visitForIterLoopStmt method

@override Object? visitForIterLoopStmt(ForIterLoopStmt forIterLoopStmt)

Implementation

@override
Object? visitForIterLoopStmt(ForIterLoopStmt forIterLoopStmt) {
  final prevScope = scope;
  pushScope();
  final String lineInfo = this.lineInfo(forIterLoopStmt.token);

  try {
    final List<String> vars = forIterLoopStmt.vars.map((e) => e.lexeme).toList(growable: false);
    final List<LuaObject> exprs = [];
    final int len = forIterLoopStmt.exprs.length;
    for(int i = 0; i < len; i++) {
      final expr = forIterLoopStmt.exprs[i];
      if(i == len-1) {
        final List<LuaObject> ls = switch(expr.accept(this)) {
          final LuaArgPack ls => ls,
          final List<Object> ls => ls.map((e) => e.toLuaRet()).toList(growable: false),
          final Object o => [o.toLuaRet()],
          _ => [LuaObject.nil('expr$i')],
        };
        exprs.addAll(ls);
      } else {
        exprs.add(expr.accept(this)?.unpack() ?? LuaObject.nil('expr$i'));
      }
    }

    // Read only the first 3 evaluated expression result values.
    // See: https://www.lua.org/pil/7.2.html
    LuaObject f = exprs.elementAt(0);
    if(f.isCallable) {
      f = f.readMetatable('__call')?.unpack() ?? LuaObject.nil('iter');
    } else if(f.isNotFunc) {
      throw '$lineInfo Expected an iterator found ${f.luaTypeInfo}.';
    }

    final LuaObject s = exprs.elementAtOrNull(1) ?? LuaObject.nil('state');
    LuaObject v = exprs.elementAtOrNull(2) ?? LuaObject.nil('value');

    for(final String v in vars) {
      defLocal(LuaObject.nil(v));
    }

    bool loop = true;
    while(loop) {
      final args = callLuaFunction(f, args: [s, v]);

      for(int i = 0; i < vars.length; i++) {
        LuaObject vs = findVar(vars[i])!;
        if(i >= args.length) {
          vs.value = null;
          continue;
        }
        vs.value = args[i];
        if(i == 0) {
          v = vs;
        }
      }

      if(v.isNil) {
        loop = false;
        break;
      }

      for (Stmt stmt in forIterLoopStmt.body) {
        try {
          stmt.accept(this);
        } on LuaBreakStmtException {
          loop = false;
          break;
        } catch (e) {
          loop = false;
          addError(e.toString());
        }
      }
    }
  } catch (e) {
    rethrow;
  } finally {
    restoreScope(prevScope);
  }

  return null;
}