Implement noreturn procedure declarations

boot/parser.yy

@@ -85,13 +85,12 @@ along with GCC; see the file COPYING3.  If not see
 %token CONST VAR PROCEDURE TYPE RECORD UNION
 %token BEGIN_BLOCK END_BLOCK EXTERN DEFER
 %token LEFT_PAREN RIGHT_PAREN LEFT_SQUARE RIGHT_SQUARE SEMICOLON DOT COMMA
-%token AND OR NOT CAST SHIFT_LEFT SHIFT_RIGHT
-%token GREATER_EQUAL LESS_EQUAL LESS_THAN GREATER_THAN NOT_EQUAL EQUALS
-%token PLUS MINUS MULTIPLICATION DIVISION REMAINDER
+%token NOT CAST EXCLAMATION
 %token ASSIGNMENT COLON HAT AT NIL ARROW
 
 %left OR AND XOR
 %left EQUALS NOT_EQUAL LESS_THAN GREATER_THAN LESS_EQUAL GREATER_EQUAL
+%left SHIFT_LEFT SHIFT_RIGHT
 %left PLUS MINUS
 %left MULTIPLICATION DIVISION REMAINDER
 
@@ -169,6 +168,12 @@ procedure_heading:
                  $2.first, $2.second);
             std::swap($3, $$->parameters);
         }
+    | PROCEDURE identifier_definition formal_parameter_list ARROW EXCLAMATION SEMICOLON
+        {
+            $$ = new elna::boot::procedure_definition(elna::boot::make_position(@1),
+                 $2.first, $2.second, elna::boot::procedure_definition::no_return_t{});
+            std::swap($3, $$->parameters);
+        }
     | PROCEDURE identifier_definition formal_parameter_list ARROW type_expression SEMICOLON
         {
             $$ = new elna::boot::procedure_definition(elna::boot::make_position(@1),