Partial revert of r290511.

The rules around typechecking deduced template arguments during partial
ordering are not clear, and while the prior behavior does not seem to be
correct (it doesn't follow the general model of partial ordering where each
template parameter is replaced by a non-dependent but unique value), the new
behavior is also not clearly right and breaks some existing idioms.

The new behavior is retained for dealing with non-type template parameters
with 'auto' types, as without it even the most basic uses of that feature
don't work. We can revisit this once CWG has come to an agreement on how
partial ordering with 'auto' non-type template parameters is supposed to
work.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@292183 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index 1c19f67cb0fc2d9b10b76fc7695a4a6641d8057a..2920ede3b5eea3de477e0ab2e6a8e2fa993edfac 100644 (file)
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -5123,18 +5123,22 @@ ExprResult Sema::CheckTemplateArgument(NonTypeTemplateParmDecl *Param,
   if (CTAK == CTAK_Deduced &&
       !Context.hasSameType(ParamType.getNonLValueExprType(Context),
                            Arg->getType())) {
-    // C++ [temp.deduct.type]p17: (DR1770)
-    //   If P has a form that contains <i>, and if the type of i differs from
-    //   the type of the corresponding template parameter of the template named
-    //   by the enclosing simple-template-id, deduction fails.
-    //
-    // Note that CTAK will be CTAK_DeducedFromArrayBound if the form was [i]
-    // rather than <i>.
-    //
-    // FIXME: We interpret the 'i' here as referring to the expression
-    // denoting the non-type template parameter rather than the parameter
-    // itself, and so strip off references before comparing types. It's
-    // not clear how this is supposed to work for references.
+    // FIXME: If either type is dependent, we skip the check. This isn't
+    // correct, since during deduction we're supposed to have replaced each
+    // template parameter with some unique (non-dependent) placeholder.
+    // FIXME: If the argument type contains 'auto', we carry on and fail the
+    // type check in order to force specific types to be more specialized than
+    // 'auto'. It's not clear how partial ordering with 'auto' is supposed to
+    // work.
+    if ((ParamType->isDependentType() || Arg->isTypeDependent()) &&
+        !Arg->getType()->getContainedAutoType()) {
+      Converted = TemplateArgument(Arg);
+      return Arg;
+    }
+    // FIXME: This attempts to implement C++ [temp.deduct.type]p17. Per DR1770,
+    // we should actually be checking the type of the template argument in P,
+    // not the type of the template argument deduced from A, against the
+    // template parameter type.
     Diag(StartLoc, diag::err_deduced_non_type_template_arg_type_mismatch)
       << Arg->getType()
       << ParamType.getUnqualifiedType();

diff --git a/test/SemaTemplate/class-template-spec.cpp b/test/SemaTemplate/class-template-spec.cpp
index 518ec78e6f7d03a4cb935fa0911a04f8611e614a..00e03ef61eb07fe3a3ef526ba2fdd0e8d31f7249 100644 (file)
--- a/test/SemaTemplate/class-template-spec.cpp
+++ b/test/SemaTemplate/class-template-spec.cpp
@@ -207,19 +207,19 @@ namespace NTTPTypeVsPartialOrder {
   struct X { typedef int value_type; };
   template<typename T> struct Y { typedef T value_type; };
 
-  template<typename T, typename T::value_type N> struct A; // expected-note {{template}}
+  template<typename T, typename T::value_type N> struct A;
   template<int N> struct A<X, N> {};
-  template<typename T, T N> struct A<Y<T>, N> {}; // expected-error {{not more specialized}} expected-note {{'T' vs 'typename Y<type-parameter-0-0>::value_type'}}
+  template<typename T, T N> struct A<Y<T>, N> {};
   A<X, 0> ax;
   A<Y<int>, 0> ay;
 
 
-  template<int, typename T, typename T::value_type> struct B; // expected-note {{template}}
-  template<typename T, typename T::value_type N> struct B<0, T, N>; // expected-note {{matches}}
+  template<int, typename T, typename T::value_type> struct B;
+  template<typename T, typename T::value_type N> struct B<0, T, N>;
   template<int N> struct B<0, X, N> {};
-  template<typename T, T N> struct B<0, Y<T>, N> {}; // expected-error {{not more specialized}} expected-note {{'T' vs 'typename Y<type-parameter-0-0>::value_type'}} expected-note {{matches}}
+  template<typename T, T N> struct B<0, Y<T>, N> {};
   B<0, X, 0> bx;
-  B<0, Y<int>, 0> by; // expected-error {{ambiguous}}
+  B<0, Y<int>, 0> by;
 }
 
