[Bug c++/44283] bad error recovery for explicit template instantiation in wrong namespace

2017-08-18 Thread egallager at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44283

Eric Gallager  changed:

   What|Removed |Added

   Keywords||error-recovery
 Status|UNCONFIRMED |NEW
   Last reconfirmed||2017-08-18
 CC||egallager at gcc dot gnu.org
 Ever confirmed|0   |1

--- Comment #2 from Eric Gallager  ---
(In reply to Jonathan Wakely from comment #0)
> namespace NS
> {
> typedef int X;
> 
> template void f(X f, T t) { }
> }
> 
> template void f(X, int); // (1)
> 
> template void f(int, char);  // (2)
> 
> 
> The code is invalid, the explicit instantiations should be inside NS or
> should be qualified e.g.
> template void NS::func(X, int);
> 
> But the diagnostic for instantiation (1) is unhelpful:
> 
> bug.cc:8:17: error: variable or field 'f' declared void
> bug.cc:8:16: error: expected ';' before '(' token
> 
> This is closely related to Bug 16663 but the diagnostic for (2) implies it
> might be possible to improve things without fixing bug 16663, as this is
> much better:
> 
> bug.cc:10:26: error: 'f' is not a template function
> 
> Is it possible to give the same "is not a template function" diagnostic for
> (1)?

The message is now:

$ /usr/local/bin/g++ -c -Wall -Wextra -pedantic 44283.cc
44283.cc:8:17: error: variable or field ‘f’ declared void
 template void f(X, int); // (1)
 ^
44283.cc:8:16: error: expected ‘;’ before ‘(’ token
 template void f(X, int); // (1)
^
44283.cc:10:26: error: ‘f’ is not a template function
 template void f(int, char);  // (2)
  ^
$

so it has the "is not a template function" diagnostic now, but it could still
probably be improved.

> 
> Comeau does significantly better, reporting:
>identifier "X" is undefined
> and 
>"f" is not a class or function template name in the current scope
> 
> 
> 
> If the invalid instantiation is for a class template the diagnostic is fine:
> 
> namespace NS
> {
> template struct S;
> }
> 
> template struct S;
> 
> bug2.cc:6:17: error: 'S' is not a template
> bug2.cc:6:19: error: 'X' was not declared in this scope
> bug2.cc:6:17: error: explicit instantiation of non-template type 'S'
> 
> The only improvement I would make would be to add something like "in this
> scope" to the first error.
> 

With carets, this is now:

$ /usr/local/bin/g++ -c -Wall -Wextra -pedantic 44283_2.cc
44283_2.cc:6:17: error: ‘S’ is not a class template
 template struct S;
 ^
44283_2.cc:6:19: error: ‘X’ was not declared in this scope
 template struct S;
   ^
44283_2.cc:6:17: error: explicit instantiation of non-template type ‘S’
 template struct S;
 ^
$

(note the addition of the word 'class')

> 
> Here's another bad diagnostic for instantiating a template function, which
> doesn't have any undeclared type:
> 
> namespace NS
> {
> template void g() { }
> }
> 
> template void g<0>();
> 
> bug3.cc:6:15: error: variable or field 'g' declared void
> bug3.cc:6:16: error: expected ';' before '<' token
> 
> Surely it's possible to say "g is not a template function" when the compiler
> sees "template ... g<...>" ?
> 

This is still bad even with carets:

$ /usr/local/bin/g++ -c -Wall -Wextra -pedantic 44283_3.cc
44283_3.cc:6:15: error: variable or field ‘g’ declared void
 template void g<0>();
   ^
44283_3.cc:6:16: error: expected ‘;’ before ‘<’ token
 template void g<0>();
^
$

> Comeau is much better again:
> 
> "ComeauTest.c", line 6: error: g is not a template,
>   Should it be XX::g?, where XX is some namespace?
>   Did you #include the right header?
>   template void g<0>();
> ^
> 
> "ComeauTest.c", line 6: error: invalid explicit instantiation declaration
>   template void g<0>();
>^

So, confirmed that the errors could be improved.

[Bug c++/44283] bad error recovery for explicit template instantiation in wrong namespace

2012-04-12 Thread redi at gcc dot gnu.org 
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44283

--- Comment #1 from Jonathan Wakely redi at gcc dot gnu.org 2012-04-12 
12:35:07 UTC ---
(In reply to comment #0)
 namespace NS
 {
 typedef int X;
 
 templatetypename T void f(X f, T t) { }
 }
 
 template void f(X, int); // (1)
 
 template void f(int, char);  // (2)


Clang does very well for this:

t.cc:8:15: error: explicit instantiation of 'f' does not refer to a function
template, member function, member
  class, or static data member
template void f(X, int); // (1)
  ^
t.cc:10:15: error: explicit instantiation of 'f' does not refer to a function
template, member function,
  member class, or static data member
template void f(int, char);  // (2)
  ^
2 errors generated.



 If the invalid instantiation is for a class template the diagnostic is fine:
 
 namespace NS
 {
 templatetypename T struct S;
 }
 
 template struct SX;
 
 bug2.cc:6:17: error: 'S' is not a template
 bug2.cc:6:19: error: 'X' was not declared in this scope
 bug2.cc:6:17: error: explicit instantiation of non-template type 'S'


Clang is similar:

t.cc:6:19: error: use of undeclared identifier 'X'
template struct SX;
  ^
t.cc:6:17: error: explicit instantiation of non-template struct 'S'
template struct SX;
^
2 errors generated.



 namespace NS
 {
 templateint N void g() { }
 }
 
 template void g0();
 
 bug3.cc:6:15: error: variable or field 'g' declared void
 bug3.cc:6:16: error: expected ';' before '' token


Clang is not much better here:

t.cc:6:16: error: expected ';' after top level declarator
template void g0();
   ^
1 error generated.



EDG's diagnostics are still the best for these examples.