Correct deferred concepts with NTTP placeholder constraints

Seemingly we never tested this, but the constraint on a NTTP was being swtiched to the 'instantiated' version, but constraints need to be relative to the 'top level', so this was causing us to not be able to check the constraint on final use. This patch corrects the issue by making the constraint created with the un-instantiated version in the case of dependent constraint attachment. Fixes: #61777
llvm · Mar 30, 2023 · 18fe663 · 18fe663
1 parent 1f04aeb
commit 18fe663
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Showing 4 changed files with 44 additions and 11 deletions.
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
@@ -8123,7 +8123,8 @@ class Sema final {
                             SourceLocation EllipsisLoc);
 
   bool AttachTypeConstraint(AutoTypeLoc TL,
-                            NonTypeTemplateParmDecl *ConstrainedParameter,
+                            NonTypeTemplateParmDecl *NewConstrainedParm,
+                            NonTypeTemplateParmDecl *OrigConstrainedParm,
                             SourceLocation EllipsisLoc);
 
   bool RequireStructuralType(QualType T, SourceLocation Loc);

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
@@ -1251,35 +1251,41 @@ bool Sema::AttachTypeConstraint(NestedNameSpecifierLoc NS,
   return false;
 }
 
-bool Sema::AttachTypeConstraint(AutoTypeLoc TL, NonTypeTemplateParmDecl *NTTP,
+bool Sema::AttachTypeConstraint(AutoTypeLoc TL,
+                                NonTypeTemplateParmDecl *NewConstrainedParm,
+                                NonTypeTemplateParmDecl *OrigConstrainedParm,
                                 SourceLocation EllipsisLoc) {
-  if (NTTP->getType() != TL.getType() ||
+  if (NewConstrainedParm->getType() != TL.getType() ||
       TL.getAutoKeyword() != AutoTypeKeyword::Auto) {
-    Diag(NTTP->getTypeSourceInfo()->getTypeLoc().getBeginLoc(),
+    Diag(NewConstrainedParm->getTypeSourceInfo()->getTypeLoc().getBeginLoc(),
          diag::err_unsupported_placeholder_constraint)
-       << NTTP->getTypeSourceInfo()->getTypeLoc().getSourceRange();
+        << NewConstrainedParm->getTypeSourceInfo()
+               ->getTypeLoc()
+               .getSourceRange();
     return true;
   }
   // FIXME: Concepts: This should be the type of the placeholder, but this is
   // unclear in the wording right now.
   DeclRefExpr *Ref =
-      BuildDeclRefExpr(NTTP, NTTP->getType(), VK_PRValue, NTTP->getLocation());
+      BuildDeclRefExpr(OrigConstrainedParm, OrigConstrainedParm->getType(),
+                       VK_PRValue, OrigConstrainedParm->getLocation());
   if (!Ref)
     return true;
   ExprResult ImmediatelyDeclaredConstraint = formImmediatelyDeclaredConstraint(
       *this, TL.getNestedNameSpecifierLoc(), TL.getConceptNameInfo(),
       TL.getNamedConcept(), TL.getLAngleLoc(), TL.getRAngleLoc(),
-      BuildDecltypeType(Ref), NTTP->getLocation(),
+      BuildDecltypeType(Ref), OrigConstrainedParm->getLocation(),
       [&](TemplateArgumentListInfo &ConstraintArgs) {
         for (unsigned I = 0, C = TL.getNumArgs(); I != C; ++I)
           ConstraintArgs.addArgument(TL.getArgLoc(I));
       },
       EllipsisLoc);
   if (ImmediatelyDeclaredConstraint.isInvalid() ||
-     !ImmediatelyDeclaredConstraint.isUsable())
+      !ImmediatelyDeclaredConstraint.isUsable())
     return true;
 
-  NTTP->setPlaceholderTypeConstraint(ImmediatelyDeclaredConstraint.get());
+  NewConstrainedParm->setPlaceholderTypeConstraint(
+      ImmediatelyDeclaredConstraint.get());
   return false;
 }
 
@@ -1559,7 +1565,7 @@ NamedDecl *Sema::ActOnNonTypeTemplateParameter(Scope *S, Declarator &D,
 
   if (AutoTypeLoc TL = TInfo->getTypeLoc().getContainedAutoTypeLoc())
     if (TL.isConstrained())
-      if (AttachTypeConstraint(TL, Param, D.getEllipsisLoc()))
+      if (AttachTypeConstraint(TL, Param, Param, D.getEllipsisLoc()))
         Invalid = true;
 
   if (Invalid)

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3008,8 +3008,10 @@ Decl *TemplateDeclInstantiator::VisitNonTypeTemplateParmDecl(
 
   if (AutoTypeLoc AutoLoc = DI->getTypeLoc().getContainedAutoTypeLoc())
     if (AutoLoc.isConstrained())
+      // Note: We attach the uninstantiated constriant here, so that it can be
+      // instantiated relative to the top level, like all our other constraints.
       if (SemaRef.AttachTypeConstraint(
-              AutoLoc, Param,
+              AutoLoc, Param, D,
               IsExpandedParameterPack
                 ? DI->getTypeLoc().getAs<PackExpansionTypeLoc>()
                     .getEllipsisLoc()

diff --git a/clang/test/SemaTemplate/concepts.cpp b/clang/test/SemaTemplate/concepts.cpp
@@ -792,3 +792,27 @@ int foo() {
     return b;
 }
 } // namespace GH48182
+
+namespace GH61777 {
+template<class T> concept C = sizeof(T) == 4; // #61777_C
+template<class T, class U> concept C2 = sizeof(T) == sizeof(U); //#61777_C2
+
+template<class T>
+struct Parent {
+  template<class, C auto> struct TakesUnary { static const int i = 0 ; }; // #UNARY
+  template<class, C2<T> auto> struct TakesBinary { static const int i = 0 ; }; //#BINARY
+};
+
+static_assert(Parent<void>::TakesUnary<int, 0>::i == 0);
+// expected-error@+3{{constraints not satisfied for class template 'TakesUnary'}}
+// expected-note@#UNARY{{because 'decltype(0ULL)' (aka 'unsigned long long') does not satisfy 'C'}}
+// expected-note@#61777_C{{because 'sizeof(unsigned long long) == 4' (8 == 4) evaluated to false}}
+static_assert(Parent<void>::TakesUnary<int, 0uLL>::i == 0);
+
+static_assert(Parent<int>::TakesBinary<int, 0>::i == 0);
+// expected-error@+3{{constraints not satisfied for class template 'TakesBinary'}}
+// expected-note@#BINARY{{because 'C2<decltype(0ULL), int>' evaluated to false}}
+// expected-note@#61777_C2{{because 'sizeof(unsigned long long) == sizeof(int)' (8 == 4) evaluated to false}}
+static_assert(Parent<int>::TakesBinary<int, 0ULL>::i == 0);
+}
+