Fix messages leaking via suspended messages

It isn't clear what StoreReporter's purpose is.  Is it simply a store of
all messages, or is it a store of "real" messages, i.e. messages that
aren't suppressed with `@nowarn` or -Wconf (i.e. configurable warnings)?
I believe StoreReporter is often used as a way to get programmatic
access to the real messages.

Typer, with its TyperState, uses StoreReporter as a more general buffer
while making typing attempts, such as when trying to apply an implicit
conversion.  But with configurable warnings, we don't know if a warning
is real or not until we've typed all the `@nowarn` annotation in the
code, which is why we suspend the messages, on Run.

So we add an override for TyperState, so that StoreReporter is used as
simply a buffer.  When it then unbuffers its messages in flush to the
parent context's reporter, it will run through the regular
"issueIfNotSuppressed" code (assuming it's not another store reporter).

Author: dwijnand

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

@@ -103,7 +103,7 @@ class TyperState() {
     this
 
   /** A fresh typer state with the same constraint as this one. */
-  def fresh(reporter: Reporter = StoreReporter(this.reporter),
+  def fresh(reporter: Reporter = StoreReporter(this.reporter, fromTyperState = true),
       committable: Boolean = this.isCommittable): TyperState =
     util.Stats.record("TyperState.fresh")
     TyperState().init(this, this.constraint)

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

@@ -7,7 +7,7 @@ import core.Contexts.Context
 import Diagnostic._
 
 /** A re-usable Reporter used in Contexts#test */
-class ExploringReporter extends StoreReporter(null):
+class ExploringReporter extends StoreReporter(null, fromTyperState = false):
   infos = new mutable.ListBuffer[Diagnostic]
 
   override def hasUnreportedErrors: Boolean =

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

@@ -137,42 +137,44 @@ abstract class Reporter extends interfaces.ReporterResult {
 
   var unreportedWarnings: Map[String, Int] = Map.empty
 
+  /** Issue the diagnostic, ignoring `-Wconf` and `@nowarn` configurations,
+   *  but still honouring `-nowarn`, `-Werror`, and conditional warnings. */
+  def issueUnconfigured(dia: Diagnostic)(using Context): Unit = dia match
+    case w: Warning if ctx.settings.silentWarnings.value    =>
+    case w: ConditionalWarning if w.isSummarizedConditional =>
+      val key = w.enablingOption.name
+      val count = unreportedWarnings.getOrElse(key, 0)
+      unreportedWarnings = unreportedWarnings.updated(key, count + 1)
+    case _                                                  =>
+      // conditional warnings that are not enabled are not fatal
+      val d = dia match
+        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
+        withMode(Mode.Printing)(doReport(d))
+        d match {
+          case _: Warning => _warningCount += 1
+          case e: Error   =>
+            errors = e :: errors
+            _errorCount += 1
+            if ctx.typerState.isGlobalCommittable then
+              ctx.base.errorsToBeReported = true
+          case _: Info    => // nothing to do here
+          // match error if d is something else
+        }
+  end issueUnconfigured
+
   def issueIfNotSuppressed(dia: Diagnostic)(using Context): Unit =
     def go() =
       import Action._
-
-      val toReport = dia match
-        case w: Warning =>
-          def fatal(w: Warning) = if ctx.settings.XfatalWarnings.value && !w.isSummarizedConditional then Some(w.toError) else Some(w)
-          if ctx.settings.silentWarnings.value then None
-          else WConf.parsed.action(dia) match
-            case Silent  => None
-            case Info    => Some(w.toInfo)
-            case Warning => fatal(w)
-            case Verbose => fatal(w).tap(_.foreach(_.setVerbose()))
-            case Error   => Some(w.toError)
-        case _ => Some(dia)
-
-      toReport foreach {
-        case cw: ConditionalWarning if cw.isSummarizedConditional =>
-          val key = cw.enablingOption.name
-          unreportedWarnings =
-            unreportedWarnings.updated(key, unreportedWarnings.getOrElse(key, 0) + 1)
-        case d if !isHidden(d) =>
-          withMode(Mode.Printing)(doReport(d))
-          d match {
-            case _: Warning => _warningCount += 1
-            case e: Error =>
-              errors = e :: errors
-              _errorCount += 1
-              if ctx.typerState.isGlobalCommittable then
-                ctx.base.errorsToBeReported = true
-            case _: Info => // nothing to do here
-            // match error if d is something else
-          }
-        case _ => // hidden
-      }
-    end go
+      dia match
+        case w: Warning => WConf.parsed.action(w) match
+          case Error   => issueUnconfigured(w.toError)
+          case Warning => issueUnconfigured(w)
+          case Verbose => issueUnconfigured(w.setVerbose())
+          case Info    => issueUnconfigured(w.toInfo)
+          case Silent  =>
+        case _ => issueUnconfigured(dia)
 
     // `ctx.run` can be null in test, also in the repl when parsing the first line. The parser runs early, the Run is
     // only created in ReplDriver.compile when a line is submitted. This means that `@nowarn` doesnt work on parser

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

@@ -17,7 +17,7 @@ import Diagnostic._
   * - The reporter is not flushed and the message containers capture a
   *   `Context` (about 4MB)
   */
-class StoreReporter(outer: Reporter = Reporter.NoReporter) extends Reporter {
+class StoreReporter(outer: Reporter = Reporter.NoReporter, fromTyperState: Boolean = false) extends Reporter {
 
   protected var infos: mutable.ListBuffer[Diagnostic] = null
 
@@ -40,4 +40,11 @@ class StoreReporter(outer: Reporter = Reporter.NoReporter) extends Reporter {
   override def pendingMessages(using Context): List[Diagnostic] = if (infos != null) infos.toList else Nil
 
   override def errorsReported: Boolean = hasErrors || (outer != null && outer.errorsReported)
+
+  // If this is a TyperState buffering reporter then buffer the messages,
+  // so that then only when the messages are unbuffered (when the reporter if flushed)
+  // do they go through -Wconf, and possibly then buffered on the Run as a suspended message
+  override def report(dia: Diagnostic)(using Context): Unit =
+    if fromTyperState then issueUnconfigured(dia)
+    else super.report(dia)
 }

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

@@ -6,7 +6,7 @@ import collection.mutable
 import Diagnostic._
 
 /** A re-usable Reporter used in Contexts#test */
-class TestingReporter extends StoreReporter(null):
+class TestingReporter extends StoreReporter(null, fromTyperState = false):
   infos = new mutable.ListBuffer[Diagnostic]
   override def hasUnreportedErrors: Boolean = infos.exists(_.isInstanceOf[Error])
   def reset(): Unit = infos.clear()