Fix PHP version check for function calls with static/variable functions

Summary: D10132 improved this check by eliminating some false postives, but assumes an `n_FUNCTION_CALL` always starts with `n_SYMBOL_NAME`. This is true for `f()`, but not true for `C::m()` or `$v()`.

Test Plan: Added and ran unit tests.

Reviewers: btrahan, joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D10467

src/lint/linter/ArcanistXHPASTLinter.php

@@ -384,9 +384,15 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
         continue;
       }
 
-      $function_name = $function
+      $function_token = $function
-        ->getChildOfType(0, 'n_SYMBOL_NAME')
+        ->getChildByIndex(0);
-        ->getConcreteString();
+
+      if ($function_token->getTypeName() != 'n_SYMBOL_NAME') {
+        // This may be `Class::method(...)` or `$var(...)`.
+        continue;
+      }
+
+      $function_name = $function_token->getConcreteString();
 
       switch ($function_name) {
         case 'class_exists':

src/lint/linter/__tests__/xhpast/conditional-usage.lint-test

@@ -11,6 +11,11 @@ if (class_exists('CURLFile')) {
   new CURLFile('');
   new DateTimeImmutable();
 }
+
+// These shouldn't fatal.
+if (SomeClass::someStaticMethod($param)) {}
+$var = 'some_func';
+if ($var()) {}
 ~~~~~~~~~~
 error:5:3
 error:7:3