Add pickling/unpickling of stable modifier

src/dotty/tools/dotc/core/tasty/TastyFormat.scala

@@ -172,6 +172,7 @@ Standard-Section: "ASTs" TopLevelStat*
                   SCALA2X                           // Imported from Scala2.x
                   DEFAULTparameterized  // Method with default params
                   INSUPERCALL           // defined in the argument of a constructor supercall
+                  STABLE                // Method that is assumed to be stable
                   Annotation
   Annotation    = ANNOTATION     Length tycon_Type fullAnnotation_Term
 
@@ -220,7 +221,7 @@ object TastyFormat {
   final val DEFAULTGETTER = 7
   final val SHADOWED = 8
 
-// AST tags
+  // AST tags
 
   final val UNITconst = 2
   final val FALSEconst = 3
@@ -252,6 +253,7 @@ object TastyFormat {
   final val SCALA2X = 29
   final val DEFAULTparameterized = 30
   final val INSUPERCALL = 31
+  final val STABLE = 32
 
   final val SHARED = 64
   final val TERMREFdirect = 65
@@ -362,6 +364,7 @@ object TastyFormat {
        | SCALA2X
        | DEFAULTparameterized
        | INSUPERCALL
+       | STABLE
        | ANNOTATION
        | PRIVATEqualified
        | PROTECTEDqualified => true
@@ -409,6 +412,7 @@ object TastyFormat {
     case SCALA2X => "SCALA2X"
     case DEFAULTparameterized => "DEFAULTparameterized"
     case INSUPERCALL => "INSUPERCALL"
+    case STABLE => "STABLE"
 
     case SHARED => "SHARED"
     case TERMREFdirect => "TERMREFdirect"

src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -534,6 +534,7 @@ class TreePickler(pickler: TastyPickler) {
         if (flags is Accessor) writeByte(FIELDaccessor)
         if (flags is CaseAccessor) writeByte(CASEaccessor)
         if (flags is DefaultParameterized) writeByte(DEFAULTparameterized)
+        if (flags is Stable) writeByte(STABLE)
       } else {
         if (flags is Sealed) writeByte(SEALED)
         if (flags is Abstract) writeByte(ABSTRACT)

src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -465,6 +465,7 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table) {
           case SCALA2X => addFlag(Scala2x)
           case DEFAULTparameterized => addFlag(DefaultParameterized)
           case INSUPERCALL => addFlag(InSuperCall)
+          case STABLE => addFlag(Stable)
           case PRIVATEqualified =>
             readByte()
             privateWithin = readType().typeSymbol

test/dotc/tests.scala

@@ -231,4 +231,5 @@ class tests extends CompilerTest {
   @Test def tasty_dotc_reporting = compileDir(dotcDir, "reporting", testPickling)
   @Test def tasty_dotc_util = compileDir(dotcDir, "util", testPickling)
   @Test def tasty_tools_io = compileDir(toolsDir, "io", testPickling)
+  @Test def tasty_tests = compileDir(testsDir, "tasty", testPickling)
 }

tests/tasty/i982.scala

@@ -0,0 +1,8 @@
+trait Z {
+  type Q
+  def test: Q
+}
+class X(val x: Z)
+class Y(x: Z) extends X(x) {
+  x.test
+}