repo mode: check trait requirements after all other traits applied

... since a (textually later) "use ProvidingTrait;" can
 result in a class implementing an interface and thus satisfy the
 'require interface' of a textually earlier "use RequiringTrait;".

Reviewed By: @paroski

Differential Revision: D1250792

Author: Eugene Letuchy

hphp/compiler/analysis/class_scope.cpp

@@ -861,7 +861,12 @@ void ClassScope::importUsedTraits(AnalysisResultPtr ar) {
 
     // Import any interfaces implemented
     tCls->getInterfaces(ar, m_bases, false);
-
+  }
+  for (unsigned i = 0; i < m_usedTraitNames.size(); i++) {
+    // Requirements must be checked in a separate loop because the
+    // interfaces required by one trait may be implemented by another trait
+    // whose "use" appears later in the class' scope
+    ClassScopePtr tCls = ar->findClass(m_usedTraitNames[i]);
     importTraitRequirements(ar, tCls);
   }
 

hphp/test/run

@@ -930,7 +930,7 @@ function print_success($tests, $options) {
         _\\__|__/_
        (___/ \\___)
 CLOWN
-."\n\n";
+."\n\n"; /**/
     return;
   }
   print "\nAll tests passed.\n\n".<<<SHIP

hphp/test/slow/traits/require_constraint_repo_ifaces.inc

@@ -0,0 +1,5 @@
+<?php
+
+interface IDY {}
+
+trait MyT { require implements IDY; }

hphp/test/slow/traits/require_constraint_repo_ifaces.php

@@ -0,0 +1,15 @@
+<?hh
+require __DIR__.'/require_constraint_repo_ifaces.inc';
+
+trait DYI implements IDY {}
+
+class C {
+  use MyT; // requires IDY
+  use DYI; // provides IDY
+}
+
+function main() {
+  $c = new C();
+  echo 'Done', "\n";
+}
+main();

hphp/test/slow/traits/require_constraint_repo_ifaces.php.expect

@@ -0,0 +1 @@
+Done