Support recovery from Foo::

grammar/php7.y

@@ -696,6 +696,10 @@ constant:
       name                                                  { $$ = Expr\ConstFetch[$1]; }
     | class_name_or_var T_PAAMAYIM_NEKUDOTAYIM identifier
           { $$ = Expr\ClassConstFetch[$1, $3]; }
+    /* We interpret and isolated FOO:: as an unfinished class constant fetch. It could also be
+       an unfinished static property fetch or unfinished scoped call. */
+    | class_name_or_var T_PAAMAYIM_NEKUDOTAYIM error
+          { $$ = Expr\ClassConstFetch[$1, Expr\Error[]]; $this->errorState = 2; }
 ;
 
 array_short_syntax:

test/code/parser/errorHandling/recovery.test

@@ -336,4 +336,38 @@ array(
         name: Expr_Error(
         )
     )
+)
+-----
+<?php
+Foo::$
+-----
+!!php7
+Syntax error, unexpected EOF, expecting T_VARIABLE or '{' or '$' from 2:7 to 2:7
+array(
+    0: Expr_StaticPropertyFetch(
+        class: Name(
+            parts: array(
+                0: Foo
+            )
+        )
+        name: Expr_Error(
+        )
+    )
+)
+-----
+<?php
+Foo::
+-----
+!!php7
+Syntax error, unexpected EOF from 2:6 to 2:6
+array(
+    0: Expr_ClassConstFetch(
+        class: Name(
+            parts: array(
+                0: Foo
+            )
+        )
+        name: Expr_Error(
+        )
+    )
 )