Merge branch 'topic/instance_error' into 'master'

Add a help message when instantiating the same name multiple times

Closes #314

See merge request eng/libadalang/langkit-query-language!277

Author: HugoGGuerrier

lkql_checker/src/gnatcheck-options.ads

@@ -189,6 +189,10 @@ package Gnatcheck.Options is
    --  This variable should contain a full list of compilation options to be
    --  passed to gcc.
 
+   Instance_Help_Emitted : Boolean := False;
+   --  Whether the help message about the new instance system has already been
+   --  emitted. This message should be removed in 26.0.
+
    --------------------------------------
    -- Controlling the gnatcheck report --
    --------------------------------------

lkql_checker/src/gnatcheck-rules-rule_table.adb

@@ -1051,6 +1051,13 @@ package body Gnatcheck.Rules.Rule_Table is
                (if Instance.Defined_At /= ""
                 then To_String (Instance.Defined_At)
                 else "command line") & Diag_Defined_At);
+            if not Instance_Help_Emitted then
+               Warning
+                 ("if you want to pass multiple parameters to a rule you " &
+                  "should use the comma separated notation: e.g. " &
+                  "+RMy_Rule:Param1,Param2");
+               Instance_Help_Emitted := True;
+            end if;
             Bad_Rule_Detected := True;
             return;
          elsif not Enable and then Instance = null then

testsuite/tests/gnatcheck_errors/already_existing_instance/test.out

@@ -1,3 +1,4 @@
 gnatcheck: rule instance with the same name already exists: "goto_statements" previously instantiated at command line
+gnatcheck: if you want to pass multiple parameters to a rule you should use the comma separated notation: e.g. +RMy_Rule:Param1,Param2
 main.adb:3:04: goto statement [goto_statements]
 >>>program returned status code 5

testsuite/tests/gnatcheck_errors/same_name_instances/test.out

@@ -1,4 +1,5 @@
 gnatcheck: rule instance with the same name already exists: "same_alias" previously instantiated at command line
+gnatcheck: if you want to pass multiple parameters to a rule you should use the comma separated notation: e.g. +RMy_Rule:Param1,Param2
 gnatcheck: rule instance with the same name already exists: "comp_check" previously instantiated at command line
 gnatcheck: rule instance with the same name already exists: "comp_check" previously instantiated at command line
 >>>program returned status code 5