3 files changed, 25 insertions, 12 deletions
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index dcf2876..419f3e1 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -3822,14 +3822,19 @@ QualType Sema::CheckTemplateIdType(ElaboratedTypeKeyword Keyword,
         AliasTemplate->getTemplateParameters()->getDepth());
 
     LocalInstantiationScope Scope(*this);
-    InstantiatingTemplate Inst(
-        *this, /*PointOfInstantiation=*/TemplateLoc,
-        /*Entity=*/AliasTemplate,
-        /*TemplateArgs=*/TemplateArgLists.getInnermost());
 
     // Diagnose uses of this alias.
     (void)DiagnoseUseOfDecl(AliasTemplate, TemplateLoc);
 
+    // FIXME: The TemplateArgs passed here are not used for the context note,
+    // nor they should, because this note will be pointing to the specialization
+    // anyway. These arguments are needed for a hack for instantiating lambdas
+    // in the pattern of the alias. In getTemplateInstantiationArgs, these
+    // arguments will be used for collating the template arguments needed to
+    // instantiate the lambda.
+    InstantiatingTemplate Inst(*this, /*PointOfInstantiation=*/TemplateLoc,
+                               /*Entity=*/AliasTemplate,
+                               /*TemplateArgs=*/CTAI.SugaredConverted);
     if (Inst.isInvalid())
       return QualType();
 
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 1f762ca..7b05e4c 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1271,6 +1271,12 @@ void Sema::PrintInstantiationStack(InstantiationContextDiagFuncRef DiagFunc) {
                PDiag(diag::note_building_deduction_guide_here));
       break;
     case CodeSynthesisContext::TypeAliasTemplateInstantiation:
+      // Workaround for a workaround: don't produce a note if we are merely
+      // instantiating some other template which contains this alias template.
+      // This would be redundant either with the error itself, or some other
+      // context note attached to it.
+      if (Active->NumTemplateArgs == 0)
+        break;
       DiagFunc(Active->PointOfInstantiation,
                PDiag(diag::note_template_type_alias_instantiation_here)
                    << cast<TypeAliasTemplateDecl>(Active->Entity)
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index e2dc703..3819f77 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1580,17 +1580,19 @@ Decl *TemplateDeclInstantiator::InstantiateTypeAliasTemplateDecl(
   if (!InstParams)
     return nullptr;
 
-  TypeAliasDecl *Pattern = D->getTemplatedDecl();
-  Sema::InstantiatingTemplate InstTemplate(
-      SemaRef, D->getBeginLoc(), D,
-      D->getTemplateDepth() >= TemplateArgs.getNumLevels()
-          ? ArrayRef<TemplateArgument>()
-          : (TemplateArgs.begin() + TemplateArgs.getNumLevels() - 1 -
-             D->getTemplateDepth())
-                ->Args);
+  // FIXME: This is a hack for instantiating lambdas in the pattern of the
+  // alias. We are not really instantiating the alias at its template level,
+  // that only happens in CheckTemplateId, this is only for outer templates
+  // which contain it. In getTemplateInstantiationArgs, the template arguments
+  // used here would be used for collating the template arguments needed to
+  // instantiate the lambda. Pass an empty argument list, so this workaround
+  // doesn't get confused if there is an outer alias being instantiated.
+  Sema::InstantiatingTemplate InstTemplate(SemaRef, D->getBeginLoc(), D,
+                                           ArrayRef<TemplateArgument>());
   if (InstTemplate.isInvalid())
     return nullptr;
 
+  TypeAliasDecl *Pattern = D->getTemplatedDecl();
   TypeAliasTemplateDecl *PrevAliasTemplate = nullptr;
   if (getPreviousDeclForInstantiation<TypedefNameDecl>(Pattern)) {
     DeclContext::lookup_result Found = Owner->lookup(Pattern->getDeclName());