From f72af4f1f315cbce7e470002f90bf8aebe3cc13a Mon Sep 17 00:00:00 2001
From: Tom Hvitved <hvitved@github.com>
Date: Mon, 21 Oct 2024 14:04:50 +0200
Subject: [PATCH] Rust: Use `Callable` to define `CfgScope`

---
 .../internal/ControlFlowGraphImpl.qll         | 26 +++----------
 .../rust/controlflow/internal/Scope.qll       | 38 ++++++++-----------
 2 files changed, 20 insertions(+), 44 deletions(-)

diff --git a/rust/ql/lib/codeql/rust/controlflow/internal/ControlFlowGraphImpl.qll b/rust/ql/lib/codeql/rust/controlflow/internal/ControlFlowGraphImpl.qll
index 688f0d1e96a9..54e61d531b3a 100644
--- a/rust/ql/lib/codeql/rust/controlflow/internal/ControlFlowGraphImpl.qll
+++ b/rust/ql/lib/codeql/rust/controlflow/internal/ControlFlowGraphImpl.qll
@@ -40,10 +40,12 @@ private module CfgInput implements InputSig<Location> {
   predicate successorTypeIsCondition(SuccessorType t) { t instanceof Cfg::BooleanSuccessor }
 
   /** Holds if `first` is first executed when entering `scope`. */
-  predicate scopeFirst(CfgScope scope, AstNode first) { scope.scopeFirst(first) }
+  predicate scopeFirst(CfgScope scope, AstNode first) {
+    first(scope.(CfgScopeTree).getFirstChildNode(), first)
+  }
 
   /** Holds if `scope` is exited when `last` finishes with completion `c`. */
-  predicate scopeLast(CfgScope scope, AstNode last, Completion c) { scope.scopeLast(last, c) }
+  predicate scopeLast(CfgScope scope, AstNode last, Completion c) { last(scope.getBody(), last, c) }
 }
 
 private module CfgSplittingInput implements SplittingInputSig<Location, CfgInput> {
@@ -65,7 +67,7 @@ private module CfgImpl =
 
 import CfgImpl
 
-class FunctionTree extends StandardTree, Function {
+class CfgScopeTree extends StandardTree, Scope::CfgScope {
   override predicate first(AstNode first) { first = this }
 
   override predicate last(AstNode last, Completion c) {
@@ -319,24 +321,6 @@ module ExprTrees {
     override AstNode getChildNode(int i) { i = 0 and result = super.getExpr() }
   }
 
-  class ClosureExprTree extends StandardTree, ClosureExpr {
-    override predicate first(AstNode first) { first = this }
-
-    override predicate last(AstNode last, Completion c) {
-      last = this and
-      completionIsValidFor(c, this)
-    }
-
-    override predicate propagatesAbnormal(AstNode child) { none() }
-
-    override AstNode getChildNode(int i) {
-      result = this.getParamList().getParam(i)
-      or
-      i = this.getParamList().getNumberOfParams() and
-      result = this.getBody()
-    }
-  }
-
   class ContinueExprTree extends LeafTree, ContinueExpr {
     override predicate last(AstNode last, Completion c) { none() }
 
diff --git a/rust/ql/lib/codeql/rust/controlflow/internal/Scope.qll b/rust/ql/lib/codeql/rust/controlflow/internal/Scope.qll
index 8a49ab975632..24148eaaf771 100644
--- a/rust/ql/lib/codeql/rust/controlflow/internal/Scope.qll
+++ b/rust/ql/lib/codeql/rust/controlflow/internal/Scope.qll
@@ -3,34 +3,26 @@ private import Completion
 private import ControlFlowGraphImpl
 private import codeql.rust.elements.internal.generated.ParentChild
 
-abstract class CfgScope extends AstNode {
-  /** Holds if `first` is executed first when entering scope. */
-  abstract predicate scopeFirst(AstNode first);
-
-  /** Holds if scope is exited when `last` finishes with completion `c`. */
-  abstract predicate scopeLast(AstNode last, Completion c);
-}
-
-final class FunctionScope extends CfgScope, Function {
-  FunctionScope() {
+/**
+ * A control-flow graph (CFG) scope.
+ *
+ * A CFG scope is a callable with a body.
+ */
+class CfgScope extends Callable {
+  CfgScope() {
     // A function without a body corresponds to a trait method signature and
     // should not have a CFG scope.
-    this.hasBody()
+    this.(Function).hasBody()
+    or
+    this instanceof ClosureExpr
   }
 
-  override predicate scopeFirst(AstNode node) {
-    first(this.(FunctionTree).getFirstChildNode(), node)
+  /** Gets the body of this callable. */
+  AstNode getBody() {
+    result = this.(Function).getBody()
+    or
+    result = this.(ClosureExpr).getBody()
   }
-
-  override predicate scopeLast(AstNode node, Completion c) { last(this.getBody(), node, c) }
-}
-
-final class ClosureScope extends CfgScope, ClosureExpr {
-  override predicate scopeFirst(AstNode node) {
-    first(this.(ExprTrees::ClosureExprTree).getFirstChildNode(), node)
-  }
-
-  override predicate scopeLast(AstNode node, Completion c) { last(this.getBody(), node, c) }
 }
 
 /**