diff --git src/interpret.c src/interpret.c
index 5a6cf07..bed664f 100644
--- src/interpret.c
+++ src/interpret.c
@@ -36,6 +36,7 @@ struct InterState
     Expression *localThis;      // value of 'this', or NULL if none
     bool awaitingLvalueReturn;  // Support for ref return values:
            // Any return to this function should return an lvalue.
+    Loc loc;
     InterState();
 };

@@ -56,6 +57,74 @@ ArrayLiteralExp *createBlockDuplicatedArrayLiteral(Type *type, Expression *elem,
 Expression * resolveReferences(Expression *e, Expression *thisval, bool *isReference = NULL);
 Expression *getVarExp(Loc loc, InterState *istate, Declaration *d);

+
+namespace rsinfu
+{
+    Expression* interpret_writeln(InterState* istate, Expressions* arguments)
+    {
+        Expression* result = EXP_VOID_INTERPRET;
+
+        if (arguments)
+        {
+            size_t const dim = arguments->dim;
+
+            for (size_t i = 0; i < dim; ++i)
+            {
+                if (i > 0)
+                    printf(", ");
+
+                Expression*   arg = static_cast<Expression*>(arguments->data[i]);
+                Expression* value = arg->interpret(istate);
+
+                if (!value || value == EXP_CANT_INTERPRET)
+                {
+                    result = EXP_CANT_INTERPRET;
+                    break;
+                }
+                printf("%s", value->toChars());
+            }
+        }
+        putchar('\n');
+        return result;
+    }
+
+    Expression* dump_variables(Dsymbols const* vars)
+    {
+        if (vars)
+        {
+            size_t const nvars = vars->dim;
+
+            for (size_t i = 0; i < nvars; ++i)
+            {
+                VarDeclaration* var = static_cast<VarDeclaration*>(vars->data[i]);
+                printf("\t%s %s = %s\n", var->type->toChars(),
+                                         var->ident->toChars(),
+                                         var->value->toChars());
+            }
+        }
+        return EXP_VOID_INTERPRET;
+    }
+
+    Expression* dump_istate(InterState const* istate)
+    {
+        if (istate)
+        {
+            printf("@ %s(%u)\n", istate->loc.filename,
+                                 istate->loc.linnum);
+
+            if (FuncDeclaration* fd = istate->fd)
+            {
+                printf("# %s %s\n", fd->type->toChars(),
+                                    fd->ident->toChars());
+                dump_variables(fd->parameters);
+            }
+            dump_variables(&istate->vars);
+            puts("--------------------");
+        }
+        return EXP_VOID_INTERPRET;
+    }
+}
+
 /*************************************
  * Attempt to interpret a function given the arguments.
  * Input:
@@ -90,6 +159,13 @@ Expression *FuncDeclaration::interpret(InterState *istate, Expressions *argument
     if (cantInterpret || semanticRun == PASSsemantic3)
         return NULL;

+#if 1
+    if (strcmp(ident->string, "writeln") == 0)
+        return rsinfu::interpret_writeln(istate, arguments);
+    if (strcmp(ident->string, "dump_istate") == 0)
+        return rsinfu::dump_istate(istate);
+#endif
+
     if (!fbody)
     {   cantInterpret = 1;
         error("cannot be interpreted at compile time,"
@@ -307,7 +383,30 @@ Expression *FuncDeclaration::interpret(InterState *istate, Expressions *argument
     {   if (istate->start != this)      \
             return NULL;                \
         istate->start = NULL;           \
-    }
+    }                                   \
+    rsinfu::location_keeper location_keeper_(this, istate);
+
+namespace rsinfu
+{
+    struct location_keeper
+    {
+        location_keeper(Statement const* stmt, InterState* istate)
+            : oldloc_(istate ? istate->loc : 0),
+              istate_(istate)
+        {
+            if (istate_) istate_->loc = stmt->loc;
+        }
+
+        ~location_keeper()
+        {
+            if (istate_) istate_->loc = oldloc_;
+        }
+
+     private:
+        Loc         oldloc_;
+        InterState* istate_;
+    };
+}

 /***********************************
  * Interpret the statement.
@@ -2830,12 +2929,12 @@ Expression *CallExp::interpret(InterState *istate)
         }
         else
         {
-            if (!fd->fbody)
-            {
-                error("%s cannot be interpreted at compile time,"
-                    " because it has no available source code", fd->toChars());
-                return EXP_CANT_INTERPRET;
-            }
+//          if (!fd->fbody)
+//          {
+//              error("%s cannot be interpreted at compile time,"
+//                  " because it has no available source code", fd->toChars());
+//              return EXP_CANT_INTERPRET;
+//          }
             Expression *eresult = fd->interpret(istate, arguments);
             if (eresult)
                 e = eresult;