Weaken assertion for duplicate attachments

Fixes #13218

The test shows that there are situations where an error is reported
in a different context than where the assertion is tested.

Author: odersky

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

@@ -144,6 +144,17 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
   /** Actions that need to be performed at the end of the current compilation run */
   private var finalizeActions = mutable.ListBuffer[() => Unit]()
 
+  /** A variable that records that some error was reported in a globally committable context.
+   *  The error will not necessarlily be emitted, since it could still be that
+   *  the enclosing context will be aborted. The variable is used as a smoke test
+   *  to turn off assertions that might be wrong if the program is erroneous. To
+   *  just test for `ctx.reporter.errorsReported` is not always enough, since it
+   *  could be that the context in which the assertion is tested is a completer context
+   *  that's different from the context where the error was reported. See i13218.scala
+   *  for a test.
+   */
+  var errorsToBeReported = false
+
   def compile(files: List[AbstractFile]): Unit =
     try
       val sources = files.map(runContext.getSource(_))

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

@@ -157,6 +157,8 @@ abstract class Reporter extends interfaces.ReporterResult {
         case dia: Error =>
           errors = dia :: errors
           _errorCount += 1
+          if ctx.typerState.isGlobalCommittable then
+            ctx.run.errorsToBeReported = true
         case dia: Info => // nothing to do here
         // match error if d is something else
 

compiler/src/dotty/tools/dotc/util/Attachment.scala

@@ -117,7 +117,7 @@ object Attachment {
     }
 
     final def pushAttachment[V](key: Key[V], value: V)(using ctx: Context): Unit = {
-      assert(!hasAttachment(key) || ctx.reporter.errorsReported, s"duplicate attachment for key $key")
+      assert(!hasAttachment(key) || ctx.run.errorsToBeReported, s"duplicate attachment for key $key")
       next = new Link(key, value, next)
     }
 

tests/neg/i13218.scala

@@ -0,0 +1,14 @@
+class TagTest extends AnyFreeSpec:
+  "a" - {
+    "b" in {
+      class TF[F[_]]
+      meow // error
+    }
+  }
+
+trait AnyFreeSpec:
+  protected class Wrapper(s: String):
+    def -(f: => Unit): Unit = ???
+    def in(f: => Unit): Unit = ???
+
+  implicit def wrap(s: String): Wrapper = ???