PR32185: Revert r291512 and add a testcase for PR32185.

This reverts an attempt to check that types match when matching a
dependently-typed non-type template parameter. (This comes up when matching the
parameters of a template template parameter against the parameters of a
template template argument.)

The matching rules here are murky at best. Our behavior after this revert is
definitely wrong for certain C++17 features (for 'auto' template parameter
types within the parameter list of a template template argument in particular),
but our behavior before this revert is wrong for some pre-existing testcases,
so reverting to our prior behavior seems like our best option.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@300262 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 50 insertions, 16 deletions

diff --git a/test/SemaTemplate/deduction.cpp b/test/SemaTemplate/deduction.cpp
index 8ac65aacd5..74eb5a6ee5 100644
--- a/test/SemaTemplate/deduction.cpp
+++ b/test/SemaTemplate/deduction.cpp
@@ -483,16 +483,15 @@ namespace check_extended_pack {
 }
 
 namespace dependent_template_template_param_non_type_param_type {
-  template<int N> struct A { // expected-note 2{{candidate}}
+  template<int N> struct A {
     template<typename V = int, V M = 12, V (*Y)[M], template<V (*v)[M]> class W>
-    A(W<Y>); // expected-note {{[with V = int, M = 12, Y = &dependent_template_template_param_non_type_param_type::n]}}
+    A(W<Y>);
   };
 
   int n[12];
   template<int (*)[12]> struct Q {};
   Q<&n> qn;
-  // FIXME: This should be accepted, but we somehow fail to deduce W.
-  A<0> a(qn); // expected-error {{no matching constructor for initialization}}
+  A<0> a(qn);
 }
 
 namespace dependent_list_deduction {
diff --git a/test/SemaTemplate/temp_arg_template.cpp b/test/SemaTemplate/temp_arg_template.cpp
index b0df9149c6..8f59dd724c 100644
--- a/test/SemaTemplate/temp_arg_template.cpp
+++ b/test/SemaTemplate/temp_arg_template.cpp
@@ -102,7 +102,42 @@ void foo() {
 }
 
 namespace CheckDependentNonTypeParamTypes {
-  template<template<typename T, typename U, T v> class> struct A {}; // expected-note {{previous}}
-  template<typename T, typename U, U v> struct B {}; // expected-note {{different type}}
-  A<B> ab; // expected-error {{different template parameters}}
+  template<template<typename T, typename U, T v> class X> struct A {
+    void f() {
+      X<int, void*, 3> x; // expected-error {{does not refer to any declaration}}
+    }
+    void g() {
+      X<int, long, 3> x;
+    }
+    void h() {
+      // FIXME: If we accept A<B> at all, it's not obvious what should happen
+      // here. While parsing the template, we form
+      //   X<unsigned char, int, (unsigned char)1234>
+      // but in the final instantiation do we get
+      //   B<unsigned char, int, (int)1234>
+      // or
+      //   B<unsigned char, int, (int)(unsigned char)1234>
+      // ?
+      X<unsigned char, int, 1234> x;
+      int check[x.value == 1234 ? 1 : -1];
+    }
+  };
+
+  template<typename T, typename U, U v> struct B { // expected-note {{parameter}}
+    static const U value = v;
+  };
+
+  // FIXME: This should probably be rejected, but the rules are at best unclear.
+  A<B> ab;
+
+  void use() {
+    ab.f(); // expected-note {{instantiation of}}
+    ab.g();
+    ab.h();
+  }
+}
+
+namespace PR32185 {
+  template<template<typename T, T> class U> struct A {};
+  template<template<typename T, T> class U> struct B : A<U> {};
 }
diff --git a/test/SemaTemplate/temp_arg_template_cxx1z.cpp b/test/SemaTemplate/temp_arg_template_cxx1z.cpp
index e3f228e7ef..03ef78f8cf 100644
--- a/test/SemaTemplate/temp_arg_template_cxx1z.cpp
+++ b/test/SemaTemplate/temp_arg_template_cxx1z.cpp
@@ -78,7 +78,7 @@ namespace Auto {
   template<int*> struct IntPtr;
 
   TInt<Auto> ia;
-  TInt<AutoPtr> iap; // expected-error {{different template parameters}}
+  TInt<AutoPtr> iap; // FIXME: ill-formed (?)
   TInt<DecltypeAuto> ida;
   TInt<Int> ii;
   TInt<IntPtr> iip; // expected-error {{different template parameters}}
@@ -90,18 +90,18 @@ namespace Auto {
   TIntPtr<IntPtr> ipip;
 
   TAuto<Auto> aa;
-  TAuto<AutoPtr> aap; // expected-error {{different template parameters}}
-  TAuto<Int> ai; // expected-error {{different template parameters}}
-  TAuto<IntPtr> aip; // expected-error {{different template parameters}}
+  TAuto<AutoPtr> aap; // FIXME: ill-formed (?)
+  TAuto<Int> ai; // FIXME: ill-formed (?)
+  TAuto<IntPtr> aip; // FIXME: ill-formed (?)
 
   TAutoPtr<Auto> apa;
   TAutoPtr<AutoPtr> apap;
-  TAutoPtr<Int> api; // expected-error {{different template parameters}}
-  TAutoPtr<IntPtr> apip; // expected-error {{different template parameters}}
+  TAutoPtr<Int> api; // FIXME: ill-formed (?)
+  TAutoPtr<IntPtr> apip; // FIXME: ill-formed (?)
 
   TDecltypeAuto<DecltypeAuto> dada;
-  TDecltypeAuto<Int> dai; // expected-error {{different template parameters}}
-  TDecltypeAuto<IntPtr> daip; // expected-error {{different template parameters}}
+  TDecltypeAuto<Int> dai; // FIXME: ill-formed (?)
+  TDecltypeAuto<IntPtr> daip; // FIXME: ill-formed (?)
 
   // FIXME: It's completely unclear what should happen here, but these results
   // seem at least plausible:
@@ -111,7 +111,7 @@ namespace Auto {
   // parameters (such as 'user-defined-type &') that are not valid 'auto'
   // parameters.
   TDecltypeAuto<Auto> daa;
-  TDecltypeAuto<AutoPtr> daa; // expected-error {{different template parameters}}
+  TDecltypeAuto<AutoPtr> daap; // FIXME: should probably be ill-formed
 
   int n;
   template<auto A, decltype(A) B = &n> struct SubstFailure;