[CSDiag] Removing invalid_optional_chain diagnostic from CSDiag

Author: LucianoPAlmeida

lib/Sema/CSDiag.cpp

@@ -291,8 +291,6 @@ class FailureDiagnosis :public ASTVisitor<FailureDiagnosis, /*exprresult*/bool>{
   bool visitDictionaryExpr(DictionaryExpr *E);
   bool visitObjectLiteralExpr(ObjectLiteralExpr *E);
 
-  bool visitBindOptionalExpr(BindOptionalExpr *BOE);
-
   bool visitSubscriptExpr(SubscriptExpr *SE);
   bool visitApplyExpr(ApplyExpr *AE);
   bool visitAssignExpr(AssignExpr *AE);
@@ -3320,24 +3318,6 @@ bool FailureDiagnosis::visitCoerceExpr(CoerceExpr *CE) {
   return false;
 }
 
-bool FailureDiagnosis::visitBindOptionalExpr(BindOptionalExpr *BOE) {
-  auto argExpr = typeCheckChildIndependently(BOE->getSubExpr());
-  if (!argExpr) return true;
-  auto argType = CS.getType(argExpr);
-
-  // If the subexpression type checks as a non-optional type, then that is the
-  // error.  Produce a specific diagnostic about this.
-  if (!isUnresolvedOrTypeVarType(argType) &&
-      argType->getOptionalObjectType().isNull()) {
-    diagnose(BOE->getQuestionLoc(), diag::invalid_optional_chain, argType)
-      .highlight(BOE->getSourceRange())
-      .fixItRemove(BOE->getQuestionLoc());
-    return true;
-  }
-
-  return false;
-}
-
 bool FailureDiagnosis::visitIfExpr(IfExpr *IE) {
   auto typeCheckClauseExpr = [&](Expr *clause, Type contextType = Type(),
                                  ContextualTypePurpose convertPurpose =