Use names instead of type symbols when scanning for pickling annotations

When scanning for Scala pickling annotations, all annotations in all
classfiles (including those produced by the Java compiler) are considered.

Before this commit, a Type and Symbol were created for each discovered
annotation and comparared to the known Scala signature annotation types.
In certain situations (as in tests/pos/i15166), this is problematic, as
the denotation of an annotation symbol defined as a Java inner class may
be forced before the inner class table is populated and setClassInfo is
called on the class root.

Comparing names (as strings) rather than type symbols avoids this situation.

Fixes scala#15166

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

@@ -961,13 +961,9 @@ class Definitions {
   @tu lazy val NativeAnnot: ClassSymbol = requiredClass("scala.native")
   @tu lazy val RepeatedAnnot: ClassSymbol = requiredClass("scala.annotation.internal.Repeated")
   @tu lazy val SourceFileAnnot: ClassSymbol = requiredClass("scala.annotation.internal.SourceFile")
-  @tu lazy val ScalaSignatureAnnot: ClassSymbol = requiredClass("scala.reflect.ScalaSignature")
-  @tu lazy val ScalaLongSignatureAnnot: ClassSymbol = requiredClass("scala.reflect.ScalaLongSignature")
   @tu lazy val ScalaStrictFPAnnot: ClassSymbol = requiredClass("scala.annotation.strictfp")
   @tu lazy val ScalaStaticAnnot: ClassSymbol = requiredClass("scala.annotation.static")
   @tu lazy val SerialVersionUIDAnnot: ClassSymbol = requiredClass("scala.SerialVersionUID")
-  @tu lazy val TASTYSignatureAnnot: ClassSymbol = requiredClass("scala.annotation.internal.TASTYSignature")
-  @tu lazy val TASTYLongSignatureAnnot: ClassSymbol = requiredClass("scala.annotation.internal.TASTYLongSignature")
   @tu lazy val TailrecAnnot: ClassSymbol = requiredClass("scala.annotation.tailrec")
   @tu lazy val ThreadUnsafeAnnot: ClassSymbol = requiredClass("scala.annotation.threadUnsafe")
   @tu lazy val ConstructorOnlyAnnot: ClassSymbol = requiredClass("scala.annotation.constructorOnly")

compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

@@ -50,6 +50,12 @@ object ClassfileParser {
         mapOver(tp)
     }
   }
+
+  private inline def sigOfClassName(n: String) = s"L$n;"
+  val ScalaSignatureAnnot: String = sigOfClassName("scala.reflect.ScalaSignature")
+  val ScalaLongSignatureAnnot: String = sigOfClassName("scala.reflect.ScalaLongSignature")
+  val TASTYSignatureAnnot: String = sigOfClassName("scala.annotation.internal.TASTYSignature")
+  val TASTYLongSignatureAnnot: String = sigOfClassName("scala.annotation.internal.TASTYLongSignature")
 }
 
 class ClassfileParser(
@@ -1004,19 +1010,19 @@ class ClassfileParser(
         val nAnnots = in.nextChar
         var i = 0
         while (i < nAnnots) {
-          val attrClass = pool.getType(in.nextChar).typeSymbol
+          val attrSig = pool.getExternalName(in.nextChar).value
           val nArgs = in.nextChar
           var j = 0
           while (j < nArgs) {
             val argName = pool.getName(in.nextChar)
             if (argName.name == nme.bytes) {
-              if (attrClass == defn.ScalaSignatureAnnot)
+              if attrSig == ScalaSignatureAnnot then
                 return unpickleScala(parseScalaSigBytes)
-              else if (attrClass == defn.ScalaLongSignatureAnnot)
+              else if attrSig == ScalaLongSignatureAnnot then
                 return unpickleScala(parseScalaLongSigBytes)
-              else if (attrClass == defn.TASTYSignatureAnnot)
+              else if attrSig == TASTYSignatureAnnot then
                 return unpickleTASTY(parseScalaSigBytes)
-              else if (attrClass == defn.TASTYLongSignatureAnnot)
+              else if attrSig == TASTYLongSignatureAnnot then
                 return unpickleTASTY(parseScalaLongSigBytes)
             }
             parseAnnotArg(skip = true)

tests/pos/i15166/InterfaceAudience_JAVA_ONLY_1.java

@@ -0,0 +1,8 @@
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+@InterfaceStability_JAVA_ONLY_1.Evolving(bytes="no")
+public class InterfaceAudience_JAVA_ONLY_1 {
+    @Retention(RetentionPolicy.RUNTIME)
+    public @interface Public { String bytes(); }
+}

tests/pos/i15166/InterfaceStability_JAVA_ONLY_1.java

@@ -0,0 +1,8 @@
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+@InterfaceAudience_JAVA_ONLY_1.Public(bytes="yes")
+public class InterfaceStability_JAVA_ONLY_1 {
+    @Retention(RetentionPolicy.RUNTIME)
+    public @interface Evolving { String bytes(); }
+}

tests/pos/i15166/Test_2.scala

@@ -0,0 +1,4 @@
+// scalac: -Xfatal-warnings
+object Test {
+  val x: InterfaceAudience_JAVA_ONLY_1.Public = ???
+}