pairwiseCompare produces confusing 'Which: has <null> which is not <null> at index null' error on type mismatch

[derdilla]

When pairwiseCompare compares values of different types a confusing (more confusing if the types get longer) error message appears:

Log

Building package executable... (7.9s)
Built test:test.
00:01 +0 -1: test/bug_test.dart: throws has <null> which is not description <null> at index null [E]                                                                                            
  Expected: pairwise  ['a']
    Actual: [1]
     Which: has <null> which is not  <null> at index null
  type 'int' is not a subtype of type 'String' in type cast at #0      _PairwiseCompare.typedMatches (package:matcher/src/iterable_matchers.dart:266:44)
  #1      FeatureMatcher.matches (package:matcher/src/feature_matcher.dart:16:42)
  #2      _expect (package:matcher/src/expect/expect.dart:138:30)
  #3      expect (package:matcher/src/expect/expect.dart:56:3)
  #4      main.<anonymous closure> (file:///home/rrausch/Code/bug/test/bug_test.dart:6:5)
  #5      Declarer.test.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/declarer.dart:229:19)
  <asynchronous suspension>
  #6      Declarer.test.<anonymous closure> (package:test_api/src/backend/declarer.dart:227:7)
  <asynchronous suspension>
  #7      Invoker._waitForOutstandingCallbacks.<anonymous closure> (package:test_api/src/backend/invoker.dart:258:9)
  <asynchronous suspension>
  
  
  package:matcher         expect
  test/bug_test.dart 6:5  main.<fn>
  

To run this test again: /home/rrausch/Code/flutter/bin/cache/dart-sdk/bin/dart test test/bug_test.dart -p vm --plain-name 'throws has <null> which is not description <null> at index null'
00:01 +0 -1: Some tests failed.                                                                                                                                                                 

Consider enabling the flag chain-stack-traces to receive more detailed exceptions.
For example, 'dart test --chain-stack-traces'.
dart test  9.71s user 1.13s system 101% cpu 10.649 total

To reproduce

• dart create bug
• add code sample to test/bug_test.dart
• dart test

Code sample

test('throws has <null> which is not description <null> at index null', () {
  expect([1], pairwiseCompare(['a'], (String a, String b) => a == b, ''));
});

env

dart --version:
Dart SDK version: 3.6.1 (stable) (Tue Jan 7 09:50:00 2025 -0800) on "linux_x64"

