Revert "[Clang][Sema] Fix crash when using name of UnresolvedUsingValueDecl with template arguments (#83842)"

clang/docs/ReleaseNotes.rst

@@ -332,8 +332,6 @@ Bug Fixes to C++ Support
   our attention by an attempt to fix in (#GH77703). Fixes (#GH83385).
 - Fix evaluation of some immediate calls in default arguments.
   Fixes (#GH80630)
-- Fix a crash when an explicit template argument list is used with a name for which lookup
-  finds a non-template function and a dependent using declarator.
 - Fixed an issue where the ``RequiresExprBody`` was involved in the lambda dependency
   calculation. (#GH56556), (#GH82849).
 - Fix a bug where overload resolution falsely reported an ambiguity when it was comparing

clang/lib/Sema/SemaDecl.cpp

@@ -1110,9 +1110,7 @@ Sema::NameClassification Sema::ClassifyName(Scope *S, CXXScopeSpec &SS,
     //   unqualified-id followed by a < and name lookup finds either one
     //   or more functions or finds nothing.
     if (!IsFilteredTemplateName)
-      FilterAcceptableTemplateNames(Result,
-                                    /*AllowFunctionTemplates=*/true,
-                                    /*AllowDependent=*/true);
+      FilterAcceptableTemplateNames(Result);
 
     bool IsFunctionTemplate;
     bool IsVarTemplate;
@@ -1122,7 +1120,6 @@ Sema::NameClassification Sema::ClassifyName(Scope *S, CXXScopeSpec &SS,
       Template = Context.getOverloadedTemplateName(Result.begin(),
                                                    Result.end());
     } else if (!Result.empty()) {
-      assert(!Result.isUnresolvableResult());
       auto *TD = cast<TemplateDecl>(getAsTemplateNameDecl(
           *Result.begin(), /*AllowFunctionTemplates=*/true,
           /*AllowDependent=*/false));

clang/lib/Sema/SemaTemplate.cpp

@@ -491,20 +491,18 @@ bool Sema::LookupTemplateName(LookupResult &Found,
     // To keep our behavior consistent, we apply the "finds nothing" part in
     // all language modes, and diagnose the empty lookup in ActOnCallExpr if we
     // successfully form a call to an undeclared template-id.
-    bool AnyFunctions =
-        getLangOpts().CPlusPlus20 && llvm::any_of(Found, [](NamedDecl *ND) {
+    bool AllFunctions =
+        getLangOpts().CPlusPlus20 && llvm::all_of(Found, [](NamedDecl *ND) {
           return isa<FunctionDecl>(ND->getUnderlyingDecl());
         });
-    if (AnyFunctions || (Found.empty() && !IsDependent)) {
+    if (AllFunctions || (Found.empty() && !IsDependent)) {
       // If lookup found any functions, or if this is a name that can only be
       // used for a function, then strongly assume this is a function
       // template-id.
       *ATK = (Found.empty() && Found.getLookupName().isIdentifier())
                  ? AssumedTemplateKind::FoundNothing
                  : AssumedTemplateKind::FoundFunctions;
-      FilterAcceptableTemplateNames(Found,
-                                    /*AllowFunctionTemplates*/ true,
-                                    /*AllowDependent*/ true);
+      Found.clear();
       return false;
     }
   }