Generate signature for local class

compiler/src/dotty/tools/dotc/transform/GenericSignatures.scala

@@ -33,8 +33,8 @@ object GenericSignatures {
    *  @return The signature if it could be generated, `None` otherwise.
    */
   def javaSig(sym0: Symbol, info: Type)(using Context): Option[String] =
-    // Avoid generating a signature for local symbols.
-    if (sym0.isLocal) None
+    // Avoid generating a signature for non-class local symbols.
+    if (sym0.isLocal && !sym0.isClass) None
     else atPhase(erasurePhase)(javaSig0(sym0, info))
 
   @noinline

tests/generic-java-signatures/i6349.check

@@ -0,0 +1,2 @@
+Foo<java.lang.String>
+Foo<java.lang.String>

tests/generic-java-signatures/i6349.scala

@@ -0,0 +1,12 @@
+class Foo[T]
+object Test {
+  class Inner extends Foo[String]
+
+  def main(args: Array[String]): Unit = {
+    class Local extends Foo[String]
+
+    println((new Inner).getClass.getGenericSuperclass) // Foo<java.lang.String>
+
+    println((new Local).getClass.getGenericSuperclass) // Foo<java.lang.String>
+  }
+}