[clang] Bugfix for chosing the correct deduction guide (PR #66487)

[Botond István Hprváth via cfe-commits]

https://github.com/HoBoIs updated https://github.com/llvm/llvm-project/pull/66487

>From 258462cc65403af147bb47cbeb95210df8e18cd3 Mon Sep 17 00:00:00 2001
From: hobois <horvath.botond.istvan at gmial.com>
Date: Fri, 15 Sep 2023 09:28:21 +0200
Subject: [PATCH] Choose the correct deduction guide

If there are two guides, one of them generated from a non-templated constructor
and the other from a templated constructor, then the standard gives priority to
the first. Clang detected ambiguity before, now the correct guide is chosen.

As an unrelated minor change, fix the issue #64020, which could've led to
incorrect behavior if further development inserted code after a call to
isAddressSpaceSubsetOf() which specified the two parameters in the wrong order.
---
 clang/lib/Sema/SemaOverload.cpp                 | 17 ++++++++++++++++-
 clang/lib/Sema/SemaTemplateInstantiateDecl.cpp  |  2 +-
 .../over.match.class.deduct/p2.cpp              | 10 ++++++++++
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 45a9e5dc98c032d..1bb81238520173a 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -10153,6 +10153,21 @@ bool clang::isBetterOverloadCandidate(
       //  -- F1 is the copy deduction candidate(16.3.1.8) and F2 is not
       if (Guide1->getDeductionCandidateKind() == DeductionCandidate::Copy)
         return true;
+      if (Guide2->getDeductionCandidateKind() == DeductionCandidate::Copy)
+        return false;
+
+      //  --F1 is generated from a non-template constructor and F2 is generated
+      //  from a constructor template
+      const auto *Constructor1 = Guide1->getCorrespondingConstructor();
+      const auto *Constructor2 = Guide2->getCorrespondingConstructor();
+      if (Constructor1 && Constructor2) {
+        bool isC1Templated = Constructor1->getTemplatedKind() !=
+                             FunctionDecl::TemplatedKind::TK_NonTemplate;
+        bool isC2Templated = Constructor2->getTemplatedKind() !=
+                             FunctionDecl::TemplatedKind::TK_NonTemplate;
+        if (isC1Templated != isC2Templated)
+          return isC2Templated;
+      }
     }
   }
 
@@ -10196,7 +10211,7 @@ bool clang::isBetterOverloadCandidate(
     if (AS1 != AS2) {
       if (Qualifiers::isAddressSpaceSupersetOf(AS2, AS1))
         return true;
-      if (Qualifiers::isAddressSpaceSupersetOf(AS2, AS1))
+      if (Qualifiers::isAddressSpaceSupersetOf(AS1, AS2))
         return false;
     }
   }
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 9e5f85b0f9166bd..b9c4a9db842b9ee 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2129,7 +2129,7 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(
     Function = CXXDeductionGuideDecl::Create(
         SemaRef.Context, DC, D->getInnerLocStart(),
         InstantiatedExplicitSpecifier, NameInfo, T, TInfo,
-        D->getSourceRange().getEnd(), /*Ctor=*/nullptr,
+        D->getSourceRange().getEnd(), DGuide->getCorrespondingConstructor(),
         DGuide->getDeductionCandidateKind());
     Function->setAccess(D->getAccess());
   } else {
diff --git a/clang/test/CXX/over/over.match/over.match.funcs/over.match.class.deduct/p2.cpp b/clang/test/CXX/over/over.match/over.match.funcs/over.match.class.deduct/p2.cpp
index 4eac0a1ac510f1d..d939d724dc7a0fd 100644
--- a/clang/test/CXX/over/over.match/over.match.funcs/over.match.class.deduct/p2.cpp
+++ b/clang/test/CXX/over/over.match/over.match.funcs/over.match.class.deduct/p2.cpp
@@ -85,3 +85,13 @@ int main() {
 
 
 }
+
+namespace deduceTemplatedConstructor{
+template <class T> struct A {
+  A(T, T, int);
+  template<class U>
+    A(int, T, U);
+};
+
+A x(1, 2, 3);       // no-error
+}