QL: Merge pull request #75 from github/aschackmull/isclosure

Expose transitive closure syntax.

Author: aschackmull

ql/src/codeql_ql/ast/Ast.qll

@@ -783,6 +783,9 @@ class Call extends TCall, Expr, Formula {
 
   final int getNumberOfArguments() { result = count(this.getArgument(_)) }
 
+  /** Holds if this call is a transitive closure of `kind` either `+` or `*`. */
+  predicate isClosure(string kind) { none() }
+
   /**
    * Gets the module that contains the predicate.
    * E.g. for `Foo::bar()` the result is `Foo`.
@@ -814,6 +817,10 @@ class PredicateCall extends TPredicateCall, Call {
 
   override string getAPrimaryQlClass() { result = "PredicateCall" }
 
+  override predicate isClosure(string kind) {
+    kind = expr.getChild(_).(Generated::Closure).getValue()
+  }
+
   /**
    * Gets the name of the predicate called.
    * E.g. for `foo()` the result is "foo".
@@ -850,6 +857,10 @@ class MemberCall extends TMemberCall, Call {
     result = expr.getChild(_).(Generated::QualifiedRhs).getName().getValue()
   }
 
+  override predicate isClosure(string kind) {
+    kind = expr.getChild(_).(Generated::QualifiedRhs).getChild(_).(Generated::Closure).getValue()
+  }
+
   /**
    * Gets the supertype referenced in this call, that is the `Foo` in `Foo.super.bar(...)`.
    *