[NF] Fix typing of when statements too.

- Use correct origin when typing when-conditions in statements.
- Propagate the when-flag properly when marking variables inside
  when-clauses as discrete.

Belonging to [master]:
  - OpenModelica/OMCompiler#2781
  - OpenModelica/OpenModelica-testsuite#1074

Compiler/NFFrontEnd/NFInst.mo

@@ -3119,7 +3119,7 @@ algorithm
                   all_params := false;
                 end if;
 
-                updateImplicitVariabilityEql(branch.body);
+                updateImplicitVariabilityEql(branch.body, inWhen);
               then
                 ();
           end match;
@@ -3178,7 +3178,7 @@ algorithm
         // 'when' is not allowed in 'for', so we only need to keep going if
         // we're already in a 'when'.
         if inWhen then
-          updateImplicitVariabilityStmts(stmt.body);
+          updateImplicitVariabilityStmts(stmt.body, true);
         end if;
       then
         ();
@@ -3189,7 +3189,7 @@ algorithm
         // we're already in a 'when.
         if inWhen then
           for branch in stmt.branches loop
-            updateImplicitVariabilityStmts(Util.tuple22(branch));
+            updateImplicitVariabilityStmts(Util.tuple22(branch), true);
           end for;
         end if;
       then
@@ -3208,7 +3208,7 @@ algorithm
         // 'when' is not allowed in 'while', so we only need to keep going if
         // we're already in a 'when.
         if inWhen then
-          updateImplicitVariabilityStmts(stmt.body);
+          updateImplicitVariabilityStmts(stmt.body, true);
         end if;
       then
         ();

Compiler/NFFrontEnd/NFTyping.mo

@@ -2685,7 +2685,7 @@ algorithm
         tybrs := list(
           match br case(cond, body)
             algorithm
-              e1 := typeCondition(cond, next_origin, st.source, Error.WHEN_CONDITION_TYPE_ERROR, allowVector = true);
+              e1 := typeCondition(cond, origin, st.source, Error.WHEN_CONDITION_TYPE_ERROR, allowVector = true);
               sts1 := list(typeStatement(bst, next_origin) for bst in body);
             then (e1, sts1);
           end match