[clang] [clang-tools-extra] Reland "[clang] Preserve found-decl when constructing VarTemplateIds" (PR #82612)

[kadir çetinkaya via cfe-commits]

https://github.com/kadircet created https://github.com/llvm/llvm-project/pull/82612

Update include-cleaner tests. Now that we have proper found-decls set up
for VarTemplates, in case of instationtations we point to primary
templates and not specializations. To be changed in a follow-up patch.


>From 1ae249119856ae2d8c1d2d4a3c3e311fa3d66dd0 Mon Sep 17 00:00:00 2001
From: Kadir Cetinkaya <kadircet at google.com>
Date: Thu, 22 Feb 2024 13:22:11 +0100
Subject: [PATCH] Reland "[clang] Preserve found-decl when constructing
 VarTemplateIds"

Update include-cleaner tests. Now that we have proper found-decls set up
for VarTemplates, in case of instationtations we point to primary
templates and not specializations. To be changed in a follow-up patch.
---
 .../include-cleaner/unittests/WalkASTTest.cpp  | 16 ++++++++--------
 clang/include/clang/Sema/Sema.h                |  2 +-
 clang/lib/Sema/SemaTemplate.cpp                | 18 ++++++++----------
 clang/test/AST/ast-dump-using.cpp              |  7 +++++++
 4 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp b/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp
index bdfc24b8edee38..0be5db36b1fc51 100644
--- a/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp
+++ b/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp
@@ -200,24 +200,24 @@ TEST(WalkAST, VarTemplates) {
   EXPECT_THAT(testWalk(R"cpp(
     template <typename T> T $explicit^Foo = 0;)cpp",
                        "int z = ^Foo<int>;"),
-              ElementsAre(Decl::VarTemplateSpecialization));
+              ElementsAre(Decl::VarTemplate));
   EXPECT_THAT(testWalk(R"cpp(
-    template<typename T> T Foo = 0;
-    template<> int $explicit^Foo<int> = 1;)cpp",
+    template<typename T> T $explicit^Foo = 0;
+    template<> int Foo<int> = 1;)cpp",
                        "int x = ^Foo<int>;"),
-              ElementsAre(Decl::VarTemplateSpecialization));
+              ElementsAre(Decl::VarTemplate));
   // FIXME: This points at implicit specialization, instead we should point to
   // explicit partial specializaiton pattern.
   EXPECT_THAT(testWalk(R"cpp(
-    template<typename T> T Foo = 0;
-    template<typename T> T* $explicit^Foo<T*> = nullptr;)cpp",
+    template<typename T> T $explicit^Foo = 0;
+    template<typename T> T* Foo<T*> = nullptr;)cpp",
                        "int *x = ^Foo<int *>;"),
-              ElementsAre(Decl::VarTemplateSpecialization));
+              ElementsAre(Decl::VarTemplate));
   EXPECT_THAT(testWalk(R"cpp(
     template<typename T> T $explicit^Foo = 0;
     template int Foo<int>;)cpp",
                        "int x = ^Foo<int>;"),
-              ElementsAre(Decl::VarTemplateSpecialization));
+              ElementsAre(Decl::VarTemplate));
 }
 TEST(WalkAST, FunctionTemplates) {
   // Explicit instantiation and (partial) specialization references primary
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index fcccac10f4733a..e457694e4625db 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -8540,7 +8540,7 @@ class Sema final {
   /// if the arguments are dependent.
   ExprResult CheckVarTemplateId(const CXXScopeSpec &SS,
                                 const DeclarationNameInfo &NameInfo,
-                                VarTemplateDecl *Template,
+                                VarTemplateDecl *Template, NamedDecl *FoundD,
                                 SourceLocation TemplateLoc,
                                 const TemplateArgumentListInfo *TemplateArgs);
 
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 1a975a8d0a0df5..7d3d665194add1 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -4958,11 +4958,10 @@ Sema::CheckVarTemplateId(VarTemplateDecl *Template, SourceLocation TemplateLoc,
   return Decl;
 }
 
-ExprResult
-Sema::CheckVarTemplateId(const CXXScopeSpec &SS,
-                         const DeclarationNameInfo &NameInfo,
-                         VarTemplateDecl *Template, SourceLocation TemplateLoc,
-                         const TemplateArgumentListInfo *TemplateArgs) {
+ExprResult Sema::CheckVarTemplateId(
+    const CXXScopeSpec &SS, const DeclarationNameInfo &NameInfo,
+    VarTemplateDecl *Template, NamedDecl *FoundD, SourceLocation TemplateLoc,
+    const TemplateArgumentListInfo *TemplateArgs) {
 
   DeclResult Decl = CheckVarTemplateId(Template, TemplateLoc, NameInfo.getLoc(),
                                        *TemplateArgs);
@@ -4978,8 +4977,7 @@ Sema::CheckVarTemplateId(const CXXScopeSpec &SS,
                                        NameInfo.getLoc());
 
   // Build an ordinary singleton decl ref.
-  return BuildDeclarationNameExpr(SS, NameInfo, Var,
-                                  /*FoundD=*/nullptr, TemplateArgs);
+  return BuildDeclarationNameExpr(SS, NameInfo, Var, FoundD, TemplateArgs);
 }
 
 void Sema::diagnoseMissingTemplateArguments(TemplateName Name,
@@ -5066,9 +5064,9 @@ ExprResult Sema::BuildTemplateIdExpr(const CXXScopeSpec &SS,
   bool KnownDependent = false;
   // In C++1y, check variable template ids.
   if (R.getAsSingle<VarTemplateDecl>()) {
-    ExprResult Res = CheckVarTemplateId(SS, R.getLookupNameInfo(),
-                                        R.getAsSingle<VarTemplateDecl>(),
-                                        TemplateKWLoc, TemplateArgs);
+    ExprResult Res = CheckVarTemplateId(
+        SS, R.getLookupNameInfo(), R.getAsSingle<VarTemplateDecl>(),
+        R.getRepresentativeDecl(), TemplateKWLoc, TemplateArgs);
     if (Res.isInvalid() || Res.isUsable())
       return Res;
     // Result is dependent. Carry on to build an UnresolvedLookupEpxr.
diff --git a/clang/test/AST/ast-dump-using.cpp b/clang/test/AST/ast-dump-using.cpp
index 5a4e910ffb8654..8e5c60d3aabf4a 100644
--- a/clang/test/AST/ast-dump-using.cpp
+++ b/clang/test/AST/ast-dump-using.cpp
@@ -2,6 +2,7 @@
 
 namespace a {
 struct S;
+template <typename T> T x = {};
 }
 namespace b {
 using a::S;
@@ -21,4 +22,10 @@ typedef S e; // check the same UsingType is reused.
 // CHECK-NEXT:   `-UsingType [[TYPE_ADDR]] 'a::S' sugar
 // CHECK-NEXT:     |-UsingShadow [[SHADOW_ADDR]] 'S'
 // CHECK-NEXT:     `-RecordType {{.*}} 'a::S'
+using a::x;
+
+void foo() {
+  x<int> = 3;
+  // CHECK: DeclRefExpr {{.*}} 'x' {{.*}} (UsingShadow {{.*}} 'x')
+}
 }