Add location for implicitly declared variables

Author: owen-mc

go/ql/lib/semmle/go/Scopes.qll

@@ -158,15 +158,16 @@ class Entity extends @object {
     string filepath, int startline, int startcolumn, int endline, int endcolumn
   ) {
     // take the location of the declaration if there is one
-    this.getDeclaration().hasLocationInfo(filepath, startline, startcolumn, endline, endcolumn)
-    or
-    // otherwise fall back on dummy location
-    not exists(this.getDeclaration()) and
-    filepath = "" and
-    startline = 0 and
-    startcolumn = 0 and
-    endline = 0 and
-    endcolumn = 0
+    if this.hasRealLocationInfo(_, _, _, _, _)
+    then this.hasRealLocationInfo(filepath, startline, startcolumn, endline, endcolumn)
+    else (
+      // otherwise fall back on dummy location
+      filepath = "" and
+      startline = 0 and
+      startcolumn = 0 and
+      endline = 0 and
+      endcolumn = 0
+    )
   }
 }