diff --git a/src/applications/audit/editor/comment/PhabricatorAuditCommentEditor.php b/src/applications/audit/editor/comment/PhabricatorAuditCommentEditor.php
index 9ef8b1ad06..4b27424ff8 100644
--- a/src/applications/audit/editor/comment/PhabricatorAuditCommentEditor.php
+++ b/src/applications/audit/editor/comment/PhabricatorAuditCommentEditor.php
@@ -258,7 +258,7 @@ final class PhabricatorAuditCommentEditor {
     array $other_comments,
     array $inline_comments) {
     assert_instances_of($other_comments, 'PhabricatorAuditComment');
-    assert_instances_of($inline_comments, 'PhabricatorAuditInlineComment');
+    assert_instances_of($inline_comments, 'PhabricatorInlineCommentInterface');
 
     $commit = $this->commit;
 
@@ -350,7 +350,7 @@ final class PhabricatorAuditCommentEditor {
     PhabricatorObjectHandle $handle,
     PhabricatorMailReplyHandler $reply_handler,
     array $inline_comments) {
-    assert_instances_of($inline_comments, 'PhabricatorAuditInlineComment');
+    assert_instances_of($inline_comments, 'PhabricatorInlineCommentInterface');
 
     $commit = $this->commit;
     $user = $this->user;
diff --git a/src/applications/differential/controller/revisionlist/DifferentialRevisionListController.php b/src/applications/differential/controller/revisionlist/DifferentialRevisionListController.php
index 40abaaf016..88df056855 100644
--- a/src/applications/differential/controller/revisionlist/DifferentialRevisionListController.php
+++ b/src/applications/differential/controller/revisionlist/DifferentialRevisionListController.php
@@ -344,6 +344,7 @@ final class DifferentialRevisionListController extends DifferentialController {
     array $handles,
     PhutilURI $uri,
     array $params) {
+    assert_instances_of($handles, 'PhabricatorObjectHandle');
     switch ($control) {
       case 'subscriber':
       case 'phid':
@@ -422,6 +423,8 @@ final class DifferentialRevisionListController extends DifferentialController {
   }
 
   private function buildViews($filter, $user_phid, array $revisions) {
+    assert_instances_of($revisions, 'DifferentialRevision');
+
     $user = $this->getRequest()->getUser();
 
     $template = id(new DifferentialRevisionListView())
diff --git a/src/applications/differential/controller/revisionview/DifferentialRevisionViewController.php b/src/applications/differential/controller/revisionview/DifferentialRevisionViewController.php
index 4e637b97da..c48f9eb172 100644
--- a/src/applications/differential/controller/revisionview/DifferentialRevisionViewController.php
+++ b/src/applications/differential/controller/revisionview/DifferentialRevisionViewController.php
@@ -546,6 +546,8 @@ final class DifferentialRevisionViewController extends DifferentialController {
   }
 
   private function loadInlineComments(array $comments, array &$changesets) {
+    assert_instances_of($comments, 'DifferentialComment');
+    assert_instances_of($changesets, 'DifferentialChangeset');
 
     $inline_comments = array();
 
@@ -585,7 +587,12 @@ final class DifferentialRevisionViewController extends DifferentialController {
     return $inline_comments;
   }
 
-  private function loadChangesetsAndVsMap(array $diffs, $diff_vs, $target) {
+  private function loadChangesetsAndVsMap(
+    array $diffs,
+    $diff_vs,
+    DifferentialDiff $target) {
+    assert_instances_of($diffs, 'DifferentialDiff');
+
     $load_ids = array();
     if ($diff_vs) {
       $load_ids[] = $diff_vs;
@@ -695,6 +702,7 @@ final class DifferentialRevisionViewController extends DifferentialController {
     DifferentialDiff $target,
     PhabricatorRepositoryArcanistProject $arc_project,
     array $visible_changesets) {
+    assert_instances_of($visible_changesets, 'DifferentialChangeset');
 
     $engine = PhabricatorSyntaxHighlighter::newEngine();
 
