* Forbid use of string alias in system unit

compiler/msg/errore.msg

@@ -1654,6 +1654,9 @@ parser_e_suspending_externals_not_supported_on_current_platform=03368_E_Declarin
 parser_w_widechar_set_reduced=03369_W_Reducing Widechar set to single-byte AnsiChar set.
 % The base type of a set can only have 255 elements. Sets of wide characters
 % are reduced to sets of 1-byte characters.
+parser_e_nostringaliasinsystem=03370_e_Using 'string' alias is not allowed in the system unit. Use short-,ansi- or unicodestring.
+% As a safeguard, the system unit may only use basic string types, not the
+% string alias which is dependent on the mode in which a unit is compiled.
 %
 % \end{description}
 %

compiler/msgidx.inc

@@ -483,6 +483,7 @@ const
   parser_e_promising_exports_not_supported_on_current_platform=03367;
   parser_e_suspending_externals_not_supported_on_current_platform=03368;
   parser_w_widechar_set_reduced=03369;
+  parser_e_nostringaliasinsystem=03370;
   type_e_mismatch=04000;
   type_e_incompatible_types=04001;
   type_e_not_equal_types=04002;
@@ -1168,9 +1169,9 @@ const
   option_info=11024;
   option_help_pages=11025;
 
-  MsgTxtSize = 91613;
+  MsgTxtSize = 91712;
 
   MsgIdxMax : array[1..20] of longint=(
-    28,109,370,134,102,63,148,38,223,71,
+    28,109,371,134,102,63,148,38,223,71,
     68,20,30,1,1,1,1,1,1,1
   );

compiler/pbase.pas

@@ -372,7 +372,7 @@ implementation
                             exit(true);
                         end;
                       { system.char? (char=widechar comes from the implicit
-                        uuchar unit -> override) }
+                        uachar/uuchar unit -> override) }
                       if (pattern='CHAR') and
                          (tmodule(tunitsym(srsym).module).globalsymtable=systemunit) then
                         begin
@@ -399,6 +399,8 @@ implementation
                      end;
                   _STRING:
                     begin
+                      if cs_compilesystem in current_settings.moduleswitches then
+                        Message(parser_e_nostringaliasinsystem);
                       { system.string? }
                       if tmodule(tunitsym(srsym).module).globalsymtable=systemunit then
                         begin

compiler/pexpr.pas

@@ -141,6 +141,9 @@ implementation
            end
           else
             begin
+             // string[x] is allowed in system unit since it is a shortstring.
+             if cs_compilesystem in current_settings.moduleswitches then
+               Message(parser_e_nostringaliasinsystem);
               if cs_refcountedstrings in current_settings.localswitches then
                 begin
                   if m_default_unicodestring in current_settings.modeswitches then
@@ -4036,6 +4039,8 @@ implementation
 
              _STRING :
                begin
+                 if cs_compilesystem in current_settings.moduleswitches then
+                   Message(parser_e_nostringaliasinsystem);
                  string_dec(hdef,true);
                  { STRING can be also a type cast }
                  if try_to_consume(_LKLAMMER) then
@@ -5017,11 +5022,11 @@ implementation
         end
       else if (tstringconstnode(p).cst_type in [cst_unicodestring,cst_widestring]) then
          begin
-         pw:=pcompilerwideString(tstringconstnode(p).value_str);
+           pw:=pcompilerwideString(tstringconstnode(p).value_str);
-         pc:=getmem(getlengthwidestring(pw));
+           pc:=getmem(getlengthwidestring(pw));
-         unicode2ascii(pw,pc,current_settings.sourcecodepage);
+           unicode2ascii(pw,pc,current_settings.sourcecodepage);
-         get_stringconst:=strpas(pc);
+           get_stringconst:=strpas(pc);
-         freemem(pc);
+           freemem(pc);
          end
       else
         get_stringconst:=strpas(snode.value_str);

compiler/ptype.pas

@@ -495,7 +495,6 @@ implementation
              case token of
                _STRING:
                  string_dec(def,stoAllowTypeDef in options);
-
                _FILE:
                  begin
                     consume(_FILE);
@@ -1324,8 +1323,8 @@ implementation
                      begin
                      if (m_default_unicodestring in current_settings.modeswitches) then
                        begin
-                       Message(parser_w_widechar_set_reduced);
+                         Message(parser_w_widechar_set_reduced);
-                       def:=csetdef.create(cansichartype,torddef(cansichartype).low.svalue,torddef(cansichartype).high.svalue,true);
+                         def:=csetdef.create(cansichartype,torddef(cansichartype).low.svalue,torddef(cansichartype).high.svalue,true);
                        end
                      else
                        Message(sym_e_ill_type_decl_set);  

compiler/scanner.pas

@@ -1635,7 +1635,7 @@ type
                     case current_scanner.preproc_token of
                       _ID:
                         { system.char? (char=widechar comes from the implicit
-                          uuchar unit -> override) }
+                          uachar/uuchar unit -> override) }
                         if (current_scanner.preproc_pattern='CHAR') and
                            (tmodule(tunitsym(srsym).module).globalsymtable=systemunit) then
                           begin