Allow a 'final virtual' classes to be declared.

Virtual final classes are helpful in the case someone is wrapping common functions that are static, but the common class itself cannot be instantiated.

engine/compiler.c

@@ -4007,22 +4007,29 @@ done:
  *   protected or public, but not private. Furthermore the signatures of the methods must
  *   match, i.e. the type hints and the number of required arguments must be the same.
  */
-static sxi32 PH7_CompileVirtualClass(ph7_gen_state *pGen) {
-	sxi32 rc;
-	pGen->pIn++; /* Jump the 'virtual' keyword */
-	rc = PH7_GenStateCompileClass(&(*pGen), PH7_CLASS_VIRTUAL);
-	return rc;
-}
-/*
- * Compile a user-defined final class.
- *    Aer introduces the final keyword, which prevents child classes from overriding
- *    a method by prefixing the definition with final. If the class itself is being defined
- *    final then it cannot be extended.
- */
-static sxi32 PH7_CompileFinalClass(ph7_gen_state *pGen) {
-	sxi32 rc;
-	pGen->pIn++; /* Jump the 'final' keyword */
-	rc = PH7_GenStateCompileClass(&(*pGen), PH7_CLASS_FINAL);
+static sxi32 PH7_CompileFinalVirtualClass(ph7_gen_state *pGen) {
+	sxi32 nKwrd, rc;
+	sxi32 iFlags = 0;
+	for(;;) {
+		nKwrd = SX_PTR_TO_INT(pGen->pIn->pUserData);
+		if(nKwrd == PH7_KEYWORD_FINAL) {
+			if(iFlags & PH7_CLASS_FINAL) {
+				PH7_GenCompileError(pGen, E_ERROR, pGen->pIn->nLine, "Duplicate 'final' modifier");
+			}
+			iFlags |= PH7_CLASS_FINAL;
+		} else if(nKwrd == PH7_KEYWORD_VIRTUAL) {
+			if(iFlags & PH7_CLASS_VIRTUAL) {
+				PH7_GenCompileError(pGen, E_ERROR, pGen->pIn->nLine, "Duplicate 'virtual' modifier");
+			}
+			iFlags |= PH7_CLASS_VIRTUAL;
+		} else if(nKwrd == PH7_KEYWORD_CLASS) {
+			break;
+		} else {
+			PH7_GenCompileError(pGen, E_ERROR, pGen->pIn->nLine, "Unexpected token '%z' in class declaration", &pGen->pIn->sData);
+		}
+		pGen->pIn++;
+	}
+	rc = PH7_GenStateCompileClass(&(*pGen), iFlags);
 	return rc;
 }
 /*
@@ -4858,14 +4865,10 @@ static ProcLangConstruct PH7_GenStateGetGlobalScopeHandler(
 			return PH7_CompileDefine;
 		} else if(nKeywordID == PH7_KEYWORD_INTERFACE) {
 			return PH7_CompileClassInterface;
+		} else if(nKeywordID == PH7_KEYWORD_FINAL || nKeywordID == PH7_KEYWORD_VIRTUAL) {
+			return PH7_CompileFinalVirtualClass;
 		} else if(nKeywordID == PH7_KEYWORD_CLASS) {
 			return PH7_CompileClass;
-		} else if(nKeywordID == PH7_KEYWORD_VIRTUAL && (pLookahead->nType & PH7_TK_KEYWORD)
-				&& SX_PTR_TO_INT(pLookahead->pUserData) == PH7_KEYWORD_CLASS) {
-			return PH7_CompileVirtualClass;
-		} else if(nKeywordID == PH7_KEYWORD_FINAL && (pLookahead->nType & PH7_TK_KEYWORD)
-				&& SX_PTR_TO_INT(pLookahead->pUserData) == PH7_KEYWORD_CLASS) {
-			return PH7_CompileFinalClass;
 		} else if(nKeywordID == PH7_KEYWORD_NAMESPACE) {
 			return PH7_CompileNamespace;
 		} else if(nKeywordID == PH7_KEYWORD_USING) {