Rust: Add some helper predicates for finding enclosing blocks.

Author: geoffw0

rust/ql/lib/codeql/rust/elements/internal/AstNodeImpl.qll

@@ -59,6 +59,17 @@ module Impl {
       )
     }
 
+    /** Gets the block that encloses this node, if any. */
+    cached
+    BlockExpr getEnclosingBlock() {
+      exists(AstNode p | p = this.getParentNode() |
+        result = p
+        or
+        not p instanceof BlockExpr and
+        result = p.getEnclosingBlock()
+      )
+    }
+
     /** Holds if this node is inside a macro expansion. */
     predicate isInMacroExpansion() { MacroCallImpl::isInMacroExpansion(_, this) }
 

rust/ql/lib/codeql/rust/elements/internal/VariableImpl.qll

@@ -127,6 +127,10 @@ module Impl {
      */
     Name getName() { variableDecl(definingNode, result, text) }
 
+    /** Gets the block that encloses this variable, if any. */
+    cached
+    BlockExpr getEnclosingBlock() { result = definingNode.getEnclosingBlock() }
+
     /** Gets the `self` parameter that declares this variable, if any. */
     SelfParam getSelfParam() { result.getName() = this.getName() }