------------------------------
 
@@ -5006,7 +5028,7 @@ Text => empty
 Language => Scala
 Symbols => 50 entries
 Occurrences => 78 entries
-Diagnostics => 4 entries
+Diagnostics => 5 entries
 Synthetics => 2 entries
 
 Symbols:
@@ -5142,6 +5164,7 @@ Occurrences:
 [25:33..25:36): ??? -> scala/Predef.`???`().
 
 Diagnostics:
+[5:19..5:20): [warning] unused private member
 [9:30..9:31): [warning] unused explicit parameter
 [9:36..9:37): [warning] unused explicit parameter
 [9:42..9:43): [warning] unused explicit parameter
@@ -5161,7 +5184,7 @@ Text => empty
 Language => Scala
 Symbols => 143 entries
 Occurrences => 246 entries
-Diagnostics => 4 entries
+Diagnostics => 5 entries
 Synthetics => 1 entries
 
 Symbols:
@@ -5565,6 +5588,7 @@ This construct can be rewritten automatically under -rewrite -source 3.4-migrati
 This construct can be rewritten automatically under -rewrite -source 3.4-migration.
 [71:31..71:31): [warning] `_` is deprecated for wildcard arguments of types: use `?` instead
 This construct can be rewritten automatically under -rewrite -source 3.4-migration.
+[96:13..96:14): [warning] unused explicit parameter
 
 Synthetics:
 [68:20..68:24):@ann => *[Int]

tests/semanticdb/metac.expect

@@ -213,7 +213,8 @@ package testImportsInImports:
   package c:
     import a.b // OK
     import b.x // OK
-    val y = x
+    import b.x as z // OK
+    val y = x + z
 
 //-------------------------------------
 package testOnOverloadedMethodsImports:
@@ -265,4 +266,4 @@ package foo.test.typeapply.hklamdba.i16680:
     import foo.IO // OK
 
     def f[F[_]]: String = "hello"
-    def go = f[IO]
+    def go = f[IO]

tests/warn/i15503a.scala

@@ -117,7 +117,7 @@ package foo.scala2.tests:
 
   object Types {
     def l1() = {
-      object HiObject { def f = this } // OK
+      object HiObject { def f = this } // warn
       class Hi { // warn
         def f1: Hi = new Hi
         def f2(x: Hi) = x
@@ -141,4 +141,4 @@ package test.foo.twisted.i16682:
     }
     isInt
 
-  def f = myPackage("42")
+  def f = myPackage("42")

tests/warn/i15503b.scala

@@ -1,4 +1,4 @@
-//> using options  -Wunused:explicits
+//> using options -Wunused:explicits
 
 object Foo {
   /* This goes around the "trivial method" detection */
@@ -31,7 +31,7 @@ package scala3main:
 package foo.test.lambda.param:
   val default_val = 1
   val a = (i: Int) => i // OK
-  val b = (i: Int) => default_val // OK
+  val b = (i: Int) => default_val // warn
   val c = (_: Int) => default_val // OK
 
 package foo.test.trivial:
@@ -64,7 +64,7 @@ package foo.test.i16865:
   trait Bar extends Foo
 
   object Ex extends Bar:
-    def fn(a: Int, b: Int): Int = b + 3 // OK
+    def fn(a: Int, b: Int): Int = b + 3 // warn
 
   object Ex2 extends Bar:
-    override def fn(a: Int, b: Int): Int = b + 3 // OK
+    override def fn(a: Int, b: Int): Int = b + 3 // warn

tests/warn/i15503e.scala

@@ -6,8 +6,8 @@ val default_int = 1
 object Xd {
   private def f1(a: Int) = a // OK
   private def f2(a: Int) = 1 // OK
-  private def f3(a: Int)(using Int) = a // OK
-  private def f4(a: Int)(using Int) = default_int // OK
+  private def f3(a: Int)(using Int) = a // warn
+  private def f4(a: Int)(using Int) = default_int // warn
   private def f6(a: Int)(using Int) = summon[Int] // OK
   private def f7(a: Int)(using Int) = summon[Int] + a // OK
   private def f8(a: Int)(using foo: Int) = a // warn