integer_types_as_enum: missing case

Context

In the following exemple:

https://github.com/AdaCore/langkit-query-language/blob/75cec794bacac95cd20906998872ca484f728346/lkql_checker/share/lkql/integer_types_as_enum.lkql#L41-L45

The line 43 should be a conditional check. In the case of a type that is used by a subtype, and none of them uses operators, that case is not handled.

Solution

If types does not have a reference of the type, the we continue the other condition (this is actually what the code does).

However, if types have reference of the type, then we have to check instantiations and arithmetic_ops for every references.

So that, we can display a integer type may be replaced by an enumeration for type that do not have arithmetic operator, but have reference to this type (subtype, etc.) which also do not use operators.

Example:

procedure Integer_Types_As_Enum is
   type T1 is mod 10;
   type T2 is new T1;
   V1  : T1;
   V2  : T2;

begin
   declare
      type T11 is range 1 .. 10;          -- FLAGGED
      type T12 is new T1;                 -- FLAGGED

      V11 : T11;
      V12 : T12;
   begin
      if V1 > 1 then
         null;
      end if;
      if V12 in 5 .. 7 then
         null;
      end if;
   end;

   V1 := V1 and 1;
   V2 := V2 + 1;

   declare
      type T13 is range 1 .. 10;
      type T14 is new T13;                 -- FLAGGED
      subtype ST13 is T13 range 1 .. 5;
      function "+" (L, R : ST13) return ST13 is
      begin
         return L;
      end "+";

      type Arr_1_13 is array (T1) of Character;
      V13 : array (T14) of T2;

      VST13 : ST13;
   begin
      VST13 := VST13 + 1;
   end;

   declare
      type T15 is range 1 .. 10;           -- FLAGGED
      type T16 is new T15 range 1 .. 5;    -- FLAGGED
      subtype ST15 is T15 range 1 .. 5;
      subtype ST16 is T16 range 1 .. 2;

      VST15 : ST15;
      VST16 : ST16;
   begin
      if VST16 in 1 .. 1 then
         VST16 := 1;
      elsif VST15 < 3 or VST15 = 10 then
         VST15 := 9;
      end if;
   end;
end Integer_Types_As_Enum;

Start with lkql_checker/share/lkql/integer_types_as_enum.lkql at lines 41-45 and compare its handling of referenced types with the Ada example in the issue. The change is complete when types referenced through subtypes or derived types are checked for instantiations and arithmetic operators, and the expected integer-type warnings appear for the shown cases.