[Bug c++/103921] New: [modules] ICE requires in explicit-specifier of instantiation of imported template

[Bug c++/103921] New: [modules] ICE requires in explicit-specifier of instantiation of imported template

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103921

            Bug ID: 103921
           Summary: [modules] ICE requires in explicit-specifier of
                    instantiation of imported template
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: johelegp at gmail dot com
                CC: johelegp at gmail dot com
  Target Milestone: ---

See https://godbolt.org/z/Tb1eMbE3W.
I think it's valid because Clang accepts it: https://godbolt.org/z/xcK7Kenb5.

mod.cpp:
```C++
export module mod;

export template<class N> struct quantity {
  template<class N2>
  explicit(requires { 0; }) operator quantity<N2>() const;
};

export template<class N1, class N2>
bool operator==(const quantity<N1>& l, const quantity<N2>& r);
```

test.cpp:
```C++
import mod;
int main() {
  return requires { quantity<int>{} == quantity<double>{}; };
}
```

Output:
```
In module mod, imported at /app/test.cpp:1:
mod.cpp: In instantiation of 'struct quantity@mod<int>':
test.cpp:3:35:   required from here
mod.cpp:5:29: internal compiler error: Segmentation fault
    5 |   explicit(requires { 0; }) operator quantity<N2>() const;
      |                             ^~~~~~~~
0x2139bd9 internal_error(char const*, ...)
        ???:0
0x9ada27 tsubst(tree_node*, tree_node*, int, tree_node*)
        ???:0
0x9f2c99 instantiate_class_template(tree_node*)
        ???:0
0xa184bc finish_compound_literal(tree_node*, tree_node*, int, fcl_t)
        ???:0
0x97a00d c_parse_file()
        ???:0
0xb08022 c_common_parse_file()
        ???:0
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
```

[Bug c++/103921] [modules] ICE requires in explicit-specifier of instantiation of imported template

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103921

--- Comment #1 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
Simplified: https://godbolt.org/z/zzbjj7W3K.

mod.cpp:
```C++
export module mod;

export template<class N> struct quantity {
  template<class N2>
  explicit(requires { 0; }) operator quantity<N2>() const;
};
```

test.cpp:
```C++
import mod;
int main() {
  return requires { (quantity<double>)quantity<int>{}; };
}
```

Output:
```
In module mod, imported at /app/test.cpp:1:
mod.cpp: In instantiation of 'struct quantity@mod<int>':
test.cpp:3:53:   required from here
mod.cpp:5:29: internal compiler error: Segmentation fault
    5 |   explicit(requires { 0; }) operator quantity<N2>() const;
      |                             ^~~~~~~~
0x2139bd9 internal_error(char const*, ...)
        ???:0
0x9ada27 tsubst(tree_node*, tree_node*, int, tree_node*)
        ???:0
0x9f2c99 instantiate_class_template(tree_node*)
        ???:0
0xa184bc finish_compound_literal(tree_node*, tree_node*, int, fcl_t)
        ???:0
0x97a00d c_parse_file()
        ???:0
0xb08022 c_common_parse_file()
        ???:0
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
```

[Bug c++/103921] [modules] ICE dependent expression in explicit-specifier of instantiation of imported template

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103921

Johel Ernesto Guerrero Peña <johelegp at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[modules] ICE requires in   |[modules] ICE dependent
                   |explicit-specifier of       |expression in
                   |instantiation of imported   |explicit-specifier of
                   |template                    |instantiation of imported
                   |                            |template

--- Comment #2 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
It actually ICEs whenever the expression is dependent:
https://godbolt.org/z/oqbnanoex.

mod.cpp:
```C++
export module mod;

template<class> constexpr bool b{true};

export template<class N> struct quantity {
  template<class N2>
  explicit(b<N>) operator quantity<N2>() const;
};
```

[Bug c++/103921] [modules] ICE dependent expression in explicit-specifier of instantiation of imported template

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103921

--- Comment #3 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
Simplified: https://godbolt.org/z/rnfKrzYaP.

mod.cpp:
```C++
export module mod;

export template<bool B> struct Int {
  explicit(B) operator int() const;
};
```

test.cpp:
```C++
import mod;
int main() {
  return Int<true>{};
}
```

Output:
```
In module mod, imported at /app/test.cpp:1:
mod.cpp: In instantiation of 'struct Int@mod<true>':
test.cpp:3:20:   required from here
mod.cpp:4:15: internal compiler error: Segmentation fault
    4 |   explicit(B) operator int() const;
      |               ^~~~~~~~
0x2139bd9 internal_error(char const*, ...)
        ???:0
0x9ada27 tsubst(tree_node*, tree_node*, int, tree_node*)
        ???:0
0x9f2c99 instantiate_class_template(tree_node*)
        ???:0
0xa184bc finish_compound_literal(tree_node*, tree_node*, int, fcl_t)
        ???:0
0x97a00d c_parse_file()
        ???:0
0xb08022 c_common_parse_file()
        ???:0
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
```

[Bug c++/103921] [modules] ICE dependent expression in explicit-specifier of instantiation of imported template

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103921

--- Comment #4 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
For the above, when it's fixed:
```diff
-  explicit(B) operator int() const;
+  explicit(B) operator int() { return 0; }
```

[Bug c++/103921] [modules] ICE dependent expression in explicit-specifier of instantiation of imported template

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103921

Johel Ernesto Guerrero Peña <johelegp at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #5 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
Resolved by https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103752#c2.

*** This bug has been marked as a duplicate of bug 103752 ***