@@ -768,6 +776,8 @@ final class DifferentialRevisionViewController extends DifferentialController {
   }
 
   private function renderOtherRevisions(array $revisions) {
+    assert_instances_of($revisions, 'DifferentialRevision');
+
     $view = id(new DifferentialRevisionListView())
       ->setRevisions($revisions)
       ->setFields(DifferentialRevisionListView::getDefaultFields())
diff --git a/src/applications/differential/editor/revision/DifferentialRevisionEditor.php b/src/applications/differential/editor/revision/DifferentialRevisionEditor.php
index 5972b5bb2f..496b4766fb 100644
--- a/src/applications/differential/editor/revision/DifferentialRevisionEditor.php
+++ b/src/applications/differential/editor/revision/DifferentialRevisionEditor.php
@@ -761,6 +761,7 @@ final class DifferentialRevisionEditor {
     DifferentialRevision $revision,
     DifferentialDiff $diff,
     array $changesets) {
+    assert_instances_of($changesets, 'DifferentialChangeset');
 
     $project = $diff->loadArcanistProject();
     if (!$project) {
diff --git a/src/applications/differential/field/selector/base/DifferentialFieldSelector.php b/src/applications/differential/field/selector/base/DifferentialFieldSelector.php
index 320dfe3f38..d4070e5564 100644
--- a/src/applications/differential/field/selector/base/DifferentialFieldSelector.php
+++ b/src/applications/differential/field/selector/base/DifferentialFieldSelector.php
@@ -29,6 +29,7 @@ abstract class DifferentialFieldSelector {
   abstract public function getFieldSpecifications();
 
   public function sortFieldsForRevisionList(array $fields) {
+    assert_instances_of($fields, 'DifferentialFieldSpecification');
     return $fields;
   }
 
diff --git a/src/applications/differential/field/selector/base/__init__.php b/src/applications/differential/field/selector/base/__init__.php
index 6c8eeefe6f..09f7eb4cf4 100644
--- a/src/applications/differential/field/selector/base/__init__.php
+++ b/src/applications/differential/field/selector/base/__init__.php
@@ -8,5 +8,7 @@
 
 phutil_require_module('phabricator', 'infrastructure/env');
 
+phutil_require_module('phutil', 'utils');
+
 
 phutil_require_source('DifferentialFieldSelector.php');
diff --git a/src/applications/differential/field/selector/default/DifferentialDefaultFieldSelector.php b/src/applications/differential/field/selector/default/DifferentialDefaultFieldSelector.php
index 1a2baecbf1..9184424492 100644
--- a/src/applications/differential/field/selector/default/DifferentialDefaultFieldSelector.php
+++ b/src/applications/differential/field/selector/default/DifferentialDefaultFieldSelector.php
@@ -62,6 +62,8 @@ final class DifferentialDefaultFieldSelector
   }
 
   public function sortFieldsForRevisionList(array $fields) {
+    assert_instances_of($fields, 'DifferentialFieldSpecification');
+
     $map = array();
     foreach ($fields as $field) {
       $map[get_class($field)] = $field;
diff --git a/src/applications/differential/field/specification/base/DifferentialFieldSpecification.php b/src/applications/differential/field/specification/base/DifferentialFieldSpecification.php
index ba24c74f32..e0953b1a3b 100644
--- a/src/applications/differential/field/specification/base/DifferentialFieldSpecification.php
+++ b/src/applications/differential/field/specification/base/DifferentialFieldSpecification.php
@@ -741,6 +741,7 @@ abstract class DifferentialFieldSpecification {
    * @task context
    */
   final public function setHandles(array $handles) {
+    assert_instances_of($handles, 'PhabricatorObjectHandle');
     $this->handles = $handles;
     return $this;
   }
diff --git a/src/applications/differential/mail/base/DifferentialMail.php b/src/applications/differential/mail/base/DifferentialMail.php
index 9358446b3a..686eecbc4c 100644
--- a/src/applications/differential/mail/base/DifferentialMail.php
+++ b/src/applications/differential/mail/base/DifferentialMail.php
@@ -343,6 +343,7 @@ EOTEXT;
   }
 
   public function setInlineComments(array $inline_comments) {
+    assert_instances_of($inline_comments, 'PhabricatorInlineCommentInterface');
     $this->inlineComments = $inline_comments;
     return $this;
   }
@@ -388,6 +389,7 @@ EOTEXT;
   }
 
