Weaken assertion for duplicate attachments

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

@@ -929,6 +929,17 @@ object Contexts {
     /** Flag to suppress inlining, set after overflow */
     private[dotc] var stopInlining: Boolean = false
 
+    /** 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.
+     */
+    private[dotc] var errorsToBeReported = false
+
     // Reporters state
     private[dotc] var indent: Int = 0
 
@@ -958,6 +969,7 @@ object Contexts {
       uniqueNamedTypes.clear()
       emptyTypeBounds = null
       emptyWildcardBounds = null
+      errorsToBeReported = false
       errorTypeMsg.clear()
       sources.clear()
       files.clear()

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.base.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.base.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 = ???