Revert "[Clang] Fix dependent local class instantiation bugs" (llvm#135870)

Reverts llvm#134038

This crashes clang as reported here:
llvm#134038 (comment)

Author: mizvekov

clang/docs/ReleaseNotes.rst

@@ -457,7 +457,6 @@ Bug Fixes to C++ Support
   by template argument deduction.
 - Clang is now better at instantiating the function definition after its use inside
   of a constexpr lambda. (#GH125747)
-- Fixed a local class member function instantiation bug inside dependent lambdas. (#GH59734), (#GH132208)
 - Clang no longer crashes when trying to unify the types of arrays with
   certain differences in qualifiers (this could happen during template argument
   deduction or when building a ternary operator). (#GH97005)

clang/lib/Sema/SemaTemplateInstantiate.cpp

@@ -4126,6 +4126,9 @@ Sema::InstantiateClassMembers(SourceLocation PointOfInstantiation,
       if (FunctionDecl *Pattern =
               Function->getInstantiatedFromMemberFunction()) {
 
+        if (Function->isIneligibleOrNotSelected())
+          continue;
+
         if (Function->getTrailingRequiresClause()) {
           ConstraintSatisfaction Satisfaction;
           if (CheckFunctionConstraints(Function, Satisfaction) ||

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -5597,61 +5597,7 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
   Function->setLocation(PatternDecl->getLocation());
   Function->setInnerLocStart(PatternDecl->getInnerLocStart());
   Function->setRangeEnd(PatternDecl->getEndLoc());
-  // Let the instantiation use the Pattern's DeclarationNameLoc, due to the
-  // following awkwardness:
-  //
-  //   1. There are out-of-tree users of getNameInfo().getSourceRange(), who
-  //   expect the source range of the instantiated declaration to be set to
-  //   point to the definition.
-  //
-  //   2. That getNameInfo().getSourceRange() might return the TypeLocInfo's
-  //   location it tracked.
-  //
-  //   3. Function might come from an (implicit) declaration, while the pattern
-  //   comes from a definition. In these cases, we need the PatternDecl's source
-  //   location.
-  //
-  // To that end, we need to more or less tweak the DeclarationNameLoc. However,
-  // we can't blindly copy the DeclarationNameLoc from the PatternDecl to the
-  // function, since it contains associated TypeLocs that should have already
-  // been transformed. So, we rebuild the TypeLoc for that purpose. Technically,
-  // we should create a new function declaration and assign everything we need,
-  // but InstantiateFunctionDefinition updates the declaration in place.
-  auto NameLocPointsToPattern = [&] {
-    DeclarationNameInfo PatternName = PatternDecl->getNameInfo();
-    DeclarationNameLoc PatternNameLoc = PatternName.getInfo();
-    switch (PatternName.getName().getNameKind()) {
-    case DeclarationName::CXXConstructorName:
-    case DeclarationName::CXXDestructorName:
-    case DeclarationName::CXXConversionFunctionName:
-      break;
-    default:
-      // Cases where DeclarationNameLoc doesn't matter, as it merely contains a
-      // source range.
-      return PatternNameLoc;
-    }
-
-    TypeSourceInfo *TSI = Function->getNameInfo().getNamedTypeInfo();
-    // TSI might be null if the function is named by a constructor template id.
-    // E.g. S<T>() {} for class template S with a template parameter T.
-    if (!TSI) {
-      // We don't care about the DeclarationName of the instantiated function,
-      // but only the DeclarationNameLoc. So if the TypeLoc is absent, we do
-      // nothing.
-      return PatternNameLoc;
-    }
-
-    QualType InstT = TSI->getType();
-    // We want to use a TypeLoc that reflects the transformed type while
-    // preserving the source location from the pattern.
-    TypeLocBuilder TLB;
-    TLB.pushTrivial(
-        Context, InstT,
-        PatternNameLoc.getNamedTypeInfo()->getTypeLoc().getBeginLoc());
-    return DeclarationNameLoc::makeNamedTypeLoc(
-        TLB.getTypeSourceInfo(Context, InstT));
-  };
-  Function->setDeclarationNameLoc(NameLocPointsToPattern());
+  Function->setDeclarationNameLoc(PatternDecl->getNameInfo().getInfo());
 
   EnterExpressionEvaluationContext EvalContext(
       *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);