   protected function renderHandleList(array $handles, array $phids) {
+    assert_instances_of($handles, 'PhabricatorObjectHandle');
     $names = array();
     foreach ($phids as $phid) {
       $names[] = $handles[$phid]->getName();
diff --git a/src/applications/differential/mail/comment/DifferentialCommentMail.php b/src/applications/differential/mail/comment/DifferentialCommentMail.php
index 0889e05325..03973d33a5 100644
--- a/src/applications/differential/mail/comment/DifferentialCommentMail.php
+++ b/src/applications/differential/mail/comment/DifferentialCommentMail.php
@@ -35,6 +35,8 @@ final class DifferentialCommentMail extends DifferentialMail {
     DifferentialComment $comment,
     array $changesets,
     array $inline_comments) {
+    assert_instances_of($changesets, 'DifferentialChangeset');
+    assert_instances_of($inline_comments, 'PhabricatorInlineCommentInterface');
 
     $this->setRevision($revision);
     $this->setActorHandle($actor);
diff --git a/src/applications/differential/mail/reviewrequest/DifferentialReviewRequestMail.php b/src/applications/differential/mail/reviewrequest/DifferentialReviewRequestMail.php
index caff1f1dd3..fac9fc6f79 100644
--- a/src/applications/differential/mail/reviewrequest/DifferentialReviewRequestMail.php
+++ b/src/applications/differential/mail/reviewrequest/DifferentialReviewRequestMail.php
@@ -33,6 +33,7 @@ abstract class DifferentialReviewRequestMail extends DifferentialMail {
     DifferentialRevision $revision,
     PhabricatorObjectHandle $actor,
     array $changesets) {
+    assert_instances_of($changesets, 'DifferentialChangeset');
 
     $this->setRevision($revision);
     $this->setActorHandle($actor);
diff --git a/src/applications/differential/parser/changeset/DifferentialChangesetParser.php b/src/applications/differential/parser/changeset/DifferentialChangesetParser.php
index 2a70a466dc..e5c98033e3 100644
--- a/src/applications/differential/parser/changeset/DifferentialChangesetParser.php
+++ b/src/applications/differential/parser/changeset/DifferentialChangesetParser.php
@@ -169,6 +169,7 @@ final class DifferentialChangesetParser {
   }
 
   public function setHandles(array $handles) {
+    assert_instances_of($handles, 'PhabricatorObjectHandle');
     $this->handles = $handles;
     return $this;
   }
@@ -1173,6 +1174,9 @@ final class DifferentialChangesetParser {
     $feedback_mask,
     array $old_comments,
     array $new_comments) {
+    foreach (array_merge($old_comments, $new_comments) as $comments) {
+      assert_instances_of($comments, 'PhabricatorInlineCommentInterface');
+    }
 
     $context_not_available = null;
     if ($this->missingOld || $this->missingNew) {
diff --git a/src/applications/differential/query/revision/DifferentialRevisionQuery.php b/src/applications/differential/query/revision/DifferentialRevisionQuery.php
index e38f1d9c30..2e512a613f 100644
--- a/src/applications/differential/query/revision/DifferentialRevisionQuery.php
+++ b/src/applications/differential/query/revision/DifferentialRevisionQuery.php
@@ -750,6 +750,7 @@ final class DifferentialRevisionQuery {
   }
 
   private function loadRelationships($conn_r, array $revisions) {
+    assert_instances_of($revisions, 'DifferentialRevision');
     $relationships = queryfx_all(
       $conn_r,
       'SELECT * FROM %T WHERE revisionID in (%Ld) ORDER BY sequence',
@@ -766,6 +767,7 @@ final class DifferentialRevisionQuery {
   }
 
   private function loadCommitPHIDs($conn_r, array $revisions) {
+    assert_instances_of($revisions, 'DifferentialRevision');
     $commit_phids = queryfx_all(
       $conn_r,
       'SELECT * FROM %T WHERE revisionID IN (%Ld)',
@@ -780,6 +782,8 @@ final class DifferentialRevisionQuery {
   }
 
   private function loadDiffIDs($conn_r, array $revisions) {
+    assert_instances_of($revisions, 'DifferentialRevision');
+
     $diff_table = new DifferentialDiff();
 
