Revise duplicate diagnostics logic

compiler/src/dotty/tools/dotc/reporting/Reporter.scala

@@ -153,6 +153,7 @@ abstract class Reporter extends interfaces.ReporterResult {
         case w: Warning if ctx.settings.XfatalWarnings.value => w.toError
         case _                                               => dia
       if !isHidden(d) then // avoid isHidden test for summarized warnings so that message is not forced
+        markReported(d)
         withMode(Mode.Printing)(doReport(d))
         d match {
           case _: Warning => _warningCount += 1
@@ -236,6 +237,8 @@ abstract class Reporter extends interfaces.ReporterResult {
   def isHidden(dia: Diagnostic)(using Context): Boolean =
     ctx.mode.is(Mode.Printing)
 
+  def markReported(dia: Diagnostic)(using Context): Unit = ()
+
   /** Does this reporter contain errors that have yet to be reported by its outer reporter ?
    *  Note: this is always false when there is no outer reporter.
    */

compiler/src/dotty/tools/dotc/reporting/UniqueMessagePositions.scala

@@ -12,24 +12,27 @@ trait UniqueMessagePositions extends Reporter {
 
   private val positions = new mutable.HashMap[(SourceFile, Integer), Diagnostic]
 
+  extension (dia1: Diagnostic)
+    private def hides(dia2: Diagnostic)(using Context): Boolean =
+      if dia2.msg.showAlways then dia1.msg.getClass == dia2.msg.getClass
+      else dia1.level >= dia2.level
+
   /** Logs a position and returns true if it was already logged.
    *  @note  Two positions are considered identical for logging if they have the same point.
    */
   override def isHidden(dia: Diagnostic)(using Context): Boolean =
-    extension (dia1: Diagnostic) def hides(dia2: Diagnostic): Boolean =
-      if dia2.msg.showAlways then dia1.msg.getClass == dia2.msg.getClass
-      else dia1.level >= dia2.level
-    super.isHidden(dia) || {
+    super.isHidden(dia)
+    ||
       dia.pos.exists
       && !ctx.settings.YshowSuppressedErrors.value
-      && {
-        var shouldHide = false
-        for (pos <- dia.pos.start to dia.pos.end)
-          positions get (ctx.source, pos) match {
-            case Some(dia1) if dia1.hides(dia) => shouldHide = true
-            case _ => positions((ctx.source, pos)) = dia
-          }
-        shouldHide
-      }
-    }
+      && (dia.pos.start to dia.pos.end).exists(pos =>
+            positions.get((ctx.source, pos)).exists(_.hides(dia)))
+
+  override def markReported(dia: Diagnostic)(using Context): Unit =
+    if dia.pos.exists then
+      for (pos <- dia.pos.start to dia.pos.end)
+        positions.get(ctx.source, pos) match
+          case Some(dia1) if dia1.hides(dia) =>
+          case _ => positions((ctx.source, pos)) = dia
+    super.markReported(dia)
 }

tests/neg-custom-args/erased/tupled-function-instances.scala

@@ -4,7 +4,7 @@ object Test {
     type T
     type R
 
-    summon[TupledFunction[(erased T) => R, erased Tuple1[T] => R]] // error
+    summon[TupledFunction[(erased T) => R, erased Tuple1[T] => R]] // error // error
     summon[TupledFunction[(erased T, T) => R, (erased (T, T)) => R]] // error
     summon[TupledFunction[(erased T, T, T) => R,(erased (T, T, T)) => R]] // error
     summon[TupledFunction[(erased T, T, T, T) => R,(erased (T, T, T, T)) => R]] // error

tests/neg/i12457.scala

@@ -0,0 +1,3 @@
+import language.`3.1-migration`
+
+trait X [ X <: Z , Z >: X [ R     ] ] // error

tests/neg/i14834.scala

@@ -0,0 +1,2 @@
+type F[_] = A
+type A = F[?]  // error: cyclic

tests/neg/i6056.scala

@@ -2,6 +2,6 @@ object i0{
     import i0.i0   // error
     def i0={
         import _  // error
-        import
+        import    // error
     }             // error
 }

tests/neg/i7818.scala

@@ -1 +1 @@
-def foo = (x: @) => ()  // error
+def foo = (x: @) => ()  // error // error

tests/neg/i9328.scala

@@ -7,7 +7,7 @@ class Foo2[T <: Id[T]] // error // error
 
 object Foo { // error
   object Foo { }
-  Foo { }
+  Foo { } // error
 }
 implicit class Foo(a: Float)  // error
 case class Foo()

tests/neg/parser-stability-17.scala

@@ -1,2 +1,2 @@
 trait x0[] {      x0: x0 => }      // error // error
-        class x0[x1] extends x0[x0 x0] x2 x0  // error // error
+        class x0[x1] extends x0[x0 x0] x2 x0  // error // error // error

tests/neg/parser-stability-9.scala

@@ -1,2 +1,2 @@
-import
+import // error
 // error

tests/neg/t5702-neg-bad-and-wild.check

@@ -27,7 +27,7 @@
    |
    | longer explanation available when compiling with `-explain`
 -- [E032] Syntax Error: tests/neg/t5702-neg-bad-and-wild.scala:23:17 ---------------------------------------------------
-23 |    val K(ns @ _*, xx) = k // error: pattern expected
+23 |    val K(ns @ _*, xx) = k // error: pattern expected // error
    |                 ^
    |                 pattern expected
    |
@@ -50,3 +50,9 @@
    |                    Not found: *
    |
    | longer explanation available when compiling with `-explain`
+-- [E045] Cyclic Error: tests/neg/t5702-neg-bad-and-wild.scala:23:19 ---------------------------------------------------
+23 |    val K(ns @ _*, xx) = k // error: pattern expected // error
+   |                   ^
+   |                   Recursive value $1$ needs type
+   |
+   | longer explanation available when compiling with `-explain`

tests/neg/t5702-neg-bad-and-wild.scala

@@ -20,7 +20,7 @@ object Test {
 // good syntax, bad semantics, detected by typer
 //gowild.scala:14: error: star patterns must correspond with varargs parameters
     val K(x @ _*) = k
-    val K(ns @ _*, xx) = k // error: pattern expected
+    val K(ns @ _*, xx) = k // error: pattern expected // error
     val K(x) = k // error: x is already defined as value x
     val (b, _ * ) = (5,6) // ok
 // no longer complains