Method newFunction

src/main/java/net/starlark/java/eval/Eval.java:162–231

(StarlarkThread.Frame fr, Resolver.Function rfn)

  }

  private static StarlarkFunction newFunction(StarlarkThread.Frame fr, Resolver.Function rfn)
      throws EvalException, InterruptedException {
    // Evaluate default value expressions of optional parameters.
    // We use MANDATORY to indicate a required parameter
    // (not null, because defaults must be a legal tuple value, as
    // it will be constructed by the code emitted by the compiler).
    // As an optimization, we omit the prefix of MANDATORY parameters.
    Object[] defaults = null;
    int nparams =
        rfn.getParameters().size() - (rfn.hasKwargs() ? 1 : 0) - (rfn.hasVarargs() ? 1 : 0);
    CallableType functionType = rfn.getFunctionType();
    boolean dynamicTypeCheckingEnabled =
        fr.thread.getSemantics().getBool(StarlarkSemantics.EXPERIMENTAL_STARLARK_TYPE_CHECKING);
    for (int i = 0; i < nparams; i++) {
      Expression expr = rfn.getParameters().get(i).getDefaultValue();
      if (expr == null && defaults == null) {
        continue; // skip prefix of required parameters
      }
      if (defaults == null) {
        defaults = new Object[nparams - i];
      }
      Object defaultValue = expr == null ? StarlarkFunction.MANDATORY : eval(fr, expr);
      defaults[i - (nparams - defaults.length)] = defaultValue;

      if (dynamicTypeCheckingEnabled && functionType != null) {
        // Typecheck the default value
        StarlarkType parameterType = functionType.getParameterTypeByPos(i);
        if (!TypeChecker.isValueSubtypeOf(defaultValue, parameterType)) {
          throw Starlark.errorf(
              "%s(): parameter '%s' has default value of type '%s', declares '%s'",
              rfn.getName(),
              rfn.getParameterNames().get(i),
              TypeChecker.type(defaultValue),
              parameterType);
        }
      }
    }
    if (defaults == null) {
      defaults = EMPTY;
    }

    // Capture the cells of the function's
    // free variables from the lexical environment.
    Object[] freevars = new Object[rfn.getFreeVars().size()];
    int i = 0;
    for (Resolver.Binding bind : rfn.getFreeVars()) {
      // Unlike expr(Identifier), we want the cell itself, not its content.
      switch (bind.getScope()) {
        case FREE:
          freevars[i++] = fn(fr).getFreeVar(bind.getIndex());
          break;
        case CELL:
          freevars[i++] = fr.locals[bind.getIndex()];
          break;
        default:
          throw new IllegalStateException("unexpected: " + bind);
      }
    }