     $diff_ids = queryfx_all(
@@ -798,6 +802,8 @@ final class DifferentialRevisionQuery {
   }
 
   private function loadActiveDiffs($conn_r, array $revisions) {
+    assert_instances_of($revisions, 'DifferentialRevision');
+
     $diff_table = new DifferentialDiff();
 
     $load_ids = array();
diff --git a/src/applications/differential/storage/auxiliaryfield/DifferentialAuxiliaryField.php b/src/applications/differential/storage/auxiliaryfield/DifferentialAuxiliaryField.php
index 5bd7d51a77..49246fdcf6 100644
--- a/src/applications/differential/storage/auxiliaryfield/DifferentialAuxiliaryField.php
+++ b/src/applications/differential/storage/auxiliaryfield/DifferentialAuxiliaryField.php
@@ -1,7 +1,7 @@
 <?php
 
 /*
- * Copyright 2011 Facebook, Inc.
+ * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,6 +35,7 @@ final class DifferentialAuxiliaryField extends DifferentialDAO {
   public static function loadFromStorage(
     DifferentialRevision $revision,
     array $aux_fields) {
+    assert_instances_of($aux_fields, 'DifferentialFieldSpecification');
 
     $storage_keys = array_filter(mpull($aux_fields, 'getStorageKey'));
     $field_data = array();
diff --git a/src/applications/differential/storage/changeset/DifferentialChangeset.php b/src/applications/differential/storage/changeset/DifferentialChangeset.php
index 20eadd08d4..3485e50bc1 100644
--- a/src/applications/differential/storage/changeset/DifferentialChangeset.php
+++ b/src/applications/differential/storage/changeset/DifferentialChangeset.php
@@ -58,6 +58,7 @@ final class DifferentialChangeset extends DifferentialDAO {
   }
 
   public function attachHunks(array $hunks) {
+    assert_instances_of($hunks, 'DifferentialHunk');
     $this->hunks = $hunks;
     return $this;
   }
diff --git a/src/applications/differential/storage/diff/DifferentialDiff.php b/src/applications/differential/storage/diff/DifferentialDiff.php
index 5a04f8de35..9ae0fa4a9b 100644
--- a/src/applications/differential/storage/diff/DifferentialDiff.php
+++ b/src/applications/differential/storage/diff/DifferentialDiff.php
@@ -55,6 +55,7 @@ final class DifferentialDiff extends DifferentialDAO {
   }
 
   public function attachChangesets(array $changesets) {
+    assert_instances_of($changesets, 'DifferentialChangeset');
     $this->changesets = $changesets;
     return $this;
   }
@@ -107,6 +108,7 @@ final class DifferentialDiff extends DifferentialDAO {
   }
 
   public static function newFromRawChanges(array $changes) {
+    assert_instances_of($changes, 'ArcanistDiffChange');
     $diff = new DifferentialDiff();
 
     $lines = 0;
diff --git a/src/applications/differential/view/inlinecomment/DifferentialInlineCommentView.php b/src/applications/differential/view/inlinecomment/DifferentialInlineCommentView.php
index e420afa57d..b5f77fc392 100644
--- a/src/applications/differential/view/inlinecomment/DifferentialInlineCommentView.php
+++ b/src/applications/differential/view/inlinecomment/DifferentialInlineCommentView.php
@@ -42,6 +42,7 @@ final class DifferentialInlineCommentView extends AphrontView {
   }
 
   public function setHandles(array $handles) {
+    assert_instances_of($handles, 'PhabricatorObjectHandle');
     $this->handles = $handles;
     return $this;
   }
diff --git a/src/applications/differential/view/inlinecomment/__init__.php b/src/applications/differential/view/inlinecomment/__init__.php
index aee6d7ccc2..68a8893618 100644
--- a/src/applications/differential/view/inlinecomment/__init__.php
+++ b/src/applications/differential/view/inlinecomment/__init__.php
@@ -11,6 +11,7 @@ phutil_require_module('phabricator', 'infrastructure/javelin/markup');
 phutil_require_module('phabricator', 'view/base');
 
