[Bug c++/57570] New: Deduction succeeds despite type mismatch of non-type template parameter and deduced argument

[hstong at ca dot ibm.com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57570

            Bug ID: 57570
           Summary: Deduction succeeds despite type mismatch of non-type
                    template parameter and deduced argument
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hstong at ca dot ibm.com

GCC does not consistently fail deduction for type mismatch of a non-type
template parameter and the corresponding deduced argument.

See N3690 subclause 14.8.2.5 [temp.deduct.type] paragraph 17.

### STANDALONE SOURCE:
template <short, char> struct A;

int foo(void *);
template <short x> int foo(A<x, x> *ap)
   // neither clang++ nor g++ bother to look at the second instance of x
   // for deduction
{ return noGood(ap); }

int bar(void *);
template <char y> int bar(A<y, y> *ap)
   // okay; clang++ and g++ both realize that deducing from the first instance
   // of y is no good
{ return noGood(ap); }

int zip(void *, void *);
template <short x, char y> int zip(A<x, y> *ap, A<y, x> *)
   // clang++ does not bother to look at the second function argument
   // for deduction, g++ does
{ return noGood(ap); }

A<0, 0> *ap = 0;

int a = foo(ap);  // clang++ and g++ both fail to fail the argument deduction
int b = bar(ap);  // clang++ and g++ both successfully fail the deduction
int c = zip(ap, ap);  //
   // clang++ fails to fail and g++ successfully fails the argument deduction

// For all three:
// - MSVC 17.00.51025 fails to fail the argument deduction
// - ICC 13.0.1 20121010 and IBM XL C/C++ for AIX 12.1.0.3 work fine


### COMPILER INVOCATION:
g++ -std=c++11 -c main.cpp


### EXPECTED OUTPUT:
Successful compile.


### ACTUAL OUTPUT:
main.cpp: In instantiation of 'int foo(A<x, x>*) [with short int x = 0]':
main.cpp:23:15:   required from here
main.cpp:7:12: error: 'noGood' was not declared in this scope


### g++ -v OUTPUT:
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
4.8.1-2ubuntu1~12.04' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.8 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin
--with-system-zlib --disable-browser-plugin --enable-java-awt=gtk
--enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre
--enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64 --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.8.1 (Ubuntu 4.8.1-2ubuntu1~12.04)