pubspec.lock

# Generated by pub
# See https://dart.dev/tools/pub/glossary#lockfile
packages:
  _fe_analyzer_shared:
    dependency: transitive
    description:
      name: _fe_analyzer_shared
      sha256: "03f6da266a27a4538a69295ec142cb5717d7d4e5727b84658b63e1e1509bac9c"
      url: "https://pub.dev"
    source: hosted
    version: "79.0.0"
  _macros:
    dependency: transitive
    description: dart
    source: sdk
    version: "0.3.3"
  analyzer:
    dependency: transitive
    description:
      name: analyzer
      sha256: c9040fc56483c22a5e04a9f6a251313118b1a3c42423770623128fa484115643
      url: "https://pub.dev"
    source: hosted
    version: "7.2.0"
  args:
    dependency: transitive
    description:
      name: args
      sha256: bf9f5caeea8d8fe6721a9c358dd8a5c1947b27f1cfaa18b39c301273594919e6
      url: "https://pub.dev"
    source: hosted
    version: "2.6.0"
  async:
    dependency: transitive
    description:
      name: async
      sha256: d2872f9c19731c2e5f10444b14686eb7cc85c76274bd6c16e1816bff9a3bab63
      url: "https://pub.dev"
    source: hosted
    version: "2.12.0"
  boolean_selector:
    dependency: transitive
    description:
      name: boolean_selector
      sha256: "8aab1771e1243a5063b8b0ff68042d67334e3feab9e95b9490f9a6ebf73b42ea"
      url: "https://pub.dev"
    source: hosted
    version: "2.1.2"
  collection:
    dependency: transitive
    description:
      name: collection
      sha256: "2f5709ae4d3d59dd8f7cd309b4e023046b57d8a6c82130785d2b0e5868084e76"
      url: "https://pub.dev"
    source: hosted
    version: "1.19.1"
  convert:
    dependency: transitive
    description:
      name: convert
      sha256: b30acd5944035672bc15c6b7a8b47d773e41e2f17de064350988c5d02adb1c68
      url: "https://pub.dev"
    source: hosted
    version: "3.1.2"
  coverage:
    dependency: transitive
    description:
      name: coverage
      sha256: e3493833ea012784c740e341952298f1cc77f1f01b1bbc3eb4eecf6984fb7f43
      url: "https://pub.dev"
    source: hosted
    version: "1.11.1"
  crypto:
    dependency: transitive
    description:
      name: crypto
      sha256: "1e445881f28f22d6140f181e07737b22f1e099a5e1ff94b0af2f9e4a463f4855"
      url: "https://pub.dev"
    source: hosted
    version: "3.0.6"
  file:
    dependency: transitive
    description:
      name: file
      sha256: a3b4f84adafef897088c160faf7dfffb7696046cb13ae90b508c2cbc95d3b8d4
      url: "https://pub.dev"
    source: hosted
    version: "7.0.1"
  frontend_server_client:
    dependency: transitive
    description:
      name: frontend_server_client
      sha256: f64a0333a82f30b0cca061bc3d143813a486dc086b574bfb233b7c1372427694
      url: "https://pub.dev"
    source: hosted
    version: "4.0.0"
  glob:
    dependency: transitive
    description:
      name: glob
      sha256: c3f1ee72c96f8f78935e18aa8cecced9ab132419e8625dc187e1c2408efc20de
      url: "https://pub.dev"
    source: hosted
    version: "2.1.3"
  http_multi_server:
    dependency: transitive
    description:
      name: http_multi_server
      sha256: aa6199f908078bb1c5efb8d8638d4ae191aac11b311132c3ef48ce352fb52ef8
      url: "https://pub.dev"
    source: hosted
    version: "3.2.2"
  http_parser:
    dependency: transitive
    description:
      name: http_parser
      sha256: "178d74305e7866013777bab2c3d8726205dc5a4dd935297175b19a23a2e66571"
      url: "https://pub.dev"
    source: hosted
    version: "4.1.2"
  io:
    dependency: transitive
    description:
      name: io
      sha256: dfd5a80599cf0165756e3181807ed3e77daf6dd4137caaad72d0b7931597650b
      url: "https://pub.dev"
    source: hosted
    version: "1.0.5"
  js:
    dependency: transitive
    description:
      name: js
      sha256: c1b2e9b5ea78c45e1a0788d29606ba27dc5f71f019f32ca5140f61ef071838cf
      url: "https://pub.dev"
    source: hosted
    version: "0.7.1"