 phutil_require_module('phutil', 'markup');
+phutil_require_module('phutil', 'utils');
 
 
 phutil_require_source('DifferentialInlineCommentView.php');
diff --git a/src/applications/differential/view/primarypane/DifferentialPrimaryPaneView.php b/src/applications/differential/view/primarypane/DifferentialPrimaryPaneView.php
index 9fc9e5fae5..1562fdd92b 100644
--- a/src/applications/differential/view/primarypane/DifferentialPrimaryPaneView.php
+++ b/src/applications/differential/view/primarypane/DifferentialPrimaryPaneView.php
@@ -1,7 +1,7 @@
 <?php
 
 /*
- * Copyright 2011 Facebook, Inc.
+ * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,6 +32,7 @@ final class DifferentialPrimaryPaneView extends AphrontView {
   }
 
   public function setLineWidthFromChangesets(array $changesets) {
+    assert_instances_of($changesets, 'DifferentialChangeset');
     if (empty($changesets)) {
       return;
     }
diff --git a/src/applications/differential/view/primarypane/__init__.php b/src/applications/differential/view/primarypane/__init__.php
index ec28cedc88..d7e8c5647a 100644
--- a/src/applications/differential/view/primarypane/__init__.php
+++ b/src/applications/differential/view/primarypane/__init__.php
@@ -9,6 +9,7 @@
 phutil_require_module('phabricator', 'view/base');
 
 phutil_require_module('phutil', 'markup');
+phutil_require_module('phutil', 'utils');
 
 
 phutil_require_source('DifferentialPrimaryPaneView.php');
diff --git a/src/applications/differential/view/revisioncomment/DifferentialRevisionCommentView.php b/src/applications/differential/view/revisioncomment/DifferentialRevisionCommentView.php
index fdec2a3b1d..d74e2e719b 100644
--- a/src/applications/differential/view/revisioncomment/DifferentialRevisionCommentView.php
+++ b/src/applications/differential/view/revisioncomment/DifferentialRevisionCommentView.php
@@ -35,6 +35,7 @@ final class DifferentialRevisionCommentView extends AphrontView {
   }
 
   public function setHandles(array $handles) {
+    assert_instances_of($handles, 'PhabricatorObjectHandle');
     $this->handles = $handles;
     return $this;
   }
@@ -50,11 +51,13 @@ final class DifferentialRevisionCommentView extends AphrontView {
   }
 
   public function setInlineComments(array $inline_comments) {
+    assert_instances_of($inline_comments, 'PhabricatorInlineCommentInterface');
     $this->inlines = $inline_comments;
     return $this;
   }
 
   public function setChangesets(array $changesets) {
+    assert_instances_of($changesets, 'DifferentialChangeset');
     // Ship these in sorted by getSortKey() and keyed by ID... or else!
     $this->changesets = $changesets;
     return $this;
diff --git a/src/applications/differential/view/revisioncommentlist/DifferentialRevisionCommentListView.php b/src/applications/differential/view/revisioncommentlist/DifferentialRevisionCommentListView.php
index ece96a750d..5dc3411e13 100644
--- a/src/applications/differential/view/revisioncommentlist/DifferentialRevisionCommentListView.php
+++ b/src/applications/differential/view/revisioncommentlist/DifferentialRevisionCommentListView.php
@@ -27,21 +27,25 @@ final class DifferentialRevisionCommentListView extends AphrontView {
   private $versusDiffID;
 
   public function setComments(array $comments) {
+    assert_instances_of($comments, 'DifferentialComment');
     $this->comments = $comments;
     return $this;
   }
 
   public function setInlineComments(array $inline_comments) {
+    assert_instances_of($inline_comments, 'PhabricatorInlineCommentInterface');
     $this->inlines = $inline_comments;
     return $this;
   }
 
   public function setHandles(array $handles) {
+    assert_instances_of($handles, 'PhabricatorObjectHandle');
     $this->handles = $handles;
     return $this;
   }
 
