Avoid adding redundant Deferred flag to type parameters in Namer

[Cherry-picked a782148]

Author: odersky

compiler/src/dotty/tools/dotc/sbt/ExtractAPI.scala

@@ -445,7 +445,7 @@ private class ExtractAPICollector(using Context) extends ThunkHolder {
     if (sym.isAliasType)
       api.TypeAlias.of(name, access, modifiers, as.toArray, typeParams, apiType(tpe.bounds.hi))
     else {
-      assert(sym.isAbstractType)
+      assert(sym.isAbstractOrParamType)
       api.TypeDeclaration.of(name, access, modifiers, as.toArray, typeParams, apiType(tpe.bounds.lo), apiType(tpe.bounds.hi))
     }
   }

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -271,7 +271,7 @@ class Namer { typer: Typer =>
                 analyzeRHS(body)
               case _ =>
                 if rhs.isEmpty || flags.is(Opaque) then flags |= Deferred
-            analyzeRHS(tree.rhs)
+            if flags.is(Param) then tree.rhs else analyzeRHS(tree.rhs)
 
         // to complete a constructor, move one context further out -- this
         // is the context enclosing the class. Note that the context in which a