Fix tests/pos/i5655

The commits 5cf9e0b incorrectly throw the prefix away
and construct the type from the symbol by ignoring
type parameters of generic classes.

As prefix is already in the "inner normal form",
it suffices to select member on it. The commit 22ab968
calls `processInner`, which is effectively an no-op.

Also found that we should reset `skiptvs` in reading
method parameter and result types.

Author: liufengyun

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

@@ -349,7 +349,10 @@ class ClassfileParser(
       val tag = sig(index); index += 1
       (tag: @switch) match {
         case 'L' =>
-          /** A type representation where inner classes become `A#B` instead of `A.this.B` (like with `typeRef`) */
+          /** A type representation where inner classes become `A#B` instead of `A.this.B` (like with `typeRef`)
+           *
+           *  Note: the symbol must not be nested in a generic class.
+           */
           def innerType(symbol: Symbol): Type =
             if symbol.is(Flags.Package) then
               symbol.thisType
@@ -358,7 +361,7 @@ class ClassfileParser(
             else
               throw new RuntimeException("unexpected term symbol " + symbol)
 
-          def processClassType(tp: Type): Type = tp match {
+          def processTypeArgs(tp: Type): Type = tp match {
             case tp: TypeRef =>
               if (sig(index) == '<') {
                 accept('<')
@@ -392,12 +395,12 @@ class ClassfileParser(
 
           val classSym = classNameToSymbol(subName(c => c == ';' || c == '<'))
           val classTpe = if (classSym eq defn.ObjectClass) defn.FromJavaObjectType else innerType(classSym)
-          var tpe = processClassType(classTpe)
+          var tpe = processTypeArgs(classTpe)
           while (sig(index) == '.') {
             accept('.')
             val name = subName(c => c == ';' || c == '<' || c == '.').toTypeName
-            val clazz = tpe.member(name).symbol
-            tpe = processClassType(innerType(clazz))
+            val tp = tpe.select(name)
+            tpe = processTypeArgs(tp)
           }
           accept(';')
           tpe
@@ -435,15 +438,15 @@ class ClassfileParser(
             paramtypes += {
               if isRepeatedParam(index) then
                 index += 1
-                val elemType = sig2type(tparams, skiptvs)
+                val elemType = sig2type(tparams, skiptvs = false)
                 // `ElimRepeated` is responsible for correctly erasing this.
                 defn.RepeatedParamType.appliedTo(elemType)
               else
-                sig2type(tparams, skiptvs)
+                sig2type(tparams, skiptvs = false)
             }
 
           index += 1
-          val restype = sig2type(tparams, skiptvs)
+          val restype = sig2type(tparams, skiptvs = false)
           JavaMethodType(paramnames.toList, paramtypes.toList, restype)
         case 'T' =>
           val n = subName(';'.==).toTypeName