[PATCH 07/10] Fix g++.dg/template/ref3.C

[David Malcolm <dmalcolm at redhat dot com>]

Testcase g++.dg/template/ref3.C:

     1	// PR c++/28341
     2
     3	template<const int&> struct A {};
     4
     5	template<typename T> struct B
     6	{
     7	  A<(T)0> b; // { dg-error "constant|not a valid" }
     8	  A<T(0)> a; // { dg-error "constant|not a valid" }
     9	};
    10
    11	B<const int&> b;

The output of this test for both c++11 and c++14 is unaffected
by the patch kit:
 g++.dg/template/ref3.C: In instantiation of 'struct B<const int&>':
 g++.dg/template/ref3.C:11:15:   required from here
 g++.dg/template/ref3.C:7:11: error: '0' is not a valid template argument for type 'const int&' because it is not an lvalue
 g++.dg/template/ref3.C:8:11: error: '0' is not a valid template argument for type 'const int&' because it is not an lvalue

However, the c++98 output is changed:

Status quo for c++98:
g++.dg/template/ref3.C: In instantiation of 'struct B<const int&>':
g++.dg/template/ref3.C:11:15:   required from here
g++.dg/template/ref3.C:7:11: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression
g++.dg/template/ref3.C:8:11: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression

(line 7 and 8 are at the closing semicolon for fields b and a)

With the patchkit for c++98:
g++.dg/template/ref3.C: In instantiation of 'struct B<const int&>':
g++.dg/template/ref3.C:11:15:   required from here
g++.dg/template/ref3.C:7:5: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression
g++.dg/template/ref3.C:7:5: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression

So the 2nd:
  "error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression"
moves from line 8 to line 7 (and moves them to earlier, having ranges)

What's happening is that cp_parser_enclosed_template_argument_list
builds a CAST_EXPR, the first time from cp_parser_cast_expression,
the second time from cp_parser_functional_cast; these have locations
representing the correct respective caret&ranges, i.e.:

   A<(T)0> b;
     ^~~~

and:

   A<T(0)> a;
     ^~~~

Eventually finish_template_type is called for each, to build a RECORD_TYPE,
and we get a cache hit the 2nd time through here in pt.c:
8281	      hash = spec_hasher::hash (&elt);
8282	      entry = type_specializations->find_with_hash (&elt, hash);
8283
8284	      if (entry)
8285		return entry->spec;

due to:
  template_args_equal (ot=<cast_expr 0x7ffff19bc400>, nt=<cast_expr 0x7ffff19bc480>) at ../../src/gcc/cp/pt.c:7778
which calls:
  cp_tree_equal (t1=<cast_expr 0x7ffff19bc400>, t2=<cast_expr 0x7ffff19bc480>) at ../../src/gcc/cp/tree.c:2833
and returns equality.

Hence we get a single RECORD_TYPE for the type A<(T)(0)>, and hence
when issuing the errors it uses the TREE_VEC for the first one,
using the location of the first line.

I'm not sure what the ideal fix for this is; for now I've worked
around it by updating the dg directives to reflect the new output.

gcc/testsuite/ChangeLog:
	* g++.dg/template/ref3.C: Update locations of dg directives.
---
 gcc/testsuite/g++.dg/template/ref3.C | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/g++.dg/template/ref3.C b/gcc/testsuite/g++.dg/template/ref3.C
index 976c093..6e568c3 100644
--- a/gcc/testsuite/g++.dg/template/ref3.C
+++ b/gcc/testsuite/g++.dg/template/ref3.C
@@ -4,8 +4,10 @@ template<const int&> struct A {};
 
 template<typename T> struct B
 {
-  A<(T)0> b; // { dg-error "constant|not a valid" }
-  A<T(0)> a; // { dg-error "constant|not a valid" }
+  A<(T)0> b; // { dg-error "constant" "" { target c++98_only } }
+  // { dg-error "not a valid" "" { target c++11 } 7 }
+
+  A<T(0)> a; // { dg-error "not a valid" "" { target c++11 } }
 };
 
 B<const int&> b;
-- 
1.8.5.3