Rust: Introduce AstNode.getEnclosingCallable

Author: hvitved

rust/ql/lib/codeql/rust/controlflow/internal/ControlFlowGraphImpl.qll

@@ -21,7 +21,7 @@ private module CfgInput implements InputSig<Location> {
   /** An AST node with an associated control-flow graph. */
   class CfgScope = Scope::CfgScope;
 
-  CfgScope getCfgScope(AstNode n) { result = Scope::scopeOfAst(n) }
+  CfgScope getCfgScope(AstNode n) { result = n.getEnclosingCallable() }
 
   class SuccessorType = Cfg::SuccessorType;
 

rust/ql/lib/codeql/rust/controlflow/internal/Scope.qll

@@ -24,28 +24,3 @@ class CfgScope extends Callable {
     result = this.(ClosureExpr).getBody()
   }
 }
-
-/**
- * Gets the immediate parent of a non-`AstNode` element `e`.
- *
- * We restrict `e` to be a non-`AstNode` to skip past non-`AstNode` in
- * the transitive closure computation in `getParentOfAst`. This is
- * necessary because the parent of an `AstNode` is not necessarily an `AstNode`.
- */
-private Element getParentOfAstStep(Element e) {
-  not e instanceof AstNode and
-  result = getImmediateParent(e)
-}
-
-/** Gets the nearest enclosing parent of `ast` that is an `AstNode`. */
-private AstNode getParentOfAst(AstNode ast) {
-  result = getParentOfAstStep*(getImmediateParent(ast))
-}
-
-/** Gets the enclosing scope of a node */
-cached
-AstNode scopeOfAst(AstNode n) {
-  exists(AstNode p | p = getParentOfAst(n) |
-    if p instanceof CfgScope then p = result else result = scopeOfAst(p)
-  )
-}

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

@@ -421,8 +421,6 @@ module Impl {
     )
   }
 
-  private import codeql.rust.controlflow.internal.Scope
-
   /** A variable access. */
   class VariableAccess extends PathExprImpl::PathExpr instanceof VariableAccessCand {
     private string name;
@@ -434,7 +432,7 @@ module Impl {
     Variable getVariable() { result = v }
 
     /** Holds if this access is a capture. */
-    predicate isCapture() { scopeOfAst(this) != scopeOfAst(v.getPat()) }
+    predicate isCapture() { this.getEnclosingCallable() != v.getPat().getEnclosingCallable() }
 
     override string toString() { result = name }