   public function setChangesets(array $changesets) {
+    assert_instances_of($changesets, 'DifferentialChangeset');
     $this->changesets = $changesets;
     return $this;
   }
diff --git a/src/applications/differential/view/revisionlist/DifferentialRevisionListView.php b/src/applications/differential/view/revisionlist/DifferentialRevisionListView.php
index 5389a6b90f..5e24894ab4 100644
--- a/src/applications/differential/view/revisionlist/DifferentialRevisionListView.php
+++ b/src/applications/differential/view/revisionlist/DifferentialRevisionListView.php
@@ -28,11 +28,13 @@ final class DifferentialRevisionListView extends AphrontView {
   private $fields;
 
   public function setFields(array $fields) {
+    assert_instances_of($fields, 'DifferentialFieldSpecification');
     $this->fields = $fields;
     return $this;
   }
 
   public function setRevisions(array $revisions) {
+    assert_instances_of($revisions, 'DifferentialRevision');
     $this->revisions = $revisions;
     return $this;
   }
@@ -48,6 +50,7 @@ final class DifferentialRevisionListView extends AphrontView {
   }
 
   public function setHandles(array $handles) {
+    assert_instances_of($handles, 'PhabricatorObjectHandle');
     $this->handles = $handles;
     return $this;
   }
diff --git a/src/applications/differential/view/revisionstats/DifferentialRevisionStatsView.php b/src/applications/differential/view/revisionstats/DifferentialRevisionStatsView.php
index 4d8aaae49e..914f90831a 100644
--- a/src/applications/differential/view/revisionstats/DifferentialRevisionStatsView.php
+++ b/src/applications/differential/view/revisionstats/DifferentialRevisionStatsView.php
@@ -25,14 +25,17 @@ final class DifferentialRevisionStatsView extends AphrontView {
   private $user;
 
   public function setRevisions(array $revisions) {
+    assert_instances_of($revisions, 'DifferentialRevision');
     $this->revisions = $revisions;
     return $this;
   }
 
   public function setComments(array $comments) {
+    assert_instances_of($comments, 'DifferentialComment');
     $this->comments = $comments;
     return $this;
   }
+
   public function setUser($user) {
     $this->user = $user;
     return $this;
diff --git a/src/applications/diffusion/view/comment/DiffusionCommentView.php b/src/applications/diffusion/view/comment/DiffusionCommentView.php
index e60a499f51..8e1a8c611d 100644
--- a/src/applications/diffusion/view/comment/DiffusionCommentView.php
+++ b/src/applications/diffusion/view/comment/DiffusionCommentView.php
@@ -56,7 +56,7 @@ final class DiffusionCommentView extends AphrontView {
   }
 
   public function setInlineComments(array $inline_comments) {
-    assert_instances_of($inline_comments, 'PhabricatorAuditInlineComment');
+    assert_instances_of($inline_comments, 'PhabricatorInlineCommentInterface');
     $this->inlineComments = $inline_comments;
     return $this;
   }
diff --git a/src/applications/diffusion/view/commentlist/DiffusionCommentListView.php b/src/applications/diffusion/view/commentlist/DiffusionCommentListView.php
index d837a60ca1..fec0b549d5 100644
--- a/src/applications/diffusion/view/commentlist/DiffusionCommentListView.php
+++ b/src/applications/diffusion/view/commentlist/DiffusionCommentListView.php
@@ -35,7 +35,7 @@ final class DiffusionCommentListView extends AphrontView {
   }
 
   public function setInlineComments(array $inline_comments) {
-    assert_instances_of($inline_comments, 'PhabricatorAuditInlineComment');
+    assert_instances_of($inline_comments, 'PhabricatorInlineCommentInterface');
     $this->inlineComments = $inline_comments;
     return $this;
   }
diff --git a/src/docs/contributing/php_coding_standards.diviner b/src/docs/contributing/php_coding_standards.diviner
index 230c0ca854..72a849fce5 100644
--- a/src/docs/contributing/php_coding_standards.diviner
+++ b/src/docs/contributing/php_coding_standards.diviner
@@ -61,6 +61,7 @@ guidelines, you probably don't need to read this super thoroughly.
   - Prefer class constants over defines.
   - Avoid naked class properties; instead, define accessors.
   - Use exceptions for error conditions.
+  - Use type hints, use `assert_instances_of()` for arrays holding objects.
 
 = Examples =