  lints:
    dependency: "direct dev"
    description:
      name: lints
      sha256: c35bb79562d980e9a453fc715854e1ed39e24e7d0297a880ef54e17f9874a9d7
      url: "https://pub.dev"
    source: hosted
    version: "5.1.1"
  logging:
    dependency: transitive
    description:
      name: logging
      sha256: c8245ada5f1717ed44271ed1c26b8ce85ca3228fd2ffdb75468ab01979309d61
      url: "https://pub.dev"
    source: hosted
    version: "1.3.0"
  macros:
    dependency: transitive
    description:
      name: macros
      sha256: "1d9e801cd66f7ea3663c45fc708450db1fa57f988142c64289142c9b7ee80656"
      url: "https://pub.dev"
    source: hosted
    version: "0.1.3-main.0"
  matcher:
    dependency: transitive
    description:
      name: matcher
      sha256: dc58c723c3c24bf8d3e2d3ad3f2f9d7bd9cf43ec6feaa64181775e60190153f2
      url: "https://pub.dev"
    source: hosted
    version: "0.12.17"
  meta:
    dependency: transitive
    description:
      name: meta
      sha256: e3641ec5d63ebf0d9b41bd43201a66e3fc79a65db5f61fc181f04cd27aab950c
      url: "https://pub.dev"
    source: hosted
    version: "1.16.0"
  mime:
    dependency: transitive
    description:
      name: mime
      sha256: "41a20518f0cb1256669420fdba0cd90d21561e560ac240f26ef8322e45bb7ed6"
      url: "https://pub.dev"
    source: hosted
    version: "2.0.0"
  node_preamble:
    dependency: transitive
    description:
      name: node_preamble
      sha256: "6e7eac89047ab8a8d26cf16127b5ed26de65209847630400f9aefd7cd5c730db"
      url: "https://pub.dev"
    source: hosted
    version: "2.0.2"
  package_config:
    dependency: transitive
    description:
      name: package_config
      sha256: "92d4488434b520a62570293fbd33bb556c7d49230791c1b4bbd973baf6d2dc67"
      url: "https://pub.dev"
    source: hosted
    version: "2.1.1"
  path:
    dependency: transitive
    description:
      name: path
      sha256: "75cca69d1490965be98c73ceaea117e8a04dd21217b37b292c9ddbec0d955bc5"
      url: "https://pub.dev"
    source: hosted
    version: "1.9.1"
  pool:
    dependency: transitive
    description:
      name: pool
      sha256: "20fe868b6314b322ea036ba325e6fc0711a22948856475e2c2b6306e8ab39c2a"
      url: "https://pub.dev"
    source: hosted
    version: "1.5.1"
  pub_semver:
    dependency: transitive
    description:
      name: pub_semver
      sha256: "7b3cfbf654f3edd0c6298ecd5be782ce997ddf0e00531b9464b55245185bbbbd"
      url: "https://pub.dev"
    source: hosted
    version: "2.1.5"
  shelf:
    dependency: transitive
    description:
      name: shelf
      sha256: e7dd780a7ffb623c57850b33f43309312fc863fb6aa3d276a754bb299839ef12
      url: "https://pub.dev"
    source: hosted
    version: "1.4.2"
  shelf_packages_handler:
    dependency: transitive
    description:
      name: shelf_packages_handler
      sha256: "89f967eca29607c933ba9571d838be31d67f53f6e4ee15147d5dc2934fee1b1e"
      url: "https://pub.dev"
    source: hosted
    version: "3.0.2"
  shelf_static:
    dependency: transitive
    description:
      name: shelf_static
      sha256: c87c3875f91262785dade62d135760c2c69cb217ac759485334c5857ad89f6e3
      url: "https://pub.dev"
    source: hosted
    version: "1.1.3"
  shelf_web_socket:
    dependency: transitive
    description:
      name: shelf_web_socket
      sha256: cc36c297b52866d203dbf9332263c94becc2fe0ceaa9681d07b6ef9807023b67
      url: "https://pub.dev"
    source: hosted
    version: "2.0.1"
  source_map_stack_trace:
    dependency: transitive
    description:
      name: source_map_stack_trace
      sha256: c0713a43e323c3302c2abe2a1cc89aa057a387101ebd280371d6a6c9fa68516b
      url: "https://pub.dev"
    source: hosted
    version: "2.1.2"
  source_maps:
    dependency: transitive
    description:
      name: source_maps
      sha256: "190222579a448b03896e0ca6eca5998fa810fda630c1d65e2f78b3f638f54812"
