Revert cache for signature in denot

[Cherry-picked d9e13e5]

Author: noti0na1

Diff for: compiler/src/dotty/tools/dotc/core/Denotations.scala

@@ -621,30 +621,6 @@ object Denotations {
             throw ex
         case _ => Signature.NotAMethod
 
-    private var myCurrentJavaSig: Signature = uninitialized
-    private var myCurrentJavaSigRunId: RunId = NoRunId
-    private var myCurrentScala2Sig: Signature = uninitialized
-    private var myCurrentScala2SigRunId: RunId = NoRunId
-    private var myCurrentSig: Signature = uninitialized
-    private var myCurrentSigRunId: RunId = NoRunId
-
-    def currentSignature(sourceLanguage: SourceLanguage)(using Context): Signature = sourceLanguage match
-      case SourceLanguage.Java =>
-        if myCurrentJavaSigRunId != ctx.runId then
-          myCurrentJavaSig = signature(sourceLanguage)
-          myCurrentJavaSigRunId = ctx.runId
-        myCurrentJavaSig
-      case SourceLanguage.Scala2 =>
-        if myCurrentScala2SigRunId != ctx.runId then
-          myCurrentScala2Sig = signature(sourceLanguage)
-          myCurrentScala2SigRunId = ctx.runId
-        myCurrentScala2Sig
-      case SourceLanguage.Scala3 =>
-        if myCurrentSigRunId != ctx.runId then
-          myCurrentSig = signature(sourceLanguage)
-          myCurrentSigRunId = ctx.runId
-        myCurrentSig
-
     def derivedSingleDenotation(symbol: Symbol, info: Type, pre: Type = this.prefix, isRefinedMethod: Boolean = this.isRefinedMethod)(using Context): SingleDenotation =
       if ((symbol eq this.symbol) && (info eq this.info) && (pre eq this.prefix) && (isRefinedMethod == this.isRefinedMethod)) this
       else newLikeThis(symbol, info, pre, isRefinedMethod)
@@ -1047,8 +1023,8 @@ object Denotations {
         val thisLanguage = SourceLanguage(symbol)
         val otherLanguage = SourceLanguage(other.symbol)
         val commonLanguage = SourceLanguage.commonLanguage(thisLanguage, otherLanguage)
-        val sig = currentSignature(commonLanguage)
-        val otherSig = other.currentSignature(commonLanguage)
+        val sig = signature(commonLanguage)
+        val otherSig = other.signature(commonLanguage)
         sig.matchDegree(otherSig) match
           case FullMatch =>
             !alwaysCompareTypes || info.matches(other.info)