pkg/js_ast/test/dangling_else_label_test.dart

// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

// Test for dangling-else detection when the then-part has a label. The
// then-part of an if-then-else statement sometimes needs to be wrapped in a
// block to avoid an inner if-then 'capturing' the else part.

import 'dart:convert';
import 'package:expect/expect.dart';
import 'package:js_ast/js_ast.dart';

void check1(String expected, Statement then) {
  final actual = DebugPrint(
    If(VariableUse('x'), then, ExpressionStatement(VariableUse('E'))),
  );
  Expect.equals(
    expected,
    actual,
    '\n'
    '\nexpected ${json.encode(expected)}'
    '\nactual:  ${json.encode(actual)}',
  );
}

void check(
  String expected,
  Statement then1, [
  Statement? then2,
  Statement? then3,
  Statement? then4,
]) {
  check1(expected, then1);
  if (then2 != null) check1(expected, then2);
  if (then3 != null) check1(expected, then3);
  if (then4 != null) check1(expected, then4);
}

void main() {
  final y = VariableUse('y');
  final z = VariableUse('z');
  final S1 = ExpressionStatement(VariableUse('S1'));
  final S2 = ExpressionStatement(VariableUse('S2'));

  check(r'''
if (x)
  L:
    if (y)
      S1;
    else
      S2;
else
  E;
''', LabeledStatement('L', If(y, S1, S2)));

  check(r'''
if (x) {
  L:
    if (y)
      S1;
    else
      S2;
} else
  E;
''', Block([LabeledStatement('L', If(y, S1, S2))]));

  check(r'''
if (x)
  L: {
    if (y)
      S1;
    else
      S2;
  }
else
  E;
''', LabeledStatement('L', Block([If(y, S1, S2)])));

  check(
    r'''
if (x) {
  L:
    if (y)
      S1;
} else
  E;
''',
    LabeledStatement('L', If.noElse(y, S1)),
    Block([LabeledStatement('L', If.noElse(y, S1))]),
  );

  check(r'''
if (x) {
  L: {
    if (y)
      S1;
  }
} else
  E;
''', LabeledStatement('L', Block([If.noElse(y, S1)])));

  check(r'''
if (x)
  L: {
    if (y)
      S1;
    S2;
  }
else
  E;
''', LabeledStatement('L', Block([If.noElse(y, S1), S2])));

  check(
    r'''
if (x) {
  L:
    if (y)
      S1;
    else if (z)
      S2;
} else
  E;
''',
    LabeledStatement('L', If(y, S1, If.noElse(z, S2))),
    Block([LabeledStatement('L', If(y, S1, If.noElse(z, S2)))]),
  );

  check(r'''
if (x) {
  L: {
    if (y)
      S1;
    else if (z)
      S2;
  }
} else
  E;
''', LabeledStatement('L', Block([If(y, S1, If.noElse(z, S2))])));

  check(
    r'''
if (x) {
  L:
    if (y)
      S1;
    else {
      if (z)
        S2;
    }
} else
  E;
''',
    LabeledStatement('L', If(y, S1, Block([If.noElse(z, S2)]))),
    Block([
      LabeledStatement('L', If(y, S1, Block([If.noElse(z, S2)]))),
    ]),
  );

  check(
    r'''
if (x) {
  L:
    while (y)
      if (z)
        S1;
} else
  E;
''',
    LabeledStatement('L', While(y, If.noElse(z, S1))),
    Block([LabeledStatement('L', While(y, If.noElse(z, S1)))]),
  );

  check(r'''
if (x) {
  L: {
    while (y)
      if (z)
        S1;
  }
} else
  E;
''', LabeledStatement('L', Block([While(y, If.noElse(z, S1))])));

  check(r'''
if (x) {
  L:
    while (y) {
      if (z)
        S1;
    }
} else
  E;
''', LabeledStatement('L', While(y, Block([If.noElse(z, S1)]))));

  check(
    r'''
if (x) {
  L:
    for (;;)
      if (z)
        S1;
} else
  E;
''',
    LabeledStatement('L', For(null, null, null, If.noElse(z, S1))),
    Block([LabeledStatement('L', For(null, null, null, If.noElse(z, S1)))]),
  );

  check(r'''
if (x) {
  L: {
    for (;;)
      if (z)
        S1;
  }
} else
  E;
''', LabeledStatement('L', Block([For(null, null, null, If.noElse(z, S1))])));

  check(r'''
if (x) {
  L:
    for (;;) {
      if (z)
        S1;
    }
} else
  E;
''', LabeledStatement('L', For(null, null, null, Block([If.noElse(z, S1)]))));
}