      url: "https://pub.dev"
    source: hosted
    version: "0.10.13"
  source_span:
    dependency: transitive
    description:
      name: source_span
      sha256: "254ee5351d6cb365c859e20ee823c3bb479bf4a293c22d17a9f1bf144ce86f7c"
      url: "https://pub.dev"
    source: hosted
    version: "1.10.1"
  stack_trace:
    dependency: transitive
    description:
      name: stack_trace
      sha256: "8b27215b45d22309b5cddda1aa2b19bdfec9df0e765f2de506401c071d38d1b1"
      url: "https://pub.dev"
    source: hosted
    version: "1.12.1"
  stream_channel:
    dependency: transitive
    description:
      name: stream_channel
      sha256: "969e04c80b8bcdf826f8f16579c7b14d780458bd97f56d107d3950fdbeef059d"
      url: "https://pub.dev"
    source: hosted
    version: "2.1.4"
  string_scanner:
    dependency: transitive
    description:
      name: string_scanner
      sha256: "921cd31725b72fe181906c6a94d987c78e3b98c2e205b397ea399d4054872b43"
      url: "https://pub.dev"
    source: hosted
    version: "1.4.1"
  term_glyph:
    dependency: transitive
    description:
      name: term_glyph
      sha256: "7f554798625ea768a7518313e58f83891c7f5024f88e46e7182a4558850a4b8e"
      url: "https://pub.dev"
    source: hosted
    version: "1.2.2"
  test:
    dependency: "direct dev"
    description:
      name: test
      sha256: "8391fbe68d520daf2314121764d38e37f934c02fd7301ad18307bd93bd6b725d"
      url: "https://pub.dev"
    source: hosted
    version: "1.25.14"
  test_api:
    dependency: transitive
    description:
      name: test_api
      sha256: fb31f383e2ee25fbbfe06b40fe21e1e458d14080e3c67e7ba0acfde4df4e0bbd
      url: "https://pub.dev"
    source: hosted
    version: "0.7.4"
  test_core:
    dependency: transitive
    description:
      name: test_core
      sha256: "84d17c3486c8dfdbe5e12a50c8ae176d15e2a771b96909a9442b40173649ccaa"
      url: "https://pub.dev"
    source: hosted
    version: "0.6.8"
  typed_data:
    dependency: transitive
    description:
      name: typed_data
      sha256: f9049c039ebfeb4cf7a7104a675823cd72dba8297f264b6637062516699fa006
      url: "https://pub.dev"
    source: hosted
    version: "1.4.0"
  vm_service:
    dependency: transitive
    description:
      name: vm_service
      sha256: ddfa8d30d89985b96407efce8acbdd124701f96741f2d981ca860662f1c0dc02
      url: "https://pub.dev"
    source: hosted
    version: "15.0.0"
  watcher:
    dependency: transitive
    description:
      name: watcher
      sha256: "69da27e49efa56a15f8afe8f4438c4ec02eff0a117df1b22ea4aad194fe1c104"
      url: "https://pub.dev"
    source: hosted
    version: "1.1.1"
  web:
    dependency: transitive
    description:
      name: web
      sha256: cd3543bd5798f6ad290ea73d210f423502e71900302dde696f8bff84bf89a1cb
      url: "https://pub.dev"
    source: hosted
    version: "1.1.0"
  web_socket:
    dependency: transitive
    description:
      name: web_socket
      sha256: "3c12d96c0c9a4eec095246debcea7b86c0324f22df69893d538fcc6f1b8cce83"
      url: "https://pub.dev"
    source: hosted
    version: "0.1.6"
  web_socket_channel:
    dependency: transitive
    description:
      name: web_socket_channel
      sha256: "0b8e2457400d8a859b7b2030786835a28a8e80836ef64402abef392ff4f1d0e5"
      url: "https://pub.dev"
    source: hosted
    version: "3.0.2"
  webkit_inspection_protocol:
    dependency: transitive
    description:
      name: webkit_inspection_protocol
      sha256: "87d3f2333bb240704cd3f1c6b5b7acd8a10e7f0bc28c28dcf14e782014f4a572"
      url: "https://pub.dev"
    source: hosted
    version: "1.2.1"
  yaml:
    dependency: transitive
    description:
      name: yaml
      sha256: b9da305ac7c39faa3f030eccd175340f968459dae4af175130b3fc47e40d76ce
      url: "https://pub.dev"
    source: hosted
    version: "3.1.3"
sdks:
  dart: ">=3.6.1 <4.0.0"