diff --git a/scripts/lib/PhutilLibraryMapBuilder.php b/scripts/lib/PhutilLibraryMapBuilder.php
index 861a9352..9dc35ac0 100755
--- a/scripts/lib/PhutilLibraryMapBuilder.php
+++ b/scripts/lib/PhutilLibraryMapBuilder.php
@@ -21,7 +21,7 @@ final class PhutilLibraryMapBuilder {
   const LIBRARY_MAP_VERSION       = 2;
 
   const SYMBOL_CACHE_VERSION_KEY  = '__symbol_cache_version__';
-  const SYMBOL_CACHE_VERSION      = 8;
+  const SYMBOL_CACHE_VERSION      = 9;
 
 
 /* -(  Mapping libphutil Libraries  )---------------------------------------- */
diff --git a/scripts/phutil_symbols.php b/scripts/phutil_symbols.php
index 50a342e8..6dc693ef 100755
--- a/scripts/phutil_symbols.php
+++ b/scripts/phutil_symbols.php
@@ -211,10 +211,10 @@ foreach ($classes as $class) {
 //  - Static method call
 //  - Static property access
 //  - Use of class constant
+//  - typehints
 //
 // TODO: Possibly support these:
 //
-//  - typehints
 //  - instanceof
 //  - catch
 //  - String literal in ReflectionClass().
@@ -273,11 +273,24 @@ foreach ($static_uses as $static_use) {
     continue;
   }
   $need[] = array(
-    'type'    => 'class',
+    'type'    => 'class/interface',
     'symbol'  => $name,
   );
 }
 
+// This is "function (X $x)".
+$parameters = $root->selectDescendantsOfType('n_DECLARATION_PARAMETER');
+foreach ($parameters as $parameter) {
+  $hint = $parameter->getChildByIndex(0);
+  if ($hint->getTypeName() != 'n_CLASS_NAME') {
+    continue;
+  }
+  $need[] = array(
+    'type'    => 'class/interface',
+    'symbol'  => $hint,
+  );
+}
+
 
 // -(  Interfaces  )------------------------------------------------------------
 
@@ -355,14 +368,20 @@ foreach ($need as $key => $spec) {
   }
 
   $type = $spec['type'];
-  if (!$show_all) {
-    if (!empty($externals[$type][$name])) {
-      // Ignore symbols declared as externals.
-      continue;
+  foreach (explode('/', $type) as $libtype) {
+    if (!$show_all) {
+      if (!empty($externals[$libtype][$name])) {
+        // Ignore symbols declared as externals.
+        continue 2;
+      }
+      if (!empty($builtins[$libtype][$name])) {
+        // Ignore symbols declared as builtins.
+        continue 2;
+      }
     }
-    if (!empty($builtins[$type][$name])) {
-      // Ignore symbols declared as builtins.
-      continue;
+    if (!empty($declared_symbols[$libtype][$name])) {
+      // We declare this symbol, so don't treat it as a requirement.
+      continue 2;
     }
   }
   if (!empty($required_symbols[$type][$name])) {
@@ -370,10 +389,6 @@ foreach ($need as $key => $spec) {
     // isn't terribly informative.
     continue;
   }
-  if (!empty($declared_symbols[$type][$name])) {
-    // We declare this symbol, so don't treat it as a requirement.
-    continue;
-  }
   $required_symbols[$type][$name] = $spec['symbol']->getOffset();
 }
 
diff --git a/src/lint/linter/ArcanistPhutilLibraryLinter.php b/src/lint/linter/ArcanistPhutilLibraryLinter.php
index 0a8f772e..5b695c18 100644
--- a/src/lint/linter/ArcanistPhutilLibraryLinter.php
+++ b/src/lint/linter/ArcanistPhutilLibraryLinter.php
@@ -134,14 +134,18 @@ final class ArcanistPhutilLibraryLinter extends ArcanistLinter {
       }
     }
 
+    $types = array('class', 'function', 'interface', 'class/interface');
     foreach ($symbols as $library => $map) {
       // Check for unknown symbols: uses of classes, functions or interfaces
       // which are not defined anywhere. We reference the list of all symbols
       // we built up earlier.
       foreach ($map as $file => $spec) {
         $need = idx($spec, 'need', array());
-        foreach (array('class', 'function', 'interface') as $type) {
-          $libtype = ($type == 'interface') ? 'class' : $type;
+        foreach ($types as $type) {
+          $libtype = $type;
+          if ($type == 'interface' || $type == 'class/interface') {
+            $libtype = 'class';
+          }
           foreach (idx($need, $type, array()) as $symbol => $offset) {
             if (!empty($all_symbols[$libtype][$symbol])) {
               // Symbol is defined somewhere.