[m-rev.] for post-commit review: shut up some C# warnings

[Peter Wang]

On Fri, 11 Mar 2022 10:20:29 +1100 "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> For review by anyone.
> 
> Zoltan.

> Fix C# "declared/assigned but not used" warnings.
> 
> compiler/mlds_to_cs_stmt.m:
>     Keep warnings disabled on all components of the implementation
>     of a foreign_proc *except* the component actually written by users.
>     Specifically, we want to keep "declared/assigned but not used" warnings
>     disabled in the code that (a) declares and then (b) initializes
>     the input arguments of a foreign_proc that the foreign_proc's body
>     ignores.
> 
> library/io.file.m:
>     Turn the warnings off for a piece of code that ignores the details
>     of an exception.

That's fine.

> diff --git a/library/io.file.m b/library/io.file.m
> index a722fcc44..7f70d1ef3 100644
> --- a/library/io.file.m
> +++ b/library/io.file.m
> @@ -1603,6 +1603,7 @@ get_temp_directory(Dir, !IO) :-
>      [will_not_call_mercury, promise_pure, tabled_for_io, thread_safe,
>          may_not_duplicate],
>  "
> +#pragma warning disable 162, 168, 169, 219, 1717
>      try {
>          Dir = System.IO.Path.GetTempPath();
>          OK = (Dir != null) ? 1 : 0;
> @@ -1610,6 +1611,7 @@ get_temp_directory(Dir, !IO) :-
>          Dir = null;
>          OK = 0;
>      }
> +#pragma warning restore
>  ").

I pushed a more direct fix for the unused variable warning (168).
If it breaks some older C# compiler that we supposedly support then it
can be reverted easily.

diff --git a/library/io.file.m b/library/io.file.m
index 7f70d1ef3..61a0fc1de 100644
--- a/library/io.file.m
+++ b/library/io.file.m
@@ -1603,15 +1603,13 @@ get_temp_directory(Dir, !IO) :-
     [will_not_call_mercury, promise_pure, tabled_for_io, thread_safe,
         may_not_duplicate],
 "
-#pragma warning disable 162, 168, 169, 219, 1717
     try {
         Dir = System.IO.Path.GetTempPath();
         OK = (Dir != null) ? 1 : 0;
-    } catch (System.Exception _) {
+    } catch (System.Exception) {
         Dir = null;
         OK = 0;
     }
-#pragma warning restore
 ").

Peter