 namespace DefaultArgVsPartialSpec {

diff --git a/test/SemaTemplate/partial-order.cpp b/test/SemaTemplate/partial-order.cpp
new file mode 100644 (file)
index 0000000..0a151de
--- /dev/null
+++ b/test/SemaTemplate/partial-order.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -std=c++1z %s -verify
+
+// expected-no-diagnostics
+
+namespace hana_enable_if_idiom {
+  template<bool> struct A {};
+  template<typename, typename = A<true>> struct B;
+  template<typename T, bool N> struct B<T, A<N>> {};
+  template<typename T> struct B<T, A<T::value>> {};
+  struct C {
+    static const bool value = true;
+  };
+  B<C> b;
+}

diff --git a/test/SemaTemplate/temp_arg_nontype.cpp b/test/SemaTemplate/temp_arg_nontype.cpp
index 27a0a03f84f462c9083c972de38d90401ba30bdf..5b72b8c6549a4ac1e4f5f811d1d985ee81f3d96f 100644 (file)
--- a/test/SemaTemplate/temp_arg_nontype.cpp
+++ b/test/SemaTemplate/temp_arg_nontype.cpp
@@ -370,13 +370,13 @@ namespace PR17696 {
 }
 
 namespace partial_order_different_types {
-  // These are unordered because the type of the final argument doesn't match.
-  template<int, int, typename T, typename, T> struct A; // expected-note {{here}}
-  template<int N, typename T, typename U, T V> struct A<0, N, T, U, V> {}; // expected-note {{matches}}
-  template<typename T, typename U, U V> struct A<0, 0, T, U, V> {}; // expected-note {{matches}}
-  // expected-error@-1 {{not more specialized than the primary}}
-  // expected-note@-2 {{deduced non-type template argument does not have the same type as the corresponding template parameter ('U' vs 'type-parameter-0-0')}}
-  A<0, 0, int, int, 0> a; // expected-error {{ambiguous partial specializations}}
+  template<int, int, typename T, typename, T> struct A;
+  template<int N, typename T, typename U, T V> struct A<0, N, T, U, V>; // expected-note {{matches}}
+  // FIXME: It appears that this partial specialization should be ill-formed as
+  // it is not more specialized than the primary template. V is not deducible
+  // because it does not have the same type as the corresponding parameter.
+  template<int N, typename T, typename U, U V> struct A<0, N, T, U, V> {}; // expected-note {{matches}}
+  A<0, 0, int, int, 0> a; // expected-error {{ambiguous}}
 }
 
 namespace partial_order_references {
@@ -434,7 +434,7 @@ namespace dependent_nested_partial_specialization {
 
   template<typename T> struct E {
     template<typename U, U V> struct F; // expected-note {{template}}
-    template<typename W, T V> struct F<W, V> {}; // expected-error {{not more specialized than the primary}} expected-note {{does not have the same type}}
+    template<typename W, T V> struct F<W, V> {}; // expected-error {{not more specialized than the primary}}
   };
   E<int>::F<int, 0> e1; // expected-note {{instantiation of}}
 }

diff --git a/test/SemaTemplate/temp_arg_template_cxx1z.cpp b/test/SemaTemplate/temp_arg_template_cxx1z.cpp
index aa517c32859937e2bec2e267ce06f562f7b6314c..703935dcd5c19bfa76e6634a02fa379b11c19462 100644 (file)
--- a/test/SemaTemplate/temp_arg_template_cxx1z.cpp
+++ b/test/SemaTemplate/temp_arg_template_cxx1z.cpp
@@ -79,13 +79,13 @@ namespace Auto {
 
   TInt<Auto> ia;
   TInt<AutoPtr> iap; // expected-error {{different template parameters}}
-  TInt<DecltypeAuto> ida; // FIXME expected-error {{different template parameters}}
+  TInt<DecltypeAuto> ida;
   TInt<Int> ii;
   TInt<IntPtr> iip; // expected-error {{different template parameters}}
 
   TIntPtr<Auto> ipa;
   TIntPtr<AutoPtr> ipap;
-  TIntPtr<DecltypeAuto> ipda; // FIXME expected-error {{different template parameters}}
+  TIntPtr<DecltypeAuto> ipda;
   TIntPtr<Int> ipi; // expected-error {{different template parameters}}
   TIntPtr<IntPtr> ipip;
 
@@ -114,6 +114,6 @@ namespace Auto {
 
   int n;
   template<auto A, decltype(A) B = &n> struct SubstFailure;
-  TInt<SubstFailure> isf; // expected-error {{different template parameters}}
-  TIntPtr<SubstFailure> ipsf; // expected-error {{different template parameters}}
+  TInt<SubstFailure> isf; // FIXME: this should be ill-formed
+  TIntPtr<SubstFailure> ipsf;
 }