[Clang][Sema] Start fixing handling of out-of-line definitions of constrained templates

This diff starts fixing our handling of out-of-line definitions of constrained templates.
Initially it was motivated by https://github.com/llvm/llvm-project/issues/49620 and
https://github.com/llvm/llvm-project/issues/60231.
In particular, this diff adjusts Sema::computeDeclContext to work properly in the case of
constrained template parameters.

Test plan:
1/ ninja check-all
2/ Bootstrapped Clang passes all the tests
3/ Internal testing

Differential revision: https://reviews.llvm.org/D145034

1 files changed, 11 insertions, 2 deletions

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 3106571..da84da0 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -3380,6 +3380,8 @@ void Parser::ParseDeclarationSpecifiers(
         goto DoneWithDeclSpec;
 
       CXXScopeSpec SS;
+      if (TemplateInfo.TemplateParams)
+        SS.setTemplateParamLists(*TemplateInfo.TemplateParams);
       Actions.RestoreNestedNameSpecifierAnnotation(Tok.getAnnotationValue(),
                                                    Tok.getAnnotationRange(),
                                                    SS);
@@ -3475,7 +3477,8 @@ void Parser::ParseDeclarationSpecifiers(
                                      &SS) &&
           isConstructorDeclarator(/*Unqualified=*/false,
                                   /*DeductionGuide=*/false,
-                                  DS.isFriendSpecified()))
+                                  DS.isFriendSpecified(),
+                                  &TemplateInfo))
         goto DoneWithDeclSpec;
 
       // C++20 [temp.spec] 13.9/6.
@@ -4957,6 +4960,7 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
     assert(TemplateInfo.TemplateParams && "no template parameters");
     TParams = MultiTemplateParamsArg(TemplateInfo.TemplateParams->data(),
                                      TemplateInfo.TemplateParams->size());
+    SS.setTemplateParamLists(TParams);
   }
 
   if (!Name && TUK != Sema::TUK_Definition) {
@@ -5679,11 +5683,15 @@ bool Parser::isDeclarationSpecifier(
 }
 
 bool Parser::isConstructorDeclarator(bool IsUnqualified, bool DeductionGuide,
-                                     DeclSpec::FriendSpecified IsFriend) {
+                                     DeclSpec::FriendSpecified IsFriend,
+                                     const ParsedTemplateInfo *TemplateInfo) {
   TentativeParsingAction TPA(*this);
 
   // Parse the C++ scope specifier.
   CXXScopeSpec SS;
+  if (TemplateInfo && TemplateInfo->TemplateParams)
+    SS.setTemplateParamLists(*TemplateInfo->TemplateParams);
+
   if (ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                      /*ObjectHasErrors=*/false,
                                      /*EnteringContext=*/true)) {
@@ -6075,6 +6083,7 @@ void Parser::ParseDeclaratorInternal(Declarator &D,
     bool EnteringContext = D.getContext() == DeclaratorContext::File ||
                            D.getContext() == DeclaratorContext::Member;
     CXXScopeSpec SS;
+    SS.setTemplateParamLists(D.getTemplateParameterLists());
     ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                    /*ObjectHasErrors=*/false, EnteringContext);