[clang] 094e9f4 - PR47893: Synthesis of a comparison operator from an 'operator<=>'

[Richard Smith via cfe-commits]

Author: Richard Smith
Date: 2020-10-18T14:15:12-07:00
New Revision: 094e9f4779eb9b5c6a49014f2f80b8cbb833572f

URL: https://github.com/llvm/llvm-project/commit/094e9f4779eb9b5c6a49014f2f80b8cbb833572f
DIFF: https://github.com/llvm/llvm-project/commit/094e9f4779eb9b5c6a49014f2f80b8cbb833572f.diff

LOG: PR47893: Synthesis of a comparison operator from an 'operator<=>'
inherits the SFINAEness of its enclosing context.

Added: 
    

Modified: 
    clang/lib/Sema/SemaTemplateInstantiate.cpp
    clang/test/SemaCXX/cxx2a-three-way-comparison.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 92a887964401..67ba2b87e40e 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -856,6 +856,7 @@ Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
     case CodeSynthesisContext::DefaultTemplateArgumentInstantiation:
     case CodeSynthesisContext::PriorTemplateArgumentSubstitution:
     case CodeSynthesisContext::DefaultTemplateArgumentChecking:
+    case CodeSynthesisContext::RewritingOperatorAsSpaceship:
       // A default template argument instantiation and substitution into
       // template parameters with arguments for prior parameters may or may
       // not be a SFINAE context; look further up the stack.
@@ -874,7 +875,6 @@ Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
     case CodeSynthesisContext::DeclaringSpecialMember:
     case CodeSynthesisContext::DeclaringImplicitEqualityComparison:
     case CodeSynthesisContext::DefiningSynthesizedFunction:
-    case CodeSynthesisContext::RewritingOperatorAsSpaceship:
     case CodeSynthesisContext::InitializingStructuredBinding:
     case CodeSynthesisContext::MarkingClassDllexported:
       // This happens in a context unrelated to template instantiation, so

diff  --git a/clang/test/SemaCXX/cxx2a-three-way-comparison.cpp b/clang/test/SemaCXX/cxx2a-three-way-comparison.cpp
index 29ae95066e27..353360e052bb 100644
--- a/clang/test/SemaCXX/cxx2a-three-way-comparison.cpp
+++ b/clang/test/SemaCXX/cxx2a-three-way-comparison.cpp
@@ -31,3 +31,12 @@ struct B {
 };
 
 int &r = B().operator<=>(0);
+
+namespace PR47893 {
+  struct A {
+    void operator<=>(const A&) const;
+  };
+  template<typename T> auto f(T a, T b) -> decltype(a < b) = delete;
+  int &f(...);
+  int &r = f(A(), A());
+}