Don't report warning in migration when rewriting

Author: WojciechMazur

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

@@ -67,12 +67,13 @@ object report:
     error(ex.toMessage, pos, sticky = true)
     if ctx.settings.YdebugTypeError.value then ex.printStackTrace()
 
-  def errorOrMigrationWarning(msg: Message, pos: SrcPos = NoSourcePosition, from: SourceVersion)(using Context): Unit =
+  def errorOrMigrationWarning(msg: => Message, pos: SrcPos = NoSourcePosition, from: SourceVersion)(using Context): Unit =
     if sourceVersion.isAtLeast(from) then
-      if sourceVersion.isMigrating && sourceVersion.ordinal <= from.ordinal then migrationWarning(msg, pos)
+      if sourceVersion.isMigrating && sourceVersion.ordinal <= from.ordinal then
+        if ctx.settings.rewrite.value.isEmpty then migrationWarning(msg, pos)
       else error(msg, pos)
 
-  def gradualErrorOrMigrationWarning(msg: Message, pos: SrcPos = NoSourcePosition, warnFrom: SourceVersion, errorFrom: SourceVersion)(using Context): Unit =
+  def gradualErrorOrMigrationWarning(msg: => Message, pos: SrcPos = NoSourcePosition, warnFrom: SourceVersion, errorFrom: SourceVersion)(using Context): Unit =
     if sourceVersion.isAtLeast(errorFrom) then errorOrMigrationWarning(msg, pos, errorFrom)
     else if sourceVersion.isAtLeast(warnFrom) then warning(msg, pos)
 

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -73,6 +73,7 @@ class CompilationTests {
     aggregateTests(
       compileFile("tests/rewrites/rewrites.scala", scala2CompatMode.and("-rewrite", "-indent")),
       compileFile("tests/rewrites/rewrites3x.scala", defaultOptions.and("-rewrite", "-source", "future-migration")),
+      compileFile("tests/rewrites/rewrites3x.scala", defaultOptions.and("-rewrite", "-source", "future-migration", "-Xfatal-warnings")),
       compileFile("tests/rewrites/filtering-fors.scala", defaultOptions.and("-rewrite", "-source", "3.2-migration")),
       compileFile("tests/rewrites/refutable-pattern-bindings.scala", defaultOptions.and("-rewrite", "-source", "3.2-migration")),
       compileFile("tests/rewrites/i8982.scala", defaultOptions.and("-indent", "-rewrite")),