From: Gauthier Harnisch <tyker1@outlook.com>
Date: Fri, 14 Jun 2019 08:40:04 +0000 (+0000)
Subject: [clang] Fixing incorrect implicit deduction guides (PR41549)
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=4a58b8483cde0d2ea84c2ad9741c83b45ede8f55;p=clang

[clang] Fixing incorrect implicit deduction guides (PR41549)

Summary:
[[ https://bugs.llvm.org/show_bug.cgi?id=41549 | bug report ]]

Before this patch, implicit deduction guides were generated from the first declaration found by lookup.
With this patch implicit deduction guides are generated from the definition of the class template.
Also added test that was previously failing.

Reviewers: rsmith

Reviewed By: rsmith

Subscribers: cfe-commits, Quuxplusone

Tags: #clang

Differential Revision: https://reviews.llvm.org/D63072

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@363361 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index 2483a28b25..f7f3ccc3e2 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -2052,6 +2052,12 @@ private:
 
 void Sema::DeclareImplicitDeductionGuides(TemplateDecl *Template,
                                           SourceLocation Loc) {
+  if (CXXRecordDecl *DefRecord =
+          cast<CXXRecordDecl>(Template->getTemplatedDecl())->getDefinition()) {
+    TemplateDecl *DescribedTemplate = DefRecord->getDescribedClassTemplate();
+    Template = DescribedTemplate ? DescribedTemplate : Template;
+  }
+
   DeclContext *DC = Template->getDeclContext();
   if (DC->isDependentContext())
     return;
diff --git a/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp b/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
index 29adc8f560..c5deb9fe91 100644
--- a/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
+++ b/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
@@ -489,6 +489,21 @@ static_assert(__is_same(decltype(ta), TestSuppression<const char *>), "");
 }
 #pragma clang diagnostic pop
 
+namespace PR41549 {
+
+template <class H, class P> struct umm;
+
+template <class H = int, class P = int>
+struct umm {
+  umm(H h = 0, P p = 0);
+};
+
+template <class H, class P> struct umm;
+
+umm m(1);
+
+}
+
 #else
 
 // expected-no-diagnostics