Generators should show original name in backtrace

Use the original name instead of the outer name for generator
functions in backtraces

hphp/runtime/vm/bytecode.cpp

@@ -2390,7 +2390,14 @@ Array VMExecutionContext::debugBacktrace(bool skip /* = false */,
                 prevFp->m_func->unit()->getLineNumber(pc), true);
     }
     // check for include
-    StringData *funcname = const_cast<StringData*>(fp->m_func->name());
+    String funcname = const_cast<StringData*>(fp->m_func->name());
+    if (fp->m_func->isGenerator()) {
+      // retrieve the original function name from the inner continuation
+      TypedValue* tv = frame_local(fp, 0);
+      assert(tv->m_type == HPHP::KindOfObject);
+      funcname = static_cast<c_Continuation*>(
+                       tv->m_data.pobj)->t_getorigfuncname();
+    }
     if (fp->m_func->isClosureBody()) {
       static StringData* s_closure_label =
           StringData::GetStaticString("{closure}");
@@ -2401,8 +2408,8 @@ Array VMExecutionContext::debugBacktrace(bool skip /* = false */,
       if (!prevFp) continue;
       funcname = s_include;
     }
-    frame.set(String(s_function), String(funcname), true);
-    if (funcname != s_include) {
+    frame.set(String(s_function), funcname, true);
+    if (!funcname.same(s_include)) {
       // Closures have an m_this but they aren't in object context
       Class* ctx = arGetContextClass(fp);
       if (ctx != nullptr && !fp->m_func->isClosureBody()) {
@@ -2418,7 +2425,7 @@ Array VMExecutionContext::debugBacktrace(bool skip /* = false */,
       }
     }
     Array args = Array::Create();
-    if (funcname == s_include) {
+    if (funcname.same(s_include)) {
       if (depth) {
         args.append(String(const_cast<StringData*>(
                              fp->m_func->unit()->filepath())));

hphp/test/vm/debug_backtrace_continuation.php

@@ -0,0 +1,13 @@
+<?php
+function my_generator() {
+  $value = yield null;
+  var_dump(debug_backtrace());
+}
+
+function my_wrapper() {
+  $gen = my_generator();
+  $gen->next();
+  $gen->send(null);
+}
+
+my_wrapper();

hphp/test/vm/debug_backtrace_continuation.php.exp

@@ -0,0 +1,50 @@
+array(3) {
+  [0]=>
+  array(4) {
+    ["file"]=>
+    string(0) ""
+    ["line"]=>
+    int(-1)
+    ["function"]=>
+    string(12) "my_generator"
+    ["args"]=>
+    array(1) {
+      [0]=>
+      object(Continuation)#1 (0) {
+      }
+    }
+  }
+  [1]=>
+  array(7) {
+    ["file"]=>
+    string() "hphp/test/vm/debug_backtrace_continuation.php"
+    ["line"]=>
+    int(10)
+    ["function"]=>
+    string(4) "send"
+    ["class"]=>
+    string(12) "Continuation"
+    ["object"]=>
+    object(Continuation)#1 (0) {
+    }
+    ["type"]=>
+    string(2) "->"
+    ["args"]=>
+    array(1) {
+      [0]=>
+      NULL
+    }
+  }
+  [2]=>
+  array(4) {
+    ["file"]=>
+    string() "hphp/test/vm/debug_backtrace_continuation.php"
+    ["line"]=>
+    int(13)
+    ["function"]=>
+    string(10) "my_wrapper"
+    ["args"]=>
+    array(0) {
+    }
+  }
+}

hphp/test/vm/debug_backtrace_continuation.php.filter

@@ -0,0 +1,2 @@
+#!/bin/bash
+sed -e 's/string(.*) ".*\/hphp/string() "hphp/g'