[Bug c++/102773] New: Show fix-its for mispelled keywords like "templat" and "clas" and "typname"

[Bug c++/102773] New: Show fix-its for mispelled keywords like "templat" and "clas" and "typname"

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102773

            Bug ID: 102773
           Summary: Show fix-its for mispelled keywords like "templat" and
                    "clas" and "typname"
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: enhancement
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

templat<class T> void f(T) { }
template<clas T> void g(T) { }
template<typname T> void h(T) { }

int main()
{
  f(1);
  g(1);
  h(1);
}


c.C:1:1: error: ‘templat’ does not name a type
    1 | templat<class T> void f(T) { }
      | ^~~~~~~
c.C:2:10: error: ‘clas’ has not been declared
    2 | template<clas T> void g(T) { }
      |          ^~~~
c.C:2:23: error: variable or field ‘g’ declared void
    2 | template<clas T> void g(T) { }
      |                       ^
c.C:2:25: error: ‘T’ was not declared in this scope
    2 | template<clas T> void g(T) { }
      |                         ^
c.C:3:10: error: ‘typname’ has not been declared
    3 | template<typname T> void h(T) { }
      |          ^~~~~~~
c.C:3:26: error: variable or field ‘h’ declared void
    3 | template<typname T> void h(T) { }
      |                          ^
c.C:3:28: error: ‘T’ was not declared in this scope
    3 | template<typname T> void h(T) { }
      |                            ^
c.C: In function ‘int main()’:
c.C:7:3: error: ‘f’ was not declared in this scope
    7 |   f(1);
      |   ^
c.C:8:3: error: ‘g’ was not declared in this scope
    8 |   g(1);
      |   ^
c.C:9:3: error: ‘h’ was not declared in this scope
    9 |   h(1);
      |   ^


This is too many errors for this code! There are only three small typos. We
should suggest fix-its for "templat" and "clas" and "typname" which are very
close to known keywords.

Clang prints even more errors, but it does include "did you mean ...?"
suggestions and fix-its:

c.C:1:1: error: no template named 'templat'
templat<class T> void f(T) { }
^
c.C:1:26: error: variable has incomplete type 'T'
templat<class T> void f(T) { }
                         ^
c.C:1:15: note: forward declaration of 'T'
templat<class T> void f(T) { }
              ^
c.C:2:10: error: unknown type name 'clas'; did you mean 'class'?
template<clas T> void g(T) { }
         ^~~~
         class
c.C:2:16: error: non-type template parameter has incomplete type 'class T'
template<clas T> void g(T) { }
               ^
c.C:1:15: note: forward declaration of 'T'
templat<class T> void f(T) { }
              ^
c.C:2:26: error: variable has incomplete type 'T'
template<clas T> void g(T) { }
                         ^
c.C:1:15: note: forward declaration of 'T'
templat<class T> void f(T) { }
              ^
c.C:3:10: error: unknown type name 'typname'; did you mean 'typename'?
template<typname T> void h(T) { }
         ^~~~~~~
         typename
c.C:3:18: error: expected a qualified name after 'typename'
template<typname T> void h(T) { }
                 ^
c.C:3:19: error: non-type template parameter has incomplete type 'T'
template<typname T> void h(T) { }
                  ^
c.C:1:15: note: forward declaration of 'T'
templat<class T> void f(T) { }
              ^
c.C:3:29: error: variable has incomplete type 'T'
template<typname T> void h(T) { }
                            ^
c.C:1:15: note: forward declaration of 'T'
templat<class T> void f(T) { }
              ^
c.C:7:3: error: no matching function for call to 'f'
  f(1);
  ^
c.C:1:23: note: candidate function not viable: no known conversion from 'int'
to 'T' for 1st argument
templat<class T> void f(T) { }
                      ^
c.C:8:3: error: no matching function for call to 'g'
  g(1);
  ^
c.C:2:23: note: candidate template ignored: couldn't infer template argument ''
template<clas T> void g(T) { }
                      ^
c.C:9:3: error: no matching function for call to 'h'
  h(1);
  ^
c.C:3:26: note: candidate template ignored: couldn't infer template argument ''
template<typname T> void h(T) { }
                         ^
12 errors generated.

[Bug c++/102773] Show fix-its for mispelled keywords like "templat" and "clas" and "typname"

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102773

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-10-27

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Another example:

long i = reintepret_cast<long>((void*)0);


cast.C:1:10: error: ‘reintepret_cast’ was not declared in this scope
    1 | long i = reintepret_cast<long>((void*)0);
      |          ^~~~~~~~~~~~~~~
cast.C:1:26: error: expected primary-expression before ‘long’
    1 | long i = reintepret_cast<long>((void*)0);
      |                          ^~~~



And this one with -std=c++20:

template<class T>
void
f(const void* v)
{
  auto u = reintepret_cast<long>(v);
}

cast.C: In function 'void f(const void*)':
cast.C:5:12: error: there are no arguments to 'reintepret_cast' that depend on
a template parameter, so a declaration of 'reintepret_cast' must be available
[-fpermissive]
    5 |   auto u = reintepret_cast<long>(v);
      |            ^~~~~~~~~~~~~~~~~~~~~
cast.C:5:12: note: (if you use '-fpermissive', G++ will accept your code, but
allowing the use of an undeclared name is deprecated)