[PATCH] D63072: [clang] Fixing incorrect implicit deduction guides (PR41549)

[Tyker via Phabricator via cfe-commits]

Tyker created this revision.
Tyker added a reviewer: rsmith.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

bug report <https://bugs.llvm.org/show_bug.cgi?id=41549>

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.


Repository:
  rC Clang

https://reviews.llvm.org/D63072

Files:
  clang/lib/Sema/SemaTemplate.cpp
  clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp


Index: clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
===================================================================
--- clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
+++ clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
@@ -489,6 +489,21 @@
 }
 #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
Index: clang/lib/Sema/SemaTemplate.cpp
===================================================================
--- clang/lib/Sema/SemaTemplate.cpp
+++ clang/lib/Sema/SemaTemplate.cpp
@@ -2052,6 +2052,12 @@
 
 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;


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